I took off the decompressor and am getting a reading a reading of 140 PSI. Is this normal for a 500? I know on the DS650 stock it reads between 180 and 210 psi.

I am tearing into this machine due to it burning oil like no other and smokes way worse than my 2-smoker. Do you think it is due to bad rings? My guess is cracked oiler ring. Or could it be due to valve seats and adjustment?

How do you check the valve lap on these and what measurement should they be at??

Thank so much for your help on this.

 

Valve seats and valve adjustment had nothing to do with burning oil.

 

I kinda worded that bad. I was getting at the lower compression due to the valves, not the oil burning. Sorry bout that.

Well I took the motor apart and there was some small grooves on one side of the cylinder. The rings looked ok but it is so hard to tell. I will have to do a better inspection when I have some daylight and get the parts properly cleaned up and dry. I hope I can only hone the cylinder enough to not have to get a new piston but I will do whatever I need to to do it right. I dont like to take shortcuts at all.

The piston surface was actually pretty clear but the head was very carboned up and the plug was also big time gunked up and that was only after one ride on it, it was a new plug.

 

If you want to do it right go to the first oversize piston and rings and have the cylinder bored.

Do the valves while you are at it and check the timing chain.

 

i would put take one of the old rings off the piston and put it in the cylinder. position it in the cylinder the way in normally rides, and push it down about an inch or so, then look a the gap at the edge of the rings. worn cylinder/rings will give you a large gap.

If you feel lucky, buy a new set of rings. put a new ring in the cylinder the same way. measure the gap with a feeler guage. Now find out what the "piston ring gap" clearance is, a factory manual will tell you, or a service manual. if the gap is still larger than the spec, then you have a worn cylinder. if not, your cylinder is fine and can be LIGHTLY honed, and the rings were what wore out.

if the gap is fine with the old rings, your cylinder is fine and your rings are probably fine, then i would concentrate on the valves being stuck open (not enough clearance) or the carbon on the cylinder head (carbon interfering with valve seating) also, the carbon could be from the oil leaking down from the VALVE SEALS into the intake runner. 140psi really doesnt sound that bad for compression.

when you rode the machine, riding up to a high speed and then letting off the gas and doing hard deceleration, and then hitting the gas again, if it made a puff of smoke when hitting the gas again then it was probably the valve seals.

any other questions feel free to p/m me.

 

I am taking the head, jug, and piston down to the dealer today, who is a very good mechanic on these things just too danged spendy to have work on your stuff. I will have him check it out and get his .02 worth and will report back what I find.

 

Well after a good cleaning and thurogh inspection it apears the jug and piston are just fine. I figure while I got it out I will have the jug cross hatched and put in some new rings. The problem is deffinatly in the head. The valves were extremely tight and the carbon had built up holding the valves open a smidge on the exaust side. So I clened the carbon up and adjusted the valves properly but I am still concerned that the valve seals ( not seats like I said before ooops) are leaking. How spendy is it to get the seals replaced? Is it something someone can do themselves?