Need a little help please!!!!!!

shady16

Registered
I have a little problem that i can't get sorted out on a 2001 busa. I took my bike to the track and during the first pass it got to breaking up pretty bad. I pulled the plugs to make sure i didn't foul one out. They looked fine except for cylinder #2 so i changed out the whole set. It ran a little better. It will break up and spit and pop around 2500 RMS. If i hold the throttle steady the RMS will fluctuate up and down. And it is also popping back threw # 2 and #3 throttle bodies. I could see the flames up under the butterflies. But it revs fine. And the upper RMS seem fine. I am stumped at the point. Thanks in advance for any and all info.

Shady
 
Any body else have any ideas?
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What year bike is it? And what is done to the bike!
 
have you done anything with the overflow tanks
years ago i was racing a fzr400
we redid all the overflow lines into one tank and we were getting vacum applied to the float bowls through the air box overflow
the bike would break up BAD around 4,000rpm only under a load
granted the busa is injected but it may not be the bike as it may be the mods you did to get it track legal
 
(GIXERHP @ Sep. 04 2007,23:16) What year bike is it? And what is done to the bike!
It is a 2001 model. With a 1999 block. 1397, ported@polished heads 1mm intake valves, Web cams 109/110, bored throttle bodies, small box mod@k@n, brockshindle exhaust, power commander pc3.
Thanks for any and all info gixxerhp,
Shady
 
What are your plugs are you using and what are they gapped at and what are you using for fuel?
 
(shady16 @ Sep. 05 2007,07:03)
(GIXERHP @ Sep. 04 2007,23:16) What year bike is it? And what is done to the bike!
It is a 2001 model. With a 1999 block. 1397, ported@polished heads 1mm intake valves, Web cams 109/110, bored throttle bodies, small box mod@k@n, brockshindle exhaust, power commander pc3.
                         Thanks for any and all info gixxerhp,
                                                        Shady
Stock compression ratio
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What fuel did you have it tuned for
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The 110 is probably your problem
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Not sure on the compression ratio?? What ever lees puts in his stage 4 kits. I haven't had the bike tuned yet i know this could be some of the problem. but i bought the bike with 2 bent valves. And i just got it together. I wanted to make sure that some other things werent wrong with the bike before i get it tuned witch i have found quite i few things. But right know i am running a brocks performance 1397 map.I haven't even ran a 1/4 tank of gas threw it. That is y the 110 is still in there. But the bike was running fine before the one pass down the track. Know i have the popping and surging and backfire threw throttle body number 2.
 
Backfiring out of the throttle bodies is usually caused by extremely rich mixtures or (most commonly) timing being off. You should check your compression in 2 and 3 and go from there. Good luck
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Missing some info here but the popping out the throttle bodies could be a few things: (going to need to check the basics first, compression test, leak down test, verify valve adj, spring pressures, fuel pressure, fuel flow, etc) If engine temperature makes a difference, you could have even have something like a tight valve guide or 2.

The RPM wandering up and down however starts to point to a fuel issue, fuel pressure and flow are pretty important on any FI system. It is possible to have good pressure and crappy flow. The flow will manifest as a low pressure under high fuel demand

Popping out the intakes is normally associated with a "lean" condition if fuel mixture is at fault
Weak, or broken valve springs , mis-adjusted valve lash or bent valves (over rev problems) can also do this. A compression test and a leak down test can usually pinpoint bent valves. Pulling a valve cover and physically checking valve springs and lash are the only ways to eliminate them from the list. I have not had the head off one of these motors myself but if the cylinders are Siamesed, you could have a head gasket issue. You can not "assume" anything is ok until you have physically checked it... Lots of brand new stuff breaks..

Ignition issues can also do this but again, you need to check basics 1 at a time.

when they start popping out the exhaust (shooting ducks we call it) an overly rich/lean condition (more rich typically) or ignition problem can be the cause. Again however the basic mechanical needs verified as in the above issues

Sometimes key can often be found by "un-doing" what ever you did that started the problem. Fresh racing header for instance could knock your fuel map out of whack and a simple remap could fix you right up and even find the new power hiding in those empty pipes. (hard to replace good dyno time with track time, first stop...dyno)

If I had access to a dyno (and I do for our cars) I would never visit the racetrack without making a series of pulls on the dyno. This can isolate issues and save you tons of money from broken parts and time trying to fix issues. I would most certainly find someone locally if possible and schedule an hour of time to start.

I can not even count the times we tried to make a few changes at one time only to go slower or have some oddball issue crop up.
 
Sounds like bogusLogon has layed it all out for you
great advise bogusLogon
this is all the more proof that your better off coming here with problems than a dealership
 
Just a little update. I found a donor bike and switched out the throttle bodies, and the coils. Still the same problem. My compression gauge will not fit the spark plug threads. So i had to go and buy a new one this week. Maybe i will find some time to work on it some this weekend. I am praying it is not a bent valve. I don't want to have to pull it down again.
 
If it is a bent valve, you should not need a compression gauge. Just crank the motor over and listen to it. The drag will be even from hole to hole. The sound of the engine cranking over will be "even" A low hole will allow the engine to spin faster on that one cylinder and you should be able to hear that.
 
remember i posted up topic simular to this not to long ago,mine backfires from under the tank,all i have done is put a full yoshi 4into1 system on and a pc3usb im hopeing thatonce on the dyno should sort it out.
 
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