Is 2" of chain slack too little?


16 replies to this topic
  • nickeenoo

Posted September 11, 2008 - 10:34 AM

#1

Hi All,

I have an 07 450 and I know the manual calls for 2" to 2 3/8" (approximately) of chain slack checked with the bike on a stand at the rear bolt of the chain slider on the swingarm. I have also heard of several hub failures for overtightening the chain. Is two inches of slack too tight?

Thanks,

Nate

  • grayracer513

Posted September 11, 2008 - 10:51 AM

#2

it actually calls for 1 7/8" to 2 5/16", so no, 2" is not too tight, if you are measuring it on the stand, as shown in the manual.

  • nickeenoo

Posted September 11, 2008 - 11:01 AM

#3

Thanks Gray,

I tightened the chain last night and it just seemed too tight. I have always set it at two inches with no problems so I don't know why I was worried.

Nate

  • grayracer513

Posted September 11, 2008 - 11:07 AM

#4

Bike on the stand (wheels of the ground), lift the chain, measure 2-2 1/4" from the chain to the rear slider bolt = :thumbsup:

  • matt4x4

Posted September 11, 2008 - 11:09 AM

#5

also make sure you spin your wheel a few times to make sure you are not hitting tight spots etc.

  • rdrata

Posted September 12, 2008 - 07:22 AM

#6

and 2~2-1/4 to bottom of chain... Some manufacturers show it to center of link. YZ's manuals are not that detailed, as they show graphic (ilo pictures) representations. I checked mine again and it is approx 2-1/8 from rear slider bolt to bottom of chain. good point on spinning wheel too

  • SXP

Posted September 12, 2008 - 07:31 AM

#7

So, that begs the question how hard do you pull the chain up? I can get about a 1/4 inch between lightly pulling the chain up vs. putting some muscle into pulling the chain up.

  • rdrata

Posted September 12, 2008 - 07:38 AM

#8

good question, i would guess a "firm" pull, certainly not "cranking" on it...

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  • Beaz

Posted September 13, 2008 - 01:03 PM

#9

I always do the 3 fingers right behind the black guide on the swingarm

  • grayracer513

Posted September 13, 2008 - 07:39 PM

#10

Better measure your fingers.

  • mike_dean

Posted September 14, 2008 - 07:18 AM

#11

I use the three fingers also, mine are 2 3/8", just ran a very muddy MX, I loosened the chain to 2 1/2", by the end of the race the chain was bound tight with mud build up in the sprockets, there are some situations where more is better. You can always remove the shock and move the swingarm thru its travel and check different adjustments to see if it gets too tight, too tight is very bad for sprockets and hubs. Mike

  • Dan_187

Posted September 14, 2008 - 01:09 PM

#12

i run about 1.3 inches on my 450 :excuseme: i know its tighter than recommended but i get too much slapping around when i run it proper, i havent had anything bad happen because of it

  • grayracer513

Posted September 14, 2008 - 04:57 PM

#13

i run about 1.3 inches on my 450 :excuseme: i know its tighter than recommended but i .... havent had anything bad happen because of it

You will. If you ever want to see why, have two of your friends sit on your bike at the same time and check out your chain. A better thing to do would be to pull the relay arm bolt out of the swing arm, then lift the rear wheel through its travel.

The reason that much play is called for is that the chain is not at its tightest when the bike is on the stand. The tightest point is when the centers of the output shaft, swing arm pivot,and rear axle are aligned. At this point, the chain must have about 1/4" per foot of free chain of actual slack (push down, pull up, measure). If you set it that way, then replace the bolt and check the chain per the manual, you'll find the chain will measure 1.9" if it's an '06 or later, 1.6" if it's an '05 or earlier.

You will find yours nearly impossible to swing through the center point. The load this places on everything the chain is directly connected to, hub, sprocket and bolts, trans and swing arm bearings, and the chain itself, is extremely high, easily exceeding 7000 psi in most cases.

Why the difference in the model years? The lower chain roller on the '06+ is placed lower on the frame than on the earlier models, so that the roller does not take out as much of the slack with the wheel extended as on the older bikes.

  • BASSic

Posted September 15, 2008 - 01:00 PM

#14

i run about 1.3 inches on my 450 :excuseme: i know its tighter than recommended but i get too much slapping around when i run it proper, i havent had anything bad happen because of it


I run what my 426 manual calls for (1.6" to 2.0") and I get a lot of slapping. I don't know if it's just the 426 or if all YZ models are like this, but because of this slack the top of my chain is wearing rapidly from the chain making contact with the rear chain guide wear block which is also wearing rapidly.

Despite this, I feel comfortable knowing that it's easier (and cheaper) to replace a chain than a hub or countershaft or transmission gears.

  • grayracer513

Posted September 15, 2008 - 01:49 PM

#15

I run what my 426 manual calls for (1.6" to 2.0") and I get a lot of slapping. I don't know if it's just the 426 or if all YZ models are like this, but because of this slack the top of my chain is wearing rapidly from the chain making contact with the rear chain guide wear block which is also wearing rapidly.

That's the nature of things. The ORN6 chains I run usually wear out one master link clip during their useful life, and it gets to be a tossup as to whether the chain will wear the pins enough to need replacing before the top of the chain wears down to the rollers.

  • WB450

Posted September 16, 2008 - 09:19 AM

#16

i run about 1.3 inches on my 450 :lol: i know its tighter than recommended but i get too much slapping around when i run it proper, i havent had anything bad happen because of it



It's just me, but I would rather hear slapping than snapping. I would go a little looser.:excuseme:

  • grayracer513

Posted September 16, 2008 - 09:50 AM

#17

BTW, I have a simple three inch long wooden block in my tool box. It's the cut off end of a longer piece that I ran through my table saw. It measures 2" thick one way, and 2.4" the other. I slide the thinner side under the chain, and if I can't roll it up on it's other edge, the chain's good.





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