Author Topic: The life of a primary chain... (Read 5821 times)

Tretnine · « **on:** September 22, 2009, 05:44:10 pm »

So, primary chains do not come with tensioners. That seems like an engineering oversight and I don't think I'm the only one who holds that opinion. How long do these chains last, really? Has anyone (other than Mec, with his righteous custom build) put a tensioner down there? Are there many chains to choose from... maybe something that lasts longer?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #1 on:** September 22, 2009, 05:48:50 pm »

You have to purchase tensioners seperately. Both of my 750 engines utilize tensioners. What bike are you referring to?

oldfett · « **Reply #2 on:** September 22, 2009, 05:50:27 pm »

There is a tensioner... I know they do on the 750 so I assume they do on the other bikes as well.

Clyde · « **Reply #3 on:** September 22, 2009, 06:14:06 pm »

The 750 does have a chain tensioner, it is supplied separate to the primary cains.
The primary chains under road use last a long time.
I have seen an F2 with 208,000kms and the engine had not been out of the frame.
If you are concerned then there is a procedure to check the wear wihout taking the engine apart or even out of the frame.

Tretnine · « **Reply #4 on:** September 22, 2009, 06:21:38 pm »

I'm talking 550s here. Do they have primary chain tensioners, too? I thought the problem was they would saw through the case with relatively low milage.

TwoTired · « **Reply #5 on:** September 22, 2009, 06:30:12 pm »

The 550s do not have primary chain tensioners. I have a 550 with 47K miles on the original primary chain. It's been kept well tuned though. Which has an impact on how much chain whip has occurred over it life.

I think BryanJ said they should be changed at 30K miles, though. But, he might have said that to make me feel guilty, though.

I think there was some reason why the Cb500 chewed on cases faster than the 550, But, I can't remember why. Maybe something about the oil passage channels.

Tretnine · « **Reply #6 on:** September 22, 2009, 06:33:54 pm »

Quote from: TwoTired on September 22, 2009, 06:30:12 pm

The 550s do not have primary chain tensioners. I have a 550 with 47K miles on the original primary chain. It's been kept well tuned though. Which has an impact on how much chain whip has occurred over it life.

I think BryanJ said they should be changed at 30K miles, though. But, he might have said that to make me feel guilty, though.

I think there was some reason why the Cb500 chewed on cases faster than the 550, But, I can't remember why. Maybe something about the oil passage channels.

I'm pretty abusive and the previous owners were, well, not the best. Is there a mod floating to install one? I saw mec put one in, but I have no idea on how that goes down.

TwoTired · « **Reply #7 on:** September 22, 2009, 07:06:24 pm »

The danger is at the top of the case. This is where the chain is tensioned under load. It is the deceleration engine braking where the slack is at the top of the chain and it can fly up under centrifugal force to contact the cases when worn/stretched.

I don't know of a tensioner mod for the 550.

An uneven idle, or unequal power pulses from the cylinders that make the primary chain whip about. I suspect this is what makes the chain wear more rapidly, rather than a power on flog of the motor. Lord knows I did plenty of that on my 74 with 47K miles.

The 500 was worse, I think, and it may have something to do with the primary chain sprocket ratios/sizes that put the chain closer to the casework. (this is really a guess, though)

Spanner 1 · « **Reply #8 on:** September 22, 2009, 07:33:20 pm »

Wow, that was the first thing I looked at when I got the 78K motor apart !! The primary chain rides close to the top case maybe 1/2 inch away from it and lack of a tensioner would for sure make it contact the casing with a few 10's of thousands of miles, the K motors (750) have a tensioner fixed to the bottom case that rides on the bottom ( slack ) part of the chain. Reason I was keen to see the set-up was because I lived with the primary chain lashing off the case on my 750A ( no tensioner ) for 2 years !!

bikebitzofvt · « **Reply #9 on:** September 22, 2009, 08:23:00 pm »

The cb650 has a tensioner on the primary chain. From what I've recall of Paulages 550/650 hybrid stuff he says the cases are nearly identical. It might be possible to adapt the 650 tensioner to the 550.
I haven't had the two apart next to each other to be able to tell...

Raul CB750K1 · « **Reply #10 on:** September 23, 2009, 12:10:08 am »

i have a friend with a 550 that complains about primary chain noise too.

I never thought primary chain stretch would be an issue though. If transmission chain stretch is in fact not stretch but wear of the pin-roller area, that shouldn't happen -or at least not too much- on the primary chain, being oiled all the time and enclosed and protected from road debris. OK, we can argue about oil contamination and tiny particles that are abrasive, but in that case, all moving parts inside the engine would be subject to the same wear than the primary chain.

Furthermore, if the wear is cumulative, the longer the chain, the bigger the slack, and the primary chain travel is indeed short as to mean a really noticeable slack from the cumulative wear of a few links.

Allright, bike abuse could lead on chain stretch, but the primary chain goes between crankshaft and gearshaft, and in low gears, speed is converted into torque, therefore the primary chain is not -or shouldn't be- exposed to really violent surges of torque.

mmmmmmmmmm

BVCB650 · « **Reply #11 on:** September 23, 2009, 05:43:54 am »

Quote from: Raul CB750K1 on September 23, 2009, 12:10:08 am

i have a friend with a 550 that complains about primary chain noise too.

I never thought primary chain stretch would be an issue though. If transmission chain stretch is in fact not stretch but wear of the pin-roller area, that shouldn't happen -or at least not too much- on the primary chain, being oiled all the time and enclosed and protected from road debris. OK, we can argue about oil contamination and tiny particles that are abrasive, but in that case, all moving parts inside the engine would be subject to the same wear than the primary chain.

Furthermore, if the wear is cumulative, the longer the chain, the bigger the slack, and the primary chain travel is indeed short as to mean a really noticeable slack from the cumulative wear of a few links.

Allright, bike abuse could lead on chain stretch, but the primary chain goes between crankshaft and gearshaft, and in low gears, speed is converted into torque, therefore the primary chain is not -or shouldn't be- exposed to really violent surges of torque.

mmmmmmmmmm

What about at an uneven idle, like when the carbs are out of sinc? $:-\$

Tretnine · « **Reply #12 on:** September 23, 2009, 05:54:20 am »

yeah, I've got an uneven idle now and I hear a lot of clonky grindy, something at low rpms. I've put a few thousand miles on this thing and I'm starting to learn enough to do SERIOUS work. (maintenance is not an issue, I'm talking full engine rebuild) Sounds like most people do not worry about the primary chain too much. I also do not want to be the one to make up a mod, as I've never done enough serious work to take on a task like this. I was hoping something simple could be done to add a tensioner... it seems like a rather uncomplicated process. Tensioners are not the most complicated of devices.

BVCB650 · « **Reply #13 on:** September 23, 2009, 06:59:25 am »

I have read that the bottom end of these are pretty much bullet-proof. Top ends need some care after 30K miles, but for the most part, you may need to live with the groans and creaks coming from the bottom end. I replaced the cam chain and tensioner and it sounds the same as before I rebuilt it. Nature of the beast I suppose.

Raul CB750K1 · « **Reply #14 on:** September 23, 2009, 08:19:55 am »

What's the worst that could happen?

Chain would gradually eat the crankcases, either at the top or the bottom -or both.

If it is at the top, someday you will see a hole.

If it is at the bottom, you shouldn't expect to run out of oil. A tiny hole will develop first from where oil would drop, and you will see the stain on your parking spot. If it takes 30K miles or more to eat through the case, I don't think a huge hole will develop in the middle of a ride, at least not huge enough to leave you out of oil.

Long story short, ride it like you stole it and leave the rebuild for when the time comes. If it ain't broke, don't fix it.

Deltarider · « **Reply #15 on:** September 23, 2009, 08:55:11 am »

My 500 has done 130.000 km+ and the original primary chain is still there. Can somebody explain what I've done wrong?

bryanj · « **Reply #16 on:** September 23, 2009, 09:02:20 am »

Not quite Raul, main problem is on 500 and the chain eats into the oil gallery from the oil pump to the oil filter and a little bit into the main cross engine oil gallery,

Now a hole in either of those will cause a catastrophic drop in oil pressure/flow to the engine bearings,

I have seen very high mileages with little wear and low mileages with high wear so there is NO consistent time/mileage to schedule replacement------easiest way to find out it is when sump pan is off for the annual/12,000 mile oil screen cleaning that of course we all do as Honda spec it in the service sheet (Large tongue in cheek moment there) you can run a finger along the cast gallery from pump to filter and see just how big a groove has been milled by the chain and work from there.

The Hy-Vo chain is supposed to self tension by the movement of the links on the sprocket teeth causing the chain to climb the teeth which works great when a steady load is applied but when the 4 cylinders are hunting and fighting each other the chain slaps about, also the bottom run is the "slack" side and so has all the slap.

I have not actually measure it but my belief is that when the 550 castings were altered for the different gearbox the galleries were modded as well as they do not seem to wear as much.

One of these days i will take some pictures of 500 cases to go in the FAQ's then you can see what the problem is.

754 · « **Reply #17 on:** September 23, 2009, 09:58:39 am »

Sure tensioners are not a complicated thing..
IF.. big IF..
You have room to install it and a means to mount it.. oh yeah, if you have a tensioner..

Sounds like it CAN be a problem, but is not ALWAYS a problem..

BVCB650 · « **Reply #18 on:** September 23, 2009, 10:30:01 am »

For all you 650 guys......

http://www.jasonkent.ca/manuals/79%20CB650%20Service%20011.pdf

Raul CB750K1 · « **Reply #19 on:** September 23, 2009, 10:31:42 am »

Very informative Bryan. Obviously, perforating an oil passage means oil will flow from there instead from where it should go.

Then Bryan, you say the 550 is less prone to this happening? I would like to give my friend some peace of mind.

Tretnine · « **Reply #20 on:** September 23, 2009, 11:11:59 am »

I could also use some peace of mind for this. It is, of course, why I started the thread. I'm making a list of work that could be done on this bike.

Dave-and-his-550 · « **Reply #21 on:** September 23, 2009, 11:16:46 am »

Ahhhh another thing I should have checked when I had the engine apart! My 550 has 26k so maybe I shouldn't over look this...

Tretnine · « **Reply #22 on:** September 23, 2009, 12:45:05 pm »

Quote from: Dave-and-his-550 on September 23, 2009, 11:16:46 am

Ahhhh another thing I should have checked when I had the engine apart! My 550 has 26k so maybe I shouldn't over look this...

I hear they can start to get a bit squirrely when you've broken 20k miles (or less) but sounds like it's really dependent on how you use it or, how it idles. (has idled)

bistromath · « **Reply #23 on:** September 23, 2009, 01:20:21 pm »

My 550 with 40K on the clock was slack enough to juuuust barely touch the cases. Probably still had an easy 10K in it, but I split the cases to replace anyway.

haill · « **Reply #24 on:** September 23, 2009, 04:49:34 pm »

just have been through this operation. the primary chain ate the cases. was really close to going through the oil galley. signs to look for. remove your oil pan, check for aluminum in the bottom. get your finger and press on the primary chain if it has slack it's going. with your finger feel up were it moves up towards the top of the motor. if you can feel ruff sections order a new one.

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Author Topic: The life of a primary chain... (Read 5821 times)