Fire shooting out my tailpipe!!!

[kineo3]

Ok, I know there are a million jetting topics and I have read most of them but I am stumped. I have a 450r, complete hrc kit, stock air filter, and full yoshi pipe. The jetting is still the same that came with the hrc kit. I just got the pipe on and was running great all day out on a frozen lake. I got up the next day and it runs strong through all gears it just backfires big time when letting of the throttle. I have the air screw out about 2.5 turns. To me this sounds like a lean condition, but why did it run perfect one day and the next develope this condition? It has been sitting for a week because I have not had the time to mess with it. I went in my garage to start it last night and when I fired it up and jacked the throttle about a 6inch flame shoots out my tailpipe when I let of it. Can someone please point me in the right direction. Should I change the pilot jet, turn the screw out another turn. If so why would it run fine one day and not the next??

[chad502ex]

re-tighten your exhaust header nuts again. They have come loose and need re-torque'd. The air causes an extreme lean condition and causes a hotter flame. I also found this condition out the hard way after three hours of debugging on the dyno.

doh!

[kineo3]

Awesome, that makes sense. I will take a look when I get home tonight. I hope that is the problem. Thanks!! Your the man.

[Mobile Dyno]

Chad beat me to it. I was going to say the same thing.:D

[chad502ex]

Yea, those "Mobile Dyno" guys are extremely helpful with their services.

[steveatv3]

there might be water in your carb, it did the same thing to mine when i got snow in my airbox and it would backfire and stall out. Flush your carb out that may help

[DirtDevilBT]

Well, I have been told this could be 2 things. Only one of them I can back up. It could be an exhaust leak like Chad said or a rich condition caused by the pilot.

As for the exhaust leak I think there might be unburned fuel mist that comes out of the head and when it reaches where ever the leak is, it ignites that fuel and throws your flame.

The rich condition I had. When you let off the throtle the slide closes and shuts off most of the air. Now you're running mostly off the pilot. I had a 50 pilot in and it was too rich, even at 3/4 of a turn out. When I would let off the gas it would pop or backfire I guess. When I went back to the 48 and 3 turns out, it stopped.

Anywho, check these and maybe that water idea. If it didn't happen one time but did the next, are you at different drastic elevations? Just giving you some options.:cool:

[kineo3]

When I got home I checked the header pipe bolts. One nut was gone and the other was finger tight. So I guess I have found my problem. Thanks everyone for saving many hours of trial and error. This sight is absolutley priceless!!!

[chad502ex]

;)

[400exBro]

do you have to tighten the bolts for the exhuast every time??
i had the same problem he was explaining and found in deed that one of the bolts was very loose!!! i tightened them back up, but haven't rode it yet...
Will the bolts coming lose also cause the head pipe to discolour a lot?? I have curtuis spark stainless steel exhuast system and the head pipe around the exhuast manifold is a blue purplish colour??
i hope this will cause the poping to stop at the slow circuit, if not i will continue to play with the pilot jet.

[chad502ex]

Originally posted by 400exBro
do you have to tighten the bolts for the exhuast every time??
i had the same problem he was explaining and found in deed that one of the bolts was very loose!!! i tightened them back up, but haven't rode it yet...
Will the bolts coming lose also cause the head pipe to discolour a lot?? I have curtuis spark stainless steel exhuast system and the head pipe around the exhuast manifold is a blue purplish colour??
i hope this will cause the poping to stop at the slow circuit, if not i will continue to play with the pilot jet.

yea Bro! when youu first install the head pipe if you install a new crush gasket and tighten the header there is a good chance that when you heat cycle the engine your heade bolts will be loose. The blu'ish condition occurred on my setup too. Made me have to polish up my whole header after that.. oh well, i was going to polish it up anyway,..... If the header leaks the air is pulled into the exhaust and mixes with the exhaust gases and causes the gases to get hotter. Think about blowing into a fire- the fire gets hotter and grows a bit. The same condition occurs if the header leaks. It cracks me up when i see blue head pipes on quads and they think that its ok- its not. a blue header is indication that the engine is too hot probally due to lean condition.

[400exBro]

Originally posted by chad502ex
yea Bro! when youu first install the head pipe if you install a new crush gasket and tighten the header there is a good chance that when you heat cycle the engine your heade bolts will be loose. The blu'ish condition occurred on my setup too. Made me have to polish up my whole header after that.. oh well, i was going to polish it up anyway,..... If the header leaks the air is pulled into the exhaust and mixes with the exhaust gases and causes the gases to get hotter. Think about blowing into a fire- the fire gets hotter and grows a bit. The same condition occurs if the header leaks. It cracks me up when i see blue head pipes on quads and they think that its ok- its not. a blue header is indication that the engine is too hot probally due to lean condition.

Ya that is what i thought, i have never seen that shade of blue on a header before... I will continue to check the bolts to make sure they don't losen on me, and play around with my slow circuit and see if i can get it to run a bit better... When the engine is still cold and under no load and i run the throttle from idle to 3/4 throttle it will pop, and want to die out... This was before i tightened the header bolts... I will test it out now with then tightened, but if the same problem occurs with it cutting out as a jab the throttle really fast under a no load condition, and the engine idling for a few minutes do i have a to lean slow circuit?? I usually know what is going on, but i want to hear it from a pro first.

[ProConcept]

What is the torque spec for header bolts? You know some stainless steel will turn a goldish blue when exposed to pretty much any high temperature, my quad is like that and it runs great.

[chad502ex]

this is the color header ya want

GOLDEN

[chad502ex]

this is more what i mean.

The sparks was old and ran hot once on the dyno and that is why there is slight blu'ish color near header flange.

The RE was completely new out of the box

[chad502ex]

new color stainless steel header/pipe after few runs on dyno

[ProConcept]

What do you torque the header bolts to???

[middleman102002]

so what about a titanium header i heard there supposed to turn that color cause titanium reacts differently to the heat
thanks

[chad502ex]

Originally posted by ProConcept
What do you torque the header bolts to???

ahh, the 450r service manual says "muffler mounting nut to 24ftlbs". i believe this is the header bolts but unsure here. no where else in the manual does it indicate header nuts just says tighten securely or until the header flange bracket starts to bend LOL

:confused:

[400exBro]

Chad, my head pipe doesn't even look that gold, it seems to be a bit darker, after riding it this weekend, hard, it has seemed to tone down a bit on the blueish colour, but i also tightend the header bolts... So this looks like a good sign, but i still may be lean on the slow circuit.... Will the head pipe turn back into that golden colour once the jetting is poper?? or will the head pipe stay the blueish tone possibly throwing off my "reading" of proper jetting??

[chad502ex]

Originally posted by 400exBro
Chad, my head pipe doesn't even look that gold, it seems to be a bit darker, after riding it this weekend, hard, it has seemed to tone down a bit on the blueish colour, but i also tightend the header bolts... So this looks like a good sign, but i still may be lean on the slow circuit.... Will the head pipe turn back into that golden colour once the jetting is poper?? or will the head pipe stay the blueish tone possibly throwing off my "reading" of proper jetting??

once the header turns blue there is no more "visual" indication that jetting is near dial'd in. The only way to re-establish the gold is to polish and start again.

in other words, it will not turn from blue to gold only from gold to blue if not right.

good to hear your on track tho!! The slow if not dial'd in will glow hot and turn blue, but if not dial'd in on top (lean) you kill the engine.