glamisaurus Posted January 10, 2007 Report Share Posted January 10, 2007 Came across an article about this and decided to check mine which is at .054". Did some searching and found that .030"-.035" is considered optimal. When I did the top end a while back I used some thick gasket material I had laying around and the motor never seemed as snappy as it was all else being the same. Would it be worth it to swap out the base gasket to bring the clearance down? It is a 400 T-Rex with 35 pwk's, V-Force reeds, LRD pipes, +4 timing, lightened flywheel, porting, and has about 150psi compression according to my guage. Quote Link to comment Share on other sites More sharing options...
gregbowler Posted January 10, 2007 Report Share Posted January 10, 2007 Just swap in some real gaskets. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted January 10, 2007 Report Share Posted January 10, 2007 That is what i would do. Only cost a couple of bucks for new ones and your time. Quote Link to comment Share on other sites More sharing options...
Sprntr81 Posted January 10, 2007 Report Share Posted January 10, 2007 tightening the squish clearance will definately raise your squish velocity making power hit harder.dropping it .-024 is a big jump though.Try setting your squish clearance around .040-.045 see how goes. Quote Link to comment Share on other sites More sharing options...
majicmike Posted January 10, 2007 Report Share Posted January 10, 2007 tightening the squish clearance will definately raise your squish velocity making power hit harder.dropping it .-024 is a big jump though.Try setting your squish clearance around .040-.045 see how goes. IMO it is a bit lose but I would not tear down the whole motor to change base gaskets. I like to see it between .040-.050 so you would not gain much. .030-.035 it pushing it making your squish that tight could make problems for your self. depending on your timing it could start to detonate. I had a 7mm cub that was set up a .033 and at high rpms the piston hit the head (dome) still not good.Also it depends on the squish angle of the dome, as well If you get that tight and your squish angle on the dome is different than the angle on the piston it could make things worse for you. I would say if it runs the way you think it should you may want to leave it. Quote Link to comment Share on other sites More sharing options...
glamisaurus Posted January 10, 2007 Author Report Share Posted January 10, 2007 The T-Rex uses flat top pistons and the squish is even across the dome. When I first got the bike it had a paper thin base gasketc ompared to what is in it now. I never had any signs of detonation running a 50/50 mix of 110 and 91. Changing the gasket is not a big deal to me if I will gain some power back. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted January 10, 2007 Report Share Posted January 10, 2007 I agree with Mikey. 40ish is where I like to run mine at. Plus, is your crank welded? Good idea if not already done, 'specially with a "rex on it. I've said it time and time again, I'm a bigger fan of less compression and more timing, it seems to be less harsh on the bottom end. Quote Link to comment Share on other sites More sharing options...
glamisaurus Posted January 11, 2007 Author Report Share Posted January 11, 2007 Crank is welded. How much timing do you get away with? It is at +4 now. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted January 11, 2007 Report Share Posted January 11, 2007 I'd keep the squish in the 40s, run race fuel, and put your timing at 8 to 10. Listen to your motor....but changing from .054 to mid 40s isn't going to raise your compression a ton, probably 10 PSI or so... Quote Link to comment Share on other sites More sharing options...
Fireman-hott Posted January 11, 2007 Report Share Posted January 11, 2007 Daj is right on the compression. You dont wanna get too high or you'll rob your top end RPM level. Too low and you'll rob your bottom end hardcore. Quote Link to comment Share on other sites More sharing options...
glamisaurus Posted January 11, 2007 Author Report Share Posted January 11, 2007 The bike delivers extremely smooth power bottom to top and is used only for duning. I was considering tightening up the squish to try to bring back some hit into the powerband and changing the domes to run straight pump gas. The domes would pay for themselves in two trips if I did this plus not having to deal with race fuel would be nice. An easier option might be to leave it as is and maybe pull the timing back to run pump gas. I did a search and found that 150psi is pretty much the limit as far as compression and pump gas. What do you guys think? I am not out to win races and would like the conveience of filling up at the local gas station. Thanks for the replies so far. Quote Link to comment Share on other sites More sharing options...
creamsickle Posted January 11, 2007 Report Share Posted January 11, 2007 stock banshee compression is 150 to 155. there is no reason why you cant run 91octane pump gas with that compression. even with advanced timing it will be ok. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted January 11, 2007 Report Share Posted January 11, 2007 stock banshee compression is 150 to 155. there is no reason why you cant run 91octane pump gas with that compression. even with advanced timing it will be ok. I've never seen a stock banshee with more than 130PSI out of the crate, and I'm at or within a few hundred feet of sea level... Every bike is different....150 and timing may cause one bike to need race gas, the next bike might be fine with 91 octane... If you're over 150PSI and advance your timing, it would be good/safe practice to at least mix a little race gas, and just listen to your engine very carefully....and check your plugs OFTEN!!! They don't ping/detonate for very long, kaBOOM shortly follows after, and then it gets $$$$ Quote Link to comment Share on other sites More sharing options...
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