Primary chain noise?

I need to pick a few brains, my Maxim (750) has been making some strange noises as of late. It's a ticking, almost light knocking sound that comes and goes, mainly at low RPMs. It sounds like it's coming from the cam area and will be absent for a length of time and then reappear. The bike has 12,000 miles and the valves were put in spec when I bought the bike with 7800 miles. I have not yet pulled the valve cover off to see if anything obvious is going on and to check clearances. I don't see any foreign material when I change the oil. The starter clutch on this bike is hit and miss so I wonder if that might somehow be related.

So I guess what I'm asking is what kind of noise/symtoms does a failing chain guide cause?

Thanks.

 

That does sound like one or more of your guides could be toast, but it could also be the tensioner (although it should be automatic for the 750,i think). I would open up your valve cover off first, since that is where the sound is coming from. There are two guides under there to check. If you don't find anything there (and even if you do) it might be worth pulling the oil sump and seeing if any chunks are present in there.

 

there should be some threads here from Rick-o-matic and the method he used. it was something about spin the engine forward three times then stop and jerk it backwards.
his original post goes into more detail though

 

There are thee main things it could be.

A disintegrated alternator chain tensioner.

A slack cam chain, or worn cam chain tensioner.

Cam cap endplay that is on the loose side.

The last one is nothing to worry about, but I've never heard of that coming and going. It's just there all the time, from idle on up.

 

What I can't figure out is the intermittent nature of the noise. I'll pull the valve cover and look for the obvious but I'm thinking this will be a larger project for hopefully next year. As I said the starter clutch isn't 100% anyway so since that's a teardown anyway I can investigate this further. Sucks because I really like riding this bike.

 

Things could be migrating down there, maybe it's just the cam chain guide popped out of its home and all you have to do is relocate it. Unfortunately, the guides seem to break down due to age as much as miles at this point. If you do need to replace the alternator chain guide, you could do it over the winter, I pop started my bike for months before I tackled the job (started in February, still going, ha ha). I don't think I caused any lasting damage, but my guide was only cracked, and still mostly in one piece. If you were serious about getting it done, and had the space and time, you could probably get it done in a couple of weekends without rushing.

If you're lucky, though, it's something simple like the guide or worn chain, which are relatively easy to fix.

 

In my mind the alternator chain guide is the most likely to be intermittent. A big enough hunk of the guide could be bouncing around making the noise.

 

So after much deliberation I've decided to scrap both bikes as I don't want to put the work into them. Since the Seca's a 'ticking time bomb' it's going too.







Kidding!

I really don't think I'll get a start on the repairs this year due to a busy schedule the next month and a half. One thing I don't want is to be trying to do delicate work in a cold garage (I know, I could get a heater). After I do the Max I'm going to do the Seca while everything's fresh in my mind as I have my suspicions that the same thing's happening in it's bowels as well. I hear intermittent ticking that's not as pronounced as the Maxims but there none the less. It also sounds as if it's coming from the valve-train. My guess is it's just how the sound resonates through the engine.

Anyone who has done this already please fell free to offer hints and suggestions as I will surely need them. I will occasionally (and shamelessly) bump this thread. Reading through the factory service manual I see (and have read here) that you need a special tool to remove the alternator. Is that tool still available? If not is there a workaround?

So in parting for now here are a few 'goodnight for the season' pics of the pair. Good thing I've got a few other bike to ride. (anyone want to buy a Ninja? It'll make you grin)

 

The 650 and 750 engines had a TSB about ticking in the valvetrain. The culprit was cam caps that were machned to allow greater can endplay than was specified (though not excessive endplay). The Yamaha TSB called for replacement of the cam caps ONLY if the customer complained about the noise. My bike has the tick. I ride it wothout a bit of concern.

 

Is there any chance you could post a video of the noise? You mentioned that it happens mostly at low RPMs, does it happen at idle as well?

 

I will try to get a video. With sound of course.