Note: This was lifted from Jon Wallis's old 2smoked.com website and I have obtained explicit permission to rehost. See post. Prices are old and may not be inidicative of today's market.
All content copyright Jon Wallis 2009-Present.
No photograph or text from this article can be
reproduced without prior permission from Jon Wallis. As such all
text on this page is protected by enforceable copyright.
Regarding the pictures on this page - Jon
Wallis either owns the rights to these pictures, has permission to use
these pictures or has taken every step possible to contact the owner of
any borrowed pictures – As such all pictures on this page are protected
by enforceable copyright.
As the word gets out, more and more people are
building larger capacity RD/RZ motors.... of course as you may know from
reading this site, I feel that's no bad thing! They offer power and
performance from all new parts instead of messing about working on ‘well
used’ (a somewhat kind euphemism for 30+ year old worn out) OEM parts.
But, there are a lot of options out there and you really do need your
wits about you to choose and build one... and honestly no one person has
all the answers.
With that in mind, I've created this page as a
'Big Bore Primer' to help those who are thinking about building their
own monster motor to gather some grounding in what this subject is all
about. I make no claims that it is comprehensive and as time moves on it
certainly won’t be complete, but if you are looking to do this work I
believe reading it will help you get started.
Ok, first a few things to get us all on the same page...
Firstly... A bigger cc motor is generally created in two ways, increasing the bore or the stoke, or both.
E.g. Adding a +4mm crank to a 66mm bore takes
you to 385cc. Adding a 68mm bore to a standard crank is 392cc, adding a
+4mm crank to a 68mm bore is 421cc... And so on.
Secondly... All of the larger bore
cylinders were created for the Banshee ATV. Many were designed for
racers who wanted to drag race (on sand or road) and as such they have
either drag porting out of the box, or are quite ‘bare’ when new as they
guys who fit them port them themselves, or have their supplier do it.
Bear in mind that these guys will spend a lot of money to create a
special engine to win races... spending money and racing always go hand
in hand...
Thirdly... If you want to fit
these units to a road bike, then you really need to do a lot of due
diligence and read up and talk to suppliers about the products they
sell. Most have never fitted them to a bike, only ATVs and some just
sell products they don’t use themselves. So, often they have no idea
about road tunes for use in traffic situations. Many cylinders have wide
ports that eat rings and need a lot of maintenance as befits a race
machine. You must strive get the package that you wanted at the outset;
perhaps you didn't really want a peaky drag racer for your daily commute
at 7am through city traffic, or a noisy Mx'er’s sound when coming home
from the lateshift?
Finally... Lots of ebay sellers
and others websites just on-sell boxed kits that look good value. They
may work fine but a specialist who builds engines and works on them
daily will be a better bet than a cheap kit and no after sales backup.
After all, you will need to set it up once you have it fitted and a
supplier who shrugs and walks away from your questions about airfilters,
ignition maps or jetting is going to cost you more money than the
initial savings you made on an ‘bargain kit’. Always talk to the
supplier and get a feel for what they know before you buy.
And one Postscript... No, you cannot fit the banshee parts to the LC motor. People ask this all the time and the answer is still the same. The LC uses a different stud pattern so the cylinders do not fit the older LC cases. The YPVS/Banshee crank is also slightly wider so is not a drop in fit to the LC cases either. You can easily machine to fit the crank but changing the stud spacing is more involved. Its not all bad news though, Fahron do a 370cc kit using 250 cylinders and others have got to 400cc but you will need to search that info out elsewhere as the rest of this page is about the YPVS bottom ends.
Ok, All that said... what prompted me to create
this page was that on the forums there had been a lot of people asking
the same questions over and over in different forms, so rather than the
same few guys keep answering I tried to write up what is needed in a
single place.
So without further ado, here is my FAQ for
these ‘big bore’ motors, I hope it will help any prospective builder get
a better understanding of what they want/need to move forwards with
their project.
Q. Can I go bigger with my old Yamaha 350 cylinders?
A. Yes, you can increase both bore
and stroke to add cc's. Standard bore of the OEM cylinders is 64mm,
Yamaha will sell you pistons and rings up to 65mm, aftermarket maximum
bore is 66mm (some say larger but it leaves a thin wall in the sleeve
and potentially cuts into the PV area). Adding a stroked crank will also
add capacity, but is a little more involved.
Q. Can I do anything like this with my 250 motor?
A. Certainly... and the old 250
cylinders make good paperweights. The 250 bottom end will take any of
the larger cylinders mentioned here, including the OEM 350s.
Q. How does the stroked crank work?
A. The throw of the crank is
longer than standard, so the pistons move up and down a few mm more than
OEM, giving a larger cubic capacity.
Q. So, I can just fit one of those to my old OEM pistons and run it in my motor?
A. No, you need to change the
pistons (or use an offset pin) and also you may need to machine the
domes to get the fit, squish and compression ration you require. That
machining depends on your head and also whether you use 110mm or 115mm
rods and as to what pistons you use and all that dictates what profile
the domes ned to be machined at.
Q. Can I stroke a 250?
A. What is it with you 250 boys?
haha. Ok.... No one has yet stroked a 250, most builders feel that if
you’re going to the trouble to build a trick motor then you wouldn’t
keep the 250cc top end. One day I might stoke a 250, just to see what it
goes like. The OEM standard crank was designed to offset the weight of
the 250 pistons, so I reckon it might be a nice revvy machine. Perhaps
I’ll report back one day on that.. watch this space...
Q. A supplier suggested I fit a spacer plate but you say I should use offset wrist pins / different pistons, why is that?
A. Honestly, fit new pistons, the
spacer plate will effect the port timing and tends to leave a 350 YPVS
feeling 'flat' to ride. It’s been done, tested and found wanting...
Q. I’m thinking of ditching my OEM cylinders and getting one of these bigger bore kits on ebay, they seem good value...
A. They are, but you need to read
the rest of this page before you get too excited... Don't worry it’s not
a nightmare but don't rush into this! Read on...
Q. I just noticed that many of these
aftermarket cylinders don't have powervalves like my YPVS, how will that
work on my YPVS bike?
A. That's right, they don’t. They
are made for the banshee which doesn't have them as it’s an off road ATV
and low down tractability (good for road use) did not really figure in
it’s design. You disconnect the YPVS electronics when using these
cylinders.
Q. Hmm, No PVs... Doesn't that mean no low down torque and power all at the top end?
A. Well that depends on lots of
factors like porting and port/ignition timing and pipes/carb setups but
generally I will say that is ‘somewhat incorrect’ as even right out of
the box Athena kits don't lack torque, although it may feel so as there
is less power low down than there is later in the rev range, but the
engine is actually quite powerful low down. This is because the larger
cc and port timing will give the low end torque, but yes you will
experience the old school burst of power as you hit the powerband, like
the LC really, only more so as it’s more powerful than the venerable old
LC’s 40ish bhp.
Q. Will the bike with these bigger cylinders use more fuel?
A. Yes! If you want an eco friendly engine maybe get a Prius instead?
Q. So, I’m keen... What size is best?
A. If you look at the market you
will see most suppliers and kits come in 68mm bore sizes... That's 392cc
on a standard crank and 421cc on a +4mm, and of course more if you go
longer throw. This is really the entry level of the Banshee upgrade
market, hence there are lots of options as suppliers try to get a piece
of that action, and yes it does include some cylinders with PVs. Costs
vary, as does the experience of suppliers and bike builders alike.
Q. I’ve seen lots of names out there like Cheetah, Cub, Serval, CPI, TSS, Wicked, Athena and others, what do they mean?
A. Those are manufacturers,
resellers and/or products. The market is full of options and it feels
like more and more appear ever time you look. The Banshee upgrade market
is huge and lots of players want part of it as it’s lucrative. You can
fit any/all of them to a YPVS bottom end (but as I’ve said above, not
the LC without work, the cases and studs are different), and they all
offer something a bit different. The different names are often subtly
different products, some are single casting for the twin cylinders and
some are single cylinders. They often use different ports, port timings.
Come as kits or just loose parts and some suppliers have designed and
had built parts to their own spec of both kits and parts. It’s quite a
mine field really...
Q. So what do you suggest I do to get my head round all this?
A. Build what you like/want/need.
Sounds obvious, but... My advice is decide on what your usage will be,
road or track, look at torque and power curves and go from there. Many
pick a bhp target (bragging rights always help when spending money!) but
really decide how you will use the bike. Talk to suppliers and buy what
is right for what you need and your budget. Picking a cc or budget also
work, but really the 'need' is about ‘power-use’ and I would suggest
you start there.
N.B. I should add that bhp is not really a
measure of performance, a ‘tuned to the max’ 125 can make as much
horsepower but will have a very narrow powerband and while great on the
track it would be useless on the road. That’s why you need to think
about how you will use your bike... and if its road use, then I humbly
suggest that you sacrifice ultimate bhp for torque.
Q. Hold on, that's not helpful, you didn't answer the question, instead you've just given me homework...
A. Well yes that's true, but what I
want (cost and everyday performance with reliability) and what you want
might be different... but, if you push me, I will say most people would
be happy with something like the Athena with +4mm crank as a first
build. It's the most well documented and easy enough conversion to
achieve on a budget, with the added ‘plus’ that plenty of forum guys
have now done it. Click this link for my LC421 Athena engine build here, it may help understanding of what’s involved.
It’s perhaps not perfect, but the cost of the parts is much the same as
messing about with old cylinders and it’s a fun setup as the engines
tend to be very free revving and powerful, with a step up into the
powerband.
Q. Ok, so an Athena kit is sub $1000... I can afford that, but what else might I need?
A. When building any uprated motor
it’s good practice to first check the rest of the old engine out to be
sure it can take what you’re doing as more power will soon flush out /
make bigger any issues that are lurking under the surface. Certainly the
bearings in the crank and the transmission will need to be good, so
budget for gaskets and seals to strip and check that, plus also do an
oil and water change. Above that it all depends on what you want
again... Assuming you want to get the power unlocked from the motor you
will need to invest in exhaust pipes, carbs, airfilters, programmable
ignition, thermostat housing / big head, fast flowing fuel tap/filter...
And if you really go mad then frame mods, but you can find a compromise
of power and fitment to fit all bikes.
Q. But can't I just run big cylinders with standard crank, carbs, ignition and pipes?
A. Well you can, but you won’t get
the best out of it. You could build on a budget this way for sure, but
it won’t be quite as satisfying. Plenty of guys have just bolted on the
Athena kit on their old bottom end on banshees and ran them hard at
392cc (which some say is the best for port timing and makes a nice
motor) and had fun. Why not give it a go and report what you think on
your bike?
Q. Will I need a new electronic ignition?
A. You don't have to, but to get a
map that works best with non PV cylinders you may feel its worth it.
Zeeltronic or Ignitech are most widely used. You can slot your stator
(or buy a slotted stator backing plate) and slip the timing around a
bit, while it is what we’d have done in our youth, it’s a bit ghetto for
most owners these days as programmable units offer much more ability to
tune these motors.
Q. Should I fit fuel injection?
A. You don't have to, but you
could. You would have to ‘make’ your own setup from parts or a kit
designed for something else. While FI has been done on LC and YPVS
bikes, it’s not documented enough to ‘just do’ yet, and at the time of
writing, there isn't a kit that is made for our bikes yet, but it will
come I expect, Suppliers have talked about it over the years, but unless
the banshee market finds it desirable then I suspect we bike guys won’t
see it anytime soon as we are too small a market for a big supplier to
target.
Q. What exhaust pipes are available for big cc’s?
A. Wicked and TSA are the only ones I know of who do pipes for larger than 350cc for our bikes.
Q. What clutch should I use? will I need one of those ‘locking’ clutches?
A. Well, the minimum you need is a
set of uprated clutch springs and possibly larger frictions (some
bigger Yam model parts fit without machining) and with really big cc’s
you maybe need the locker, but it really depends on the power. Up to
80bhp standard or uprated friction plates with uprated springs will
work, above 100bhp you will need to invest time and money to avoid
clutch slip.
Q. Should I fit uprated gearbox bearings?
A. I do, but its up to you. A few
suppliers still offer the now defunct Two Stroke Shop kit that is very
good, Fast From the Past and Legend to name two.
Q. What about uprated crank bearings?
A. Talk to your supplier about
what they suggest. I like to uprate, but not everyone does. Bear in mind
that this crank was designed for the 250 engine and not modified for
the 350 when Yamaha upped the cc's. As it was already out of balance at
350cc, it works hard because of that. Adding more cc's and upping the
compression ratio then rev'ing it hard will not endear you to the poor
overworked thing. Uprating seems advisable, and balancing seems a good
idea if you want it to be smoother, revvier and have a long and happy
life.
Q. A supplier is offering me a balanced crank, good idea or not?
A. Well, kinda... Bear in mind
that true balancing of an engine component needs to be matched with the
other parts you will use, else what are you balancing against? To
balance our cranks tungsten inserts are added in the webs to increase
weight, this offsets the pistons and longer rods if its a long throw
unit. Ideally it would be balanced to the actual pistons you will use,
not just a generic addition of tungsten. However that said adding weight
does help to get a smoother crank as even generic additions will offset
more weight than OEM.
Q. Sounds like a balanced crank is a good thing?
A. It can be, but there is quite a
bit more to cranks than just adding weight and it should be borne in
mind that more weight means greater forces to act on the bearings. There
are many things to take into account here including, rocking couple as
well as the reciprocating and rotation forces. Have a bit of a google
and read around these subjects to get a greater understanding of them
before blindly buying a balanced crank.
Q. So you’re saying that a balanced crank is a bad thing?
A. No, not necessarily. I have a
generically balanced unit in my 421 and Ive ridden a 385 with one, both
are very smooth running engines and appear to work very well.
Q. Should I add straight cut gears?
A. This will depend on your crank
bearings and I’ve never felt the need as Ive not run huge horsepower
engines and my feeling is that for most guys it adds complexity (and
noise) for no real gain on most motors. If you’re a racer then maybe you
will see the need, but for road use on medium power bikes it’s not
required. You will also need to seek out an oil pump drive that works
with these gears if you wish to continue with the pump.
Q. What about cooling... do I need to improve this?
A. Well heat kills 2 stroke motors
so yes its not a bad idea at all. The general consensus is that the
temps should be kept around 55degC if you can and various products are
available to achieve this.
This is a lost of mods to help keep these
engines cool, bear in mind that in a colder climate you may not need all
of these mods.
.. And finally...
I can't state this enough... I really, really (yes REALLY!)
do urge you to read up and talk to as many people who have done this
type of thing as you can before you jump into buying these parts to be
sure you know what you're getting into. You need to know some things
about what you want to have at the end, that will answer the questions
for the supplier about the domes sizes they need to cut etc. I wouldn't
buy any cylinder kit blind without asking about the sort of engines the
supplier has sold, and bear in mind that not all Athena cylinders are
clean enough to be usable out of the box and bigger cylinders often can
eat rings... food for thought... So, find out what is what, then make
your choices and spend your heard earned money and then share the build
so we can all hear the roar of your motor!
Above all, have fun.... and... go big or go home!
Q. What carbs should I fit?
A. It all depends on what you
want, but generally bigger carbs equates to more power... and also more
fuel consumption. Carb choice will depend on your top end choice and
also on your fitment, bike buggy atv etc. Be aware that large carbs are
hard to fit in a bike frame, they are often too tall and deep for the
chassis/engine, necessitating custom manifolds and/or bowls to clear the
clutch arm. You may also need cable angles for the tops and then locate
filters to fit what space is left... They also need fast flowing fuel
taps and filters or you may lean out the mixture at high revs. Some guys
even add pumps to feed these greedy beasts.
Ok, that sounds bad but bear in mind that
something like an Athena will run on anything from the OEM 350’s 26mm to
massive 39mm carbs. Ultimate power and delivery will be different with
each setup of course.
Q. What inlet technology should I use?
A. Some cylinders come with
moulded in manifolds, and some will accept OEM parts as they use OEM
fixings. The the aftermarket has also delivered in both areas with some
clever technology; For reeds (rad valve for the ‘muricans’) VForce is
well known to work on our bikes, but on smaller motors you could run
anything you like of course including the OEM banshee setup which is
cheapish and proven to be quite effective on a standard motor. On the
larger builds I would suggest that you go with what your supplier
advises. I run VF3s on a Wicked X-over manifold on my 421, the manifold
allows the larger carbs to fit above the clutch actuation lever as well
as working a little better better than the standard units.
Q. Can I fit an oil pump and run autolube or am I stuck on premix?
A. Arrow offers uprated pumps, I
will be fitting Arrow's version to my 421 soon - Check back for info on
that. TSS did offer an uprated pump but I’ve never found anyone who ran
one. These days Arrow is the man for all things pump, you would be mad
not to use him as he is the industry go-to guy for oil pumps.
Q. Will I need to modify the cases?
A. You don’t have to, but you
should. Yamaha had these cases made by the thousands and they were done
to a spec, but the process varied and anyone who’s ever tuned a two
stroke bike will have matched the cases to their cylinders in a
blueprinting exercise, and here is no exception. My advice is to always
match the inlet port transfers where the cylinders meet the case to get
all that fuel/air mix in. If you go above +4mm on the crank you will
need to trench the cases as well. The YPVS case is not a thick as a
banshee case, so +7mm seems to be it's max, whereas it is said that the
banshee will take machining for +10mm cranks. Of course you can weld up
and otherwise modify the OEM cases, but aftermarket billet banshee cases
are available for really big crank throws, they are not cheap as you
can imagine. FYI OEM Banshee cases are still available new from Yamaha
at the time of writing.
Q. How much will this big cc engine really cost me?
A. How long is a piece of string? Depending on your setup you can spend anywhere from US$2k - 10k+
Q. I just saw a cheapo (insert random cc size) mega kit on ebay, what do you think?
A. Sure, knock yourself out... I
wouldn't but it's your money. Due diligence will always pay off with
work like this. Speak to the supplier and read up on the forums before
you spend your money, not after... And please don't email me about it
asking my ‘advice’... All my knowledge and the best help I can hope to
give you is condensed into these web pages. Read here, read the forums
and pour over the supplier websites. Learn everything you can, before
you buy. Doing it the other way round will cost you more money and much
more time in the long run, you can trust me and all those who went
before you on that!
Q. How about I buy a bargain Athena kit from
one supplier and then other parts from other places and maybe at
different times to spread the costs?
A. Of course you can, but if you
do that and then stroke the crank then you should know that the Athena
supplied pistons will be no good to you, hence why most guys like the
kits as they have everything you need so you are ‘ready to go’. Buying a
slightly cheaper Athena kit from ebay and throwing away pistons isn't
really great economy. You might think you will sell the old pistons, but
there isn’t much of a market for Athena’s not-that-hot 68mm pistons so
selling on doesn’t really work either. Plus, you will get more
after-sales help from a single supplier as they should back their
product, if you build a motor with other parts than they have tried and
tested then a single supplier may not have the knowledge to help you fix
a problem or advise on fitment, they might want to help more, but just
can’t, or they might just blame the other part and it’s supplier...
Q. The supplier site / ebay listing I just read said it will make 100bhp on 97RON pump fuel!!!!
A. Ohh nice...! But... Well... But
the real nub of the issues is that of course nothing is more variable
than different Dyno results of the same engine... take most dyno results
with a pinch of salt unless a comparison was done on the same dyno, the
same day, without changing any settings.
An aside (more of an ‘upside’ perhaps?!) is
that just like how many liters go into a gallon, the USA fuel ‘RON’
ratings are not same as the ROW. In fact they are lower octane than many
of us get at our pumps elsewhere, so you might get more power, who
knows. And.... Remember jetting is depending on elevation as well, so
beware of jetting out of the box if you live up a mountain.
Q. How big can I really go?
A. 600+cc is possible from our parallel twins...
Q. Hold on, you make it sound like I can do something else... Can I build a triple?
A. Yes, billet cases are available
for triples at around US$2k. You will need a new crank and 3 cylinders,
3 carbs and the space in your frame to mount it all in... Would be a
fun project though, email me if you are building one, I’d love to know
more.
Q. Can I supercharge or turbo charge these engines?
A. Well the short answer is 'yes'.
But while you can do that it's not a common occurrence outside the
banshee drag racers or salt flat speed kings. From what I've read a
Turbo is the more obvious setup on a two stroke, supercharging is much
more expensive and less helpful to the way a 2 stroke engine works due
to pushing the fuel straight though the motor. None of this is easy and
there are no fit-and-forget kits. Again email if you're doing one, I
would love to know more.
Q. This all sounds great, I will ring a few suppliers and buy one then!
A. Cool, and do join a forum (click this text to see the friends pages here on this site for links)
and show people what you are up to. When talking to the supplier
remember that anyone who doesn't know road bikes, just wants to sell you
the kit as it stands in its box, or just wants to build you a sand drag
racer quad is not going to be an ideal partner for a road bike project.
Q. How can I get more info?
A. Join and read the forums... For
the most about this kind of project you should check out the RDLCCRAZY
and RZRD500 forums using the link above, that's where most of the info
resides for these engines in bikes, but the banshee forums are also full
of good info as well of course, even if their use is different.
Q. So all this said... you seem to favour the Athena kit right?
A. Everything in life is a
compromise, it’s the same with these engines. The Athena 421 is what
most people build as it works, and also it's well known on the forums as
a reasonable road solution - it’s also not *that* expensive. Bear in
mind that people read the builds on forums (and here I guess) and Athena
sells another few kits, happy days for them but perhaps it skews the
market, especially when new players enter the fray with what could be
better units and while there are other solutions available and there is
plenty more power to be had, there are a lot of Athena builds about.
Cost comes into it of course for any build and
Athena is a well priced entry level unit, although not without it’s
limitations. People who should know have said that as a cylinder it’s
not got great port timing, and that the tune is minimal from the
factory. I’ve also been told the casting is variable and differs
fractionally from cylinder to cylinder and judging by the rough castings
that need a clean up that sounds plausible. That said, I have found it a
good setup. It’s well known, simple to build and tune and easy to live
with. It can be ported and tuned and makes for a fun road bike. Could it
be better, probably... But what setup couldn’t...
Like other cylinders, with the Athena setup as
just the top end you can also stroke to +7 or +10 with case trenching.
This means you can build all sorts of sizes to give you more bhp and
different engine characteristics depending on the porting. E.g. a ported
443cc Athena should get you around 100bhp.
But, bear in mind, Athena and 421 is really
just the start point and banshee owners were there a long time back,
that is a budget build for them, they go bigger and badder (600+) and
chuck upwards of 10k in their motors for racing... you can even go for a
triple with billet cases and then build up the cylinders in whatever
size you can dream of on that... Potentially 900cc+! But it depends on
what you want out of it, and what you want to spend.... that's the
kicker, you must know what you want before you start.
Ok, I was one of the first to document a 421
Athena LC on the forums (and here) and others have done them since and
have theirs on the road, I've dragged my heels by getting involved with
other projects but since we have so many documented builds done now this
had become a well known setup and it works. Sure you can go it alone
with the some random blah blah 467.8cc kit off ebay, and while it might
be a great setup and make a fast bike, I fear that won't be a quick
build... If its an ATV setup, you may well be the first one 'making it
work in a bike' and having to find parts that fit like carbs, carb tops,
an ignition, air filters, pipes that work and a curve etc. That stuff
eats time up! If that's what you're happy to do, then I'm all ears and
eyes to read about it as you tell us what you find, I might even build
one in my next build if its a rocket ship, but if you want quick power
with all new parts then doing something few (no one?) has done isn’t the
path I'd say... just my 2c.
Q. Don’t want to be rude, but what did this cost you then?
A1. Check out this thought on costs at the bottom of this page: My Yamaha RD Athena 421cc
A2. I tried to produce a table based on what it might cost for a number of the more popular options if you were upgrading from a 250, i.e. the bike that needs the most parts replaced even when upgrading to a 350 (which is the first option in the table), so if you already have a 350 you might sell some of those parts to offset the cost of the bigger bore kit. While the table might not fit exactly what you you have or want to do it should give you some ideas of what is involved wallet-wise, please do bear in mind that some of the prices will not be current as the market changes over time and you might get a bargain that I didn’t find.
Fan: Some builders have found the
need for a fan to cool the engine in traffic. The R6 unit is a firm
favourite of builders as its small and easy to control.
Uprated water pump impeller: This
is a useful unit to move the water around a bit faster. But, just
sloshing water through the system faster is not a panacea, it needs time
to be heated before its cooled again or the heat will stay in the
engine. Ive found a larger radiator and fast impeller works in Australia
but wont be the fix for everyone as that may be too cold. Check the
actual temp of your setup when its running. Amusingly no one has yet
provided any stats for these impellers over the standard unit, so who
knows how much extra ooomph they actually have... if you’ve tested one
against standard, let me know.
Cool heads: While others sell
banshee heads, Wicked sells a CNC-from-billet aluminium 'cool head' that
is designed for our bikes and comes with provision for the YPVS
thermostat fitting, it’s outlet located where it should be for bike
fitting - The Athena (and other banshee units) have the banshee outlet
design which is different as it sticks straight out the front. This head
also includes the bypass. My advice is to check this head out, it was
wholly designed for our installation, none of the others were.
Thermostat: If you don’t get the Wicked head you will need an external thermostat as the other units don't include them since the banshee does not run a thermostat.
Temp gauge: Fit one that is
digital. It is imperative to know exactly what's going on and you
absolutely cannot rely on the lazy sweeping needle of the OEM gauge.
They don’t need to be expensive, the stand alone Koso is cheap and
effective, but there are plenty of others out there.
Radiator Pt1: The YPVS has a 450ml
rad, the older LC’s was 750ml. Whilst capacity is only one part of the
cooling system, this does seem a backward step when we are tuning the
later bikes as it means that in some climates the YPVS was only just
borderline when new. Upping the cc’s and running it harder requires more
cooling than these machines came with for sure. There are many bigger
cc rads from Chinese sellers on ebay now, but some buyers have had
fitment issues, myself included. Economy Cycle in the USA had a few
batches made that fitted properly but have now stopped selling them so
ebay is the only game in town. My advice with these is to test fit it
ASAP when it lands.
Radiator Pt 2: Make sure if you buy a big rad that it has the bypass fitting and also is wide enough not to be covered by your suspension (i.e. RGV and other USD upgrades really kill the moving air due to the size of the fork legs, wheel and guard). You may need to add a scoop to get the cold air from outside of the fork legs in in warm climates. While many of us have considered, and even tested, small bent alloy scoops for our bikes. One owner built a vast scoop for his - Thanks to him for the pics below! - as his bike was ridden in very hot dry weather.
On my own 421 I used a rad from a Quad as it was wider and will catch more air from either side of the forks, height wise it is much the same as the OEM radiator.