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

Terrence R · Senior Member

Who's using what pilots?

PlumasDude · Senior Member

I have the size 50 (stock US) pilot, no obvious problems but I can't get a good steady idle -- it wants to "race" at idle, or to avoid the racing idle I have to set idle speed so low it dies. The racing idle happens when fully warm, especially while riding. There aren't too many things to adjust at this point, so I'm wondering if going up to a 52 pilot jet would give a more stable idle. Interesting that your Canadian bike has a 52 pilot, I thought all US/CA versions had the size 50.

Terrence R · Senior Member

I didn't say anything about me running a 52...

Mine also came with a 50 pj. After doin lots of mods, I now have a 6sigma 52.5 pj. Unfortunately, it still won't idle right. I've tried everything. I also did a complete carb rebuild. I've tried leaner and richer jets. I've checked every possible vent hose. Still, won't idle right. Wants to stall and has a fluctuating idle. Also terrible 1/4 throttle response from time to time. I think I'm ganna sell this lemon.

PlumasDude · Senior Member

Right, reading more carefully ... so the 52.5 doesn't help, bummer. I've noticed no change in my idle symptoms based on elevation (from 2000 to 7000 feet). I also did a rebuild.

Terrence R · Senior Member

I can't figure it out. It's driving me crazy! It runs like crap down low. Keeps wanting to stall. Any suggestions from anyone? Fuel screw does nothing.

TT-R250M · Super Guru

PlumasDude wrote:
Interesting that your Canadian bike has a 52 pilot, I thought all US/CA versions had the size 50.

It does not have a #52 fitted standard, it is the same as US specs- 50/137.

About to put a 54 pilot in myself, I'll let you know how it goes if you want (Terrence)?

Jarrah

TT-R250M · Super Guru

Terrence R wrote:
I can't figure it out. It's driving me crazy! It runs like crap down low. Keeps wanting to stall. Any suggestions from anyone? Fuel screw does nothing.

Sounds to me that the #52.5 is too large for your set-up. I have already told you what I recommend but I don't think you want to listen.

Jarrah

TT-R250M · Super Guru

PlumasDude wrote:
I have the size 50 (stock US) pilot, no obvious problems but I can't get a good steady idle -- it wants to "race" at idle, or to avoid the racing idle I have to set idle speed so low it dies. The racing idle happens when fully warm, especially while riding. There aren't too many things to adjust at this point, so I'm wondering if going up to a 52 pilot jet would give a more stable idle. Interesting that your Canadian bike has a 52 pilot, I thought all US/CA versions had the size 50.

If it only happens when warm it suggests that you are running rich as the engine needs more fuel when cold. I would try removing the air filter side cover, if it helps, a 48 should sort you out.

Jarrah

Terrence R · Senior Member

I finally figured it out!!!

I checked the spark plug. It was showing very lean, which is odd cause ( like jarrah said) it was acting as if it was rich cause of it being much worse when warm and the fuel screw having no effect. I was pretty interested to see what kind of results u got from the 54 pj. Thought it was probably the best pj to try considering how white my plug looked. Then... Ooh, I put an iridium plug in right before these symtoms started. Would that be the problem after all this time? Yes! It was! I put the regular cr9e back in and it's running better than ever! Odd cause a lot of ttr guys swear by the iridium plugs.

TT-R250M · Super Guru

The Iridium spark plug must have been a dud, never had that problem with them. If anything it gives better performance and starting ability. That said, the US/CA uses ethanol in their petrol so the quality of the fuel is far worst than AU and may have an effect on this.

Jetting is a VERY hard thing to do over the internet, especially if the symptoms are not described in full and clearly. It is not like I can take the bike for a spin to asses the problem.

Glad you got it sorted finally Terrence, will let you know how the 54 goes.

Jarrah

Terrence R · Senior Member

Thanx jarrah. I'm beginning to think that my iridium was in fact a dud aswell. Everyone else seems to have great results with them in their ttr250's. Ethanol is big problem here. It's not in the supreme gas though. I go to all lengths to avoid it. When I bring a gas can to the pumps, I always pump the first 10 litres into my truck, then I fill the gas can. By doing this, I avoid getting the regular gas with ethanol in it from the previous gas pumper that's still in the lines.

TT-R250M · Super Guru

If the Iridium plug does not work for you, try a CR8E, it will give the same result (basically). If it is below about 30 degrees Celsius there you may also want to try a CR7E.

Not sure about your state but the only fuel that does not have ethanol in the US is racing fuel. Some states do not even need to specify it on the pump. It seems to be practically the same in Canada...

Taken from HERE-

Ethanol-blended gasoline

Ethanol-blended gasoline is a fuel that typically contains up to 10% ethanol in unleaded gasoline. We use ethanol in our gasoline where legislation requires its use and where conditions warrant. The Federal Government has regulated that motor gasoline sold in Canada after Sept. 1, 2010 must contain an annual pool average of 5% ethanol. Different provincial mandates also exist, some with higher ethanol pool requirements. Because of these mandates, most grades of Petro-Canada fuel may now contain up to 10% ethanol. This represents a change from the previous state, where premium fuel was ethanol-free at Petro-Canada. To find out if ethanol-blended gasoline is sold at a station look for the yellow labels in the pump area indicating that the fuel may contain a maximum of 10% ethanol.

More info HERE and HERE and HERE

Enjoy!

Jarrah

PlumasDude · Senior Member

Interesting idea on the smaller pilot. I cut up the air box and that has helped quite a bit, much to my surprise, but it was sucking like a Hoover through the snorkel so I tried it and eliminated the slightly rich condition at lower elevations but no change in the idle.

TT-R250M · Super Guru

I would suggest to check the air jets are not partially blocked, that the fuel metering screw O-ring is not perished and the fuel metering passage is not blocked. More info HERE.

Jarrah

PlumasDude · Senior Member

It only took me 3 months to get around to it, but after cleaning the jets twice I took a tip from Brian and just replaced the #50 pilot (rather than pay the bucks for a #52), and my idle is now good and stable and I'm psyched. So yes Brian and Jarrah are right again, if you're cleaning jets you might just buy a new pilot they're cheap.

I tried a few larger main jets (140 and 145) but I figure without a new pipe its probably a waste of time and just makes it too rich -- so, results inconclusive. For public relations purposes I don't want to get a new pipe until I can find something quieter than the quietcore. So I'm back to 100% stock (US 2003), #50 pilot and #137 main, needle clip 1 notch up (to the lean), cut the top out of the airbox, and it runs just fine at a range of altitudes.

And replaced a leaky fuel pet**** so my garage doesn't stink all summer.

Off to burn up a tank of regular so I can refill with nonethanol/racing gas (finally found some!).

TTRfan · Super Guru

Great news - glad to hear you got it sorted biggrin biggrin

Brian