My 1996 banshee was recently rebuilt, due to low compression. I have maybe put 10 hrs on it since then. The problem is 1 cylinder is not getting hot, the exhaust stays cold to the touch, and blows smoke. I have changed plugs a few times, checked the carbs, and the reeds were replaced. I have also checked spark and ignition, all is working to that cylinder. Compression is 100psi in bad cylinder and 115 psi in working cylinder.
Any suggestion before i tear down the motor again.
Thanks

 

You may have a blown gasket.Can you find any where it's leaking around the cylinders?
You did put on new gaskets when you rebuilt it?

 

ya i replaced all gaskets, it seems lke it is running on only 1 cylinder, the exhaust blows white smoke, and lots of raw unburnt fuel and oil, doesnt seem to smell like coolant, ran another compression test only 90 psi now in bad cylinder.

 

If it is on the right side it may be a bad crank seal. If the left side goeas bad it will make it run lean because it creates an air leak. On the right(clutch)side when the crank seal goeas bad it sucks your tranny oil into the cylinder and makes it nun like crap and smoke.

 

You need to be getting consistant and repeatable compression readings. If not repeatable then something is wrong with either your compression guage or your procedure. If your correct compression is 100/115 or especially 90/115 then you need top end work in any case. I believe anything close to or below 100 psi and you should be pulling things down. Running a compression test as soon as you complete the rebuild break-in is good idea. Then you have a good base line to start with. Now you don't know if your previous top end work was defective because things should not wear out in 10 hours.
A leakdown test by a good wrench will tell you if your crankcase seals are toast. I would be a little suspicious of the previous bore work and piston/ring selection. Good luck.

 

oldturtle,
your exactly right, I tore down the motor again last night, the place that bored it must have screwed up, because there is a vertical wear mark above and below one of the exhaust ports, the place that bored it and put it together didnt bore it right and left material on the port which wore the piston rings out, causing blow-by and no cylinder pressure. That sucks i bet they wont refund or bore it either.

 

You should at least take it back and tell them to either fix it for free or give you your money back.Might mention the pistons you bought too.If they are worth dealing with,they will take care of it.

 

id take it back, any good machinist should stand by his work. about getting him to pay for pistons,good luck.