Olds Eddie Posted May 1, 2007 Report Share Posted May 1, 2007 (edited) If you have followed my other threads you will know that my shee has just been freshened with new Wisco forged pistons and after rewiring it has refused to start. I did a compression test using a Snap-On compression tester and holding the throttle open while kicking it till the needle refused to go higher. At that point I had 60psi in one and 65 in another. I pulled the head and the cylinder walls looked like you would expect them to with no time on them to speak of. Would a leaking head gasket cause this low compression all at once? Edited May 1, 2007 by Olds Eddie Quote Link to comment Share on other sites More sharing options...
CRAZY-SHEE! Posted May 1, 2007 Report Share Posted May 1, 2007 did you make sure all your gaskets along with your base gasket were correctly installed? did you make sure that when you inserted the pistons your rings sat right? did you torque your head? Quote Link to comment Share on other sites More sharing options...
warbags Posted May 1, 2007 Report Share Posted May 1, 2007 well i could be wrong but if its never been started then the rings have not had a chance to seat so thats why the low compression. Quote Link to comment Share on other sites More sharing options...
blowit Posted May 1, 2007 Report Share Posted May 1, 2007 (edited) well i could be wrong but if its never been started then the rings have not had a chance to seat so thats why the low compression. Don't know your setup buy sounds like incorrect porting on the exhaust port, or your pistons are wrong. By chance, are you running long rod pistons in a stock rod motor? Check your squish clearance and that will help. The banshee should be a zero deck motor meaning the piston comes up to the top of the cylinder at TDC. There is not question that something is very wrong. Even if you comp test a new engine with no break in, ti will pump within 10lbs of run in comp. I would look for welded rings in the pistons as well. This is very common if you have higher comp with pump fuels and some detonation occurs. These really are very few things this could be but rest assured that 60 psi is not going to work. I would also be looking at that comp tester to make sure it is good. Just because it says Snapon, does not make it immune to damage. Just gotta check everything. Brandon Edited May 1, 2007 by blowit Quote Link to comment Share on other sites More sharing options...
Leadfoot350 Posted May 1, 2007 Report Share Posted May 1, 2007 can you start it? If so I dont think it has 60psi Quote Link to comment Share on other sites More sharing options...
Olds Eddie Posted May 1, 2007 Author Report Share Posted May 1, 2007 I had a cast piston come apart due to a bad W/P impellor. I had ridden it very little before I parked it and worked on the wiring. It was running great when I parked it and then refused to start after I did wiring harness. Quote Link to comment Share on other sites More sharing options...
kelly20 Posted May 1, 2007 Report Share Posted May 1, 2007 if you loose a seal on the crank would you loose compression through it or would u just suck a bunch of air in ? Quote Link to comment Share on other sites More sharing options...
Bansh-eman Posted May 1, 2007 Report Share Posted May 1, 2007 umm this might sound dumb... but have you checked your spark? not only does it souund like a you have a compression issue but my first indicator was when you said you worked on the wires and now it doesnt run? Quote Link to comment Share on other sites More sharing options...
sheefreak Posted May 1, 2007 Report Share Posted May 1, 2007 Crank seal would not affect compression readings. Did you just buy new pistons to put in it, or did you have someone check your clearences and match the piston to the bore? Quote Link to comment Share on other sites More sharing options...
J-Madd Posted May 2, 2007 Report Share Posted May 2, 2007 I accidentally installed some 795 series pistons (as mentioned above..pistons ment for a 5mm long rod) once. The cylinders had about 60 psi. It would start first kick, but wouldn't run for shit. Quote Link to comment Share on other sites More sharing options...
blowit Posted May 2, 2007 Report Share Posted May 2, 2007 I accidentally installed some 795 series pistons (as mentioned above..pistons ment for a 5mm long rod) once. The cylinders had about 60 psi. It would start first kick, but wouldn't run for shit. Kinda wondered on that. We have had plenty of customers do the same thing. I am sure the right pistons will get you back up to speed. Brandon Quote Link to comment Share on other sites More sharing options...
dwrracing Posted May 2, 2007 Report Share Posted May 2, 2007 well i doubt this could be it but when a was like 14 i put a piston in a lt250 backwards lol but it actually ran for awhile lol kinda crazy!!!! i never checked the compression on it but thought i would throw it out there Quote Link to comment Share on other sites More sharing options...
Olds Eddie Posted May 4, 2007 Author Report Share Posted May 4, 2007 Thefirst thing I checked when it wouldn't start was the spark. Since it was very weak I installed a new coil. When it still wouldn't start with a strong spark I started looking at fuel and othjer issues. Thats when I discovered that the compression was low on both cylinders. I have pulled the head and the bore looks like a newly rebuild engine should look. Looking at the rings from the exhaust port I find nothing out of whack. It dosen't look like the head was resurfaced when the work was done and since the rebuild was caused by the impellor failure and subsequent piston meltdown I would think that the head is warped. How much can you mill it and still run 93 octane pump gas? Quote Link to comment Share on other sites More sharing options...
blowit Posted May 4, 2007 Report Share Posted May 4, 2007 Thefirst thing I checked when it wouldn't start was the spark. Since it was very weak I installed a new coil. When it still wouldn't start with a strong spark I started looking at fuel and othjer issues. Thats when I discovered that the compression was low on both cylinders. I have pulled the head and the bore looks like a newly rebuild engine should look. Looking at the rings from the exhaust port I find nothing out of whack. It dosen't look like the head was resurfaced when the work was done and since the rebuild was caused by the impellor failure and subsequent piston meltdown I would think that the head is warped. How much can you mill it and still run 93 octane pump gas? You are chasing your tail on this. You should even look at milling the head until you get it running. That is not the problem. Warped heads are very rare because of the annealed state of the head casting. It would leak water like mad. An easy way to see if you are leaking is slowly kick it over with the radiator cap off and watch for air bubbles. As, try another comp gauge. You still think you have something silly happening. Brandon Quote Link to comment Share on other sites More sharing options...
blowit Posted May 4, 2007 Report Share Posted May 4, 2007 Thefirst thing I checked when it wouldn't start was the spark. Since it was very weak I installed a new coil. When it still wouldn't start with a strong spark I started looking at fuel and othjer issues. Thats when I discovered that the compression was low on both cylinders. I have pulled the head and the bore looks like a newly rebuild engine should look. Looking at the rings from the exhaust port I find nothing out of whack. It dosen't look like the head was resurfaced when the work was done and since the rebuild was caused by the impellor failure and subsequent piston meltdown I would think that the head is warped. How much can you mill it and still run 93 octane pump gas? You are chasing your tail on this. You should not even look at milling the head until you get it running. That is not the problem. Warped heads are very rare because of the annealed state of the head casting. It would leak water like mad as well. An easy way to see if you are leaking is slowly kick it over with the radiator cap off and watch for air bubbles. As, try another comp gauge. You still think you have something silly happening. Brandon Quote Link to comment Share on other sites More sharing options...
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