PLEASE HELP!! ZXR400 Engine down...
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1st Gear Member
Joined: Dec 2007
Posts: 2,092
From: terrorizing southeastern norf carolina
on race engines, if you're not racing every single weekend, i'd probably get on a rebuild schedule of a rebuild at the end of each season.. as a VERY modest base...i'd probably do a mid-season inspection and overhaul to keep this kind of thing from happening again.
al lte carbon on your valves tells the story of "coked" oil seeping past the valveguides as well, or ring blow-by.
flutter is controllable by modifying the 2nd ring gap.. closing the gap a few thousandths of an inch can raise te blow-by RPM to a point to where you may very rarely see it on te track..
that is something you should maybe look in to..
you can map blow-by and graph it with a flow meter on your next dyno tune. hook up a flowmeter to your crankcase breather pipe and run under load to redline.. you'll find a point where the blowby becomes about 6-10 times as the idle flow rate. THIS is where your ring flutter is occuring.
just one more thing to keep te motor clean.
something that came to mind.. does that motor have exhaust-side valve seals? some old-school racers uesed to remove the seals to help reduce latent heat and wear on the valves.. they didn't really care about the amount of oil seeping down the valvestem, as it was minumal.. BUT, some guys drilled the top of the valveguides to "pool" oil at the guild and therefore would allow more seepage, gnerally resulting in noticable carbon buildup.
everyone has made perfect points.. as i said, i'd honestly look at another motor and nail that piston on the wall to show it off!! haha..
best of luck again, and keep us posted on your progress!!
al lte carbon on your valves tells the story of "coked" oil seeping past the valveguides as well, or ring blow-by.
flutter is controllable by modifying the 2nd ring gap.. closing the gap a few thousandths of an inch can raise te blow-by RPM to a point to where you may very rarely see it on te track..
that is something you should maybe look in to..
you can map blow-by and graph it with a flow meter on your next dyno tune. hook up a flowmeter to your crankcase breather pipe and run under load to redline.. you'll find a point where the blowby becomes about 6-10 times as the idle flow rate. THIS is where your ring flutter is occuring.
just one more thing to keep te motor clean.
something that came to mind.. does that motor have exhaust-side valve seals? some old-school racers uesed to remove the seals to help reduce latent heat and wear on the valves.. they didn't really care about the amount of oil seeping down the valvestem, as it was minumal.. BUT, some guys drilled the top of the valveguides to "pool" oil at the guild and therefore would allow more seepage, gnerally resulting in noticable carbon buildup.
everyone has made perfect points.. as i said, i'd honestly look at another motor and nail that piston on the wall to show it off!! haha..
best of luck again, and keep us posted on your progress!!
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