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General Category => Yamaha FJ1100 / FJ1200 Running Problems => Topic started by: TheRadBaron on December 07, 2010, 08:26:27 PM

Title: Cylinder head deck machining
Post by: TheRadBaron on December 07, 2010, 08:26:27 PM
Has anyone had their cylinder head decked?  Mine looks like someone might have been a bit heavy handed while cleaning carbon from around the combustion chambers and I'd like to have it machined a bit before I reinstall it.  The Clymer manual states that the head should be replaced if it's warped and doesn't mention machining as an option.
I don't need to take much material off at all, but I don't want to take any off if it will cause problems.  Anyone here done this?  Thanks.
Title: Re: Cylinder head deck machining
Post by: racerrad8 on December 07, 2010, 08:59:03 PM
I have every head I work on surfaced. I have had them cut down so much the intake seat is cut during the process. No problems doing it; it will raise you compression ratio slightly, but a minimal cut should not have any noticeable affect.

Randy - RPM
Title: Re: Cylinder head deck machining
Post by: andyb on December 07, 2010, 09:47:27 PM
Prolly a good idea to double check your cam timing and p:v clearance afterwards, but beats having a warped head by half.
Title: Re: Cylinder head deck machining
Post by: racerrad8 on December 07, 2010, 09:57:15 PM
Quote from: andyb on December 07, 2010, 09:47:27 PM
Prolly a good idea to double check your cam timing and p:v clearance afterwards, but beats having a warped head by half.


Piston to Valve clearance is not an issue with stock pistons & cams; although it can't hurt to check, since there could be aftermarket parts involved.

Cam timing will be a little retarded as the head got a little thinner and the cams are now close to the head rolling them back slightly.

If the minimum is removed to just clean clean the surface it should not be anymore than .004 and the cam timing will only change approx .5 degrees, so not any real need to adjust to the cam timing.

Randy - RPM
Title: Re: Cylinder head deck machining
Post by: TheRadBaron on December 08, 2010, 06:53:39 AM
Thanks, that's good to hear.  I'll be talking to my machinist.
Title: Re: Cylinder head deck machining
Post by: fjman on December 08, 2010, 07:13:22 AM
QuoteI have every head I work on surfaced. I have had them cut down so much the intake seat is cut during the process. No problems doing it; it will raise you compression ratio slightly, but a minimal cut should not have any noticeable affect.

Randy - RPM

I did this last month.. I'm currently rebuilding the motor. I haven't started the motor yet. Any feedbacks on this? advantages and disadvantages?
I did this because the #3 piston has hit one of the intake valves at high rpm. I had the head resurfaced.