Mk III inner primary adjustment

I decided to do some surgery to my very low mileage Mk III ie layshaft bearing, chain and sprockets etc. Once all back together I had an oil weep coming from the primary. Thinking it was from the inner/outer cover joint I felt up on the inner cover to check if it was the cross shaft seal leaking and I could feel that the washer on the inner chaincase steady stud was loose. There was only one washer between the the inner cover and stud and I was very careful on disassembly/reassembly to ensure it went back together as it came apart.

So what is the likely problem here ? The stud lock nut on the inside of the inner cover seem to take up ok. I have noticed that the alternator clearances are quite tight on the RHS of the alternator (there was clearance but not much).

Thanks in advance for any tips.

MarkT said:

There was only one washer between the the inner cover and stud and I was very careful on disassembly/reassembly to ensure it went back together as it came apart.

I could feel that the washer on the inner chaincase steady stud was loose.


So what is the likely problem here ?

Click to expand...

If the inner washer is loose then the inner nut must also be loose.

The Mk3 inner cover isn't adjusted using shims/washers like previous Commando models. The inner cover position is adjusted using the inner and outer nuts which both need to be tightened against the inner case.

http://britmoto.com/manuals/Manuals/850_man.pdf
Section C34, 6.
"....Make sure the central adjustable support stud is fitted behind the cover with the abutment nut slackened off, in readiness for adjustment after the outrigger nuts are tightened...."


Disregard how the assembly is drawn in the Mk3 parts book, although the actual assembly often has additional washers (not shown in the manual drawing) between the hexagonal section of the support stud and the cradle.

Thanks LAB. Legend as usual. Because I assumed it would be correct (as this bike has never been apart) I didn't check this. Makes perfect sense.

Mark

The title is about primary adjustment and you also complain about oil weepage.
There are at least 8 possible sites for weepage to appear on the MKIII primary inner case, more if the inner case is fractured and shafts to seal lips are also considered.

1) engine to primary (4) hole gasket: fix in place with sealant on the primary side, grease on the crankcase side.
2) starter motor to primary o-ring seal. The o-ring can be nipped at assembly.
3) welch plug: clean with brake clean or similar and smear with sealant.
4) alternator wires to grommet: clean and smear with sealant.
5) alternator grommet to inner case: clean and smear with sealant.
6) cross shaft seal to inner case: clean and smear with sealant.
7) mainshaft seal to case: clean and smear with sealant.
lastly, chain case steady: adjust then clean and smear with sealant. I use the word lastly because the numeral 8 followed by right paren causes a 8) to appear and I'm too simple to seek the cure.

I don't recall if the tensioner studs are through holes or not and I don't have a photograph of the engine side of the inner cover to study.

Firstly though you really must identify where the leak or leaks are. Some can be rectified in place. Some can be wind blown migrating from areas not even considered.

If you must remove the cover again to address one of these reconsider the 21T mainshaft sprocket choice.
The performance will be fine with the 21T, I have the same, but the 21:42 ratio puts the chain links in a non hunting pattern and I feel there is opportunity to cyclically vibrate at speed.
Ratios other than 21:42 will also distribute the wear more evenly extending final drive component life. The 20T was standard in North America. Just my opinion.

All the Best.

Thanks AntrimMan. Once I adjusted the primary everything returned to normal including the oil weep (eliminated).

I went with a 22 tooth sprocket and it suits the engine perfectly. Where I live it is open road speeds straight away so nice relaxed engine speeds.

Mark

good to hear all is dry without much ado.
I don't know where on earth I came up with the idea you were using a 21T main shaft sprocket, sorry about the ramble on that subject.
All the Best.