150cc BMS valve problem

[taz001]

Well I was looking at the Head/valve cover gasket today on my 08 BMS:



to see if it was like the one on my 07 Xingyue. Was different, probably the correct one. Well I'd done a compression check to find there was no compresion. Tried the wiggle test for valve clearance, and the intake was really loose. Took a look down the intake port to find it'd dropped a intake seat. What typically happens in this case? Think it'll need a total rebuild? Soon as I finish up the Xingyue I'll be pulling this one apart.

[blueboy5000]

set the top valve (intake) to EXACTLY .004" and the bottom to .005" inches. "wiggle test" is completely inaccurate, and should not be used to denote proper valve rocker lash.

In the case of the "dropped seat", replace the entire head with an assembled new head and new head gasket, but be sure to clean the top of the jug with a light abrasive (cookie wheel) and check the top of jug with a machinist straight edge. Chances are, that you may have ring or other inner cylinder damages as well if you have no compression. So in reality, the safest bet is an entire new top-end. (if you are daring, now is the time for a BBK)

[qwertydude]

I hope you don't run with the engine shroud removed like the pictures. That can cause your valve seats to drop out along with other problems. The shroud is needed to direct cooling air around the engine and without it your engine will be toast in short order.

[blueboy5000]

Originally Posted by qwertydude

I hope you don't run with the engine shroud removed like the pictures. That can cause your valve seats to drop out along with other problems. The shroud is needed to direct cooling air around the engine and without it your engine will be toast in short order.

Good point Qwerty, NEVER run your engine without the cooling shroud.

[taz001]

Well as for he shroud that's the way I bought it. The PO was going to "fix" it, took it apart, decided it was beyond his abilities(I guess), put it in the corner of his garage, and bought another one. Then listed this on on craigslist, and I bought it.

As for valve clearance, a quick wiggle of the rockers can tell alot. When I wiggle the rocker and it has 1/2" of clearance there is a problem. I set the valves on my Xingyue using the wiggle test, then checked the clearance with a feeler and it was just right(.004" on the intake, .005" on the exhaust)believe it or not. No brag, just fact. The correct clearance can actually be calculated via turns on the screw(threds per inch times amount of turns, or in this case amount of turn being about a quarter of a turn for .004", and one third of a turn for .005"). After setting the clearance, usually I do verify with a feeler gauge.

[blueboy5000]

Okies. I just use the feeler gauges to begin with, as I see no point to doing additional redundant work, but whatever floats your boat man.

But 1/2" is really bad, your head is smoked at that point (these gy6 heads aren't very good quality). I suggest checking the low end as well, as if this damage occurred while the bike was running it could very likely have damaged the low end as well.