Topic: Chain and sprocket woes (pics included)

[750K]

So I got home today and as I'm putting my bike in the garage this is what I see...


This is the second time I've had the master link clip fly off, the first time was last summer on a ride up and down the Sunshine coast of B.C. On the way back to the ferry back to the mainland I kept hearing a clack when I let of the throttle, in the ferry line up I found the master link clip gone and the back link plate posts bent outwards as well as a chewed up month old 630 chain.


The bent master link was the only thing holding the chain together, I had about 4-5 inches of slack top to bottom and lots of sway left to right. Turned out the clacking noise was the chain hitting the top of the chain guard as it came off the rear sprocket, I had a spare new master link in my tool pouch I was able to swap in and limp home with. I had just replaced the chain and sprockets a month earlier, the rear wheel spun true and the chain and sprockets were lined up straight. I pulled everything off after limping home and found part of the clip and minor rubbing on the case but the chain, wheel and sprockets were still lined up and spun true.



I had the motor rebuilt by a local honda shop over the winter. While they had it all apart they checked the bearings and the sprocket shaft for wear, all were fine. They said there was a shim washer behind the front sprocket that wasnt suposed to be there. The PO must have put it there, I left it in place when I did the new JT sprockets thinking it was supossed to be there. They seemed to think with the front sprocket not having any play on the shaft while running was the issue, the chain must have worn if there was any flex in the swingarm causing the clip to break and the chain to get chewed up. All was fine since I got it back, I've put maybe 1000-1500km on it since the rebuild. I've been keeping my eye on the chain and until today it seemed fine, no excessive slop or play and the master link was still attached and facing the right direction.

I thought things were fixed but obviously I'm back to trouble shooting again, I'm thinking swingarm bushing seeing as they ran through the motor and made sure the chain and sprockets lined up and the rear wheel adjusters were equal and the wheel spun true. I havent felt any shimmy in the rear when entering or exiting curves, so I'm kinda stumped. Any thoughts on this? Im not sure where to look if the swingarm checks out, I had the rear wheel and shocks off last summer and remember checking for play in the swingarm. I guess I should pull it off for a good look when I have the wheel and chain off again...

Any ideas are welcome, I want to get this solved and back on the road for the spring.

[750K]

Oh, I forgot to add that the bike is a 77 cb750. 630 DID chain, new JT 630 sprockets front and rear in stock tooth counts

[dave500]

the clip was facing the correct way?is that just the photo or is that a dry rusty red hue around that link?you must ride softly,,im surprised just that link with no plate didnt just snap or bend and pull out!,ive never ever had a clip disappear,is the chain stamped with DID?

[dave500]

how do you fit the clip?do you flex it open,or do it like this?

[LesterPiglet]

Please don't flame, just a question. Is 630 standard fitment on a 750?

[Spiider]

^ On some of the years yes. It is a huge chain, when not used for CB750k's it is used mostly for mooring/anchoring cargo ships.


To the OP, I know clip links are "easier", but I say get a rivet link for it. 
It is just as easy to rivet if you have a good tool. And the satisfaction in knowing that it isn't coming apart is worth it.

[bollingball]

Please don't flame, just a question. Is 630 standard fitment on a 750?

Lester Yes it is for a 77-78 750.
Ken

[bollingball]

750K  You were really lucky you caught that just in time. I'm not clear who put the chain on last you or the shop. First off they were correct there should NOT be any shim on the front sprocket it should float on the shaft about 2-4 mm not sure exactly how much. I did the same same when I first got mine a 78 750K with the 630. Not only will it put the chain in a bind it puts stress on the shaft and bearing. If you have not done so take it off now. I agree with dave500 that area up front is dry but with the sprocket locked down it would not matter. I don't know if I would trust those two rollers on the end of the chain with the master link bent like that it had to put some stress on them. How much who knows that is your call but it would be on my mind all the time. Also like dave500 I have never lost a clip that I can remember I have to think it was not put on correctly unless that shim up front had something to do with it. I rode mine like that for a few thousand miles before fixing it but the clip held on. Now out to the shop to check my chain Thank a lot

Ken

[750K]

Dave500, The clip was facing the right way and its a DID chain and link, stamped DID. The red hue in the first pic is just the reflection of the Ct125 it's next to in the garage and shadowy cell phone pic, it's bright orange. I attach the clip gently, I slip it on the link over the plate and push it from the back with pliers till it clicks in.

Lester, yes on a 77-78 630 was stock. They're pretty heavy duty, probably why the back half of the link didn't snap in half from  ending first time it happened .

Spiider, I know lots of people run clip links without ever having problems, I already have a new DID630 chain waiting to go on. Chain and sprockets are not the root problem, both have less than 6 months of riding on them. They were brand new last July and the bike was off the road for a few months over the winter.

bollingball, the shop tech put the chain on last, the clip was facing the right direction. The chain was in line with the sprockets and the rear wheel adjusters were at the same mark, I remember double checking when I got it back from the shop. After the first incident I've been anal about checking and lubing the chain. The shim was removed by the shop tech, I made sure to go through it all with them and they checked the sprocket shaft and bearing when the cases were split.

Your right about the chain being in a bind, I'm pretty sure theres something flexing laterally. Everytime this has happened the chain has lots of left to right sway, as in 1-1 1/2" of sway. If the rear swing arm bushing is wearing this lateral movement would put the chain in a bind correct? If its enough pressure I can see the link breaking off. That's my guess, although I haven't felt any weirdness from the rear end and I've been really pushing it in the turns lately.

I'm going to check the whole damn thing again and pull the sprockets chain and swingarm off over the weekend, I'll give the rear wheel hub, cushdrive and wheel bearing a good inspection as well. If its not one of those I'm #$%*ing stumped..

Thanks for the replys, any input is more than welcome.

[lucky]

Please don't flame, just a question. Is 630 standard fitment on a 750?

Yes it was standard on the 77-78's. First thing you would want to get rid of. Then get #530 chain and sprockets.

Unfortunately the engine will need the bottom part of the case removed to put in a new countershaft if you can get one.
It is hard to tell from that photo if the countershaft is ruined. The photo is confusing.
The digital camera has done something that makes it unclear.

Something looks WRONG with that countershaft. Was it the correct year??

Sure would like to see that shaft from a different angle.

[lucky]

If the countershaft is still good ,I have a brand new OEM #630 countershaft sprocket I could sell you dirt cheap.

The parts breakdown on the internet shows NO SHIMS. It only has a flat washer ,and lock washer with bolt on the outside of the sprocket.
Between the sprocket and engine oil seal is nothing.

I still recommend gettiing a #530 chain and sprockets.-LUCKY
I still wonder about that countershaft. Looks WRONG. Looks short.
Need more photos.

[750K]

As far as I know Lucky the countershaft is the correct year for the bike, as well as correct length. When I replaced the front sprocket last july there was no noticable wear on the splines of the shaft, only the sprocket teeth. With the sprocket on, washer, lock washer and bolt torqued to spec there was a bit of sprocket play on the countershaft. With the shim behind, sprocket, washer lock washer and bolt torqued all play was gone and the sprocket was snug to the machined stops at the end of the splines. If it was too short I'd expect there would be no play on the shaft without the shim, which is not there anymore anyway. I'd expect if the shaft was too long I'd have excessive play and not be able to get the sprocket cover back on, there's a cast post on the cover that lines up with the center of the bolt in case the bolt loosens by the looks of it and it is close to the retaining bolt when it's all together by the looks of things.

I'll take more pics when I pull things apart, hopefully I have time over the weekend. I remember checking for movement in the countershaft with the bike in 1st gear after the first master link came apart, all seemed fine. I will be starting from there and working my way back once again. If you have a countershaft length, I'd like to compare measurements. Can you post a pic of the oem 630 sprocket or email a pic to me, I'd like to compare it to the one I replaced with the Jt 630.


Cheers

[Duanob]

I've never had a clip lijnk fail but I always carry a spare link in my tool tray. The problem with rivet links is if you're far away from home, good luck repairing a broken chain. Just my $0.02 which is worth $0.0198756453 CDN!

[750K]

I've never had a clip lijnk fail but I always carry a spare link in my tool tray. The problem with rivet links is if you're far away from home, good luck repairing a broken chain. Just my $0.02 which is worth $0.0198756453 CDN!

That's the reason I went with and am sticking with a clip link, I know the chain and sprockets are not the issue and people have been using a clip link for years without running into this problem. Process of elimination will hopefully get to the bottom of this.

[bollingball]

I've never had a clip lijnk fail but I always carry a spare link in my tool tray. The problem with rivet links is if you're far away from home, good luck repairing a broken chain. Just my $0.02 which is worth $0.0198756453 CDN!

I have had one on my key ring for years for good luck I guess.
Ken

[Lostboy Steve]

This reminds me of a crazy thing that happened to me. On my 07 yz250f I am obsessive compulsive about cleaning lubing and replacing my chain and sprockets as necessary. We ride in the middle of nowhere. Literally miles from civilization in a GIANT sandbox. No foliage at all looks kinda like Glamis only with way smaller dunes. So we go to take a water brake and I look down and my master link is gone! lol Don't know how I was riding but it was just sitting there looking like yours. Guess what? No spare. I literally backtracked though my tire trail and with the grace of God found my master link a while away. When we got back to the car hours later, it was gone again. I still to this day have no idea why it kept coming off and I've never had that problem again. Also, I never learned my lesson and I still don't carry and extra.

[lucky]

As far as I know Lucky the countershaft is the correct year for the bike, as well as correct length. When I replaced the front sprocket last july there was no noticable wear on the splines of the shaft, only the sprocket teeth. With the sprocket on, washer, lock washer and bolt torqued to spec there was a bit of sprocket play on the countershaft. With the shim behind, sprocket, washer lock washer and bolt torqued all play was gone and the sprocket was snug to the machined stops at the end of the splines. If it was too short I'd expect there would be no play on the shaft without the shim, which is not there anymore anyway. I'd expect if the shaft was too long I'd have excessive play and not be able to get the sprocket cover back on, there's a cast post on the cover that lines up with the center of the bolt in case the bolt loosens by the looks of it and it is close to the retaining bolt when it's all together by the looks of things.

I'll take more pics when I pull things apart, hopefully I have time over the weekend. I remember checking for movement in the countershaft with the bike in 1st gear after the first master link came apart, all seemed fine. I will be starting from there and working my way back once again. If you have a countershaft length, I'd like to compare measurements. Can you post a pic of the oem 630 sprocket or email a pic to me, I'd like to compare it to the one I replaced with the Jt 630.


Cheers

There should be NO shim or washer between the sprocket and the engine.
The sprocket needs some play.
The sprocket should be a tight slip fit on the shaft.
I know because I had a #630 sprocket on my CB750 1978 and it was loose.
Then I bought the brand new sprocket and it was a nice tight slip fit on shaft.

If your sprocket had too much wobble then the chain could get on a angle and twist the chain and pop off the master link.
It is VERY VERY rare to for a master link to come off.

Like I said before I would go to a #530 chain and sprockets if you can afford it.
If you cannot afford it, I would sell you my BRAND new OEM sprocket for next to nothing.

[lucky]

I've never had a clip lijnk fail but I always carry a spare link in my tool tray. The problem with rivet links is if you're far away from home, good luck repairing a broken chain. Just my $0.02 which is worth $0.0198756453 CDN!

That's the reason I went with and am sticking with a clip link, I know the chain and sprockets are not the issue and people have been using a clip link for years without running into this problem. Process of elimination will hopefully get to the bottom of this.

Master link clips are not the problem.
Many young guys have been led to believe they need O ring chains with rivet on chains.

[750K]

There should be NO shim or washer between the sprocket and the engine.
The sprocket needs some play.
The sprocket should be a tight slip fit on the shaft.
I know because I had a #630 sprocket on my CB750 1978 and it was loose.
Then I bought the brand new sprocket and it was a nice tight slip fit on shaft.

By play I meant left to right as you slide the sprocket onto the shaft, lateral play and the shim was removed when the motor was repuilt. The sprocket is a tight fit to the splines of the shaft, the the one I replaced was worn. This one is not worn, I checked it and the Honda shop checked it and they are familiar with old Hondas.

[bollingball]

As far as I know Lucky the countershaft is the correct year for the bike, as well as correct length. When I replaced the front sprocket last july there was no noticable wear on the splines of the shaft, only the sprocket teeth. With the sprocket on, washer, lock washer and bolt torqued to spec there was a bit of sprocket play on the countershaft. With the shim behind, sprocket, washer lock washer and bolt torqued all play was gone and the sprocket was snug to the machined stops at the end of the splines. If it was too short I'd expect there would be no play on the shaft without the shim, which is not there anymore anyway. I'd expect if the shaft was too long I'd have excessive play and not be able to get the sprocket cover back on, there's a cast post on the cover that lines up with the center of the bolt in case the bolt loosens by the looks of it and it is close to the retaining bolt when it's all together by the looks of things.

I'll take more pics when I pull things apart, hopefully I have time over the weekend. I remember checking for movement in the countershaft with the bike in 1st gear after the first master link came apart, all seemed fine. I will be starting from there and working my way back once again. If you have a countershaft length, I'd like to compare measurements. Can you post a pic of the oem 630 sprocket or email a pic to me, I'd like to compare it to the one I replaced with the Jt 630.

750K I put the ridge on the sprocket facing the engine. I think from what you have said I would look at the swing arm

Ken

 


Cheers

[750K]

Thanks Ken, that's OEM then? My new JT looks the same. Swingarm is my 1st guess, I got my fingers crossed. I have a spare motor from a 78 cb750k I can at least look at and compare in regards to the countershaft and worst case get parts from...

Cheers
Chris

[BobbyR]

There is one more thing to check in the rear hub are cush rubbers that absorb the shock on the chain. when worn or broken the sprocket can tilt which will also twist the chain. The best links I have found are Tsbuki. They really have to be pressed in place. Also make sure the clip is firmly in the groove. It can fool you.

When you think about it the side forces on the chain should be minimal under normal conditions.

[lucky]

I do not see a problem with that sprocket.
The "hub" side does face the engine.

[750K]

Did some digging yesterday and it looks like the font sprocket is on backwards, the cast "hub" or raised area was facing out. The flat side showed more rubbing at the outside edge, can anyone confirm that the raised face faces in?

There was some more rubbing on the engine case from the chain when I pulled the sprocket and chain off, the chain is toast having some links that were frozen from being bent outward.

On a good note, there was no play on the countershaft laterally and I compared the splines to the one on the 78 750k motor I have on the bench. The cush rubbers in the rear hub were in great shape, wheel bearings were nice as well. No play in the swingarm and rear wheel was aligned. I pulled it off and all came appart easily, swingarm bolt slid out easily.  Cleaned & inspected it and lubed it and reassembled it all back up. Checked and cleaned the rear brakes while I had it apart, just have to reinstall the front sprocket and new chain and cross my fingers.

I'll post some pics tonight when I get a moment.

[lucky]

The sprocket should be mounted with the stamped numbers facing out.

Just check to make sure the clearance between the engine and case looks sufficient.

Click on photo to enlarge. Backside shown,
Numbers on the other side.

My stock OEM sprocket has the numbers on the smooth side.
Your aftermarket sprocket has the numbers on the flanged side.
The OEM parts breakdown on Bike Bandit shows the smooth side facing out also.
seems right to me.