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

PETE · Member

Loss of Power

Cubber · Super Guru

What a bummer, Pete. bleh

Fuel/air supply problems are first on my list of suspects. confuse

To give a more accurate assessment would take a bit more detail from you than "When I get on the open road and get into 5th and 6th she Dies".

How does she die?
What death symptoms are given?
Have you tried doing anything to see what may be wrong?
If so, with what result?
Did the previous owner do anything to the bike?
Is it in standard trim or has it been modified?
Is it running the stock exhaust?

Try and tell the forum all the information you have got and we may be able to suss your problem.

Martyn

TTRfan · Super Guru

I agree with Martyn. Sounds like a bit of fuel starvation.

If it was a blue TTR then I would suggest checking the air vent in the petrol cap as a blockage will cause similar symptoms. If it is easy to reproduce the "dying" then maybe leave your cap (I know its a lockable one on your TTR) loose to see if that has an effect.

Another thought is that your garage may not have known that there is a petrol filter situated above the float needle thingy - see pic below - purple arrow points to it:

carb fiche showing filter.jpg

On older TTRs this filter can get well blocked with some sort of fibrous material.

My bet is on one of those two - both simply and cheaply fixed wink

Brian

PETE · Member

Hi Martyn

Sorry I've been away for a few days.

Symptoms;;;;;

Looses power, splutters, surges and loss of speed. No response to accelarator.

Like running out of fuel or missfire.

If I keep changing down as far as 2nd on occasions she picks up violently and revs freely through the gears for a few miles. furious

Dont seem to have, or have'nt noticed a problem on the trails in lower gears.

I've had the carb checked at a local Garage who found nothing.

Sorry. No previous owner info. confuse

Running standard exhaust with no mods to my knowledge.

Thanks

Pete

PETE · Member

Hi Brian

I'll check with garage as to what they actually did.

Hope your right in your diagnosis biggrin

Many Thanks

Pete

Cubber · Super Guru

PETE wrote:
Hi Martyn
Sorry I've been away for a few days.
Symptoms;;;;;
Looses power, splutters, surges and loss of speed. No response to accelarator.
Like running out of fuel or missfire.
If I keep changing down as far as 2nd on occasions she picks up violently and revs freely through the gears for a few miles.

To me, that sounds a classic case of a vacuum in the petrol tank. blankstare

As you run the bike the petrol used by the engine is replenished by gravity fed fuel to the carburettor.

When the motor is running strongly then it uses more petrol, but if air doesn't get into the tank then the supply can diminish.

Next time it happens try loosening the petrol filler cap.
If you hear a rush of air into the tank and the engine starts running more normally you've found your culprit.
It could be the air relief valve attached to the filler cap breather - it may be blocking the air entry to the tank. blankstare

If that is not the case, then it still sounds to be fuel starvation as your trouble but I can't think of a possibility off hand. confuse

Martyn

TTRfan · Super Guru

Just read through the messages again and wonder if you could have water in the petrol. I know the garage cleaned your carb but if there was water in the tank it may have got into the carb again. This would give similar symptoms to what you describe.

Brian

barra8 · Guru

Things to check eg.

Carby

Improper jet needle position

Loose pilot jet

Clogged pilot jet

Diaphram malfuction

Clogged or loose main jet

Clogged air filter

Water in carby

Wrong float level

Blocked fuel line or petrol tank pet**** filter

Valve and cam

Improperly seated valve

Improper valve to seat contact

Improper valve timing

Seized camshaft

Electrical

Faulty/ dirtymain switch

Faulty/dirty engine stop switch

Broken or shorted wires

Faulty/dirty neutral switch

Faulty/dirty Start switch

Faulty/dirty clutch switch

Piston and rings

Improperly installed piston ring

Worn,fatiqued or broken piston ring

Damaged piston

Snorkel on top of airbox clogged or on backwards,broken/cracked/leaking rubber intake

Also you could try taking the cover outer cover (three screws with ring thingy's in a triangle)off the air filter box to see if it is fuel or air related. You should notice a difference (not minor) if it is fuel or air related.

I took that outta the repair manual,added a few and highlighted in blue what i thought i could be. Hope it helps?

-- Edited by barra8 on Thursday 26th of July 2012 11:13:32 AM

Clutha · Veteran Member

Next time it happens try loosening the petrol filler cap.
Martyn

Well, I can rule that out as my problem

Out today, full tank, quiet road, cap off, symptoms exactly the same.

Back to the drawing board.

Runs fine 0- 40% throttle, then hunting comes in, change up a gear and it disappears. Time to fit new fuel filters. (and maybe open up carb).

I got a smooth 73 mph in 6th though aww

Cubber · Super Guru

Ah well, nothing ventured, mothing gained. hmm

It's all part of life's rich tapestry. wink

Whatever happens, don't despair. You WILL find the cause of the problem and it will disappear. It's just now down to a process of elimination.

Martyn

barra8 · Guru

Just wondering if you tried....Snorkel on top of airbox clogged or on backwards,broken/cracked/leaking rubber intake

Also you could try taking the cover outer cover (three screws with ring thingy's in a triangle)off the air filter box to see if it is fuel or air related. You should notice a difference (not minor) if it is fuel or air related.

Clutha · Veteran Member

The next 'simple' thing is to stick the exhaust it came with back on, a CRD one which wakens the dead. Maybe it was jetted to suit.

The seller gave me the OE which I put on after one run!

tracker · Veteran Member

Did you solve your problem? I have a simlair problem,and i would be interested in your solution.

PETE · Member

Hi All. Still got me problem furious My new found Guru!!!!!!!!!! Jules has tried most of the items you recommended but to no avail. hmm .

Runs absolutely fine on the lanes and fields free accelaration smooth, never skips a beat. Get out on the roads and up to road speeds 50/60 mph

in 5th and6th gear and she splutters and tries to stop. Change down through the gears and she picks up fiercely and off we go again for a time. There is no pattern to this

it seems intermittent. I been instructed to ask could the ignitor box be restricted ??????????????????????????. Any suggestions please. smile

TT-R250M · Super Guru

It would help to know what you have tried or we could be chasing our tails on this one.

Any other details?

TT-R250M · Super Guru

0h, the Cdi (if that's what you mean) does have a rev limiter but it should not be that noticable.

PETE · Member

Re the above. Question!!!!!!!!. Sorry to be ignorant on this subject but obviously this is a jap import and i been asked if this would have orriginally been fitted with the standard exhaust as seen on most of the bikes on the forum. or could it have been changed on entry to the uk. Just a thought, as my man is convinced there is a restriction somwhere which is causing my problem. confuse disbelief bleh .

PETE · Member

Sorry. Thanks for your advice Aussie Pride still work in progress. will keep the forum updated.

TT-R250M · Super Guru

If everything is clean & checks out than it suggests that you are running rich on main jet setting.

Questions that need answering

What size jets do you have installed now?- does it run right?

What mod's do you plan on doing to it?

What is the elevation that you ride at?

What is the average temp where you ride?

What fuel do you use?

What country do you live in?

PETE · Member

I live in central uk. Riding temps 5-25deg c.[Dont like the cold!!!!!!!!!!] Elevation riding at between 400 and 1100 feet above sea level. Dont plan any mods until I sort this prob. Then could possibly fit more power exhaust. Dont no wot Jets fitted. Can you tell me what should be fitted.

Cheers Pete

TT-R250M · Super Guru

PETE wrote:
I live in central uk. Riding temps 5-25deg c.[Dont like the cold!!!!!!!!!!] Elevation riding at between 400 and 1100 feet above sea level. Dont plan any mods until I sort this prob. Then could possibly fit more power exhaust. Dont no wot Jets fitted. Can you tell me what should be fitted.

Cheers Pete

In the UK the standard setttings are.

#147 main jet

#50 pilot jet

Jet needle clip position set to the middle setting (standard).

Try to raise your main jet clip position two setttings (blunt end) to see if this helps.

PETE · Member

Cheers. I'll give it a go. Nothing to loose. Keep you posted.

Pete

SussexTony · Senior Member

Hi Pete. Just seen an old post u put up , I’ve just got an oe 94 and I’m having same problem bike runs probably until flat out about 70 mph then dies , I’ve tried everything but no joy , but don’t really bother me because I’m never flat out! But I would like to get it sorted, did u have any joy?

SussexTony · Senior Member

I’ve bought new petol cap and thought that was it, but no because I only use bike on trails I’m never above 45-50 mph but when I went for a little trip it was there? Not good when you r on A roads and bike dies at 70mph , and u havt to wait a few sec,s then ok , I’ve clean Ed carb, checked plug , ( right colour) ah.

SussexTony · Senior Member

Next thing is to check needle , and jets r ok , not loose , then I might have to give up and try bigger main jet!

PlumasDude · Senior Member

I had a fuel line problem on another bike once, the line dipped down and back up and it would get a bubble or something and after running full throttle for a while sometimes (intermittent) it wouldn't get enough gas through, or at least that's what I thought. I rerouted the fuel line and the problem seemed to go away. But who knows maybe in changing the fuel line I knocked out some dirt or something else and opened it up and that fixed it.

I get that a small main could starve out fuel at full throttle, but I don't see how that could "develop" unless the main got clogged.

You mention the speed but I'm guessing its not speed just a function of throttle and time (open too much for too long)? Draining the bowl/line faster than it can refill?

PlumasDude · Senior Member

And then I went and read the earlier posts

There's a fuel filter in the carb? I don't remember that but it would be a suspect.

SussexTony · Senior Member

I tried to get to filler in carb but no joy , looked at fuel line seems fine , so u don’t think it could be main jet, ! I’m wondering if it’s worth getting carb looked at , and rebuilt by a top marcanic, But want be cheap. , one of my friends is going to look at it at weekend, and I might have a nother go at small filler in carb again until then , thanks for your help