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case ventilator hose pinched

Started by zeroice, May 27, 2003, 09:28:28 AM

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 ???My ventilator hose managed to work its way and not only pinch its self in between the fuel pump and starter, but it kinked at the other end. this happened over the course of three races this past weekend @ summit point. On the third race, MW superbike am, the pressure was so great that the oil blew out the vavle cover gasket; the tabs where the camshafts are. they flagged me and I pulled off the track.
Now I cant get the bike to start. I checked all the plugs, they were black, no aluminum, so thats good. I checked for spark, and they spark. The engine does crank over and sounds quite normal. The funny thing is that after 3-4 seconds of trying to start it (durring that time I hold my thumb over the case ventilator) it builds up excessive pressure which I feel with my thumb. I haven't done a leakdown test (don't own the tool.. yet). Is it possible that perhaps the piston rings are damaged? can the pistons be forcing the fuel/air gas into the crank case during the compression stroke? I'm confused on this one... The bike is an 89 FZR 600, I have a wiseco bigbore piston kit w/ 1000 miles on it.... what do you think???
Krishna A. Pribadi
CCS #707


I had the fortune of being directly behine you and breathing heaps of smoke... yum...

Next time I'll make sure to have 2 functioning controllers for Grand Turismo.



Took engine apart today!!! all cyl are toast >:( gotta get a new wiseco kit. another minus $500. It apears that the bike was running lean. Though it apeared to run fine for 1000mi on the street before I took it to the track this past memorial weekend. I did tune the carbs on the street and dont understand why it would lean out so much such that it would discintigrate the piston faces. The bike always had so much power. Maybe its because I was ALWAYS wide open on the track vs SOMETIMES wide open on the street. Also the fuel tank seemded to be quite low on fuel (close to res). Perhaps that added to the leannes. I guess this is an expensive lesson on checking the fuel level and A/F mixture :-/

Hey am137, is your name ryan? I'll bring my ps2 controller and forcefeedback steeringwheel hehehe. Will you be at VIR? I'll be there!
Krishna A. Pribadi
CCS #707


When street riding you are using mostly the pilot circuit and the needle/needle jet. You spend little time using the main jet. While on the track, you will use the main jet much more. The main can be lean on the street and not be any problem.
Brian McLaughlin
Donate at
2 strokes smoke, 4 strokes choke


So the carbs are stock, and I've had 120 jets installed. the needles are moved up one notch (one notch short of richest, there are 5 notches). a friend of mine used to race these bikes and he said that he always used 120 jets. once I tried moving the needles up to the max and it didn't run too well, any sugesstions? Should I install larger jets? 125 maybe?
The bike is overbored to 628.2cc and little under 13:1 comp.
Krishna A. Pribadi
CCS #707


Can you post some good close ups of the pistons? that would make it easier to determine the cause of failure.


OK!!! Here we go, I finaly figured it out! My mixture was lean, pistons gave. Pressure builds up in the crankcase during the compression stroke such that the kinked hose would not allow for excessive pressure to relieve. hence my engine exploded. Now I have larger jets and steel braided kink-free hoses; the engine wont grenade again. ;D
Krishna A. Pribadi
CCS #707

Nate R

So you think. Look at mightyduc!  ;)
Nate Reik
MotoSliders, LLC
Missing my SV :-(