back fire !!!

[tomzxr400]

hi all took the bike out for a long ride and managed to go through a full tank and all was ok then filled up again not long after doing so i was going hard down some country lanes showing my mate on his vfr400 what a real 400 is
when i reached red line the bike stalled backfired then threw a flame out the back . got it started agin and it did the same thing but instead of pulling over i wound the throttle back and it went crazy bangs and flames everwhere !!! bike runs fine till i hit redline any ideas???

[masterofinsanity]

could be coils /leads or plugs breaking down under the pressure mate?

[RedexRobB]

erm, if your bouncing off the redline id expect it to do that to be honest. when it reaches the limiter its cuts the engine, but its still sucking fuel as the engine is still spinning, then when the ignition cuts back in it ignites the fuel thats been sucked in and it backfires.

[tomzxr400]

erm, if your bouncing off the redline id expect it to do that to be honest. when it reaches the limiter its cuts the engine, but its still sucking fuel as the engine is still spinning, then when the ignition cuts back in it ignites the fuel thats been sucked in and it backfires.

never had this problem before. didnt know there was a limiter never hit it any way.
ive been told a few things now 1 guy said he had this once so he drained his tank and refilled it with new and it ran ok,
another said electrics or incorrect set up on carbs so guess its elimination i will check the electrics and drain the tank and see if its ok if not al get it on a dyno al let you all know either way thanks

[RedexRobB]

Theres a limiter on most if not all engines, because after that engine speed there is no useful power. They would also rev till they destroyed themselves otherwise.

It could well be your fuel, i had some running problems on another bike which turned out to be dirt in the fuel. Did you run the bike on reserve at all?

[tomzxr400]

no didnt run it that time on res but have done in the past and its been ok also ive cleaned the inside of the tank not long ago when i stripped it down will do it again though if it continues to do so after a new lot of fuel goes in

[superman]

I dont think its supposed to backfire when you hit red line mine doesnt. so in the time it red lines the fuel still pours in an then ignites causing the bbq of the guy behind

[Caz]

half way accross belgium, and i had just pulled in to get petrol. I apparently had managed to flick the kill switch to half way between on and off. End result, it ran OK at idle but at any revs it was back firing like a mad thing.

The rev limiter is there to protect the engine, you are past any useful torque and power at that point and should have changed up!

if its not happening anywhere else in the rev range, i suggest changing up a bit earlier

sorry - not the answer you were after I know!

[superman]

Plus dont constant red lining ruin your engine i imagine it does.

[rene]

on english roads/motorways you'll never get to sit on the read line for long as some plonker will be in the way

[tomzxr400]

i dont red line it as in have it run outa revs and bounce just to the top end of the power curve maybe redline is bad choice of words how bout high rev range instead!!!

[Caz]

what RPM?

[superman]

I think i get what you mean, when you ride hard an forget to change up intime so you bounce of the limiter (this is worse for your engine if you keep doin it) iv had afew mates blow cars up by doin this.

well anyway to avoid this like caz said change gear lol an it still shouldnt back fire. too much fuel is going through an then igniting i get it if i leave the bike more than a day standing with the fuel turned on an try to start.

[tomzxr400]

sorted it now ive bin a right daft git and lucky at the same time i changed the cam chain and tentioner a couple of weeks ago and must not have tightened the bolt on the crank tight enough it rattled loose and then at high revs the pick up coil was getting the wrong readings so out came 2 ft flames by the way it was only a figure of speach it happened around the 12 to 13k mark