Heli coil from the factory?

fiatfan

fiatfan

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I´m going to run a belt drive and dry clutch in my -73 850 and I´m a bit worried that it might be some oil seeping through past the three small bolts that hold the inner TC to the crankcase. There is Helicoils in the three holes in the crankcase, are they fitted from the factory? I´m not sure how to stop the oil from coming past the threads, since there´s no gasket or anything on the bolts, would an O-ring help? But then there´s the locking tab..... Has anyone running a dry clutch had this specific problem?
 
I have been running a dry clutch and belt drive for years and never had any problem with oil seeping past the threads.
There are no helicoils in the bolt holes of my bike, so I suppose that the Helicoils are a mod or repair done by a previous owner.
 
My 72 version has helicoils from the factory in those positions. I use a bit of silicon sealant on the threads as I have a belt drive. I don't use the tab washers and have never had a problem with them coming loose.
 
MichaelD said:
How about some PTFE plumbers tape to seal the threads?
Click to expand...
fiatfan said:
I´m going to run a belt drive and dry clutch in my -73 850 and I´m a bit worried that it might be some oil seeping through past the three small bolts that hold the inner TC to the crankcase. There is Helicoils in the three holes in the crankcase, are they fitted from the factory? I´m not sure how to stop the oil from coming past the threads, since there´s no gasket or anything on the bolts, would an O-ring help? But then there´s the locking tab..... Has anyone running a dry clutch had this specific problem?
Click to expand...
My '74 850 has the helicoils, which I believe were factory installed. I believe that because all three are perfectly executed. I've seen (done) hundreds of helicoil REPAIRS, and seen THOUSANDS of factory installed examples.
 
Those helicoils might allow you to torque beyond the ~65 inch/lbs recommendation, but I would stick to it regardless. You want to pull each 1/4 coarse bolt, clean it and the case threads (Q-tip) thoroughly, then apply some non-drying gasket sealant (Wellseal; Threebond 1104) very sparingly to the underside of the tabbed washer and the underside of the bolt head as well. Finally, a touch of purple or blue Loctite to the thread (cleaned of any sealant when you pushed the bolt through the tabbed washer) and torque it up.
 
Jdub said:
Those helicoils might allow you to torque beyond the ~65 inch/lbs recommendation, but I would stick to it regardless. You want to pull each 1/4 coarse bolt, clean it and the case threads (Q-tip) thoroughly, then apply some non-drying gasket sealant (Wellseal; Threebond 1104) very sparingly to the underside of the tabbed washer and the underside of the bolt head as well. Finally, a touch of purple or blue Loctite to the thread (cleaned of any sealant when you pushed the bolt through the tabbed washer) and torque it up.
Click to expand...
Good advice.
 
Blue loctite or loctite #545 thread sealer should do the job.
Any of the anaerobic thread lockers can function as a thread sealer. Avoid the high strength types in this application.

One other caveat....... if you are going to run ATF in the primary, you might consider seaing the threads with Pematex 81880 gasket sealer. ATF degrades many types of sealers, and 81880 is specially formulated for ATF


Slick
 
Last edited:
Little late but my 69 750 has Heli coils from factory! I use grey gasket maker to seal them.
 
Jdub said:
Those helicoils might allow you to torque beyond the ~65 inch/lbs recommendation, but I would stick to it regardless. You want to pull each 1/4 coarse bolt, clean it and the case threads (Q-tip) thoroughly, then apply some non-drying gasket sealant (Wellseal; Threebond 1104) very sparingly to the underside of the tabbed washer and the underside of the bolt head as well. Finally, a touch of purple or blue Loctite to the thread (cleaned of any sealant when you pushed the bolt through the tabbed washer) and torque it up.
Click to expand...
That´s more or less exactly what I ended up with.
 
texasSlick said:
Blue loctite or loctite #545 thread sealer should do the job.
Any of the anaerobic thread lockers can function as a thread sealer. Avoid the high strength types in this application.

One other caveat....... if you are going to run ATF in the primary, you might consider seaing the threads with Pematex 81880 gasket sealer. ATF degrades many types of sealers, and 81880 is specially formulated for ATF


Slick
Click to expand...
It´ll be a dry clutch, no oil.
 
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