2000 FC 501 Auto decompression cam spring

Hakan · Dec 20, 2020

Hi
Please look at the attached photo after reading below.

Background:
I had the bike apart forever after breaking an exhaust pivot arm. When I put it back together I think I either did not set the auto decomp spring correctly or it is broken.

With engine off the spring should always keep the auto decomp cam tight against the cam shaft, correct?

It only opens up by centrifugal force when spinning up, correct?

Note, the pictures are with the cam lobes pointing up, so not at TDC.

Also, would this make bike impossible to start? I have clean carb and good spark

Help is appreciated, thank you!
Hakan

heidenberg · Dec 20, 2020

Yes the spring needs to be wound so the centrifugal sledge is tight against the cam and snaps back when pulled. Not too tight or it won't be able to swing.

This will in fact make the bike damn near impossible to start

Taffy · Dec 21, 2020

you need to spend a few dollars there if you can afford it. those valve springs are way too hard. go to dual springs. already, your inlet valves will be distorted.

if you have the half moon decomp then do as above requests. if you have the rowing boat decomp - forget it. they are too soft.

the dilemma is that to upgrade to the 2004 decomp, you need a steel cam sprocket and the end shoulder of the cam grinding down 2mm. almost too much to ask you to spend that when you're ona budget.

the w/p impeller looks like dog **** too.

don't clean your carb, get an easy start kit. renew, refresh, upgrade.

Taffy

2000 FC 501 Auto decompression cam spring

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