98 600 valve seal or rings?

Cougarsquatch · Feb 15, 2011

My 98 600 smokes at start up for a couple of minutes then stops, but still smells like burnt oil. I always have to ride in the back. As for the back story, I bought it in September from a coworker for $500. He was in a bind for cash and never rode it anymore so I swooped in. It was in good running order, started fine, ran ok. I cleaned and rebuilt the carb, ran great. Changed the oil and put new OEM style muffler to replace the God awful loud and hideous car muffler that was a temporary replacement for the one he sold. After the oil change and muffler replacement, I ran it to the hunting lease about 3/4 mile from the camp (kinda high speed), when I slowed down to make the turn, it started backfiring pretty bad and shut off. I restarted it and ran it the rest of the way with no problems. From then on it smokes like I stated in the beginning of my post. It hasn't backfired again even when going fast.
He told me later that it was bored to 675 or something in that range.
Could it be that I restricted the exhaust flow with a muffler designed for a 600 and caused a comperssion issue that messed up the valve seals or rings?
Could I have maybe overfilled the oil and messed up the valve seals, I have tried changing the oil again and paid extra attention to the refill (per the manual) only a couple of days after the problem started, it continued.

While I have your attention, my oil temp light doesn't come on when I turn the key on. And possibly a stupid question, does the 600 have a brake light or just a tail light?

How hard is it to work on the top end if it is my valve seals or rings? I am no mechanic but I can hold my own with the right instruction. I do have the service manual.

Sorry for the long post, I was trying to give the most info possible. Though I'm sure I left something out.

Thanks for reading

keith20mm · Feb 15, 2011

The 600 has both tail and brake light. Check the bulb.

Oil temp bulb is burned out. Both should come on when switch is turned on, before start button is pressed.

Rings are probably shot. And if you do a ring job, just go ahead and do a valve job. The valves are probably in fine shape, and whoever regrinds the seats and valves will know if there's any damage, i.e., when grinding the valves, they will wobble in the grinder chuck.

It is very easy to work on the cylinder, head, rockers... all very straight forward.

The things to have ready are a motor gasket set (cylinder base and head gasket), some Permatex Ultra Black RTV, a left stator cover gasket, and a valve seal set (of 4). Probably should also have a new timing chain. You might be able to get away with the existing exhaust header gaskets, but those come in the top end set, anyway. Gasket set comparisons are shown under my handle on this forum.

The entire procedure is documented on this forum, on my user handle.

The oil temp light bulb is held in a little rubber thing that you can push through from above, to below.

The bulb can be replaced with an OEM bulb or one from radio shack. The RS bulb has a slightly different length, but will still work just fine.

From Harbor Freight, get the 1/4" drive torque wrench, and 1/2" torque wrench, and, especially, the 100 piece security bit set.

The torque wrenches can be borrowed, but it is important to adhere to service manual specifications on torque.

Nothing on the right side of the engine needs to be touched.

Cougarsquatch · Feb 16, 2011

Thanks Keith, you are a beast of knowledge.

98 600 valve seal or rings?

Our Vendors

Top Contributors this Month

Recommended Communities