T250 - Bad low end performance.

[Dougnemeth]

Hi all... Good to see that there are plenty of these old girls on here.

We've just got a '72 T250 all back together... Not the best resto but it's functional.

My problem is with low end performance. Problem #1 is I can't get the left cylinder running at idle I've tried the mixture screw all the way in to out a hell of a long way and nothing. Problem #2 is I need to use a lot of revs to get the thing off the line or it dies. Problem #3 is it has very little power down low.

All problems are most likely related I assume. It is fine in Mid and top end. Unfortunately the Tacho isn't working at the moment so I can't say at what revs it good/bad. It's got a whole new top end rebuild but we haven't touched the bottom end. I'm worried that it could be the crankcase seals but it starts basically first kick and is fine with a few revs. The carbs have been cleaned several times, we had many problems with them so last time I went over then with magnifying glasses on and checked every little orifice, funny bit is I found more problems in the righthand side carb idle jets. The carbs are set to factory (seems to be where they want to be anyway). We had to replace the stator and the two seem to be different (but the current looks the same as in the factory manual photos) but I couldn't get the timing perfect as I ran out of room the the screw slots etc. but it only retarded by about 2-3 degrees from factory (I can't imagine that would be enough to make a major difference).

We will probably get it registered as is so we can ride it more to get a better understanding of the problem (I've only had one chance to get it out on the road so far). But it rides, handles, stops and feels great.... I don't like new bikes....

Also I'm not real knowledgable with two strokes of sorts... I've had a few but they've always ran great and I've only had to do standard mechanical work on they, never had to do any major flat finding... So looking forward to some more experienced advice.

One last question... I have a T500 Tacho coming... Is there any reason to think they'd be different?

Thanks in advance... Doug.

[Craig380]

Hi, if the bike starts easily from stone cold (i.e. after standing overnight) then the crank seals are usually good enough.

Did you clean the faces of the contact breaker points with residue-free cleaner? That can cause a problem with brand-new points. Are the spark plugs and caps new?

If all those things check out, I'd pull the left carb again, remove the pilot jet and make sure it's as clean as a whistle. Check all the little air-bleed holes too, and remove the pilot air screw completely and blow a tin of carb cleaner through the whole lot.

Good luck!

[Dougnemeth]

Update...

Took it for a ride over some hilly country and the tachometer decided to work so I can now give a little better info.

On hills, below about 3000rpm it has nothing and will slowly slow down even at full throttle. Above 4000rpm it's fine... Now I know these should rev but I suspect it should be better than it is?

As for carbs and spark... I've cleaned the carbs several times but I've only used petrol so I guess I'll try some carb cleaner? As for spark, it's the right I've had troubles with the left has always been spot on....

It's funny, it's the right I've had all the troubles with but it runs fine...

Also what should one of these idle at... I have trouble with idle below 1500rpm.

Thanks again. Doug.

[Dougnemeth]

Also worth noting, it's pumping plenty of air out the exhaust so we have flow.

[tricky1962]

We had to replace the stator and the two seem to be different (but the current looks the same as in the factory manual photos) but I couldn't get the timing perfect as I ran out of room the the screw slots etc. but it only retarded by about 2-3 degrees from factory (I can't imagine that would be enough to make a major difference).

This I think may be your problem. On my T500, the timing slipped and I didn't notice except pulling up hills at low revs got worse.
I would suggest you get the file out, enlarge the slots and get the timing right before going any further

[jabcb]

The timing marks will be wrong if you used a GT250 stator.

The T250 & T350 had the same timing: 24 degrees / 2.88mm BTDC.
But the GT250 timing depended on the year.

See service bulletins: Specification-6, Specification-11, GT-30 & GT-32.
http://www.ozebook.com/compendium/techb ... %206-9.pdf
http://www.ozebook.com/compendium/techb ... 010-14.pdf
http://www.ozebook.com/compendium/techb ... 027-33.pdf