Chain tightening problem with hybrid

[YZ400EX]

I already posted this in the Powertrain section, but thought more people would see it here and I wanna get this fixed asap..Ok after trying many times to tighten my chain this is what I have figured out and I dont know why.. well when I have shock fully extended out (swingarm all the way down, quad rear end is in the air) and get the chain to where it needs to be and then drop it down on the ground and put any weight on it the chain gets so tight it wants to break, so I let it down to where it would sit normally and tightened the chain, but when there is more pressure down like if I jumped and landed the chain gets really tight and if I had jumped and the shock extended all the way out like it would if I was in the air the chain is really loose..I dont know how to fix this problem. I cant tell what is making it do this..I dont see anything moving when the rear end is moved up and down..It might be the chain slider?? Just wondering if anyone has any suggestions to help me fix this..Any info is appreciated..Thanks

[Fred55]

all quads do that..just adjust it enough so when the shock is fully compressed, the chain can still move.

[YZ400EX]

I dont remember my 400ex doing it especially as bad as this one is..Like I said if I was jumping and in the air I would be afraid of the chain falling off..thats how loose it is and when the shock is compressed way down with someone sitting on it it seems tight enough to snap..I guess if I never jumped it would be ok, but thats all I do..anyone else?? I mean there is no reason for it to get tight and loose like this..The swingarm just pivots..Doesnt make it longer or shorter by moving up and down..

[Fred55]

Mine gets tighter as the shock compresses, and it loosens if i lift the rear end up, i bet your noticing it just because you most likely have a long travel rear end, correct? it has a greater range or motion than a 400ex.

[YZ400EX]

No I still have a stock swingarm..The shock is just a stock with rebuild, revalve and made dual rate, but still setup for stock location..it is all stock back there..

[Mxjunkie]

maybe you need a half link? is the gearing any differnt then before/placement of motor? The chain and such will loosen and tighten as you move the backend up and down, sit you or someone on the seat and adjust it WHILE on the ground.

[YZ400EX]

No the amount of links wouldnt create this problem..I actually had to remove one link on the chain to even get it to tighten at all..the gearing is the same, but the position of the motor/front sprocket is back a little more then the EX was..I am completely stumped..I know it may slack and unslack a little when moving, but not as much as it does..

[Mxjunkie]

Originally posted by YZ400EX
No the amount of links wouldnt create this problem..I actually had to remove one link on the chain to even get it to tighten at all..the gearing is the same, but the position of the motor/front sprocket is back a little more then the EX was..I am completely stumped..I know it may slack and unslack a little when moving, but not as much as it does..


The chain will stretch as soon as you ride it. 1 inch or so is about the play you want in a chain

[SRH]

your suppose to adjust the chain with it sitting on the ground, run about a inch and a half of slack

[SGA]

Originally posted by YZ400EX
No the amount of links wouldnt create this problem..I actually had to remove one link on the chain to even get it to tighten at all..the gearing is the same, but the position of the motor/front sprocket is back a little more then the EX was..I am completely stumped..I know it may slack and unslack a little when moving, but not as much as it does..

I'll betcha the new engine sprocket sits a bit lower than the original.

If the front sprocket is lower than the original, its going to be to looser than normal with the swingarm down and too tight with the swing arm up.
You may need to install a chain roller tensioner.

[SGA]

Or raise the rear of the motor up a half inch or so. That should cure the problem. Did you buy a kit with the motor mounts or make your own?
Put the quad on a stand. Disconnect the rear shock, disconnect the rear motor mount and loosen the other mounts so the rear of the engine can move up and down.. Raise the swing arm up and down and adjust the rear of the motor up or down until the chain stays more or less the same tension throughout the swing arm travel. Thats the correct height for the rear of the motor.

[YZ400EX]

I have talked to a few other people that have done these conversion and I guess my problem is normal on these..kinda wierd, but whatever..as far as raising the motor there would be absolutely no possible way to do this..the swingarm pivot bolt goes through the motor..

[SGA]

If the rear of the engine wont go up or down, then thats where it stays. Maybe you can lower the front of the motor some or add a spring loaded chain tensioner to keep slack out of the chain when the swing arm is all the way down.

[YZ400EX]

Yea..It's where its gonna stay..nothing can be moved, but the spring loaded chain tensioner is a good idea..I will look into that..Thanks for all the help..

[Flynbryan19]

Your making it way harder than this has to be. :) SRH had the answer to your problem. Don't make it so hard on yourself. You do NOT adjust the chain with no load on the suspension. You always measure your chain slack with the suspension loaded. The best point to measure it is when the swingarm is in line with the front sprocket. I do this by using a tie-down strap from the rear of the axle to the grab bar to pull it down.

[SGA]

Originally posted by Flynbryan19
Your making it way harder than this has to be. :) SRH had the answer to your problem. Don't make it so hard on yourself. You do NOT adjust the chain with no load on the suspension. You always measure your chain slack with the suspension loaded. The best point to measure it is when the swingarm is in line with the front sprocket. I do this by using a tie-down strap from the rear of the axle to the grab bar to pull it down.
I agree, but what do you do when the chain is about to fall off when the swing arm all the way down (jumping) and about to break when its all the way up? (landing from a jump)
Remember, he changed the engine type and if the rear sprocket is not the exact height as the original, you will run into binding problems. Thats basic geometry.
Im sure he could look around on the net or call one of the quad builder professionals if its going to give problems.
YZ400EX, post a close up picture of the side of the quad in the rear sprocket area. Im curious to see it.