riderofthestorm Posted May 20, 2008 Report Share Posted May 20, 2008 I recently busted a skirt on one of my wiseco's and decided to try the namura piston kit just for shits and giggles. With the wiseco's i was at about 135-140 psi, when the skirt broke one was still 135 and the other was 120 psi. When i put the Namura's in i got 120 psi on both cylinders, and yes they were honed. This just don't make any sense to me, anyone else have the same issue or know why this happened? thanks in advance for the info HQ oh and yes i did clean out the crank case Quote Link to comment Share on other sites More sharing options...
okbeast Posted May 20, 2008 Report Share Posted May 20, 2008 Did you check your squish with either set? Quote Link to comment Share on other sites More sharing options...
riderofthestorm Posted May 20, 2008 Author Report Share Posted May 20, 2008 Did you check your squish with either set? no i didn't, whats the easiest way? wouldn't think they would make pistons that different from one another? Quote Link to comment Share on other sites More sharing options...
okbeast Posted May 20, 2008 Report Share Posted May 20, 2008 Take a piece of solder and bend it 90 degrees where it will go into the spark plug hole and u feel it hit the side of the dome. squish it, take it out and measure it. Quote Link to comment Share on other sites More sharing options...
endofitall9 Posted May 20, 2008 Report Share Posted May 20, 2008 unless whoever you took it too honed the shit out of the cylinders(seen this done) then your compression should be close, also you should have done a review on the Namura pistons which are cast..the skirts supposedly bust off really easy on them... Quote Link to comment Share on other sites More sharing options...
XxMeltIcexX Posted May 20, 2008 Report Share Posted May 20, 2008 With past experiences it is best to have the pistons on hand when honing so they are in tolerances, getting them honed and then buying a set of pistons is just asking for trouble im opinion. Eric Quote Link to comment Share on other sites More sharing options...
riderofthestorm Posted May 20, 2008 Author Report Share Posted May 20, 2008 unless whoever you took it too honed the shit out of the cylinders(seen this done) then your compression should be close, also you should have done a review on the Namura pistons which are cast..the skirts supposedly bust off really easy on them... I honed it myself, and i didn't hone it alot, just enough to get the glaze off, the namura's seemed to fit tighter than the wiseco's did, i dunno, whats the squish supposed to be? i'll have to check it i guess,, thanks again guys Quote Link to comment Share on other sites More sharing options...
okbeast Posted May 20, 2008 Report Share Posted May 20, 2008 I think anywhere from .040 to .050 or something like that. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted May 20, 2008 Report Share Posted May 20, 2008 Um...what caused the skirt to break in the first place, that's the first question that needs to be asked. Did you check hot or cold? Cast pistons and forged heat up and expand differently. Did you bother to check ring end gap? Quote Link to comment Share on other sites More sharing options...
notsed Posted January 6, 2010 Report Share Posted January 6, 2010 what about the fact that pro lites need a .004 clearance and namura needs .002 Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted January 6, 2010 Report Share Posted January 6, 2010 I run .oo3 on wisecos,look on the package check ring gap,but there is a reason that skirt cracked,out of round cylinder,collapsed skirt from piston cocking in bore,I would pull it down again find some one with a bore guage and check it good Quote Link to comment Share on other sites More sharing options...
FireHead Posted January 7, 2010 Report Share Posted January 7, 2010 Um...what caused the skirt to break in the first place, that's the first question that needs to be asked. Did you check hot or cold? Cast pistons and forged heat up and expand differently. Did you bother to check ring end gap? Two things (Dave noted both): 1.) The piston skirt broke for a reason. Most likely, the bore is out of round or not square to the crank (providing nothing else is wrong with the engine. 2.) You can't put a cast piston in a hole machined for a forged piston and vise versa (The machining spec. / tolerances are different). Quote Link to comment Share on other sites More sharing options...
blowit Posted January 9, 2010 Report Share Posted January 9, 2010 I am in total agreement with above but not sure if the difference in bore sizing would be causing such a drop in comp. I wonder if the holes are egged. Round rings in an oval hole never works out too good. However, the old rings would have worn to this egg shape. I would certainly want to look closely at the squish clearance. Probably a good idea to pull the topend and get a more thorough QA inspection. As mentioned above, skirts don't just break for no reason. Also keep in mind that that gauge is NOT a bible but merely a tool. Tools can fail. Mull Engineering Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.