1966nova Posted May 16, 2007 Report Posted May 16, 2007 i have a 01 banshee with 75-80 lbs compression had new weisco pistons and fresh bore still the same problem low compression bike starts fine every time it just boggs a little and at wot feels lean the plugs look great tan colored (the shop told me a crank seal on the flywheel side will cause this????) is that true will that cause low compression please help i am out of things to try... i did kick it 100 times wot and tried 3 gauges...... Quote
5150banshee Posted May 16, 2007 Report Posted May 16, 2007 it could be the crank seal letting air in or could be that the bor is a little to big and the pistons dont fit as tight as they are supposed to. Quote
Screaming Yellow Zonker Posted May 16, 2007 Report Posted May 16, 2007 The crank seal has nothing to do with compression. The compression you are looking for is at the top of the piston not the bottom. When the bottom has compression it is pushing fuel to the top end. normally a crank seal will allow trans oil to be sucked in. How reputable is you engine shop? They may have messed up on honing. Just an idea. Quote
sheefreak Posted May 16, 2007 Report Posted May 16, 2007 The crank seal has nothing to do with compression. The compression you are looking for is at the top of the piston not the bottom. When the bottom has compression it is pushing fuel to the top end. normally a crank seal will allow trans oil to be sucked in. How reputable is you engine shop? They may have messed up on honing. Just an idea. Correct. May want to check your ring end gap as an easy guage as to wether or not the piston and bore sizes are close. If you were actually looking at 70-80 lbs, your bike shouldn't even start. Out of the 5 compression guages I have purchased or recieved as gifts, one works correctly. If all 3 of the testers you have tried are cheapies, better try another. Quote
dawarriorman Posted May 16, 2007 Report Posted May 16, 2007 Correct. May want to check your ring end gap as an easy guage as to wether or not the piston and bore sizes are close. If you were actually looking at 70-80 lbs, your bike shouldn't even start. Out of the 5 compression guages I have purchased or recieved as gifts, one works correctly. If all 3 of the testers you have tried are cheapies, better try another. Yeah, 70-80 lbs your engine wouldn't run. You are kicking the engine over and over until the guage stops rising right? Usually takes me around 10 kicks. If you are, then you need a compressions tester. Quote
flyhighprerunner Posted May 17, 2007 Report Posted May 17, 2007 WELL I HAVE THE SAME PROBLEM MY BIEK HAS 75 PDS OF COMPRESSION WITH 18CC DOMES AND A NEW TOP END....IT TAKES ABOUT 5 KICKS TO START IT BUT IT RUNS SO WITH THAT LOW OF COMPRESSION IT WILL STILL RUN I THINK THAT MAYBE YOU SHOULD GET THE CYLINDERS CHECKED BY MAYBE A DIFFERENT MACHINE SHOP....5150BANSHEE (GOOD LOOKING BIKE BY THE WAY-MET YOU OUT AT PISMO THIS WEEKEND I WAS WITH THAT GUY THAT HAD THE CHEETAH) I THINK IT MIGHT BE THE BORE BECAUSE ALOT OF PEOPLE TALK ABOUT THE CRANK SEAL, THATS THE SAME THING I FIRST THOUGH, WELL I HAVE HEARD THAT IF YOU WANNA CHECK IT PULL YOUR STATOR COVER OFF AND LOOK AT THE STATOR IF IT HAS OIL ON IT THEN CRANK SEAL IS BAD BUT HEY WHO KNOWS RIGHT ALSO DO YOU HAVE MORE SMOKE ON ONE SIDE THAN THE OTHER???? Quote
Animalman294 Posted May 17, 2007 Report Posted May 17, 2007 Yeah, shit when my bike had 95 lbs. it wouldn't start at all. But that was all it took to rebuild, yahoo.............. :biggrin: Quote
1966nova Posted May 17, 2007 Author Report Posted May 17, 2007 update today i used a buddys snap-on gauge and read 125 on both cyls... so i guess it is good so now im trying to figure out the bog and wot feels like runing lean? im going to try to lower rhe needles tommorow? also i need to buy a head to get more compression because obvioulsy the shaved head didnt make any compression gains? it smokes a little out of both pipes and starts on the first kick.......... Quote
blowit Posted May 18, 2007 Report Posted May 18, 2007 update today i used a buddys snap-on gauge and read 125 on both cyls... so i guess it is good so now imtrying to figure out the bog and wot feels like runing lean? im going to try to lower rhe needles tommorow? also i need to buy a head to get more compression because obvioulsy the shaved head didnt make any compression gains? it smokes a little out of both pipes and starts on the first kick.......... What I want to know is, was there a schrader valve at the end of your cheap tester? The part that screwed right in the head? I am thinking that was the problem. Pressure gauges are generally pretty accurate. The problem with many of the testers is not the gauge but the valving 125psi with a head mod is low if you have stock porting. Smoking on a two stroke is normal. Brandon Quote
1966nova Posted May 18, 2007 Author Report Posted May 18, 2007 it has mild port work to the exhaust Quote
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