Calling Mikuni Tuning Gurus!!!!!!

The correct answer is that all 4 are identical on most motors but they should always be fitted back into the position they came out of.

Unfortunately we don't always remember to do that.
 
They have numbers on them between 50 and 80...was just wondering if that was a sign of soemthing

So I made sure the rocker arms moved freely, adjusted them again and hooked up the leak test on low while i turned the stator bolt by hand and there is a perfect position for each cylinder where there is very nearly zero leakage. I would put it all back together if it werent for the fact that my compression tests were still in the 90s
 
teazer said:
The correct answer is that all 4 are identical on most motors but they should always be fitted back into the position they came out of.

Unfortunately we don't always remember to do that.
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Thanks, haha yeah I cannibalized from another head to get smooth faced rocker arms. No telling where they originally went.
 
The numbers mean nothing significant, it out of warranty ;D
You can't just swap things without re-doing valve clearances though
 
This is interesting, I decided to try and "tune" the tappet clearance depending on compression readings for one cylinder. I found that I could get 120 psi (30 more than when I used a feeler gauge). It seems to be when the intake tappet is spaced quite a bit and the exhaust tappet is touching when fully open.

I don't know what that tells me but I found it pretty interesting.
 
Finnigan said:
This is interesting, I decided to try and "tune" the tappet clearance depending on compression readings for one cylinder. I found that I could get 120 psi (30 more than when I used a feeler gauge). It seems to be when the intake tappet is spaced quite a bit and the exhaust tappet is touching when fully open.

I don't know what that tells me but I found it pretty interesting.
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you can get like, 200 if your rockers are 1/4" off the valves... I don't recommend it though

these engines aren't designed for 0 rpm, so the intake and exhaust open and close far from where you'd expect them to if you were drawing a 4 cycle on paper. the idea of the tappet clearance is basically to put the rockers far away enough to take up any expansion due to heat and still make sure the valves close all the way, and close enough so the rockers don't contact the valves at any significant speed, resulting in chipping the metal
 
Too much clearance will damage tips of valves, but, too little clearance will destroy cam and rockers, probably cam bearings in head as well
 
I'm thinking of putting them back and calling it done, despite what my compression tests are telling me.

BTW I saw a youtube vid where someone did compression test on a royal enfield with kick first and electric start second. The readings for kick were around 100
 
You are not using a Harbor Freight Compression gauge are you? They tend to read low.
 
Hmm. See if you can borrow one for each of your local auto parts stores and check compression again. It may just be gauge error.
 
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