Rider needs advise on dinosaur swap

[nastyjones]

Seasons Greetings to all,

I realize it's nearly Christmas & everyone is busy with their own lives. It's also winter, & not a lot of you are thinking about their motorcycles. However, if some of you older riders could find a few minutes to reply to this letter, it would help me a lot.

I know this mod was common years ago & I'm trying to find someone who is familiar with using 850 parts on my 750-2v motor. I have tried to get a thread started on this subject a few times but it seems not a lot of people remember how to do it & the thread has died. I have test fitted the 850 cylinders on the 750 crankcase & it looks like I just need to grind a little bit off where the liner touches. I have many questions that are best answered by someone who has done it before & I've figured maybe this forum is not the best place. So feel free to PM me. Maybe this is because such a mod. is done so rarely anymore, I don't know.
Anyway, could I beseech someone to reply ( PM me if you like) who has a solid knowledge of the details to complete this job. If you are still running this combo that would be even better.
All answers appreciated.

[Carter Turk]

Why not just go with the whole 850 motor and modify the engine brackets if need be. Just curious, I don't know anything about the parts swapping.

[SqDancerLynn1]

I remember the post, it was done successfully without any major work. I don't remember the specifics. I thing you need to use the 750 cam sprockets, NOT sure if you still used the cam chain idler & as you have found out some grinding on the cylinders, may need to use the 850 cam chain ????. YOU just need to test fit everything

Swapping the whole 850 motor is not possible it's shaft drive

[duaneage]

I think an 1100 chain drive is a better swap, or else a bigger bike could be bought. After all the work to make it happen your still not going to make as much power as a 850 or a 1000. These bikes are pretty maxed out for performance as they are, the only way to go faster for real is to go bigger. A set of pipes, ignition upgrade, pods and rejetting would be easier and cheaper than a head swap. If you want more acceleration change the sprocket gears for immediate results.

Just my opinion, don't flame me.

[Carter Turk]

Forgot about the shaft factor.

[nastyjones]

Well Sqdancerlynn,

My understanding is that the cylinders fit w/a little grinding. As far as the rest goes the motors are the same except for the shaft drive, only the bore is different. Same head (although the inlet rubbers are different since the 850 uses cv carbs) same cams, same timing chain. I think it's mostly a drop on job.

[Hap Call]

Well Sqdancerlynn,

My understanding is that the cylinders fit w/a little grinding. As far as the rest goes the motors are the same except for the shaft drive, only the bore is different. Same head (although the inlet rubbers are different since the 850 uses cv carbs) same cams, same timing chain. I think it's mostly a drop on job.

It sounds similar to the fitting of an 1150 top end on an 1100 case....

Hap

[nastyjones]

If you can add any info to this post, please do. Nobody seems to remember this swap.

Don't let this thread die!!

[tkent02]

Did you ever put the 850 top end on the 750?
I have all the parts, just wondering if I want to dig into it.
Thanks,
Tom