Cylinder Head Resurfacing

Has anyone had a cylinder head resurfaced on a 86 87 vfr 700 or 750 ?

 

I havent, tho the thought has crossed my mind. One word of warning that I was given is to watch REAL closely as to the amount of metal you take off (if you do opt for doing this), as shaving the head lessens the valve to piston clearance. You might wanna do the silly putty test (take the head off, cover the top of the piston in silly putty, reinstall the head with head gasket, and manually turn the engine over, letting the valves all open fully and come as close to the piston as they normally would during running conditions) to check the clearance between the valves and pistons that you have now to see if you even HAVE the room to shave your heads.

by the way, if you do this, keep us all posted on your project. ppl on this board are always interested in mod projects like this.

 

I took 0.018 off of mine. My concern was the gap in the gear drive and the cams. Spent quite a bit of time measuring and thinking aboot it before making the cut. The whine from the gear drive is much louder now.

 

ooooooooooooooo, good point, Toe. I'm glad ya chimed in on this one. if 18 thousandths of an inch is what you took off and yours is safe and sound, would you say that 10-15 be a safe metric to use (just to err on the side of caution). would 10 even be worth the trouble? what kind of compression do you get out of your cylinders now?

 

head resurfacing

' I bought an 86 750 for the engine. I did hear the engine run and did a compression test to check the condition or the engine. compression was 200,200,200,180,.run a test on my 700 and it was150 on all four cylinders,hum! I decided to pull the heads ,replace the valve guide seals and and lap the valves ,maybe a little rust on the valve seat.the bike had bet sitting for a while. as I was removing the head I noticed that this engine had been apart before.The cylinder heads had been milled,could not tell how much gut it had a gouge across the sealing surface of the head.Took it to a machine shop and the removed .003 more off the head.I will have to check the lash in the gear drive before i do a total assembly.
In 86 I bought the first vfr in this area and sent the cams to Kas Yoshima and he had them modified. I do not believe valve to piston will be a problem with the stock cams .

I do appreciate any information or opinions


Thanks
Gary.

 

What's the purpose? Higher compression? A much better way would be some aftermarket pistons. You might want to do the math, cutting the heads doesn't bump the compression as much as you might think. Plus it doesn't have the aforementioned down sides!

 

What about 1mm oversized valves, Jamie? I want to say I've heard of these being used, but I haven't heard first hand accounts of their use (with stock height pistons, of course)

 

Did not look to mill the heads to increase the performance,just to solve a problem i found.The heads had been milled by the previous owner .high performance pistons are not readily available for this motor.I have had custom pistons made when i owned competition cycle in lexington. I have also had cylinder heads milled with good results in some applications, just depends.I do agree with you that it would serve little improvement in this application,I do not recommend it.very little gain if any.just wanting to make things right before i do the install,

thanks,
Gary

 

If you decide to go balls out I have a set of cosworth high compression 1mm over opistons from my old motor that will never go back together again!

 

Also, if too much has been taken off the head you can always call Cometic Gaskets (google it) and they can make a custom gasket in whatever thickness you want for a pretty reasonable price.

Found out about Cometic through some other two stroke race bike owners as they end up with machines that have had cylinders or cases machined to change deck height but can't find the old owners who did the mod to discuss what the set up is supposed to be. Cheaper to run a thicker base gasket to set back to stock setting or whatever it is you desire.

Just a thought.

BZ

 

just how high is the compression on those pistons? have they ever been run before?

 

Put a little over 20k miles on them, it was '95 when it came back apart due to valve issues and a main bearing was about to spin. I really can't recall the compression ratio. Will try to post a pic later or tomorrow. getting ready t head off to work.

 

They were 13 to 1. They do require the cases to be bored and 700 rods.

 

Ahh, yes. Apparently your memory is better than mine. And boring out that case is a pain in the ass.

 

Well since I've already procured the rotating assembly out of a 750, I'm going to to ahead and stick with my original (yet very long term) plans of an 840cc mill for the old girl. Maybe somebody can pick up those pistons and have themselves one hell of a little....hell, i dont even know what a 700 with a 1mm overbore would be, but the 13:1 compression would make it one fun little toy!