Dear Airheaders and GS'ers

[mikyh]

Returning from a 2 day trip, where on the roads back I pressed my poor GS up to true 155 Kph, I had a metalic noise from my right cylinder, accompanied by some oil drips on my right boot.

Opening the valve cover for inspection I found the front upper gudgeon pin's nut completely loose. Tightening it revealed the sad fact that the pin's housing threads, in the casing, are stripped.
In taking the right cylinder off I found out all 4 pins were inserted with Helicoils, including the stripped one, of course (I Helicoiled the left side while rebuilding, I didnt remember the right side was the same).

I intend to attempt fixing it with Big-Serts, a thread fixing system I used recently in another project successfuly.

http://www.timesert.com/html/bigsert.html

I feel that the metal around the hole is borderline regarding this, but as other measures will be much more paifull, I'll try all the same.
Please look at photos I uploaded of this and let me hear from your accumulated wisdom.

http://picasaweb.google.com/mikyheimann/StrippedThreading#

TIA, Miky

 

[Lilith]

Mikyh

BamBam has used "timesert's" in the past to fix an airhead. It had already been repaired with a helicoil but that had pulled out just as yours has.

When you put it back together just make sure all the swaf (metal flakes/bits) have been cleaned out of the engine and oilways.

 

[Duncan Richmond]

Mikyh

I had this same problem years ago, sorry to say the repairs did not last long before all the studs pulled out again. My friend who is an engineer tried helicoils first, then timeserts - thats not to say yours won't work. When you have done the repairs leave the rocker covers off to check that the oil feeds up the studs to the top end before firing the motor up ( I turned the fuel off and spun it over on the starter motor) In the end I had to get a second hand crankcase and swap all the internals over as the metal in my original crankcase seemed very weak, the older case I bought seemed better quality.

Good luck

 

[mikyh]

Thanks guys,

I'm going to try the big-sert fix first.
Miky

 

[mikyh]

some questions

I assembled my right cylinder after fixing the stud with Big-sert.
The fix itself looks succesful, but the assembly was not - i have an oil leak from the base of the cylinder, and no oil pushing through the exhaust rocker assembly.

The leak at the base is probably a pinched o-ring, this can happen, even to me...
But I can't understand the oil passage in the head. can anyone explain to me from where do the oil get to the stud tunnels?
And any suggestions to the rocker "dryness" will be also greatly appreciated.
Thanks, Miky

 

[Steptoe]

Go deep and use timeserts in the top holes because you need to drill out the oilway feed, and you can't drill helicoils.

 

[mikyh]

Found it. S...t

the insert blocks the oilway which comes from above.
Anyone knows how far inside from the outside surface of the case is the oilway?
if I knew where it is I can open it up again.
Miky

 

[Steptoe]

the insert blocks the oilway which comes from above.

Yes, read my post before yours


The oil way is only approx half /three quaters of an inch in the top of the hole.
Thats why you can't use a helicoil - If you use a wurth insert you can drill it at the oilway.