WR Valve adjustment/Compression loss

[WR400Fanatic]

i've been working on my WR400F's valves. they were out of adjustment, so i pulled it apart and found out what shims i needed by using a feeler gauge and using the chart in my manual, when i put it back together it felt odd when i'd kick it over, it felt like it had more rolling resistance but less compression (by far less compression). so i thought maybe my decompression release was messing up, but i checked it, so pulled the engine back apart and looked at my cam timing, it was right on and my piston was at TDC (i checked it by taking the spark plug out and using a wire to feel the piston position.) when the cams marks were aligned. i then thought my cam chain tensioner might be to tight so i backed it off till i could have some play in the chain and rolled the engine over, but still no good compression. next i took the cam caps loose, but not off so that i could get some additional clearance between the valves but still no compression. i've rebuilt 4 car engines and one 2 stroker motorcycle engine, so i'm not an engine idiot, but i sure do feel like one right now. i thought my rings might be dried out (very unlikely, it's only sat 2-3 wks) so tomorow i'm goin to oil them a little and see what i get. anyone's help would be much apreciated. ~ brian

 

[YZ165]

Did you check the valve clearance after adjustment?

 

[biglou]

You might have a shim that is not seated correctly in the bucket. If it gets out of its place, it gets cocked and will hold a valve open. Feels like the compression release is pulled. This happened to someone else here. I'll let her add to the story if she wants. ;) I use a magnet on a retractible stick to hold the shim in the bucket during teardown and reassembly. Keeps it right where it needs to be.

 

[WR400Fanatic]

hey, thanks biglou! that was the problem, i went in and put the valve shims in there respective place and it works great! thanks alot for your help!