Fit piston and rings on honda gxv390 engine - Honda Vertical Engine 13 HP OHV Recoil Start 1 x 3-5/32 GXV390-DA33

First clean your air filter element, a clog air filter means air will be forcebly sucked from your engine together with engine oil producing white smoke. Or it can be worse, a broken piston ring, you need to change a set of piston ring. do not run your engine if it has a broken piston ring cause it will damage your cylinder block and will cause engine seizure.

Your question is if the pistons and rings off of a VTR will fit your VT. Chances are they will, but IMO this isn't a good idea. If you blew pistons and rings, you should buy new pistons and rings. In which case why not buy the ones made to fit your bike? They should be equally available.

if its a generator No because the engine needs to be set at 3000 rpm constant or it will damage what ever its running

Hi Jim, I know of the pressure relief valve on the oil pump and another fitted into the exhaust system. What is it you would like to know? Regards John

Your description indicates when the engine started the piston wasn't receiving any lubrication or maybe the rings were too tight or both and the engine suffered pre-seizure.

It is well to observe the basics with these sort of things and take nothing for granted. Prior to fitting piston rings it is important to check the ring end gaps. Most popular repair manuals will have diagrams about this and the recommended gap for your engine which is likely to be something like 4 - 6 thou per inch of bore. Quite often the piston ring ends must be filed a little...

In addition it is important to ensure the piston ring grooves have been thoroughly cleaned of carbon and the rings fit well with a side play of 0.0015 inch. A little more is permissible and perhaps as much as 4 thou for the top ring but more than that and the piston should be replaced.

Your problem is quite simple as what you done is rebuilt it with new piston rings i expect ,,but what you dident know is how to go about it SO what you have done is to fit the rings upside down ,,or ,,you have broken the new one putting it in ,,or,, you have got the wrong ring for the job,,or you dident hone out the cylinder the correct way and you took the lip of the cylinder but to much ,,or ,,the piston groove was to big alowing the piston rings to flap as it goes up and down,,and if 2 or 3 ring piston the ring gaps have to be (being air cooled) reset at 4 thou(.0004")(per inch per bore) and all rings have to be staggered,, 4 ringed piston stag to N-S-E-WEST,3 Rings in a Triangle 2 rings Opersit each other and 1 ring any where if the piston isent pined.
So let me know how you get on and work by the above and you will have a good bike again. Ron
New gaskets and (no goo ) to fit them on with and away you go
Let me know how you get on Ron

Take out engine Strip down and replace the Piston rings and check bore if got a ridge in it where the top ring stops then rebore it and fit new oversize rings
If worn bad then also new piston as well thats the only way to stop the oil from coming out of the Breather and give you back the power you lost ..
Easy done so do it and enjoy riding the Buggy

sounds like you might have broken a piston ring. Sometimes a small piece will break-off and cause the loss of compression and if you look down the cylinder you wont see it. But it's enough to cause a problem.