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

Forgorin · Senior Member

no power over 80km/h

jasparach · Senior Member

Do you mean it runs up to 80 and then just stays running at that level? Is the throttle opening up enough? Is there enough freedom to allow the throttle to move through it's full range>
John

Forgorin · Senior Member

Ah, sorry. I should have given more info...

The throttle seems to have full range of motion. It's is as if there is no more petrol going to the engine...

TTRfan · Super Guru

if you have the petrol tap open, do you have a good flow of petrol out of the float bowl drain screw when you slacken it off?

jasparach · Senior Member

Will it start as normal with choke when cold and start as normal when hot without a choke and rev as normal? You don't have an inline filter fitted that is restricting flow?

Forgorin · Senior Member

Brian. Yup. Seems to have good flow...

John, she starts right up. With or without the choke. There is an aftermarket filter! I wonder if that could be it. I'll remove it and see if that helps.

Phlip7 · Member

I had a similar problem when I hit 100, just stopped revving higher and no extra power. Modified the stardard exhaust so it would breathe better now it revs freely right though the throttle range and way better power.

TTRfan · Super Guru

Blocked breather on the tank cap?

Jeff B · Senior Member

Another item to check is the seal of the rubber engine intake joint between the carburetor and the engine.

mossproof · Super Guru

I wonder if it is actually jetted right. What exhaust etc is on it, and what jets?

Forgorin · Senior Member

Ok. I have a confession. It's not a ttr... Please done hurt me...! If my partners Honda GB 250. I've got the same one. She replaced hers after blowing up the engine... Ya. She can ride really hard. She often rides and races with guys on bigger bikes!

Anyways. It's definitely not the breather tube. Jets are all standard. All 'gaskets' are in good condition. I'll take a look at the bike next week. I have a feeling it might be that fuel filter that the previous owner put in. If not I'll take out the carb again and take a look at it. It could be that the float bowl is not set right.

Thanks guys for your input. I was kind of stumped..

jasparach · Senior Member

Indeed, the plot thickens. An intruder in our midst!! (only joking) Try it without the fuel filter and a clean air filter and the carb set as per normal if the engine is as standard with no modifications.

-- Edited by jasparach on Monday 30th of March 2020 03:39:54 PM

Forgorin · Senior Member

Thanks Jas. I ll work on it tomorrow.