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· Banned
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Discussion Starter · #1 ·
Here's what I wanted to do this winter...Have a 907cc/JE piston big bore done and help it breathe via a '92 750 valve head. So I bought '86 & '92 valve heads on ebay for dirt and found a second cylinder head too. So I ship off the '92 VH and CH to the machinist and I get a call with two questions...

"when are you gonna send us the top case so it can be machined"

...dammit...I didn't read the instructions but they're right...907/955 big bores have to have the top case machined...argh. <>

I don't suppose there is a way around that total dissasembly of the bottom end for that there?

The other question they asked...

"were you aware the 91/92 valves are prone to tossing shims and this results in evil things to the motor"

Any anecdotal info on that claim? Is it likely? I thought the more modern design is the "better" one. Last fall I asked if I should flow bench/port the '86 head and Jeff & others suggested the '91/92 VH 'cause it is ready to take the 38mm carbs I have.

WTF am I to do? Bite the bullet and rip it apart totally? It's only money but now it is gonna cost the same $$ as a 1100 motor. <>

· Registered
109 Posts
I now about 1100 motors but not to much on 750's.
I bulta 91 1100 shim head we used ape titanium retainers , there much deeper tan stock. I had to grind some of the rocker to fit over the retainer.
no chance of shim spitting wyh the retainers.
On the upper case it does have to be totally dis assembled. When I bored a top case for a 1340 block it blew throu the oil jackets. I had a expert aluminum welder weld the hole and we had to grind a small part of the sleeve.

good luck
I pesonally would rather build a 1100 motor you can make more hp for the same $$ as doing the 750.

· Registered
678 Posts
This is what I have heard:
Sorry, but you will need to take the case apart. The bigger piston needs the extra clearence at the bottom. It's a pain in the ass but needs to be done.
On the head I have heard that it spits shims. I know because of that design it will hold revs higher and longer than previous models. I'm sure there is something out there to help keep the shims in place.
This will be a nice engine when you are done.
Keep us informed of your progress, I will be doing something similar in the next couple of months.
Good luck.
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