750 vs 800 heads on 750 motor with 800 topend.

rustman

rustman

Active member
Just wondering if anyone has any experience with putting 750 heads vs 800 heads on a '93 with an 800 topend. I am in the process of putting an 800 topend on my '93 and am curious which route to take in regards to the heads. Motor will have a cylinder lift done at the same time. Will have 800 pipes and CDI.

thanks,

Rustman
 

Thats what I run.I machined 750 heads 25 thou to remove the step and then machined squish band out to the same diameter as the 800 heads.I also run a .060 base gasket.This is a great way to regain lost compression from doing the cylinder lift.
 
I was just gonna use a .039 base gasket and peel back a layer of head gasket to get comp back. I still want to trail ride this sled when it's done. I am trying to stay away from machining costs if possible.
 
What pistons are you using, as the 800 pistons will not fit the 750 crank?

rustman said:
Just wondering if anyone has any experience with putting 750 heads vs 800 heads on a '93 with an 800 topend. I am in the process of putting an 800 topend on my '93 and am curious which route to take in regards to the heads. Motor will have a cylinder lift done at the same time. Will have 800 pipes and CDI.

thanks,

Rustman
Click to expand...
 
I didn't realize you were putting 800 jugs on your 750 until after rereading your thread.I run the 750 heads on my 95 800.Could you tell me about the bushings you had made?Do they fit tight in the piston? I have only seen pics on the Hauck website.
 
The are tight in the piston, haven't tried a pin in them yet. I am waiting for base gaskets to come in before I tear my motor apart. A fellow member here sent me a pair and I went to a local machine shop and had them copied 8 times. As soon as I open the motor up and get the 750 pins out I can let you know how they fit. I believe they are designed so the circlips still go on. The bushings themselves are designed with a small lip to keep the piston pin from just sliding through it.
 
Update, I got it all together and everything went together just great. Pins fit nice in the bushings, so i have finally put an 800 topend on a 750. Went with .039" base gasket, single layer of head gasket, although the head gasket I used was from winderosa. They measure much thicker than stock gaskets so by using one layer of the aftermarket I ended up with just under 2 layers of OEM thickness. I had shaved heads already on my 750 previously which I was not aware of, so I put them back on. I used the old 800 pistons I had and installed new rings. First compression test was 130psi. With a few drops of oil down the cylinders that number went to 140. I think I should be around 150'ish after rings seat. If you want some pictures of the bushings, better than the hauck website, I can send a few along to ya.
 
Depending on your squish and at 150 lbs compression you might have to run race gas or mix race gas in. That's pretty stout for a trail sled. Put some pics up pal. Would like to see this.
 
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