Looking down the Cam chain tunnel

[petermigreen]

Guess I'm looking for a little re-assurance here.

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Looking down the Cam chain tunnel, at the front where the chain guide sits. The casting seems a little ragged. Does this look correct.

There are no fragments in the bottom of the engine so I'm fairly confident but would like a second opinion.

Thanks, Peter.

[Bryanj]

If that's a 400 I think you need to split the cases and free off the tensioner horseshoe as it looks like its been running with a slack chain

[petermigreen]

Can the tension not be freed off without splitting cases? It moves freely around its arc.
Thanks, Peter


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[Bryanj]

If its very free it may be OK but when the chain is loose it batters the bejaysus out of the pivot point making it too stiff for the adjuster plunger to move and the only way to get at it is split the cases

[petermigreen]

The adjuster plunger is free as a bird so that's a relief. Don't really want to split the cases as otherwise the engine is sweet.
Thanks for your advice. Peter


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[mike the bike]

It might have been caused years ago by a previous owner.   If it sounds ok now don't worry about it.

[Laverda Dave]

I have rebuilt four 400 engines over the years and they have all had the same issue as yours does.  As I normally have the engines apart for a rebuild I use a fine file to clean up where the aluminium casting has been turned over by the flapping cam chain.
I've never had a problem with any engines following the rebuild and file surgery although I always install a new cam chain, both tensioner blades and the sprung tensioner horseshoe making sure the tensioner plunger has no markings caused by previous owners over-tightening the tension adjuster.

[petermigreen]

Thanks, that's good to know. As said, the mechanism is lovely and free and the chain looks very good. Given that I'm not going to split the engine any further as it is very good with hardly any wear.
Thanks again all. Peter


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[Dave_Canada]

Since the two chain tensioner rod springs have lost a lot of "spring" in 30+ years (unavoidable) the factory tensioning procedure won't work now. You need to remove the cap bolt and push on the top of the adjuster actuating rod with a nail or thin screwdriver, listen to the engine running and press down hard enough to just quiet the chain rattle, then tighten the lock bolt. Be very careful around the hot headers, of course! Too much force and it will be quieter but the blades will wear rapidly.
Be extremely gentle with the rod lock bolt: it's a 6mm thread into the engine, not the visible beefy 8mm thread which is only for its locking nut. Breaking these bolts by overtorquing is not unusual and a major PITA to fix.
Some rattling is OK but annoying, chain tension has to be quite loose for it to hit the case.
The adjuster springs 14541-333-020 and 14543-333-020 are NLA, and would require a case split to replace anyway.