Mercedes Primary Chains

Jo said:
One point isn’t clear at this stage. I understood Andy Forsdick always that way, that for cam chains it would be ok to use “roller” type chains (dimension 3/8" x 1/4"), e. g. IWIS G67WZ or Regina C121HCS.

For primary chains however the same dimensions (3/8" x 1/4") applies, but as “bush” type chain. The difference is the bigger pin diameter (4.41 vs 3.31 mm) – which is important for the primary drive, as the “bush” type chain is capable for higher loads.

Therefor you shouldn’t use the IWIS G67WZ but the G67HP for the primary drive application.



This was explained some time ago (2010) by Andy (the original chain man) and the related post can be found here:
primary chain replacement (see page 3).


Hope this sheds some more light on the topic!

Cheers,
Jo
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I have confirmation that the chains are as you say; G67WZ for timing chain, and two G67HP for primary chains.
 
above is sort of correct but you need to first, find the point where the cam marks and TDC on No 1 align with link near the middle of the sprockets, when you find that mark, turn engine back over backwards until joining link comes back around

Now split the chain, with cams removed so pistons do not hit the open valves, feed chain back through until link is back in the middle spot and piston on No 1 is at TDC
Install cams, join cam chain, all is good
 
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don't faff about and struggle with access, take the carbs off as well, a good opportunity to give them a clean and look over, plus inevitably get the jets right, you might even find 185's in there! plenty still using 140's and 145's
CLEM
 
Irritatingly I dismantled the carbs three weeks ago just after I bought the bike in order to investigate rough running at idle (blocked secondary jet). I dismantled the carbs checked jets and cleaned and blew them through with compressed air. Now running well. Hey Ho, carbs off again!
 
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