850-2v parts on a 750-2v motor

[nastyjones]

Ok, I have the parts in my hot little hands & am ready to begin. Who has done this swap? I am looking for info on planing the 850 head & deck. How much? What carbs did you use? The intake ports look a lot larger than the 750. I can see a good HP gain here. I have heard the larger motor had lower compression. True?
Give me your best story.

Paul

[duaneage]

Measure the distance from the center of the combustion chamber on the 850 Head and then measure the distance on the 750 head.

[humhead]

There are two ways to use the 850 parts on your 750. You can get a wiseco 850 kit, bore the 750 block & use the 850 head & carbs. If you also have an 850 block & pistons, you can try & fit that directly to the 750 cases. Either way, there's no need to mill the head or the block. The end result will be a chain drive 850. Use the 750 exhaust cam for the best hi rpm performance.


Terry

[duaneage]

Or you can drop a 1100 chain drive 4v motor in and have a 7-11 bike and be done with it. More bang for the buck.

[nastyjones]

I'm just using parts I have laying around so an 1100 motor is not a possibility. My understanding is the cylinders & head from the 850 will work on the 750 motor with a little machine work so I don't need to buy a Wiseco kit.
I know there is no real need to plane the head & deck but it is an inexpensive way to get a few hp.

All I am building here is a strong street motor. I will de-glaze the cylinder walls, install new rings & valve seals, do a mild street port of the head & beef up the clutch. I want 850 c.c.'s with modern cv carbs & a pipe. The chassis will get a newer style front end & I will be building a longer, wider swing arm to fit fatter rubber. That's it so far.

[humhead]

I know there is no real need to plane the head & deck but it is an inexpensive way to get a few hp.

If you decide to do this, make sure you get adjustable cam sprockets & degree your cams. You'll also want to check piston to valve clearance.

Terry

[rikusa]

"I will de-glaze the cylinder walls,"

READ THIS FIRST

http://www.angelfire.com/biz/snwvlly/bikes/dnthone.htm

[duaneage]

We discussed this guys rant about cylinder honing in a previous thread. He basically tells us that there isno need to do what thousands of people do every year with good results.

Follow his advice at your own peril, after all he is not going to help you tear it apart again.