200x Smoker - Head gasket possible?

[ps2fixer]

So here is the story... I have 2 200x machines both 85s, one engine smokes, other does not, but had bad exhaust studs and a poor attempt at fixing them. I already planned on putting the head on from the smoker on the good runner, but I wanted to check why it was smoking too since I plan to part it out.

From my understanding smoking could be caused from the following:

Worn out rings (should smoke more when you get on it, matches this case)
Worn out valve stem seals (should smoke more when you have high vacuum, aka engine braking)

Never heard of it being a head gasket, but is that possible?

When I pulled the smoker apart and checked the ring gap in the cyl, it looks compareable to the other one, and the cylinder looks better on the smoker (less deepish scratches). Piston did have a couple a nicks on the top but I don't think it effected the top ring. The top end on this engine looks really good, cam and rocker arms have less wear than the other engine, infact i'm using them on it because of that. I'll be changing the valve stem seals anyway since I have them. The head gasket pulled apart like typical, but it seemed it didn't fight so much where the timeing chain goes. Actually the gasket is kind of weird, looks like it had hondabond on it, and the gasket was a rubber like material. The other engine had a steel gasket, but it don't look to be for that machine, even though the sealing points are correct. It has 3 tabs that come out with copper like seals that looks like it should seal up oil paths or something.

Anyway... I'm half tempted to assemble the smoker engine with a 185s head and up that I have and attempt to reuse the cyl and piston to make the 2nd machine a beater. Then if it smokes I know it is the rings lol. I'm not too worried about pulling it apart again later if it needs rings etc.

EDIT:

Oh I should also say the smoker did have less compression, didn't see any oil coming out of the crank case vent.

[atc007]

99% of the time on ATV engines. Smoke is coming from cylinder seal. They won't push oil out the breather,they will smoke out the nipple on the case if you remove the breather hose. The smoke dissipates by the time it gets back into the air box. Measuring your specs is the only way to tell exactly where you are,but I would certainly hone the cylinder of your best top end,put new rings on that piston,new valve seals as you said,And you will have a very long lasting top end. That will NOT smoke at all.

[shortline10]

Easy way to tell if its the piston rings or cylinder out of round causing the smoke IS to look for blow by on the piston it self between the rings . If their is any black / brown below the top ring on the piston you have blow by .

[ps2fixer]

That was the plan, figured I could throw the 2nd engine together for a beater, the good one I'm going to be reselling to buy more projects :). I have gaskets etc for other 200cc hondas, and my research suggests they basically all use the same sized valves and the heads all interchange (atleast the gasket kits I have 200es). I'll have to find my feeler gauges and check the ring gap. If they are in spec, I don't think it would need to be replaced, but then again this is basically the first engine "rebuild" I'm doing (more of a head swap lol).

Next up I have a 250sx that needs the head/cam replaced, has the ticking of almost like a timing chain, but the last owner (he rebuilds and races bikes and is a friend) said that it is the cam because someone installed the oil filter backwards in the past. It runs much better than my other sx, and is the beater :D.

[ps2fixer]

Easy way to tell if its the piston rings or cylinder out of round causing the smoke IS to look for blow by on the piston it self between the rings . If their is any black / brown below the top ring on the piston you have blow by .

Good advice, didn't know that before! I don't recall seeing any black, but I wasn't looking between the rings. The smoker's piston did have more wear than the good one, but the good one's cyl looks worse (scratches), weird how that happens.

I should add this to the discussion, the odd carb experence these gave me. http://www.3wheelerworld.com/showthread.php/157789-2x-200x-pick-up-odd-carb-problems....

I was expecting to see an aftermarket piston in the smoker, or something different, however both pistons are identical with the same stamping marks etc.

EDIT
Also, I don't have the proper tools to check the cyl bore for roundness, spec etc. Going to check for the blow by and go off from the ring gap specs.

[shortline10]

Need to mention that even if the rig gap is within spec the tension of the ring to the cylinder might not be enough so replacing the rings with new is best .




That was the plan, figured I could throw the 2nd engine together for a beater, the good one I'm going to be reselling to buy more projects :). I have gaskets etc for other 200cc hondas, and my research suggests they basically all use the same sized valves and the heads all interchange (atleast the gasket kits I have 200es). I'll have to find my feeler gauges and check the ring gap. If they are in spec, I don't think it would need to be replaced, but then again this is basically the first engine "rebuild" I'm doing (more of a head swap lol).

Next up I have a 250sx that needs the head/cam replaced, has the ticking of almost like a timing chain, but the last owner (he rebuilds and races bikes and is a friend) said that it is the cam because someone installed the oil filter backwards in the past. It runs much better than my other sx, and is the beater :D.