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.

This evening I had a few minutes to tinker, so I pulled the fuel cock apart, confirmed: its not really an 'o-ring' exactly that seals it, but more of a rubber band. It was a little chewed up on the back side where it squished in, so I trimmed off a bit of the excess, cleaned the corrosion and general garbage out of the bore of it and put it back together: no obvious leaks, yet. I also took the opportunity to tear into the carb, take a few pictures, and look at the slide and floats in a bit more detail. The slide *DOES* have some brass showing, but its in little strips along the bottom edge, not along the vertical axis. I tried to get pictures of this, but my phone flash won't cooperate, and I just get a bit of a reflection. The floats do not leak, confirmed with the hot water test, which I was already fairly certain of, simply by shaking them close to my ear prior and hearing no sloshing. Took another opportunity to try bending in a different place on the float frame itself. This time, I bent the little ears where the inlet needle rests back close to the rest of the frame, and bent the 'wings' on the float itself, trying to get them roughly even. Nowhere have I found particular instruction on what you bend. I may have gone a little too far, as I suspect fuel level will be slightly low, but the inlet needle now has a much more positive open/closed action. This combined with the fuel cock changes may at least prove to me that something changed. I hooked my overflow tube back up and will leave it like this with the bowl full and the fuel cock off, as I've done previously. For those interested, here's a quick gallery of the carb pictures I took: http://bd.zenbsd.net/~jontow/phone/trials/ty250/carb/ I hadn't found any such teardown pictures anywhere in the past, so maybe these will come in handy for someone. Also: Couldn't read the numbers on the main jet very well, looks like it might've read "5 44" or similar on one side, and a symbol on the other. The pilot jet says pretty clearly "48". Per the manual (online one) for the TY350, the jets are supposed to be a main #145 and pilot #37 -- I'm not sure what to say about the main, but the pilot sure is a lot higher flow than factory spec. Anyone know a source for these jets?

Took a quick picture of this so everyone can see what I'm talking about. This is with the fuel cock OFF, and the bike sitting overnight. It seems to me that no matter where I put the float, this is what happens. Thats a lot of extra gas, and its at the bore of the carb.. meaning its probably flowing right into the cylinder. Argh. Again, new fuel inlet valve/seat/gasket. Leaking fuel cock should contribute to this, but if the float/inlet valve are doing their job, this should be prevented, no? It does seem to take a while to get to this point, though, so I'm not sure how much it affects the bike while its running. It'll certainly make it hard to start the next day!

Sounds like I might've done myself more harm than good, just there, then. Live and learn, I guess.

Burned out the expansion chamber today on lunch break.. made a heck of a stink, and got a fair bit of ash out, so I at least accomplished something. Ignition coil is new, behavior is the same with an old and new coil. Right now, after cleaning the exhaust, all I'm getting out of it is a bit of afterfire (backfire out of the exhaust), rather than any actual *running*. When it DID run, it did change some after it warmed up, usually getting more blubbery and acting even more rich. The slide doesn't show any brass that I can find, and seems to fit well in its confines. I just wheeled out my TW200 and used its battery to power an inductive timing light with the lead clipped around the TY250's plug wire. Firing plenty often, by my estimate. Lighting up the driveway like crazy!

guy53: I'm running QuickSilver multi-use 2 cycle oil, claims marine, but pictures power equipment and motorcycles and ATVs as well. http://www.quicksilver-products.com/water/outboard/lubricants/ ^-- that

After leaving the clear tube on the overflow (confirmed that it is indeed an overflow, per the manual) for a few hours, it DID read slightly over the bowl seam, so I popped it apart again, and theres a little factory cast notch by that upward pipe mentioned prior, which allows gas over the seam directly down into the overflow. So I adjusted the float to close a little earlier, got the bike running and cleaned it out a bit, rode it around the yard a few times; it was running better than the last time, but still not great: it eventually started loading up again, so I shut it off and brought it back inside. Mind you, I've also still got the blown up silencer on it, and it would occasionally belch a little smoke. I'm wondering if its simply not able to rid itself of as much of the exhaust gas as needed to get a clean charge in the cylinder, due to blockage? I didn't burn out the expansion chamber, but am thinking now maybe I should have. The bike ACTS like its running lean at times, but the plug never shows it.

That was the first thing I did with the bike when I unloaded it, pull the tank, drain it, pull the carb, drain and clean it thoroughly, and refill with fresh 91 octane ethanol free gas mixed at ~55:1 with the same 2T oil I run in my injected 70s kawasaki F7 & KE125. I have been battling with a small drip-leak out of what I can figure is the overflow tube: it comes out of the very bottom of the carb. The leak acts as though the float is adjusted incorrectly or the inlet valve is leaking. Does it even when the fuel cock is turned off, and takes quite a while to build up enough fuel in the bowl: usually a few hours. I've replaced the inlet jet/seat with a brand new sealed one, even though the old one was good and clean and showed no depression on the rubber cone tip. I've adjusted the float everywhere from barely running fuel into the bowl at all (taking MINUTES to fill) all the way to the other end of the spectrum, just to test. It seems to do it no matter what, although is more pronounced with the float adjusted somewhere between "properly" and "too high". I've put a piece of clear tube on it and checked, the level it reads is not even to the seam on the bowl. The tube is, I believe, the one that has an internal tube that runs up into the carb more like a vent, and then back down and out, vs. just being a hole near the top for gas to run out if you tip the bike over. Because of this drip leak, I've exchanged the fuel completely now over the last few weeks, and haven't really found much change in the matter. I've now tried with the needle clip position at #3 and all the way up on the needle (presumably to lean it out, if memory serves me). The bike came to me with it at #3, dead in the middle of the selections. I'm starting to lean toward just tossing the cash at a mikuni flat slide and getting it adapted onto the bike, but I really don't have a lot of cash to spend, and so have been trying to make due with tossing very little cash and more time at the OEM carb. It wasn't clear/obvious that someone drilled out the jets, but I guess its possible: its an old bike with an unknown history. I'm struggling to understand why it's fouling plugs like it is, even when I adjust it as lean as I can with what's available. Do I have it correct that the brass adjustment screw on this bike is an AIR screw, located on the air side of the slide, and so therefor backing it out makes the mixture more lean?

Boy, this sure is an ongoing saga of me being stumped by this bike It started today, ran a bit, then died again, started back up after unplugging the dodgy kill switch and a few kicks, but was running ragged. I got it back to the garage and later installed a new kill switch: it started up and was running ragged the same way as back in the woods: would sometimes keep running if I revved it a bit, but wanted to die at every opportunity, and backfired a bit. Later tonight (after my kids went to bed, of course), I started doing some right leg exercise on it again and it coughed a few times then *big backfire* and it opened up the silencer again, similar to the picture above. Plug reads fairly rich (black and sooty, not oily anymore), but will spark readily if I clean it up. As a bonus, for the brief moment it ran, I confirmed that my headlight works as is! Lot of good the headlight's doing at the moment. I couldn't find any numbering on the jets when I had them pulled, but I suppose the jetting could be wrong. Usually everything I get here is jetted too lean, I'm at about +750ft over sea level. Is it possible the stock jetting (if indeed it is that) would be that far off?

Crossing my fingers, here, but on recommendation of this thread: http://www.trialscentral.com/forums/topic/34488-ty250-mono-starting/ I went ahead and cut off the male/female ends of the 3 pin connector and crimped on some butt splices to test. I just rode for 30 minutes straight (longest yet!) and had an absolute blast. It got dark, and I still don't have my headlight wired up: I believe its a 6VDC bulb in it, and I believe I'll need a 6VAC bulb, and I should probably acquire a switch! Now maybe it'll start again tomorrow

Well, to continue the twists and turns of my TY mono adventures, exhaust system is back together and leaking only very little now. I took the opportunity to clean up a previous owner's work and weld the expansion chamber mount back on. I also sourced some cheap ignition coils that seem to work to fire the bike. However, I can't keep consistant spark! At times its a nice fat happy spark, sometimes its sputtering off the side of the plug, etc. When it's running, it's running really well, but all of a sudden it'll just die, not even sputter, just die. Usually when I'm on top of something, or far enough away that pushing is annoying! At some point, previous owner swapped in a 38V CDI, I think, and maybe the connector wasn't the same 3 pin plastic barrel deal as this bike, because they had cut the wires and crimp spliced + heatshrunk it back together. Because I was curious, and I'm running out of good options, I cut it open last night and soldered+heatshrunk it back together instead. It seemed to help, along with a freshly cleaned plug, but erratic spark is still with me. Again, the coils measure out to spec per the online manual I dug up, but CDIs are usually not something easy to test. Any ideas whether a dodgy CDI would do this? Or other ideas? I wish I had a known good CDI with the 3 pin plastic barrel plug to test with, but they're harder to come across than gold nuggets. Does anyone have any ideas what other CDIs might work on the bike? Sorry: a lot of questions in one post, but the theme is simple: I want to ride! Thanks all.