I use AN's website drawings, Nice photos as well. RGMs website is not quite as good. I dislike Norvils website with a passion and usually avoid it like the plague
MK 111 engine to cradle bolts .
- Thread starter Torontonian
- Start date
Yes, the earlier ones were small solid dowels. That was one of the reasons for the works team reaming the through bolt holes and using oversize stock for tighter bolts. Under hard use you could see the marks on the case halves where they had been moving
The later larger hollow dowels cured that. When I did my Mk3 cases I had to ream the dowels separately
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Yes up to '71 had solid dowels, '72-on were hollow. That's something I didn't know.
If you can, look at the Stage one High performance Modifications (or stage two) Service release N3/73 or N3/64Yes up to '71 had solid dowels, '72-on were hollow. That's something I didn't know.
It says 'The fitting of oversized high tensile centreless ground bolts into sized and reamed crankcase boss and rear engine mounting bolt holes is advised to ensure maintenance of maximum rigidity of assembly.'
They knew the engine to cradle junction was a source of bother, tune or otherwise improve the performance of the engine and that is what they recommended.
marshg246
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Unless you have a milling machine and the machinist skills to use it, I strongly believe that you should stay with the standard nuts and bolts.
The hole locations in the engine and cradle are not exact. To get a tighter fit between the cradle and engine bolts means that you must get the locations much closer to exact. Simply reaming all the holes out to allow 10mm bolts through when assembling means that you've accomplished nothing except making your bike non-standard.
If you do decide to do it, which holes do you intend to use as the currently correctly placed ones? Do you have any info on how the engine and cradle should exactly align?
A 10mm bolt will go through the 3/8 clearance holes as they are, (apart from the a fore mentioned hollow dowel) Any reaming would have to done in situ. My procedure is as follows: using four short, expanding dowels, i fasten the crankcase to the cradle using the top and bottom cradle holes (these dowels are essentially short pins,a tad over 3/8 dia but they can expand to fit the clearance holes in the cradle and engine) then ream through the cradle and engine middle hole together, Measure the resulting hole and turn up a suitable fitted stud/bolt. (or just fit a 10mm bolt, not quite as good as reaming and a fitted stud, but a lot better than std) Fit and tighten the stud/bolt. remove the btm pair of expanding dowels and do the same, either ream and fitted stud or just fit a 10mm bolt. fit the stud/bolt and then tackle the top hole, you will have to open the hollow dowel up slightly to get a 10mm bolt through, careful use of a drill does this quite easily. If you are going the reaming/ fitted stud route it would be a wise choice to invest in the proper sized reamers 10.2 mm 10.3mm or similar.
If you want to stop the engine moving around in the cradle, this is the way to do it.
At the end of the day its the owners decision.
If going the fitted stud/bolt route i would prefer it if they were studs. A fitted stud is easier to remove than a fit bolt, you have something to get hold of to pull them out.
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With a commando you already need 2 sets of spanners. AF for the chassis and BSW for the engine
It was more that the crankcase halves were moving against each other, they looked like you'd been using grinding paste on the mating faces when you split them... the small dowels did nothing to solidly locate the halves, whereas the larger ones that were relocated to the through bolt area hold the halves in much more secure alignment
