BMW K bikes (Bricks)

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1Back to top Go down    Frame to transmission bolts on Wed May 17, 2017 11:53 am

Filmcamera

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I recently managed to destroy second gear during some spirited riding on the twisties. Whilst I could have the gear repaired by undercutting the dogs in the end I decided it was cheaper and probably easier to buy a used transmission.

I found one on eBay from a 1993 K1100RS which looked great when I got it, the splines etc are almost new.

Yesterday I installed it and all was going great until I came to refit the M8 bolt on the RHS that goes through the frame into the transmission. Try as I might I could not get the M8 bolt to screw in. On closer inspection (I took the transmission back out again) I discovered the hole had been repaired with a M6 helicoil. A M6 bolt screws in no problem.

The rest of the transmission looks perfect and shows no sign of having been down or anything like that.

So I am looking for a little advice. Should I try and remove the helicoil that is in there and retap the hole for an 8mm or should I just install a 6mm bolt and ignore it?



    

2Back to top Go down    Re: Frame to transmission bolts on Wed May 17, 2017 12:19 pm

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Rechecking the correct bolt is a M10 1.5 and the helicoil that is in there is for a M8 1.25

I do have both a M10 1.5 tap and also a M10 1.5 helicoil so I might try taking out the old helicoil and just re-tapping a M10 1.5 thread first.

I will admit it makes me a little nervous

    

3Back to top Go down    Re: Frame to transmission bolts on Wed May 17, 2017 2:19 pm

club_c

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If it were me I'd repair the threads to the original size. The clever engineers at BMW put it there at that size for a reason and who are we to quevestion zem? Vee shall ask zee quevestions here! You're right there so not a big deal to make the repair. My 2 cents worth... (read my signature)


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"There's never enough time to do it right, but there's always time to do it over."

1988 K100RS SE VIN 01477554
    

4Back to top Go down    Re: Frame to transmission bolts on Wed May 17, 2017 2:29 pm

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Yep, that is what I am doing, I tried just tapping with a M10 tap but no luck so I had to use a helicoil. Seems to be pretty good. The only issue is I did not go quite deep enough so I cannot get the original bolt totally flush with the frame but a washer or two will fix that.

    

5Back to top Go down    Re: Frame to transmission bolts on Sun May 21, 2017 3:10 pm

Filmcamera

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I did manage to drill out the M8 and install a M10 helicoil and reuse the correct size bolt and now the bike is all back together and running well. So far I have only done one quick shake down ride to test out the new transmission but it feels great!

    

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