Chain Wear on Case

Chief · Feb 16, 2002

First Time I noticed this. The chain is wearing on the case. please click on the link below.

http://photos.yahoo.com/bc/chiefcam...oad+Album&.dnm=chain+wear+on+case.jpg&.src=ph

I did have my first chain break on me, I suppose that's when this could have happened, when it derailed. Chain didn't catch on anything, just fell to the ground. To me, it looks more like a slight constant rubbing. The groove gets deeper towards the bottom. There is also a nick on the fin. (upper left of pic)

I have a 12 tooth front sprocket instead of the stock 13 (1/10'' shorter) and a DID O-Ring chain (appx 1/10" wider than stock). I have checked the clearance several times over the last year, and it always looked good. I use the reference marks on the swingarm , and they are good. I measured them with the swingarm off. I have also measured from the swingarm bolt to the axle after using the reference marks, and they were both good. This kinda has me stumped, and I'm thinking I really can't ride it like this until I figure out what's going on. When I put the current sprocket and chain on the shaft right now, I can't get it to come close to the case. It looks like plenty of clearance. Is it supposed to slop around much when running?

I also pay attention to the chain tension. The chain has some wear marks on the top of the links, (shiny spots) but it's more on the outside than the inside (inside of chain would contact the case), so I chalk that up to contact with the chain guide. I have kept the stock guards in place.

Has anyone noticed this on their bike? Is the case any thicker at this point?

The only thing I noticed was once, the rear axle was not butted up against the tensioner bolt on the right side of the bike.

At this point, the only idea I have is to go back to stock, use a permanant marker on the gooves, and check to see if it's still getting worn.

Any ideas/feedback greatly appreciated.

Thanks

Joe Chief

eunos · Feb 17, 2002

Hey chief I presume its a rm 250 your running? does this bike have a spacer behind the sprocket? I know Yam, Kaw,and Honda do unsure about Suzi, is it missing, worn , wrong size? Can you fit a larger spacer?
Just a few thoughts/suggestions.

WoodsRider · Feb 18, 2002

Ouch, sounds like new chain and sprocket time.

Can only pass along some experience here. Check your chain adjustment frequently. I've always ran my chain a little looser (more freeplay) than the spec for any of the bikes I've owned. A friend of mine, coincidentally he also rode an RM, is the only person I've ever known that threw a chain. In fact it happened twice in one day. Problem was his adjusters were frozen so he couldn't adjust his chain. Three inches of freeplay was too much, so he removed a couple links. An hour or so later, when his chain snapped, he discovered a half inch of freeplay wasn't enough.

The comment about the spacer is good, also keep in mind that a smaller front sprocket wears faster.

RM_guy · Feb 18, 2002

Chief,
I haven't had the front sprocket off of my bike yet and I don't use an o_ring chain but I'll check it tonight. Did you put the sprocket on with the offset in the right direction?

Danman · Feb 18, 2002

My DR has a built in spacer on the sprocket and if you put it in backward it will rub. If there is no spacer with the sprocket or and it is supposed to have one I would definately replace it. Like RMJeff says it could be the fact that the O-ring chain is wider than the non-O-ring causing the rubbing. The marker in the groves is an exilent idea to spot any more rubbing. I've heard the same thing from other poeple about the smaller counter sprcoket causing premature chain ware. I would just calcute your ratio and the recalulate the ratio to get the same only using a 13T or 14T front sprocket. If your not sure about the spacer and if it is an RM I belive that you can find part numbers and diagrams @ www.bikebandit.com They have the for the DR but they are hard to read sometimes.

Good luck

Chief · Feb 19, 2002

Guys,

Thanks for the great responses.

eunos, There is no spacer on the shaft. Just an offset on the sprocket that when installed incorrectly wouldn't even let the o-ring roll through. I'd like to smear up the case and smooth it over w/ some alumaseal type product and go back to stock, then just make sure the back wheel stays put . A spacer on this model wouldn't let me put the clip in the groove.

RM_Jeff, lemme know when you get the chance, I have a feeling yours is in better shape than mine. 50 degrees today. Almost time to ride!!!!!

Woodsrider, I been thinking about running it a little looser. I think I may try that. A lot of pro bikes look pretty loose on the chain.

Danman, thanks for the link!!!

I guess I mainly have to keep a close eye on it.

Thanks again and Happy Riding.

Joe Chief

;)

RM_guy · Feb 19, 2002

I looked at it last night and there is no wear on the case. Sounds like no o-ring chain for me:eek:

I wonder what the team Suzuki offroad guys do when they use an o-ring chain?

Chief · Feb 20, 2002

Thanks RM_GUY!!!

I'm just glad I caught it when I did. I'm hoping it was a fluke or maybe happened when the wheel got out of line. Still seems unlikely. I guess I'll stick the O-ring back on and if it shows any more of this, someone will get a good deal on a slightly used o-ring chain. So many parts, so little $$$:whiner:

You know, I'm really starting to like online shopping:) :) :)

If I have to go to the 13 tooth front, the paragon trip may be somewhat more amusing.

Later,

Joe Chief

RM_guy · Feb 20, 2002

Joe,
I run stock gearing and have no problem with the low end. Of course I have Eric's Mo Power Everywhere porting:aj:

BTW,
I started my bike yesterday and rode it around the yard to break it in. It is nice and snappy now with the slide cut. I can't wait to get it oput in the open.

Chief · Feb 20, 2002

"I saw this in a movie about a bus that had to speed around a city, keeping its speed over 50, and if its speed changed, it would explode! I think it was called, 'The Bus That Couldn't Slow Down.'"

(The Wisdom and Wit of Homer J. Simpson)

:) :) :)

Jaybird · Feb 20, 2002

Rub or no rub, the 12T front is trouble.

Chief · Feb 21, 2002

Jaybird,

Thanks. I tend to agree with you and plan on going stock for the start of the season (start of the season, crap, it's 50 degrees, sunny and damp at 8 am here today)

The reason I feel it's trouble is because it's just too much of a jump in such a small area (simply put) changes the chain angle too much.

Could you explain why you say it's trouble?

I've thought about going up a few teeth on the rear sprocket, but then there is the issue of the chain guide. What is you opinion on this option?

Thanks for the response,

Joe Chief

Jaybird · Feb 22, 2002

Chief,
I'll try to keep it simple....
Yes, the 'angle of attack' for lack of a better term does come into play. Basically it all boils down to the fact that a smaller sprocket has to work harder to accomplish the same work a larger sprocket does.
With 14 teeth doing 100% of the work, it means each tooth carries about 7.14% of the total load in one rev. With a 12 tooth sprocket, the teeth each carry about 8.33% of the total load. ( in reality, all the teeth don't do the work, less than half of them at any time are doing the work...I just used the above figures for example)
Now the final gearing effects all this,(front to rear ratio) but even with the same ratio's, or very close, a 4:1 ratio using a 14 tooth front will be less stressful than a 4:1 ratio using a 12 tooth front.
When the 14 tooth front is used in the 4:1 ratio, it does make the sprocket teeth on the rear carry more of the total load, but there are many more teeth in the rear to distribute this transfer of workload, and it's not noticed like a trasfer of load to the front is.
By "noticed", I mean that the harder work the small front has to do, also means that less area of the chain is carrying load, so you will see accelerated wear on your chain as well as your front sprocket teeth.
Honda and maybe some others have tried to go to a 12 and it wasn't good, so they are back to 13's and 14's.

btw...we are very rough on sprockets and chains with our sport. In the industrial setting, a #50 chain (which is the same 5/8" pitch as a 520) is not recommended to be used with less than a 17 tooth driver(front) sprocket.

Chief · Feb 22, 2002

Thanks Jaybird.

It's good to have some explanation on my situation. For example, the original chain broke shortly after I installed the smaller front. It had very little time on it and was well maintained.

Joe Chief

whyz · Feb 22, 2002

Hi Chief....

http://dirtrider.net/forums3/showthread.php?s=&threadid=32703

it does it to the 02yz125's too.
See ya...:)

Jaybird · Feb 23, 2002

Chief,
You need to make certain that you are adjusting properly. Do what your manual says, then take the shock off and place the swingarm in a midpoint so you have a straight line from sprocket to sprocket with eaqual amounf of chain on both top and bottom. You should still have a bit of slack at that point, if not loosen it a bit.
Always change chain and sprockets as a set.

Chief · Feb 23, 2002

Thanks whyz and Jaybird.

Chief

smb_racing · Feb 23, 2002

Another thing to remember about a smaller front sprocket is that since the outer diameter of the sprocket is smaller it brings the chain in closer to the countershaft. Being as your cases have a recessed area away from the seal and shaft the larger sprocket might hold the chain out into that area to avoid contact with the cases. If you move the chain in closer to the center then the pins from the chain would be more likely to contact the raised area that the seal fits into. This looks like what happened on your bike.

Chain Wear on Case

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