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Hey,
Can you please give your posts useful names instead of enquiries. This is like the fourth "Enquiries" post you've made and it's not very helpful to gauge the content from the title.
"Best" in a loose term would be the Athena Kit. It's not the worlds greatest big bore for various reasons I've explained time again, search this forum for Big Bore DTR.
I think people have had good success with the 3XP00 barrel to bump the engine from 125 to 200. There are some other barrels I've seen banded about being used but never read anything about it.
I think personally it's best to use the stock 125 barrel and tune that
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Look up BAR racing on Facebook
Only real options are 200R and 200WR cylinders or complete engine swaps with either
Not heard anything that great about the Athena kit so far and at £500 I'd look for a 200cc motor or as suggested tune the 125 one
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If you have the technical knowledge 30hp on the stock barrel shouldnt be too hard to get, the athena 170cc kit is expensive for what it is, many mixed opinions and i havent heard anything too great about it either, last option would be the 3xp barrel, which from my understanding is hard to come by and expensive.
If all you want is power the easiest way would probably just be to find some cheap yz250 engine that needs a rebuild, fix it up and fabricate the frame mounts and drop it in
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@Calum you sure it doesnt break 20hp? People say they get 20+ with a dep and the derestricted head, no clue how factual that is tho since none of them have dyno papers, also might just be that you have a really torquey bike instead as high torque doesnt translate into high hp from what ive been taught
It depends what you think is too hard to get, i just bought all the tools to boost port a 3mb barrel and work on the transfers, a lad i came in contact with dyno tested his boost ported setup and reached 29hp, he didnt touch the transfers either. You get that done and you also go over the head to check that its all okay, mine had 1,1mm squishgap which is too much, get a bigger carb, software says 34mm is optimal to reach 30hp however its an old software so you cant rely on that fully. Get a good pipe made, either make one urself or get one by the portuegese dude on ebay, probably missed alot of stuff like the zeeltronic and maybe running an inner rotor ignition for top end power
Nothing is impossible, u just have to put alot of work and effort in for the desired result, and if you dont have all the knowledge thats something u have to learn aswell, however i worded myself wrong in my original comment, u wont get 30hp by just doing work to the barrel, you will need supporting mods aswell, but its very possible, think about the karting and GP guys that get 50hp out of theyre 125's(with a rebuild after every race however)
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@Arild
https://dt125r.co.uk/topic/15/the-leviathan-project/111?page=1
That's my DT.
- Zeeltronic
- VHSB 32mm Carb
- Zeeltronic Ignition
- Mick Abbey Ported Barrel and Squish Head
- Portugual Underslung exhaust
- Carbon Reeds
- Dual Radiators
It is neither torquey or over 20hp. So yeah after all of those modifications and it is slower than my RS which has similar mods except the barrel porting.
I would say 30HP on a DTR motor is hard to get. And if you're getting that sort of power, with a dyno for proof, from your porting, then please please please let me send you a barrel and head to do because that is absolutely insane!
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DT200WR only claims 33bhp so the 125 with milder porting and less cc's isnt going to be that close
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@Calum
I might be reaching for the stars and end up on the moon, i dont know yet, i have guys telling me 35hp shouldnt be too hard, they have experience porting and making other stuff like blasters go quick but idk how well it translates over to the dtr engine. I like to think that if two stroke stuffing on youtube can get 20hp out of his 50cc and Gp riders can get 50hp out of their 125s it should be possible in my mind, but idk since i havent done it yet.Im gonna try porting and try my best and go for high numbers, idk if ill break 20 or 25 or 30, im not giving up though until im satisfied, I have a gameplan in mind
- Homemade exhaust made for 30hp
- 32mm carb(chinese replica) might step up to 34 or 36mm after i get it all running and make my own manifold
- Boost ported barrel, reworked transfers, reworked head with good squish clearence and correct compression ratio
- Atleast lighten stock flyhweel, or custom mod an inner rotor ignition setup
- Advance timing a couple of degrees, calculated that moving the stator and pick up assembly 0,94mm translates to a 1 degree
- Zeeltronic or the ignitech
- Either vforce blaster reeds or just carbon petals on the stock reedcage
- Maybe maybe go for an ethanol conversion later down the line
Im gonna start porting the barrel and see where that gets me as soon as it arrives to sweden from the UK, I just picked up an electrical motor to make my own homemade dyno if i can get everything to work.
I still find it hard to believe that ur dtr doesnt break 20hp, idk if my expecations are just way too high but i feel like it should make more with that setup, im pretty sure romeu had a dyno picture on ebay with a dtr breaking 27hp with his exhaust if im not mistaken, dont know the rest of the setup however, awesome looking bike otherwise
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So my pipe is a Romeu pipe. Feel free to check out my project thread. You can physically see all of the modifications I've done to the bike which includes everything you've described. It's not more than 20hp end of.
You are talking about GP bikes, but they are not running Pump Fuel. They'll be running AvGas or the equivalent. In which case, yeah expect high 30s etc. As soon as you use a fuel with a higher octane then you can turn the compression up or advance the ignition timing without the risk of knock! So then you can VASTLY increase your numbers.
I am just tired of hearing about 30HP DTs when the engines are simply not designed to do those sorts of figures on your run of the mill pump gas. And when people say "Oh it's easy" it's like, well I've been at it for years and haven't come close to those figures so I've clearly missed something.
People talk the talk, but let's actually see it. I've done all the things you've suggested and I'm no where near to that figure. So I can't possibly see how it can be done. Again, pump fuel.
Lightening the flywheel doesn't increase Horsepower, it only reduces rideability. For a road going bike, the flywheels weight is about right.
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@Calum
Idk how hard it is, i know people talk, i do too, but im atleast gonna try and see where it gets mehttps://www.youtube.com/watch?v=bAzNrjtCfps&lc=UgynP9eLKNkNA_ldtd94AaABAg.9B3tX3LsOME9BBSXNZ7XS2
this guy has roughly the same setup as i mentioned above and he dynoed it to 29hpLightening the flywheel increases top end on the bike, its less for the engine to spin around and therefore it helps up top, it makes it easier to stall the bike however since its less weight pulling the piston crank etc around, its also better for bottom end as it mellows out the power hit you get from twostrokes
Im gonna increase the compression and timing till the edge of detonation on normal pump gas first, and then might switch over to e85 since its regularly available in sweden
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@Arild The flywheel does not increase power. Not sure where you read that. Sure it helps the engine spin up faster, but its a conservation of energy. Meaning it will decelerate faster too.
The crankshaft is connected to the output shaft via the clutch, which is attached to a chain and sprocket (and hopefully) a rear wheel with you as the pilot.
So when the clutch is disengaged you still have all that to contend with. But you don't gain Horse Power from a lighter flywheel. Otherwise the same could be said if you got off the bike. The flywheel acts as an energy store. Lightening the flywheel has both positive and negative effects.
If you bike is an all out racer, then sure remove the flywheel. But if you at all commute on the bike, I'd leave it alone.
But definitely look forward to seeing what you end up doing and how you go about it. Keep us posted!
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@Calum
Well its people telling me and me reading it, both on sites and in the twostroke r&d facebook group. Lighter flywheel helps top end while heavier helps out with bottom and stock is a compromise, thats what ive read and been told atleast.And me thinking if the flywheel is lighter, the loss of power spent on spinning the flywheel up should be less with a lighter flywheel, and therefore not waste as much power, however you wouldnt store as much energy either, so they bike would be easier to stall etc, this is from what ive been told atleast, i might be wrong, this is what ive read and the conclusion ive come to tho
An internal spinning flywheel is the extreme, flywheel might weigh 200 grams, only downsight to this its hard to find one that powers lights etc, there are some like MVT that are able to power lights and elecitricals and not just the spark but they get expensive really quickly, many people run these on their mopeds over here with only good results, pretty common that mopeds with the am6 engine break 15-20hp with bigger cylinders and all the other stuff
Im still only in the planning stages, ill start taking pictures when i begin working on my barrel whenever it arrives, i already have a thread on here about the expansion chamber i made
A page i look at sometimes where it says that lighter flywheels (internal) favours top end
https://www.apriliaforum.com/forums/showthread.php?179005-Here-learn-something-about-the-two-stroke-tuning -
@Arild Absolutely, that's what it is all about. Ultimately give it all a go and make your own decisions.
I'm telling you my experience in the matter and I have always opted to not lighten the flywheel. Not for a road going machine. Again, you are not gaining or losing power by lightening the flywheel.
It's a conservation of energy. You spin it up, and it takes longer to slow down. So yes, it's less energy required to spin it up to 10k RPM, but the inverse is true.
There is no power gain here, just that the engine can get to that "peak" power faster.
On the DTR 125 engine, peak power (15Bhp) is made at 7K RPM. So what do you gain by lightening the fly wheel.
As you start to tune the motor, you will most likely start to shift that powerband up to the higher RPMs. So a lighter flywheel will help you get there.
But you will find that keeping it within that narrow powerband becomes harder the lighter the flywheel. Peak power is not the be all end all. You could have a thousand horsepower, but if it's only made at 7999RPM and no where else, you won't be able to use it.
So often it's more about keeping the bike in that sweet spot for as long as possible.
This is what I feel the DTR does well at in the stock trim. The ability to ride it around at 4K RPM.
My RS won't pull below 6K so it's very tiresome to ride, a lighter flywheel would help it reach peak power, but it would negatively affect the performance where it matters most, above 6K to 14K.
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@Calum
Thanks for putting it that way, makes it easier to understand, so i was wrong to say it increases top end, the correct way to put it would be that it favours top end? Since it lets you get there faster?Also yeah, its what im scared of, the guy in the dyno video i sent, had around 6hp at 5k and 29hp at 10k, the bike wouldnt be fun to ride and you wouldnt be able to use all that power if ur not like on a track or something, however he had the powervalve pinned open, ill try and get it so that the boost ports are completely closed of and then they slowly begin to open with the exhaust port as the rpms climb
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I've been lurking around these forums for a while. This post actually peaked my interest enough to let out some information.... I decided to throw a model of the motor into my programs to see if it can be done. The answer is, Yes, easily. Several modifications are needed.
In order to pull off 30HP on a DTR125 with pump gas, theres a good amount of mods that are needed.
The minimum RPM would need to be around 10,250 with a BMEP of 10.5. Pushing that BMEP upwards of 11.5 would make a peaky motor, but push out quite a bit more power. It'd be on the verge of needing a different fuel type.
The mechanical limitations for the motor are closer to 12k. This doesn't account for crank balance or rod strength. Yamaha rods are inheriently strong, so it wouldn't be a concern to me.
Theres going to be a lot to cover, but heres a short list of topics.
- Port time/area
- Exhaust port shape
- Maximum squish velocity
- Carburator size
5.Pipe design - Fuel Type
- Ignition timing
I'll follow up with technical post covering each topic and numbers specific for the DTR125 needed to reach 30hp without being a light switch. Sorry for about typos, this was written from my phone.
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@RubberSalt and thats the guy thats tought me everything i know so far
I doubt my RS even touches that figure. I'd be very surprised if my DTR with Zeel, Mick Abbey ported barrel and head and underslung pipe makes 20 hp, let alone 30 