jontow

I cannot tell a lie: I have been busy riding my motorcycle. Sure is cold out.. 3 days in a row, yank it out of its napping spot in the garage, full choke, two kicks, and a few minutes of warming at high-ish idle, then ride for 30-45mins. I've put a full tank of fuel through it without tearing it apart, now. A sure sign of some kind of progress! #40 pilot, #120 main, needle clip at #2 from top, Pilot screw at ~1.75 turns out, ~60:1 premix with my fancy boat oil, ~0C/32F outside temp, running an NGK B8ES plug. Still not perfect, but it runs and rides well enough to practice on.

Figured it was a good time for an update to this thread. I've been keeping my tuning diary / motoblog thing updated and spewing less here. Seals arrived yesterday (finally!) and last night I put them in: did both sides of the crankshaft, as well as the shifter shaft, countershaft, and kicker shaft seals. The timing looked to be off its mark by maybe up to 1 degree too, so I corrected that. After reassembly, the bike starts MUCH easier, and feels like it has better compression. Now it's back to tuning.. bike runs great at idle up nearing 1/4 throttle. After that it bogs/stumbles/falls apart, although letting off and going back to low throttle allows it to recover and keep running fine. Rode for 40mins at idle / just off idle with only a few cracks nearing 1/4 throttle, just to see what a clean plug looked like. Was still carbon covered afterward, but the bike ran much cooler overall. Bedtime, now, but maybe tomorrow I can go through the jets and float level again and maybe get a bit farther.

Bad news, though: I had an hour or so to tinker, and pulled the rear wheel and swingarm+linkage apart. The linkage itself is in quite decent shape, and I intend to clean out the grease fittings and push some new grease in. The main swingarm pivot itself though, the bearings are absolutely trashed. Rusty and falling apart. I think I'll be making another parts order to take care of this. I thought it was a bit stiffer than it ought to be: figured out why! At this rate I'll have it back together by xmas! (Thats ok-- I don't mind riding in the snow)

Still waiting on my parts (seals etc) order, but had a few moments to pop the stator cover off: I cannot detect any movement at the flywheel, suggesting that the crank bearings may be fine! The bike has undergone some engine work of some sort in the past, but to what extent I'm unsure. If they did indeed replace crank bearings, I'm hoping they didn't gouge the crank leading to seal failure. I don't suspect they did the bearings, though, but it sure has been run with plenty of oil, given the amount in the exhaust system. Here's hoping I get a tracking # from stadiumyamaha tonight!

I wasn't deceived by that: the bike is downright thrashed.. but they don't come around often in this area, and certainly not for <$1k -- I'm not afraid of the Way of The Wrench, but I was hoping not to have to go so deep so early Oh well! I've already had a bit of fun on it, but I certainly haven't got my money's worth, yet. Thank you everyone for your advice.

Hmm, looking at some parts fiche images around the web, it looks like the cases DO have to be split to do main bearings, correct? Flywheel puller should be showing up before the seals, so I'll crack it open on tuesday-ish and see if I can detect any play at the flywheel. Would it be notable at the clutch, too?

Will this flywheel puller work, by the way?: https://www.denniski...2.prd/28282.sku Claims 27mm x 1.0 LH threads. Seems right, but want to verify: I can't find a listing anywhere for threading specs. EDIT: from a bit more digging, it looks like it will, and is ordered, along with some seals. Slow boat from Japan should put it all here around xmas 2014! (or .. a bit nearer to end of the month)

Well, on my old2strokes.com page, I made a table of a number of the oil seals with part #s, example pricing from partzilla, etc. I'll dig up some cash and see if I can find a place to make an order. The biggest problem is, I have a really solid feeling the insides of the head are carboned up fiercely, given what I saw in the exhaust tract. Sourcing a head/cylinder gasket is a bit harder, and I suspect the TY350 gaskets will NOT match up for this.

Hey, hey.. not the best of news: but I think I found a few things of note, that I need to solve before "tuning". Mechanical problems can't be fixed by tuning, but they can sometimes be masked. After I got home from work, I fancied a go on the bike, and fired it up (first kick, mind you), then let it idle down to an appropriate level, and promptly sprayed down a number of key areas with a magic mix of mild dish soap and water. I found a few small leaks at the rear of the expansion chamber that I suspected were there, and that was about it. So I rode it around, roughly a short jaunt from "section to section", plus a few minutes of figure 8s and such, then brought it back to the garage, put it on the stand and shut it off. As I was standing there smelling the burning soap and looking it over, I noticed some small bubbles forming (which is what I had hoped, that an air leak might appear after warm-up), right at the rubber grommet that the wiring whip passes through headed into the stator ! Now, I am sure to understand, thats not an area that should have any pressure in it.. So I grabbed a screwdriver and loosened one screw, and heard the tune of a slight 'hisssss' and the bubbles stopped. I finished removing the stator cover, and had a few drips of fuel mix in the bottom, confirmed by smell. Here's the questions, then, which seal is toast for this to be the case, and does it require case-splitting or jug removal to replace? It could certainly be my weird lean behavior, masked by jetting and crappy mix ratio as 'rich' on the plug. Air leaks are death to 2T engines, as I well know from my old Kawasaki enduros. I suppose there's a good chance if this side of the (presumably crank?) seal is dead, the other side could well be too. Bonus pic, hard to see the bubble, but look at the lower right corner of the grommet:

guy53: Definitely stiff clutch pull. I unhooked the return spring down at the arm to test and it has no effect on the stiffness. I think I'm going to crack open the side case and see what the spring arrangement looks like. Also going to get the cable cleaner/lube after it and see if theres any effect. I do understand jetting on a 4T, but the oil in 2T fuel may be throwing me off, here. I don't necessarily understand the process of elimination as well. Any recommendations on 2T oil to try, and at what ratio? Again: I'm almost out of what I have and therefor will be looking for something different (better). I'm also riding with the throttle just cracked almost all of the time, meaning I should be well within the territory of operating on pilot jet / needle clip position only. htrdoug: Running a long clutch lever (no idea if its OE the bike has been messed with), no extender/torque multiplier gadgetry inline. My TW200's clutch feels like it isn't even there compared to this bike, and my 85 honda XL600R is the same way. I've tried multiple riding patterns, imitating an event a few times. It does work better, in the sense that it won't heat up to the point of pinging as quickly, but being such a bear to start makes it a tiring effort

I haven't updated this thread in a while, since my progress is very much day-by-day tweaking and tuning and trying small variations of similar things. Figured I'd update the thread, though: At this point, I have a bike that runs most of the time, but is extremely hard to start, especially when warm. I'm running a #40 pilot and #120 main, needle in 3rd (center) position. I've tried BP6EV, B7ES, and B8ES plugs gapped from 0.030" to 0.018", and quite a few settings of the air and idle screws. With current jetting, when the bike runs, it runs VERY well for 30-40mins, which has allowed me quite a lot of good practice time out back. However, due to the hard starting issue, I have an inhumanely strong right leg, and have lost a few US pounds pushing the bike around and kicking it until I'm drenched in sweat. After 30-40mins of runtime (varies slightly with temperature, and how the bike is ridden), the bike heats up to the point of pinging (I believe thats the noise I hear), and I have to shut it off and let it cool. When this happens, I can pull the plug, and its dry fouled every time, which contributes to the hard starting issue. The bike ACTS like its running lean, but is dry fouling the plug. I'm running the same QuickSilver 2T oil at 58:1 with 91 octane non-ethanol gas. I'm almost out of this can of gas, so on the next mix, I'm tempted to try bumping my ratio up into the 60s:1. Does this seem legitimate? I'm not sure what safe ratios are for this engine with this oil. I can't find anyone anywhere that has a bike that acts lean and gets hot enough to ping on 91 octane and is actually dry fouling plugs. Revving the engine doesn't seem to clean it up or stop the pinging. My CDI is currently on an extended wiring whip and in a bag on the front of the forks, as I was troubleshooting whether or not heat had a factor in my weak/inconsistent spark issues. It seems like maybe the spark is still a little weak, but again, once the bike is running, its a monster, and certainly not lame as a sheep, as the 350 has been noted to be. I've also never rode another trials bike: maybe this one is, and I just don't know any better. Seems pretty darn ok, to me, though. Good hard hit, great throttle response, plenty of extra power, nice amount of torque down low. I do dislike the iron-man stiff clutch, though ... Pretty good amount of update for one night, and kinda sums up where I'm at. I'm thinking from here, I should go to a #42 pilot, and 65:1 premix. I don't feel like I'm getting into main jet territory much. My riding is all at/slightly above idle with a few good hits before a climb. Any thoughts, suggestions, contradictions, or otherwise?

Had a few moments today, and tonight, and wrote up some bits that may help someone (work in progress): http://old2strokes.c...aha-ty250-mono/ http://old2strokes.com/yamaha-ty250-mono/84-tuning-notes.php

On a whim, I pulled both jets and swapped the TW 40/120 in, and fired it up.. pulls like a freight train now. I'm gonna let it cool a bit and pull the plug to see how it looks. Might be getting closer though.

Well, per some advice retrieved (and translated poorly from french) from guy53's sources, I popped open the crank case drain (didn't even realize this bike had one!) and drained quite a lot of nasty old fuel out, reinstalled my busted up silencer, then cleaned the plug and the bike fired right up. It ran for a good 15mins before I shut it off (yes, *I manually shut it off!*). Waited ~15mins and then fired it up again, got another 5-10mins out of it before it quit in the side yard, flooded. Pulled the plug and have a fairly dry but very soot covered plug. Wife and kids went off adventuring somewhere, so I'm thinking about trying a much smaller pilot jet that I happen to have around (from my TW200). It's a #40 Teikei jet. ... I've also got a #120 main jet that should fit as well, from the same TW200 Teikei carb. I'm wondering if thats *too lean*. I know the french bikes got a ~#112-116 from the factory, but (?) I guess I don't (yet?) spend too much time from 1/2 open to WOT, but I really don't want to buy a new piston yet, so I'm on the fence about that one.

Quick update before I head to bed: it looks like jets can still be had for this carb in the states, but you have to mess with part numbers a little bit. xxx-14342-xx-00 is the rough template. The reason I have a #48 pilot at least is because thats the only part listed in the USA for a "38V" (which mine is technically not). 38V-14342-24-00: #48 pilot. For instance, a 14342-19-00 is a #38 pilot.. and it looks like you can get it in the states if you order it for a different model, say, 43F-14342-19-00: http://www.partzilla...4342-19-00.html On partzilla, it even lists it as valid for the TY350. Will write up more as I figure it out. With that in mind: does anyone have the *actual spec sheet* for a 1984 canadian TY250 mono that lists jet sizes as installed? The manual I have is for a TY350, and I wouldn't doubt that its slightly different, being a bigger motor.