Author Topic: Cam chain replacement (Read 2857 times)

Noel · « **on:** April 08, 2006, 11:30:38 AM »

I suppose I should first apologise for bringing up a "frequently covered" topic, but I did spend an hour with the search function and didn't find what I was looking for.

So having said that, I intend to replace the cam chain on my '73 500 without splitting the cases. I've ordered a new chain and "soft link" from David Silver spares, and the most complete chainbreaking tool set I could find from J.C. Whitney.

The most informative post I've found on the subject is from a French gentleman, and his difficulty with the language has resulted in some information that I'm not totally clear on. So before embarking on a a semi-complicated project that I've never undertaken before, I want to see how much more information I can get.

Anything will be of help, but I do have a few specific questions:

1) Does the "soft link" become a part of the new chain? That is to say, do I use it to temporarily hold the new chain to the old while turning it through the engine, and then remove it prior to riveting the new chain back together, or does it simply replace one of the links from the new chain?

2) Should I mark the chain and the cam sprocket so as to avoid changing the valve timing, or should I just ignore it and plan to remove the cam sprocket bolts and retime the cutout notch to the 1-4 "T" mark afterwards?

Thanks again for any help.

SteveD CB500F · « **Reply #1 on:** April 08, 2006, 01:02:16 PM »

Not a difficult job - you don't even have to take the engine out! (don't you just love reminding our 750 friends of that!)

1. Soft Link: Use it with the new chain.

2. Retime the cutout notch.

Is the tensioner OK?

Noel · « **Reply #2 on:** April 08, 2006, 03:22:34 PM »

Yeah, I enjoy tweaking the 750 guys.

Quote

Is the tensioner OK?

Arg, don't ask. I'm not sure, which probably means "No, it isn't". When I loosen the nut, nothing happens. I can turn the sccrew counterclockwise about a quarter turn and then it stops up hard against something. I can turn it clockwise a couple of turns but it stays there.

Between that and the 100 pounds of compression, the motor needs rebuilt. I just don't have the money to do it and won't for the next couple of months. I want to ride the bike meanwhile, but am quite afraid that the 40,000 mile cam chain will break and I will learn what REAL trouble means. So I figured I'd toss in a cam chain and keep saving my pennies.

Terry in Australia · « **Reply #3 on:** April 08, 2006, 03:33:02 PM »

Seems a bit pointless Noel, if you know the tensioner is not good, a new chain alone is not gonna make your engine any safer. Can you replace the tensioner with the engine in situ? Cheers, Terry.

And for Steve, I'd still rather have my 750, ha ha!

Noel · « **Reply #4 on:** April 08, 2006, 06:30:45 PM »

Terry, you may be right, but I think I will pretend that you are not. My hope is that 1) The tensioner is basically okay, just acting a little screwy from age, disuse, and corrosion, and 2) A new chain can withstand a poorly adjusted tensioner for a few months of gentle riding.

I just can't stand the thought of the bike sitting unridden for the next few months. And hey, if I'm wrong and the chain breaks, well, I've been toying with the idea of dropping in a modded 550 engine anyway.

As far as the 750 goes, my best bud used to race 500s back in the day. He claims that with the Yoshimura stage III kit the bike made 80 hp. I figure there was probably a lot of blue sky in manufacturer claims back in the days before Joe Average could get a dyno run for thirty bucks, but a 400 pound bike with even 65 or 70 hp should be enough to teach a CB750 owner some manners.

TwoTired · « **Reply #5 on:** April 08, 2006, 07:07:17 PM »

I'm with Terry on this one. If your tensioner is screwed up, it will screw up a new chain too. PJ said that when the tensioner goes bad, the chain flys out and starts cutting into the engine case. After not much cutting, the oil galleys are compromised, and zero oil presure pretty much trashes the engine. A new chain will cut just as quickly as the old one.

In fact the tensioner may be more important than the chain itself. The chains are pretty robust. But, if they are flapping around without proper tension, they will give up with that kind of stress. Take all the tension off the chain and measure the pivot pin wear. Only replace if you think the current wear is excessive (percent of pin diameter).

Or, just drive it like it is and hope for the best, since you're going to replace the whole motor anyway.

Cheers,

bryanj · « **Reply #6 on:** April 09, 2006, 04:13:52 AM »

You will have to remove the cam sprocket and camshaft to get at the chain properly and rivet it DONT FORGET to tie bits of wire or string to each end as i can guarantee you will drop it if you dont!.
BEFORE cutting the chain you can get your fingers into the chain tunnel and, having loosened the camchain tensioner nut check that the tensioner blade (the one at the carb side of the engine) moves freely and then lock up the nut with the tensioner pushed towards the carbs as hard as possible--otherwise you wont get the chain on.

The new chain will be endless and you will have to "split" a link which you discard then split a link on the old chain and either use that or the new one to temporarily joint the chains NOT BY RIVETING!

You will then need 3 hands or a trained spider as you have to hold both ends of the chain and turn the crank by hand, usually with a big spanner on the big nut outside the contact set.

Best of luck Bryan

bryanj · « **Reply #7 on:** April 09, 2006, 04:15:52 AM »

PS as its a 500 from 73 its almost certain that the PRIMARY chain is worn and that is the one that chews though the oil galleries and you HAVE to split the cases to get to it

supersport_CB400F · « **Reply #8 on:** April 09, 2006, 05:58:12 AM »

Why bother going to all that expense of a new chain, take a link or two out of the old one and rivet it back up.

Noel · « **Reply #9 on:** April 09, 2006, 10:37:19 AM »

Thanks Bryan, that's good info.

To tell the truth, the other folks have got me wondering whether I ought not just leave it all alone and ride it gently until I can afford to go through the whole thing.

Someone asked, on another thread, for personal experiences of broken camchains. Didn't seem like it was as prevalent as one might believe.

So what's the board's opinion? 40,000 mile camchains as disasters waiting to happen, or, well, not?

Terry in Australia · « **Reply #10 on:** April 09, 2006, 02:06:25 PM »

Just adjust your old one as best you're able Noel, use good quality oil and remember you're riding a 30 year old bike with 40,000 miles on the clock, and save your money for the inevitable rebuild next fall. Cheers, Terry.

Noel · « **Reply #11 on:** April 10, 2006, 10:26:37 AM »

Well, I took the advice proffered on another thread and played with the cam chain adjuster with the engine running. It is actually functioning; my best guess is just that age and corrosion have conspired to make things a bit sticky. I adjusted it manually to the "least noise" setting and am calling it good.

So as soon as the gasket set shows up (detail, details) I guess I'll give the cam chain replacement trick a try. Thanks for everyone's advice. Even Terry's.

Terry in Australia · « **Reply #12 on:** April 10, 2006, 10:32:47 PM »

Quote from: Noel on April 10, 2006, 10:26:37 AM

Well, I took the advice proffered on another thread and played with the cam chain adjuster with the engine running. It is actually functioning; my best guess is just that age and corrosion have conspired to make things a bit sticky. I adjusted it manually to the "least noise" setting and am calling it good.

So as soon as the gasket set shows up (detail, details) I guess I'll give the cam chain replacement trick a try. Thanks for everyone's advice. Even Terry's.

You're always welcome mate, now "Shut yer face-hole Noel" and get back to work! Cheers, Terry.

Noel · « **Reply #13 on:** April 11, 2006, 10:26:44 AM »

Noel · « **Reply #14 on:** April 22, 2006, 11:24:27 PM »

Hey, that wasn't so bad. A few hours' work, and put the wife on "Don't let that chain fall into the tunnel!" duty. Took a few tries to understand Clymer's fairly goofy instructions for timing the cutout notch to the T (1-4) mark, but overall not too bad.

Think I'll see about doing the top end next week, along with Helicoiling the three stripped bolt holes the PO left for me to find underneath the cam cover. $:-\$

Thanks again for everyone's input.

coolcat2002 · « **Reply #15 on:** June 13, 2007, 11:15:14 AM »

Do you guys recommend a new Cam sprocket when putting on new Cam chain?

I ordered an OEM one from Motogrid.com and they said they don't have it. So maybe I should get, an adjustable cam sprocket?

Adjustable cam sprocket with my stock cam can be beneficial?

SteveD CB500F · « **Reply #16 on:** June 14, 2007, 12:50:15 AM »

Unless there's something wrong with the cam sprocket, I'd leave it. It's not like a drive chain remember - it's running in an oil bath!

Adjustable sprocket if you've got hot cam or inlet work. Otherwise why bother? Nothing wrong with stock.

Noel · « **Reply #17 on:** June 21, 2007, 08:58:19 PM »

Agreed. The stock sprocket is extremely beefy. I'd consider replacing it on a 100,000 mile bike, but short of that...

dramsell · « **Reply #18 on:** June 22, 2007, 04:31:11 AM »

Noel, what forum did you check into cam-chain breakage on? I replaced mine with a rivet link about 4 years ago and was just wondering.
Dave R

Noel · « **Reply #19 on:** June 22, 2007, 05:20:00 PM »

Things were slightly different around here when I did that search, as I recall, but the bottom line was that I searched all the technical forums for every post with the words "cam" and "chain" in them. That took a fair bit of time and I only found a few posts where anyone even thought they might have broken a cam chain. I never actually found anyone who had personally broken a cam chain on a street bike, so tend to think it's pretty rare.

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Author Topic: Cam chain replacement (Read 2857 times)

supersport_CB400F