86' XJ750 Maxim engine (cam chain tensioner?) noise

Hi Guys,

My Maxim is producing some slapping noise which I believe is the cam chain tensioner.
I concluded that after reading a lot of threads on the forum, I could be wrong of course.

The slapping is more noticeable on hot engine and only on idle.
When I rev the engine the noise disappears.
When I engage the clutch, the noise stays the same.

Question is, can I remove and check if it is stuck cam chain tensioner without removing the carbs?
What kind of tensioner do I have automatic or manual?

If someone can send me useful manual pictures about this I will be very grateful.

Thank you in advance.

 

Well you could check the tech section which is located on the top right of the webpage where it says XJ4Ever, this is considered the bible of the XJ bike world and has basically rendered every aftermarket service manual obsolete. Now do keep in mind the starter clutch is also a known source of idle noise and can easily be mistaken for a loose timing chain being so close in the engine. I believe a Maxim is a manual tensioner however you're working with a 1986 750, the USA had a displacement tariff in those days and our largest I believe was 700cc before this kicked in, maybe someone here can further clarify this from across the pond? The SECA 750 had an automatic tensioner and below is a picture of it on my 1981 XJ750R SECA, its the black object with the large bolt on the end.

 

The 750 should have an automatic tensioner on it. Yes, you can remove it without pulling the carbs but it will be tighter. Remove the nut at the end of the tensioner first (the spring will pop out) as you need to do this to reinstall the tensioner anyway then the two Allen bolts and it should come right off.
But seeing as the tensioner is the automatic type this probably isn't the issue. Without actually being able to hear the noise it's hard to say what it might be.

 

Automatic chain tensioners should --- in theory --- never need attention (unless an oil leak develops on it). A naked auto-tensioner looks like this:

https://xjbikes.com/forums/threads/need-manual-and-auto-cam-chain-adjuster-pics.24597


However, like any other mechanical device, an auto-tensioner can fail to perform properly, typically due to one of 2 reasons:

a) the ratchet mechanism has stopped ratcheting, usually due to the internal "works" getting gummed up from congealed oil residue, etc. Solution is to remove the tensioner unit, take it apart (note: the case end bolt....the spring and shaft live behind it....is torqued on there really tight, and you may need to secure the tensioner body in a vice (or similar) while banging away on the wrench / socket you're using. Also note if the bolt is removed, we suggest you replace the crush washer under the bolt head, and of course a new tensioner-case-to engine gasket should be fitted).

Sometimes you can free-up the ratchet mechanism in an automatic tensioner (without removing the tensioner from the engine) by rotating the engine backwards a turn or two and then rapidly changing the direction of engine rotation. Rotating the engine backwards introduces a fair amount of slack in the cam chain at the rear guide, and tapping on the tensioner case gently during this procedure can motivate a reluctant ratchet mechanism to free itself up enough to ratchet the tensioner shaft forward and resume its proper tensioning.


b) the round rubber "head" or "cap" at the end of the shaft....which pushes on the rear face of the rear chain guide, can get fractured, cracked, or even end up missing in extreme cases. A tensioner in this condition needs that cap replaced (and it is not a part that is available) or the entire tensioner needs replacing.

Note you should follow the procedure in the service manual for ensuring proper positioning of the cam chain when removing or re-installing a chain tensioner.


Pro-tip: if you have a manual tensioner (on all XJ550 engines, 1984-85 FJ600, 1986-88 FZ600, 1986-90 YX600 Radian, 1984-91 XJ600 Euro, 1986-88 FZ600, 1980-81 XJ650 Maxim and Midnight Maxim models, and the 1982 XJ650RJ engines), you can replace it with an automatic tensioner (from a 1982-later XJ650 YICS-engined model, XJ700 air-cooled, all XJ750 air-cooled, or an XJ900RK, RL, N/FN, and F engines) as they will interchange. Note that the XJ700-X water-cooled engines use a different style tensioner which will not interchange, as well as the XJ1100/XS1100 tensioners, which are unique animals all to themselves.

 

He's like the encyclopedia of the XJ