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

widge · Veteran Member

More carb woes

TTRfan · Super Guru

Hi Rob

Not much you can check from the outside but check (a) you get a squirt of petrol out of the accelerator jet (this normally works once or twice even when the float bowl has been drained), (b) the choke operates as it should, (c) the throttle mechanism and slide are operating smoothly, and (d) the float bowl drain plug isn't seized.

The two pipes are breathers and are open at the top where they attach to the airbox. It's worth blowing through the pipes to check the one-way valves are working so they can be cleaned if not.

This thread might help the strip down.

Brian

widge · Veteran Member

Thank you,

Bearing in mind i am a complete novice at carbs I managed to remove the carb but I had done this once before so was not to much of a problem.

So next I checked the jets and the pilot was completely blocked. The main jet was fine. Where is the diaphragm as I was going to check that?

Next problem was the air screw. This was seized solid but with a bit of patience got it out. Does the air screw have a rubber seal on it above the spring if so I think I need one or a new one?

Tackled the drain screw whilst it was out and got that free :)

Is there anything else that I should look at whilst it is out?

Rob

TTRfan · Super Guru

Good progress Rob!

Have a look here and you will see that the airscrew should have an O ring.

A bit of advice, don't take the diaphragm cover off unless you have a pair of the small O rings ready to fit else, if you put the old O rings back, chances are petrol will leak from the cover cry

widge · Veteran Member

Next problem!

I replaced the jets, air screw and float bowls gasket. Then replaced the carb.

The bike started for a few secs on choke but then had petrol pouring out the overflow.

Took the carb off again removed the float bowl blew down the petrol pipe rised the floats up and down and the valve is working.

What have I done wrong?

Rob

widge · Veteran Member

The problem is the petrol is coming out of the drain if that is the bottom outlet on the carb and goes straight down

I tried tightening the screw but makes no difference any ideas?

TTRfan · Super Guru

The "straight down" drain is from the drain screw so you are in the right area biggrin

The overflow drain is horizontal as shown in the photos here.

You are going to have to take the drain screw out to see what's happening. Maybe some grit stuck behind it stopping it sealing?

Brian