GPZ600 top end rattle

[bikerg]

Hi,

My '85 GPZ600 primary drive chain snapped a few weeks ago so I swapped the entire lump for a '88 GPX600 engine with 39k miles. All was well till this week.
The top end has a very loud nasty nocking noise (it sounds very light, nothing like a heavy banging sound). Anyway, I took the valve cover off and noticed the camchain seems to be loose.
When I turn the engine over (with the flywheel) the chain seems to flop around when it reaches the top of a stroke.
I've come to the conclusion myself that the chain is loose, but what are the chances that it is just a dodgy tensioner?
Haynes say i need to remove carbs etc. to inspect and I want to try to avoid that if possible.
With the milage the engine has done, is a cam chain replacement imminent?

Thanks

[sickpup]

Long time since I worked on one but I seem to remember the tensioner is under the carbs so yes you will need to remove them for access.

Surprised the Primary chain snapped, did it get run low on oil as this would also explain a stretched cam chain?

[bikerg]

The primary drive snapped on the old engine which had done 51k miles. The new gpx engine was serviced when it went into my bike and still has plenty of oil but I dont know its history.
I can see the tensioner nut from the side and have looked at the tensioner on the old engine and can't see any benefit tampering with it without taking the carbs off.