jontow Posted September 4, 2013 Report Share Posted September 4, 2013 I recently acquired (and tonight, got running!) an 84 TY250 mono from Canada, but I'm in the states. It was brought over for use at someone's camp, and has clearly seen better days. But: it seems to have good compression, is mechanically in decent shape, and looks like crap. I've got some exhaust leaks to sort out, and it seems the muffler is full of muddy old oil. Is there a way to clean it out? Take it off, flush with gas and let air dry for a few days maybe? I'm not sure, and not willing to try that yet. I didn't see any convenient cleanout plates. Maybe an aftermarket replacement for the whole assembly? Mine's dented, and brazed, and epoxied, and in generally quite bad shape. The ignition coil (and spare I got with it) both seem toasted: secondary winding reads open on both, but a spare off an early 90s TW200 got it going for testing purposes at least. The resistance readings are pretty close to the TY manual I found online. The odd thing, it was flooding like crazy when I first got it running, and with a little help, we narrowed it down to the rubber o-ring in the main jet holder leaking. With the fuel cock on, the bike would bog and barely stay running, but if you let the bowl fill, then shut the gas off, within a few seconds the bike ran great. The leaky o-ring was letting fuel come up through and get sucked raw into the intake tract. I've got a (smaller) o-ring in it now that helps, but isn't big enough to fully seal. Which leads me to a real point.. Is there a good parts source for this bike within the USA? Or, optionally, for carb parts, is there another US-distributed bike that used the same TK carb? I understand many parts are available on ebay, but I'm not having much luck with rubber bits in the carb that have taken abuse over the years. Quote Link to comment Share on other sites More sharing options...
lineaway Posted September 4, 2013 Report Share Posted September 4, 2013 Only the cylinder and piston kit should be the only difference to the 350. Parts from the UK are not that hard to get. The TY mono was probably the best trials bike ever. But they were rode to death and Yamaha USA did not ever have much parts. Either buy a spare 350 or go modern would be my help for you. There has been quite a few almost new bikes on Ebay. The 1986 was a lot better ride, mainly the rear shock. Quote Link to comment Share on other sites More sharing options...
bestrcpilot Posted September 4, 2013 Report Share Posted September 4, 2013 Getting parts in the US is going to be hard. The best place is going to be England or ebay. If the carb is giving trouble, best to replace it. I could not get my ty250 mono running right until I replaced the carb with a 28mm flat slide Mikuni. Best $100 I've spent on it . If you have a older Yamaha Dealer near you check with them for parts. You never know what they may have on the shelf. A lot of the parts are the same as a 83-85 YZ Quote Link to comment Share on other sites More sharing options...
jontow Posted September 4, 2013 Author Report Share Posted September 4, 2013 Thanks everyone, this is a great start. Glad to hear the TY350 is similar, gives me another search term to work with No old yamaha shops nearby, just a honda dealer that I may talk to. He's done a lot of work on random machines over the years, and as you say, who knows. The carb seems to be in good shape, and I'm familiar with working on TK carbs (aforementioned yamaha TW200 uses them); as long as nothing mechanical goes wrong, they seem to work well enough. I think if I can correct the o-ring fuel leak, and get the exhaust sorted, the bike will run more consistently. Quote Link to comment Share on other sites More sharing options...
bestrcpilot Posted September 4, 2013 Report Share Posted September 4, 2013 The trouble I had with my carb was the chrome had come off the slide and the bore in the carb was out of round. The bike would run but would hunt at low revs. The carb off the TY350 is the same. The TY250 as you know was not inported into the US but there were a lot of TY350. I guess Yamaha did not think we would want the smaller motor even if it was a better motor. Good luck with it. Quote Link to comment Share on other sites More sharing options...
axulsuv Posted September 4, 2013 Report Share Posted September 4, 2013 You can Always give B&J Racing in TN. a holler , You never know what they have laying around or can source ... Glenn Quote Link to comment Share on other sites More sharing options...
searay175 Posted September 4, 2013 Report Share Posted September 4, 2013 Getting parts in the US is going to be hard. The best place is going to be England or ebay. If the carb is giving trouble, best to replace it. I could not get my ty250 mono running right until I replaced the carb with a 28mm flat slide Mikuni. Best $100 I've spent on it . If you have a older Yamaha Dealer near you check with them for parts. You never know what they may have on the shelf. A lot of the parts are the same as a 83-85 YZ Hey Bestrcpilot! If I can interfere? What was the model # of Mikuni 28mm that you used? Did you have to change the jet sizes? I would want to try one on a 350 so I'm sure that it would require different jets. Quote Link to comment Share on other sites More sharing options...
jontow Posted September 4, 2013 Author Report Share Posted September 4, 2013 I, too, am interested in this info: is it a VM28-418 by chance? is the choke lever on the wrong side as it appears? Did you have to do anything regarding the rubber boots, or is it a direct fit? Quote Link to comment Share on other sites More sharing options...
tlrmark Posted September 5, 2013 Report Share Posted September 5, 2013 VM-28 is the standard round slide Mikuni, been made for years. TM-28 is the newer flat slide Mikuni with much better throttle response. I have had great results with the flat slide carb on twinshock Hondas, cant help with the jetting for a Yamaha. Quote Link to comment Share on other sites More sharing options...
bestrcpilot Posted September 5, 2013 Report Share Posted September 5, 2013 Hi Guys I used a TM 28 Mikuni on both of mine ty350 and ty250 monos. The jets that came with them are the ones still in them, never had to change them the bikes run great with the stock jets. They were straight swap, the stock intake rubber works, the rubber boot for the airbox works as well but it is close to being to short. And yes the choke lever is "wrong" side but still works. The only thing is getting to Idle screw it hits the frame. But a little time with the grinder put a notch in the frame and once the idle is set there is no need to get to it in the last year. If you really need the jet sizes I will go out in the shop and take the carbs off and look. let me know Quote Link to comment Share on other sites More sharing options...
jontow Posted September 5, 2013 Author Report Share Posted September 5, 2013 Hi Guys I used a TM 28 Mikuni on both of mine ty350 and ty250 monos. The jets that came with them are the ones still in them, never had to change them the bikes run great with the stock jets. They were straight swap, the stock intake rubber works, the rubber boot for the airbox works as well but it is close to being to short. And yes the choke lever is "wrong" side but still works. The only thing is getting to Idle screw it hits the frame. But a little time with the grinder put a notch in the frame and once the idle is set there is no need to get to it in the last year. If you really need the jet sizes I will go out in the shop and take the carbs off and look. let me know Well, call me concerned, but is there any way I can convince you to take a (good?) picture of the fit of the carb, with the frame notch shown? Thank you: great info, and I can see I'm not the only one interested. Quote Link to comment Share on other sites More sharing options...
jontow Posted September 5, 2013 Author Report Share Posted September 5, 2013 Oh, another note, because my exhaust has seen better days. I've noticed a few TY250/350 pictures around with an aftermarket silencer of some sort, just a small round polished aluminum/stainless can type. Does anyone have any info on this, or shall I just measure and start digging? Since it seems to be a separate expansion chamber / silencer, the silencer shouldn't have a great effect on how well the engine runs, correct? Mostly just an effect on the noise output. Quote Link to comment Share on other sites More sharing options...
bestrcpilot Posted September 6, 2013 Report Share Posted September 6, 2013 I Quote Link to comment Share on other sites More sharing options...
bestrcpilot Posted September 6, 2013 Report Share Posted September 6, 2013 Sorry about the above post. please remove it. So after the Request for pictures about the flat slide on my bikes. I went out to the shop and looked at my setup again. It has been over a year since I rode them. So anyway I was wrong about having to grind a slot in the frame. I just used a couple of pieces of foam tape on the frame where the Idle screw would touch the frame. I will post pictures from work in the am and explain it all better then. too many beers to work it out tonight Quote Link to comment Share on other sites More sharing options...
bestrcpilot Posted September 6, 2013 Report Share Posted September 6, 2013 Here are some pictures of my set up The first pic is of the carb on my ty250 mono This pic is of the foam tape on the frame for the idle screw This next pic shows where the Idle Screw is touching the foam tape. And this last pic shows the spacer that I used on the back of the air box to move the airbox about 1/2 inch to the front so the rubber hose from the air box to the Carb would meet up with the carb Quote Link to comment Share on other sites More sharing options...
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