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Chain tensile strength?

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Give you an idea of where your at with it. 8200lbs tensile strength 520 chain will work on a 600cc sport bike. That's 400lbs and 100+ HP, hooked up on asphalt.

Your good.:lol:

But his 450 has a blue powerband! That's at least 120 horses and 300 ft/lb of torque:smirk:

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I used to think if a chain could handle a street bike than it would laugh at any dirt bike. When you read app charts lots of times you see the chain rated for a higher number for street use than dirt. If you think about it, many dynamics of offroad use is much worse for a chain than street. On the street there is much more HP and traction, but it is usually very smooth and not abrupt. Now think of a dirt bike running wide open over whoops. Whenever the rear wheel is in the air it accelerates, but as soon as the tire touches down there is a violent "jerk" of tension on the chain (same thing landing from a jump). This type of wind up and grab is much harder on a dirt bike chain than on the street. If you were trying the "rip" a string or rope, would you smoothly pull on it with increasing force, or wind up and "yank"?

Also to muddy the waters (literally) mud and dirt all over the chain cause a lot of further stresses. Toss a small pebble in the right place and you will break most chains in an instant (just ask me about how easy this happens).

Ever since my 5 mph case cracking experience I try to run at least 8000 lb./tensile minimum.

More importantly than tensile strength, is proper maintenance and a keen eye for warning signs!

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8100 pound tensile strength is overkill; compared to a street bike a dirt bike chain will have far less torque from the engine and much less chain tension because of less traction. But as Justin points out the dirt environment can be a lot more brutal on a chain than street riding.

Assume an engine with 20 ft-lbs of torque and a combined primary and first gear ratio of 10:1, the max torque to the countershaft sprocket would be 200 ft/lbs. A 14 tooth CS sprocket has a 1.4" radius, divide by 12 to convert to feet and then divide into 200 for the max tension in the chain (1723 pounds). A nice safety margin.

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..and a keen eye for warning signs!

.. what would those warning signs be? (new here, on a 400F)..

..a

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.. what would those warning signs be? (new here, on a 400F)..

..a

I'm almost embarassed to post this!

I never really looked at the chain, I would usually just replace everything when the back sprocket started to look bad. During the race season I would have replaced it at this point, although it only had 17.9 hours on it, so I figured I'd push it another weekend or so. I usually get more like 25 hours out a chain and sprocket set. What's the worst that could hapeen, right? Just need to replace between practice motos if teeth start shedding? Haha. I even took a pic so I could compare how it looked at beginning and end of day, since at this point they go to hell real fast.

DSC_0002.jpg

This happened a couple hours later. Hooked the back tire on a landing on a tight double right out of a corner. Bike was going about 5 MPH when I landed, tire was going like 30 MPH or however fast it goes at the rev limiter. Broke, and luckily wrapped around the sprocket instantly stopping the bike rather than braking the case.

DSC_0855.jpg

Look at how worn the chain is! The plates are square not round. It makes sense that it would wear since RMZ450s go through chain guides 5x faster than Hondas. I've never noticed that type of wear before. I don't know why I'm using a DID ERT2 here, I found the Renthal R1 last way longer; must've been out of stock.

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What is the chain contacting to physically wear the plates like that? I know there are guides and protective guards and such, but I didn't think they would wear the chain like that. I do inspect it when I clean and lube it..

..a

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Just the hard plastic or rubber in the guide blocks, swimgarm, and the lower chain roll. It looks like the guide was worn and the chain rubbed on the metal, but that is not the case.

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.. what would those warning signs be? (new here, on a 400F)..

..a

Coupla warning signs it's getting ready to bust your case.

Tight link(s) that won't loosen when it's lubed.

A chain that has been in use for a while without having to be adjusted, then all of a sudden it get's really loose. Or it get a little loose, you adjust it, and it immediately get's loose again.

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.. what would those warning signs be? (new here, on a 400F)..

..a

As mentioned any kink or tight spot even after being clean. Also, I like to use non-orings so I can easily remove and clean the chain. When doing so I look at the master link. It gives you the ability to see "inside" the chain. If the master link pins show noticeable wear or rust, you can bet the rest of the chain does too...

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To take care of your chain. I prefer to wash them with solvent and pressure washer. Then take them off and put them in lamp oil. Shake them a bit. And just leave there for the time I work with rest of the bike. In this time chain lube comes off and dirt drops on the bottom of the box. Little shake now and then. You can use the same lamp oil many times. When it is way too dirty I just burn it in an oil lamp. Usualy in the end of the day I put the clean chain on a clean rag. Next day just put them on, check the tension and lube them. In this way I havent had any rust and chains live long. I use regular chain, not O- or X-rings.

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