A forum for owners of Yamaha TTR250 trail and enduro bikes!

TTRfan · Super Guru

Calling all TTR250 carb experts!

matador · Veteran Member

sorry I'm not a carb expert Brian they are all out tonight but my TTR does the same. I just push the choke in a bit and it will tick over at a lower rate until it's warmed up a bit - quite soon.

When I had a problem with the 'check valve' being blocked, the bike needed the choke to start even when slightly cooled down a bit and took ages to warm up so it would pickup without the choke.

Plus the cam timing problem.

I still have a slight problem with the pilot air screw, the revs don't increase as I would expect when wound out. I'm going to leave it for now and have a go next week as it runs ok other wise. I normally strip the carb right down and blow every jet out.

Haggis Hunter · Veteran Member

A normal? choke cuts down the air supply to make the fuel/air ratio rich. The TTR choke just puts more fuel in to get the same fuel rich fuel/air ratio with the same air flow.

Does that make sense?? Would that do it??

Not having had too many problems with either bike in the last 10 years of so I am not over familiar with the insides of the carb.

On older cars there was a cam in the throttle shaft which would open the throttle butterfly to increase the revs. As Clifford said, pushing the choke in a bit cuts down on the revs.

I do this on mine to stop the thing revving its self to death on start-up.

The thing I worry about more, is having the bike on the side stand whilst it is warming up and the oil pump becoming starved or oil. Could this be a problem? from what I remember the oil pick up is on the right hand side.

Feel free to correct me.

Markvan · Guru

Mine does the same , revs way to high when the chokes out. I turned down the idle screw while the

choke was on and it reduced the revs , but that means i have to increase idle screw back up when

i turn off the choke. It would be alot easier if we could adjust something else. I hope there is an answer.

I also hope if theres an answer i can do it.

TT-R250M · Super Guru

It may be just normal, but sounds like a weird problem if it is a problem.

I would suggest to check that the float level is right, the fuel metering screw 0-ring is not perished/damaged, the air flow O-ring (on the side of the carb) and that you have the correct pilot jet installed (remembering that not every bike is the same). Also make sure that the cut out in the slide points to the rear of the bike (air filter side).

If all that checks out, then maybe I am missing something??? I will continue to ponder why this weird problem is happening and any new info I will update later.

The oil feed line is on the right hand side but will not cause an air-lock from using the side stand to warm up. However, the engine should be stood straight up until the oil gets up to the cylinder head as if it is on the stand the oil will be puddled up in one corner and will not lubricate as designed to do.

Jarrah

yamaha42 · Senior Member

My bike does this as well. My old TTR 225 did, and my friends TTR-125 does.