Chain Breaking

Hello All,

About a month ago i decided to put on a new chain (just because it was getting old). I bought new stock sprockets and a DID 520 120. A month later, the chain broke on me. i bought a Renthal Gold 520 120 and on my second ride the chain broke (in many spots, all on the outside). Why is this happening? It is becoming expensive and frustrating.

- The tire was aligned properly

- The sprockets are not warped

- The chain tension was to spec.

I did notice that the rear chain guide rub block has a small piece broken on the rear left side... could this be an issue?

Any insight??

Also, should i get an x-ring instead of o-ring??

Look straight down the chain and see if the sprockets align. I'm betting the spacer on the left side is missing.

thanks, I'll take a look...

what are your thoughts about the worn rub block?? should i replace it?

Yes replace it ASAP! You should not be breaking chains that easy. There is obviously something causing accelerated wear and the broken chain block is the first place to start assuming the chain is not too tight and the sprockets are aligned. Asf or the chain block I would ditch the stocker and go for either the T.M. Designworks or a BRP

chain guide. I have the T.M on my WR and it has been holing up great along with the Ironman sprockets and D.I.D X-ring chain.

If you find it misaligned and the chip was a result of the chain hitting it but wouldn't be an issue once fixed I'd leave it. Any question at all? Replace it while you're at it, better safe than sorry.

Edited by Sknight
Fixed my awful typing.

Is this bike equipped with a lead-acid battery? I've seen chains break like you describe when the battery vent tube drips acid on the chain, causing the sideplates to crack around the pins. Just a thought.....

Look straight down the chain and see if the sprockets align. I'm betting the spacer on the left side is missing.

+2 on this. Misalignment can not only cause excessive wear to one side of the chain, it can also force all the the energy through one side of link plates instead of spreading the load through both side link plates.

thanks, I'll take a look...

what are your thoughts about the worn rub block?? should i replace it?

The stock rub blocks is a POS on these bikes. and X rings are better than O rings. search as its been discussed at length

Are you running a riveted link or split link on the chain >


The number one reason by far that chains break is because they are too tight.

Gray Racer is absolutely correct in my estimation. It is a faint recollection, but I believe I broke a chain on a Husqvarna about 30 years ago. Modern chains just don't break without a reason. That reason is usually a chain that is misaligned, totally worn out (as in most of the teeth on the sprockets are gone) or too tight. My comment below was to address a problem with chain slap in another discussion thread. However, the guidance concerning adjusting the chain correctly is still appropriate whether the problem is a chain that is too tight or one that is too loose. The only thing I would add to my comment below, is to ensure that you check and adjust chain tension while your motorcycle is on a work stand.


TT Bronze Member

Join Date: May 2003

Location: California

Age: 66

Posts: 467

Your chain is probably too loose. This seems to be a common problem.

The procedure to adjust the chain is the same for all WR450F's. The slack dimension tolerance may be different between model years however. Check your owner's manual for the correct slack tolerance and pay close attention to the instructions.

I'm sure that you are familiar with the procedure to adjust chain tension. However, just to ensure that one critical point is not overlooked, I will remind you that the slack tolerance dimension is NOT the difference between the measurement shown in the illustration contained in the Owners' Manual while the chain is at rest and the measurement of the chain while the chain is under tension. In the old days, when everyone rode Husqvarnas and CZ's, that was the way chain tension was measured. If you calculate the chain tension using this method, your chain will be too loose.

The correct way to measure the tension on your WR is to record the distance from the top of the bolt in the chaffing pad which is located on the top of the swing arm up to the BOTTOM of the chain while the chain is pushed up with your hand. This dimension should be (for the 2008 WR) 48 - 58 mm or 1.9 - 2.3 in. Look closely at the illustration in the Owners' Manual to see my point.

I adjust my chain this way and I do not have chain slap and I do not have marks on the inside of the subframe or main frame near the countershaft sprocket.

Los Ancianos MC and Baja Fools

2008 Yamaha WR450F

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