84 Ty 250 Carb Specs

[spokerider]

I just bought an 84 [ as per the headtube badge ] TY 250 monoshock, Canadian version with the fire-engine red frame.

The bike had supposedly just had an engine overbore / rebuild a short time ago, as per the guy I purchased from.

It looks to be very well maintained, clean and tight, however, when running, the engine races on and can rev quite high once the throttle is blipped and often does not return to idle on it's own. When it does this [ 50% of the time the throttle is blipped ] I can use the brakes to bring the engine revs back down or unscrew the throttle-stop screw a little and the revs will come back to idle.

It does not appear that the throttle cable is sticking.......I can hear the slide closing with a "positive click" when the throttle is released [ engine not running ].

Cleaned the air filter, new gas, clean plug, all hose clamps from airbox to carb tight.

I would hope that the crank seals were replaced when the rebuild took place......I'm trying to confirm that now with previous owner.......

Turning the idle mixture secrew in to fully seated or out, has no effect on the engine running.......leads me to want to dissassemble and clean / replace gaskets etc in the carb [ it's leaking fuel as is ].

It's a TK carb, oem I'd think.....anyone know the float level setting and air screw setting are? Also, any info on what the original jets that the bike came stock with would be help full, so I can determine if anybody's been tinkering / changing them out.

Thanks for your thoughts.

[spokerider]

Well, the carb got stripped and cleaned out today, with the help of my local bike mechanic. All of the O rings were toast, and the jets were plugged with grunge.

The float was set to 23mm.

The mechanic thought that it was likely a carb-related problem and not the crank seals.....

However......to replace the crank seals, can they be accessed and changed WITHOUT splitting the case?

I've done a Cota 348 before but never a Yamaha TY

I'll hopefully get to testing the clean carb in the next few days to come.....

[dave dix]

I would say all your probs sound carb related, unlike the montesa a ty doesn't have crank seal holders but you should be able to hook them out without a complete strip but you wont need to as your problems are carb related (hopefully !!!!)

Dave

[alan_nc]

Well if the carb work didn't fix the problem do the old wd40 trick. Take the side covers off, start the bike (your going to flip some oil around). As soon as the problem starts spray the seal area with wd40 ..... if the problem goes away you need to replace the seals.

I would also try this around the carb and intake boot area - you may have a leak.

Alan

[spokerider]

Well after fitting the clean carb, the bike runs like a top. So it appears that the dirt in the carb was the culprit.

Thanks for the tip with the WD40.........good to know for future troubleshooting.

[kevin j]

just for future ref

don't know about the left, but the right side on mine popped partially out a couple times. Vast clouds of ATF from gearbox being burned. as a short term fix I pulled the cover and pressed it back into place until later changed engines. Long time back, but I assume at least the right side could be pulled with a slide hammer tool and replaced fromt he outside.

good you got it fixed much easier though.

k