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

yooper · Member

Dies When Hot? Help!

JOHNYBOY · Super Guru

sounds like carb problem / intake hose also carb adjustment check with manual for std settings has the airbox been modified & jetted to suit

TTRfan · Super Guru

Welcome to the forum yooper!

It sounds like a fuelling issue.

You have ruled out a vacuum in the tank so my suggestion is to rule out the next simple thing first.

Undo the drain screw on the float bowl with the fuel tap on and a big rag to catch the petrol. Does it flow out at a good rate on both main and reserve settings?

If so, the petrol tap filters are clear as well as the one above the float valve. Also, it should mean that the float valve isn't sticking.

Let us know what you find and, if that isn't the problem, we will need to look elsewhere.

Brian

yooper · Member

Thank you very much Brian, I am glad to be here! I did try to run the bike after it died with the fuel cap off, and I established that it was not that. Dang it. I will try the drain screw this evening. As a side question, but perhaps related- do these bikes ever leak fuel on the ground normally? Last night, after this other issue, the hose that is located on the side of the carburetor, and comes out the bottom, directly under the carburetor, had fuel leaking out for quite some time, but eventually stopped, until I would move the bike again.

Thanks again for the warm (and helpful) welcome!

TTRfan · Super Guru

I think you are referring to the float bowl overflow pipe in which case either (a) your float level is set wrong such that the float needle valve is still allowing fuel in, (b) the valve itself may have a bit of debris preventing it from fully closing or (c) its rubber seal is damaged.

There is a photo of a needle valve set here which hopefully shows what I mean.

Brian

yooper · Member

Hey Brian,

I talked with a friend about this issue, and he sounded pretty certain that it was a compression issue. disbelief Do you have any reason to believe that it could be compression related? I appreciate any advice you could give me on that.

ttboof · Super Guru

unlikely its a compression issue , if it was due to piston/rings you'd have the tell tale smoke , if it was valves you'd have poor idle , possible back firing though the carb and or the exhaust .

if you have kick start its just a case of turning the bike over with the kick start with the ign off and you should feel the compression strokes ( the simplest way of checking with out tools )

if as brain has suggested you have good fuel flow to the carb , it will most likely be a carby requiring a thorougher clean, not uncommon if the bikes been sitting for some time . it would also pay to check the inlet stub while your at it (plastic bit between the carb and motor ) as if it is loose /failed it may be more noticeable when hot.

it doesn't sound electrical as its usually intermittent (engine misfiring ) , or a sudden turn off as if it was switched off .

the fact the choke makes it a bit better its pointing more to a dirty carburetor .

keep sharing as much detail of what happens and often its the small things that can help narrow down the culprit . eg the sudden down shift combined with a closed throttle will draw the maximum amount of air /fuel through the pilot jet , or if the throttle is open drag any dirt up off the bottom of the bowl , just stopping and letting everything drop back down makes me think a carby clean is on the cards .

looking forward to hearing you out riding non stop

-- Edited by ttboof on Thursday 15th of September 2016 05:26:10 AM

yooper · Member

Alright, update time! (Plus a few more questions)

Today I decided to dive deep into the issue, and I cleaned the Carburetor, (to the best of my ability) thanks to a few other members write-ups. As I was taking the carburetor out, having it been my first time ever doing such a thing, I didn't notice the rubber boot that connects the carb to the engine was completely in shambles! When I was putting the carburetor back on I noticed it however, and I know that it is not right, so I will be ordering a new one tomorrow.

The part that I am referring to is this-

Cross-motorcycle-carburetor-pad-Carburetor-Intake-Manifold-Interface-glue-for-Yamaha-TTR-TTR250-TTR-250-motocross.jpg_640x640.jpg

This leads me to my question- Could this boot being broken (creating NO seal on the engine) be the main source of my issue? I know that it must be affecting the fuel-air ratio, but would it give the bike the problems that I am having?

Thanks!

-- Edited by yooper on Monday 19th of September 2016 12:19:29 AM

-- Edited by yooper on Monday 19th of September 2016 12:20:55 AM

krum downunder · Veteran Member

My Bike did exactly what yours is doing.

The rubber and the alloy part of that boot became seperated, but you couldnt tell while it was still on the bike.
Soon as i replaced it the problem was fixed :)

Yamaha wanted $150 for a new one so i bought one of these www.aliexpress.com/item/Free-Shipping-Dirt-Carburetor-adapter-Interface-glue-Fit-Yamaha-TTR250-TT250R/32507689371.html

leigh · Senior Member

krum - do those cheaper ones fit properly? I though they we're a mirror image and not quite the correct fit.

krum downunder · Veteran Member

Really not sure, its been on for 9 months now and the bike runs great.

It looked the same as the old one, tho i was about to torch the bike at the time if it didnt work.

P.s when i was looking for them, there were ones for $8 that said in the description that they were back to front.

i just kept looking till i came across that 1 that i linked

-- Edited by krum downunder on Monday 19th of September 2016 11:06:23 AM

leigh · Senior Member

ok cool, good to know. I remember seeing the cheaper ones on Ebay and assumed the ones you linked must have been the same.

I bought one a while back from yamaha, and yeah it must be made from unobtainium and handmade by leprechauns or something.

-- Edited by leigh on Monday 19th of September 2016 11:58:38 PM

Dutchkma · Member

The intake boot on my "01 did the same thing. I brake cleaned the living s**t out of the two part and glued it al back together with Peratex High Temp Silicone. Assembled the next day and all has been well for the last six months. Id like to say I got better power, but I rejetted up one size and installed a FMF Quiet core. . Nice results. Good luck on yours. By the way Yooper, I'm a "troll" down in Traverse City. I've done a lot of grouse hunting in the Sagola. Ralph, Gwinn area. I've always wanted to ride the Porterfield Loops, but none of my hunting buddies ride.

-- Edited by Dutchkma on Thursday 22nd of September 2016 02:10:19 AM

yooper · Member

Hello everyone. I have an update...

I ordered the replacement boot, and I installed it today. I put everything back together and went to start it. I knew it was going to take some time, since I had cleaned the carburetor, but I cannot get it to run. The closest I have gotten was with the choke out, and then turning it over for about 10 seconds, and it will fire up for about 15 seconds then die again. I now have a dead battery which I need to charge before I can try again. Any one have any ideas? I appreciate anything. Common mistakes when reinstalling everything? Maybe the busted boot wasn't my issue? Thanks.

TTRfan · Super Guru

Sounds like fuel not getting through.

If you open the drain screw on the carb does fuel flow quickly out the overflow?

yooper · Member

I will check that next. Any other ideas?

TTRfan · Super Guru

Lets get that one out the way first wink

The fact that your TTR starts and runs, albeit for only a short while, tends to point to the electrics being OK. I could be wrong but, as I said before, it sounds like a fuelling/carb issue.

If the fuel flows freely have a look here http://ttr250.activeboard.com/t45670479/help-my-ttr250-wont-start/ for more suggestions.

Brian

yooper · Member

Alright guys!

I have now emptied the gas out and replaced it (the old gas was yellow, and grimy) , but now, when i turn the gas on, it pours out of the overflow? on the bottom of the carburetor. The screw that Brian recommended I check, is stripped to hell, and I cannot get it out. Is it possible that in my times of trying to remove the screw, I loosened it enough to dump gas out? Are there two overflows on the bottom of carburetor? One right below the screw and one more centered under the carburetor? I am now suffering from a dead battery from all my messing with it.

Hopefully, with a charged battery, it will fire up.

Thanks again

yooper · Member

It turns out that the screw is still tight....

I tried to bang on the carburetor with the blunt end of a screw driver and it did not affect the flow of gas out the overflow..

TTRfan · Super Guru

The drain screw is separate to the overflow.

It sounds like your float needle valve is stuck open - maybe some of the old petrol has crusted on it.

Brian