Engine warm up

[Larnold6474]

Having a problem with lose of power on # 4cyl. when bike warms up 10 miles or so, almost acts like plug fouling, but its clean, we found that the valve ajustment its a little tight cannot slide a 1 1/2 measuring tool under it, could the valves not be closing all the way when hot, but when cold, it is. Compression is 120 when cold 60 Hot, Spark seems good, shims are already 2.50mm range do I still have some room to change to smaller ones or are valves getting time to replace? Thanks

[tkent02]

They make shims down to 2.0mm. That sounds like it is your problem, if the compression actually drops when it's hot....

Good for you catching it now, burnt valves would be along soon if you were to let it go.

[BassCliff]

Greetings and Salutations!!

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[Big T]

It sounds less like the valve itself than the adjustment

If you need a thinner shim and can't buy one or get one, the shim club can make you one

[cowboyup3371]

What's a 1 1/2 measuring tool when checking shims?

[Steve]

What's a 1 1/2 measuring tool when checking shims?

I am guessing that is a .0015" feeler gauge.

.

[tkent02]

I read it as a .015mm feeler guage.

[Larnold6474]

1 1/2 thousands feelers gauge that the smallest one I had to try, Thanks for all the info will try new shims in a week or so, let you know how it goes

[cowboyup3371]

It would be a lot easier Larnold if you could post it in the decimal format (.0015") as it's actually printed on your gauge so it's easier to understand. Plus a lot of us use the metric equivalents when working on our bikes (.03mm - .08mm)