Isuzu G-series Twin Cam

Whats the reason behind the intermittent timing chain rattle on start up....?

Motor is a g180w.

Most days it wont do it, some for a second or two, others it sounds like the chains going to snap! Peoples faces in the shopping centre carpark express my horror as it continues for up to 20-30 seconds.

The chain is near new, I took the tensioner out and cleaned the "jet nozzle", cleaned the metal feed line when I changed the oil last week, but still does it....more so if the motors hot.

Can a non rerturn valve of some sort be grafted to the metal line that I pressume feeds the tensioner on start up, to try hold oil pressure once motors off?

Any ideas are much appreciated!

Todd.

It's probably the early G180/200W chain tensioner - ie, the round assembly, not (tri)angled with an internal ratchet as below: (With thanks to Antus.)





(The above are from Ant's g200w kalmaker here on twincam. It's a Piazza G200W. Some earlier 117 G200Ws had the round ratchet-less tensioner too.)

Yeah its the early type, has a 32mm brass hex plug on end of timing case.

Wondered how it worked as a tensioner once I had it out as there is only a light spring and what looks like the oil squirter for the chain. No wonder it rattles bad! Its not even a tensioner no?

So if I ever take the head off I should run the later g200W timing case with triangular shaped tensioner, are the cases interchangable?

In the meantime ill hang my head in shame everytime it does it haha

Todd.

Greengem20B wrote:In the meantime ill hang my head in shame everytime it does

Ha! So what if they don't realise it's a G-twincam?
If the peasants don't recognise the roar and the grunt, that's their class issue.

My Ducati roundcase reads a higher dB from the front than behind the exhaust. That's because as loud as genuine Contis are, they are no match for the rattles of a real 750 twin.
But nobody laughs or comments, they just stand in awe at this legendary heap of shit. (Actually it ain't - but it has Mikunis, Jap electrics, RITA ignition....)

But the roundcase GT750s are fairly well known.
Alas G-Ws have been kept a closely guarded secret and even banished from some political speak.
And others have done their best to ridicule them by faking expensive works and destroying them. (I heard one blew up on the way to an Aussie Day event. Was that a G-W, or just a sucker with an expensive engine?)

Think of me in my old grey nurse (Florian). So sedate. So conservative. So "embarrassing" for the conventional. But I knew. I still see their open-mouthed faces, dopping back, the in the rear view.

You'll get used to it! In fact, you'll love it. "Hey bro - we woz shagged by a rattler!


But yeah - later case with the bits. I think it is interchangeable (oh so long ago).

The early is merely oil-pressure tension so as the chain wears etc, the oil needs to pump to quieten it (by tensioning).
The latter has the non-return ratchet. Much better idea!

There were some solutions, but I can't remember. (No - NOT thicker oil!!)
Maybe a stiffer spring, or putting a spacer in there to partly "pre-extend" the tensioner (but not too far!!).
But later model is the beez neez.

And you shouldn't have to take off the head. That font gasket is not part of the head gasket.
It is in fact (1) a separate gasket and (2) quite unobtainable LOL! Or at least the VRS kits do NOT supply it.
But it shouldn't be too hard to make from some neoprene or suitable material. It is rectangular and about head gasket thickness, but merely surrounds the cam valley/duct whatever - mere crankcase pressures and oil.
But don't forget to put it in! (Someone did. Apparently lots of oil over radiator etc.)
Some might use blue silastic etc provided the surfaces are spotless (and minimal inside to get in the oil supply).

But remember, until you head-off or otherwise, just head-up. Peasants simply don't count.

Late reply....but been thinking of swapping front covers, I have a G200W case at home that I can use.

Would I need to lift the head at all?

Be rather tricky trying not to butcher that gasket at the front the chain passes through when putting new case back on.

That episode with oil leaking from a home made gasket you mentioned above, was a mate of mine lol used thin paper gasket when it should have been same thickness as head gasket.

Not if you drop the (front of the) sump... I think....

The problem is "wedging" the replacement between 2 gaskets that are tightened against it.
Not to mention getting the old out is likely rip either or both.

Even dropping the sump might rip it.
And re-sealing the sump (not a problem if it's a newish & soft sump gasket; but they are rarer than head gaskets).