What was I thinking!…
-
Actually they are similar, not identical!
One thing I really am not keen on is the big fat 250 ass on this bike. It looks kinda stupid with the 150 tyre under it. I want to find a nice slimline single seat pod to fit to it. Any input appreciated…
I’m thinking 1980’s gsxr slab side kinda thing…
-
Re: the see saw linkage. I read somewhere that it’s for during overrun, when the revs are above 6-7k but the throttle is closed. It kinda makes sense as it’s activated by the power valve servo? What you recon?…
-
@SpookDog Yes I think that's one of the aims of having the see-saw linkage, to avoid the motocrosser-seizing-at-the-end-of-the-main-straight-at-a-beach-race scenario. I guess the TZR125R in its natural habitat could benefit more from this than a DTR because if you took it on a track day somewhere, you'd spend a fair bit of time per lap braking for corners whilst keeping the revs up to get on the power mid-corner and on the exit.
From memory I think the RGV250 had a similar system but don't quote me on this. The fact the TZR250 parallel twin had this and the 350YPVS didn't is IMO a factor in the TZR250 being able to reliably do everything the 350 'valve could do with 100cc less.
-
-
-
@SpookDog said in What was I thinking!…:
If anyone can tell me what the 170 Athena revs out to, please do!
If memory serves well,I saw about 13000 rpm/5th gear,136km/h on the road when it was running good last time,run out of road for the 6th gear.
-
@SpookDog My 3MB ran very well on this stuff, equal spec (JASO FD is the Japanese industry standard for racing two-stroke oil) to all the brand-named oils and I've known MX/Enduro guys to run it in modern KTMs etc with no issues:
Very good ebay seller generally, they have similar deals on grease and stuff
-
Cheers bud, looks good. Any issues with sticky power valves? I bought some cheap synthetic 2T that was fine except for it making the power valve gum/stick-y
-
@SpookDog I always found Exol very clean burning. Interestingly it's exactly the same shade of pinky red as Motorex Cross Power 2T which is nearly 4 times the price.
Are you still being cautious about revving your bike too high? It's a wise precaution but also you need to balance this with the fact two-strokes need to be revved to keep clean and a lot of carbon-seized powervalve issues are caused by spending a lot of runtime at low rpm, Enduro bikes threading a needle through the trees are more susceptible than the equivalent MX bike being thrown round a track by the local hotshoe for example. Always a good idea to give it a good thrash through the gears a couple of times every ride and blow the carbon out
-
I use Castrol power 1 race, fully synthetic can get it from halfords.
I always get mine up to temp for a few miles then always at 10k rpm most of the time in each gears, always gets a beating when it comes out and never had an issue with anything sticking
-
I do stick to around 5K with 6 being my limit. This is because of the state of the engine though! Not for any altruistic reason!
it’s rough! The last 2 pistons had the ‘ring pins’ rattled out of them. The stator side of the piston had about a MM of play in the wrist/gudgeon pin! I think the con rod is bent to one side. The barrel I put on it I used the only piston that was a close fit, it was one that has been seized twice and has a crater in the crown from overheating. So I’m nursing it till my next rebuild, I consider it to be in ‘lump mode’ It’s been so reliable considering it’s ‘pedigree’ … -
@SpookDog Understandable you're keeping the revs low in the circumstances but I'd say that's a big part of the PV being carbon seized.
Also I think your running premix is playing a part here. Besides user convenience, one of the greatest attributes of Autolube is its flexibility as the oil delivery rate is varied in two ways; engine speed and throttle opening (or three if you count the TZR-R see-saw linkage but I'm assuming we're talking about your DTR here) so it really is a mechanical form of engine management which varies the oil ratio from about 120:1 at tickover to something like 30:1 when you're absolutely full bore giving it the beans.
Premix is fine for competition bikes as it's assumed you'll be ragging the arse off it for most of the time you're riding, but road bikes have to spend time in everyday traffic situations where that kind of riding just isn't possible so you don't really need that 40:1 or whatever oil ratio sat in traffic at 4000rpm. So it oils everything up because it's not being blown out like it would be on a track. In fact it could be having a negative effect because if there's a percentage of oil as well as petrol going through any carb jet at any engine speed/throttle opening, this could translate to a lean running/overheating condition.
If you're planning on doing a full engine rebuild sometime, get a £25 Yambits oil pump repair kit and if you have a spare, do a clutch cover build with the oil pump fitted so it's ready. They also do a ball and spring kit for the outlet pipe and a transparent delivery pipe kit so you can check at a glance it's working, and after rebuilding you can pre-bleed the pump using a syringe so the final bleed on the bike is easier. The DTR Autolube is even better than most as the OEM throttle cable actually has a mechanism inside the splitter box which balances the carb and oil pump automatically (another reason to avoid those bloody awful £12 pattern throttle cables which are responsible for a lot of engine meltdowns) whereas even all other Yamahas you have to check and adjust the oil pump cable regularly. And Suzukis right up to the RGV250, the oil pump is a weedy little thing behind the front sprocket. Yamaha Autolube is one of the most reliable and user-friendly systems ever made and seeing this gives you rock-solid peace of mind.
In the 90s an American tuner called Eric Gorr wrote an article in Dirt Bike Rider (UK) Magazine about cleaning up gummy powervalves as some of them are quite complicated (the Honda Power Port valves on the '86-91 Honda CR250 had over 20 moving parts and required servicing every two hours' runtime, but the CR was the best 250MX engine of its era). He talked a lot about this, Kawasaki KIPS, Suzuki AETC etc, all of which are equally fiddly but he left out Yamaha YPVS altogether because in his own words "the Yamaha system is so simple and reliable".
-
Hey bud! I stripped and cleaned the PV when it last got gummed up. It wasn’t carbon. It happens within 2-3 days of using the ‘emergency’ 2T oil. I think that all the misfiring (20,000miles!!) has done a number on the conrod, I’m surprised the bearings are still good! I had the piston’lock’ a couple times when the head gasket was really bad & I was topping up the rad every 10 miles. I had to put it in a high gear and rock it back and forwards till it cleared!…
I plan on putting the pump back on when I rebuild the Dtr. I can’t remember why I went premix exactly, it was to cross something off a list though. I think premix can be problematic with setting up the carb…
I’m going to read through your whole post now! …Edit: I would not want to service that power valve setup!! Damn! 🫣
PPS: I have a pic of the worn piston - pin clearance on the stator side, I’ll try and find it. You’ll understand why I’m in limp mode
…
