Z1 Series Crankshaft bearing Support

[Garn 1]

Here is a Z1 mystery... Firstly, I can't find a part number for the crankshaft main alloy bearing support fitted to all Kawasaki Z1 series.
This machined alloy casting supports the two centre roller-bearings of the crankshaft and is retained by 4 x 8mm bolts.
Although these supports were probably individually line-bored, I have found these supports to be interchangeable as they merely "clamp" the crankshaft bearings.
My main query is (with ref to the photo below)..... what is the function of the protruding bolt head, that I have found on quite a few of these supports?

Protruding Bolt head on left


Close up of bolt head.


Other side of support.

RegardZ

[zed1015]

The main bearing cap is part of the crankcase assembly and is machined as such so is not available as a seperate part.

The cap with the bolt is from the later 'J' engine with HYVO silent type camchain.
The bolt is refered to as a quietning bolt in the manual and sits very close to the camchain.
Its main function is to keep the chain from dropping off the crank teeth when performing shim changes, top end work etc.

[Garn 1]

As you would all be aware, I have posted this on several sites and the commonality, with respect to the reason for no pattern number, now seems obvious... It is as suggested, part of the upper engine case.

Now regarding the line boring of these support clamps, it has been suggested, that it may give an uneven tension on the main bearings if misaligned too much. I have studied many of these and, unlike the cam caps, they are precise and surprisingly accurate over a range of different engine castings... 1972 Z1 thru to 1977 Z1000 A1. Of course, if any disparity was noticed they would not be interchanged.

Getting to the crux of the matter.... What is the function of the bolt in the middle of the support bias towards the back (note there is a direction arrow marking the front)?
Well, SlmJim, (from Classic Site) asks....
Could it serve any purpose as a rudimentary guide for the camchain during assembly, perhaps to keep it from kinking?
May be close to the answer.
Another suggestion from Zed1015 was ....
The bolt is refered to as a quietning bolt in the manual and sits very close to the camchain.
Its main function is to keep the chain from dropping off the crank teeth when performing shim changes, top end work etc
He also added that it was from a "J" engine using a HYVO chain.

These crankshaft supports shown above were removed from Z1 series engines, so perhaps, the same reason for the bolt still applies.
I think Zed1015 gets the money!
Regardz

[zed1015]

These crankshaft supports shown above were removed from Z1 series engines, so perhaps, the same reason for the bolt still applies.
I think Zed1015 gets the money!
Regardz

In thirty odd years of working on Z engines i have never come across an early roller chain motor with a ' quietning bolt' installed as std to the main bearing cap.

Neither is one illustrated or mentioned in any of my many genuine kawasaki factory service/workshop manuals.

I would say with 100% confidence that the offending item has been retro fitted from an HYVO engine at some point in the past and would disregard it in any analysis of early Z1 engine development.

[Garn 1]

Thanks Zed1015, I bow to your thirty years odd experience and even though these supports were taken from Z1 series engines, I have to agree, they could have been retro-fitted from a later model "J" motor (that has the HYVO chain).
In which case, I further agree that this subject is not relevant to the development of the Z1 engines, albeit, it's nice to know!
RegardZ.
PS. Zed1015, slow time an extract of the "J" engine maintenance manual referring to this "quitening" bolt would be appreciated.

[Rich]

chapter 6 page 50 paragraph 4 of part number 99924-1026-02

check your email

[Garn 1]

Thanks Rich, "quitening" does seem a funny name for a bolt and I haven't seen it written as such! It is not designed to contact the chain at any stage other than when chain has been loosened.
As Rich says Reference is made to the bolt in the Official Kawasaki service manual KZ1000, KZ1100 1981 1982 and it should be noted that no mention of bolt is made in KZ1000 A1/A2/A3/A4 manual or earlier Z1 manuals.
So, it appears we should never see it, as I did, in a Z1.
Zed1015 mentioned.... It does look as so its unique to HYVO cam chain use.

Regards