Birthday Present

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dougmatson

dougmatson

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Today is my B-day and guess what, the UPS guy showed up with this big box from JS Motorsports. Jim really gives good presents! I started this a few weeks ago because the engine was smoking a lot on start up and next thing you know the case is split. Good thing I did this because I found some very big problems that were about to destroy the motor! Any way I will have some questions in the next week or so about shimming the crank and other things. Big thanks to Jim for help in ordering these parts. Now back to my Birthday cake.
Birthday Present
 
I just gonna have to get more money 'cause I sure want those same parts for my bikes, I can't afford them right now and I'm really jealous dougmatson! :) Cj
 
Oh my is that ever a gear head's XXX rated naked parts sight! Please consume them responsibly .
 
hobot said:
Oh my is that ever a gear head's XXX rated naked parts sight! Please consume them responsibly .
Click to expand...

But irresponsibly would be so much more fun :mrgreen:
 
Wish I got brithday presents like that, good luck with the rebuild and let us know how it goes, do you need a test rider :twisted:

Ashley
 
Funny how guys will look at a table of parts like that and just ogle them, Beautiful. Those pistons, those rods, valves, etc.

A chick looks at that and it's like....mehh. but throw a pair of shoes in front of her and it's a different story.

Glad I was born a guy.
 
Wow Doug, the whole enchilada, very nice mate. I have just the pistons and rods from JS. And really please with the reduction in vibes. Makes an 850 more like a 750 for vibes. I have the Gapless rings too, you will find kicking her over requires a firm and full kick, no pussy footing or she will bite back.
Shimming the crank is not too hard. If you have the mains still on the crank and in the cases, reassemble the crank into the cases for a dummy set up. And check endfloat.
The manual does not clearly show the shim, but you can shim either on the crank or in the cases. The timing side bearing fits on the crank and in the cases are looser then drive side, so do your shimming on the TS. Old Brits is a valuable source for information and also he supplies a shim suitable for shimming the outer race in the case. Norton supply a smaller shim to go between the crank cheek and the inner race. Caution the inner races are pretty hard to get on and off the crank, you need a really good bearing spiltter. So it is easier and safer to do your shimming at the case.
check out Oldbrits site!

Oh when you fit your fancy new pistons, and aren't they sex? you need to get the ring gaps orientated correctly, I found it easier to fit the pistons complete with rings into the barrel first, then fit the barrel/piston assembly to the rods. Obviously fit the inner gudgeon pin circlips first. Get some spacers to hold the barrel of the cases, whilst you fit the gudgeons. Some short 3/8 unc bolts in the outer barrel stud holes works nicely.

Did you get a copper shim gasket to fit between the barrel and the crankcase? Jim has some dimensions for the piston crown to top deck height. You can fit he pistons without rings and check how low the pistons are in your barrels at TDC This will give you and ideal of the compression ratio you will end up with. I went for 9.25:1 and it runs very nicely. I used a shime to get the height I wanted. Jim has them.

Cheers richard
 
Thanks, thats some of the stuff I needed info on! I have used Old Britts quite a bit but will look at the info on shimming. The crank had no shims and was at the max tolerance of end float, .0024. The mains seem fine but i am going to replace them, both were rollers. I am glad I took it all the way down because one rod bearing was shot and the the bolts that hold the crank together were all just hand tight. I got the bike with less that 10K miles on it, had good oil pressure and 170lbs compression but in sad shape so when I restored it I left the motor alone except for polishing/painting things. Now back to my birthday cake.
 
Happy Birthday and celebrate the good parts from JS Motorsports! What type of cam you have chosen?
Good luck with the compilation of the engine. I am in the same situation and will follow the project with excitement. :D
 
Thanks for the B-Day wishes. The cam is the stage 1. I chose that after some discussion with Jim, this will give a good broad power increase and keep the nice idle.
 
Good presents. I kick myself for not putting in the light pistons and rods on my rebuild.

Dave
69S
 
stockie2 said:
Wow Doug, the whole enchilada, very nice mate. I have just the pistons and rods from JS. And really please with the reduction in vibes. Makes an 850 more like a 750 for vibes. I have the Gapless rings too, you will find kicking her over requires a firm and full kick, no pussy footing or she will bite back.
Shimming the crank is not too hard. If you have the mains still on the crank and in the cases, reassemble the crank into the cases for a dummy set up. And check endfloat.
The manual does not clearly show the shim, but you can shim either on the crank or in the cases. The timing side bearing fits on the crank and in the cases are looser then drive side, so do your shimming on the TS. Old Brits is a valuable source for information and also he supplies a shim suitable for shimming the outer race in the case. Norton supply a smaller shim to go between the crank cheek and the inner race. Caution the inner races are pretty hard to get on and off the crank, you need a really good bearing spiltter. So it is easier and safer to do your shimming at the case.
check out Oldbrits site!

Oh when you fit your fancy new pistons, and aren't they sex? you need to get the ring gaps orientated correctly, I found it easier to fit the pistons complete with rings into the barrel first, then fit the barrel/piston assembly to the rods. Obviously fit the inner gudgeon pin circlips first. Get some spacers to hold the barrel of the cases, whilst you fit the gudgeons. Some short 3/8 unc bolts in the outer barrel stud holes works nicely.

Did you get a copper shim gasket to fit between the barrel and the crankcase? Jim has some dimensions for the piston crown to top deck height. You can fit he pistons without rings and check how low the pistons are in your barrels at TDC This will give you and ideal of the compression ratio you will end up with. I went for 9.25:1 and it runs very nicely. I used a shime to get the height I wanted. Jim has them.

Cheers richard
Click to expand...


stockie, is the reduction in vibes felt at low RPMs?

The reason I ask is that my stock mK3 850 is as smooth as a new car above 3000 rpm, no discernible vibes to the rider, dead solid clear mirrors at 75 on the freeway, although I know the engine is vibrating some. If the motor ran smoother at this speed I cant see how it would make any difference to the rider, on my bike at least. A smoother running motor at idle and low RPM might be nice, tho most bikes dont spend much time idling or in that very low rpm band. I guess that was what Dr. Bauer and Bernard Hooper had in mind when they first devised the isolastics.

Glen
 
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