Join Date: Sep 2005
Location: Base of the Rocky Mountains
Thanked 499 Times in 420 Posts
ATV: ThunderLemon 1000
2008 Mileage: Depends upon Fa
Here ya go.
I first remove the front plastic to give extra room and light for the project. Clean every thing off, you don't want dirt and crude falling into the engine when you have valve covers off.
Two views of the tear down.
You may not need to tear off the plastic, when adjusting the 400 M I had more room then I do with the 650. It is good time to clean every thing out and inspect frame for cracks and everything else for leaks. when tore down to this level, access and lighting is much better I think.
I also remove the rope starter cover to access the dogs, much easier to turn the engine over. Just place a pry bar in the dog teeth to turn it over. Also remove the spark plug so you are not fighting compression. Remove the valve covers for intake and exhaust. Don't loose the O-ring seal on the covers.
Rope starter off exposing Dog teeth
Remove the inspection port plug to view the timing mark and align the mark up in the window. Make sure you are TDC on the compression stroke, not TDC on the exhaust stroke, if on the exhaust stroke, the exhaust valves will be depressed, and valve open. when on the compression stroke both intake and exhaust will have a little play or clearance if valves are not too far out of whack.
TDC timing mark in center of inspection plug.
The engine must be cold, at room temperature. It doesn't matter if you adjust exhaust or intake first. I use a go-no go method when setting clearance, if my desired clearance is 0.005" I can slip a 0.004" in feeler gauge in with a little or almost no resistance, A 0.005" feeler will have some resistance and a 0.006 will not fit at all. This would result in a tight 0.005 clearance. When using your feeler gauges, keep the gauge flat in the gap or at right angle to the valve stem. There are 2 exhaust valves opened by one rocker arm, make sure both valves are set at the same clearance.
To adjust loosen the top lock nut and turn the center stud one way or the other depending if you are too tight or too loose, snug the lock nut and re-measure, repeat as necessary. When measuring your final setting the lock nut must be tight When happy, make sure lock nut is tight, reinstall valve covers and your plastic, rope starter and you should be good to go. If you do not have a rope starter I still recommend you take the left side cover off and turn the engine over with a socket wrench, much easier to align the timing mark.There are 2 intake valves opened by one rocker arm, make sure both valves are set at the same clearance.
I'll spend about 3 hours on a job like this, most of the time is just preparing for adjustment, cleaning and putting everything back together. You can get a valve adjustment tool from your dealer that makes adjusting a little easier (no feelers required) but I trust the feeler gauges myself for better accuracy.
The method above should be the same on nearly every cat, They except those that have shims that you use to adjust clearance. I'm not sure about the 366, DVX or the 300's 250s or smaller, they may be the same as the 400's, 500's 650H1's 700H1, and Tcat or may use shims. When on a 2 cylinder engine, there are two TDC timing marks, front cylinder and rear cylinder, do each independently.
When I took these pictures there was about 350 miles on the H1, some of the valves were a little looser some were a little tighter, (top and bottom of recommended range) But all were still within recommended range of 3 thousands of an inch. When I was done, all valves were set exactly in the middle of the recommended range. I don't know if the clearance changed during break-in or if it was just a mediocre job adjusting at the factory where they just set them close but not equal.
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Last edited by Wyo_H1_Cat; 04-06-2012 at 01:10 PM.