Trouble mating the 860 crankcase halves

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darmahbum
Cucciolo - the Lil Pup
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Joined: Tue Dec 03, 2019 1:27 pm

Trouble mating the 860 crankcase halves

Post by darmahbum »

Hi all - I am hoping to build up the engine for my '78 Darmah this winter which was disassembled to replace the crankshaft and kick start shaft, and renew the pistons and cylinders.

I am at square one with checking for crankshaft endplay.

The problem is that the crankcase halves will not mate up/close all the way. These are the original crankcases and were separated a few years ago and stored carefully. For the life of me I cannot get them to mate all the way together. I tried some judicious use of a rubber mallet and even some pretty hard blows with no luck. The 3 locating dowel pins are in their proper holes and these are original to the crankcase. The thing that is throwing me off is that I have another set of crankcases that go together without much wrestling so I am not sure what is causing this. I was first trying it with the crankshaft in place with no luck and then removed it to see if that was blocking them from going together but still no luck. I am only able to remove one of the locating dowel pins to try see if they are the culprits - the others are not budging so I left them alone - so i am not sure if the halves are getting "cocked" by them. Therer are no other obstructions in either case half.

Questions:
1) What is the correct method to draw the halves together - should I install all of the bolts (large and small) and draw them together by tightening? I did not try this as I am not sure if it might cause some damage.
2) In order to check the crankshaft endplay I know that the gasket must be in place along with the crankshaft and I will get the 1st swipe at endplay with the shim I plan to use hoping to get lucky or make adjustment - but should the other shafts (trans, shift drum, kick start shaft) also be in place? One thing when doing this is that's very easy to destroy the gasket - and it is not cheap.

Thank you in advance.
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Gardner
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Re: Trouble mating the 860 crankcase halves

Post by Gardner »

The kickstart shaft has to be rotated 45° while sliding cases together for the ratchet lug to engage the stop.
It's easier to check crank end play with just the crank in the cases. Check that your bearings slide on the crank without being too tight.
They also have to slide into the steel case housings and not be too tight. Try slipping the crank in each half first. Wipe some motor oil
inside and outside of the bearings and the housings if it's all dry. You really don't want to tighten the case screws to draw the halves together because chances are you will need to alter the shim size. Best to assemble with under size shim so you have some movement to measure.
If an outer race sticks in the case housing and the inner race sticks on the crank and you pull the cases apart, bearing balls and
obscenities will fly everywhere.
1978 SD Darmah
1979 SSD Darmah
1981 900SS
2017 Desert Sled
1982 Bimota HB2
darmahbum
Cucciolo - the Lil Pup
Posts: 3
Joined: Tue Dec 03, 2019 1:27 pm

Re: Trouble mating the 860 crankcase halves

Post by darmahbum »

@ Gardner - thanks for your input - I will heed the advice you've given - however the issue is that the bare cases don't come together without any shafts in them. They get to about 1/4 inch apart and that's it. With or without the crankshaft - which I did check goes smoothly and seats all the way into the bearings in each half. I have wrestled with them from different angles and whatnot - can't figure out why. I'm going to give it another try today and if no success will try to take better pics.
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BevHevSteve
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Re: Trouble mating the 860 crankcase halves

Post by BevHevSteve »

Only the bare cases ? And they will not come together? So they are literally just sitting on the dowels? If that is a yes then you have an out or round or otherwise bent dowel it seems.
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