Need Help adjusting chain slack

[n8kdfz8]

I was told twice that my bike feels and sounds like i my chain "SLAPS!??" So I want your guys advice and help please on adjusting my chain slack. factory specs in yamaha fz8 service manual state that chain slack should be 20mm-30mm. Question is am I checking the chain slack correctly? I check chain slack from the "chain pins" in multiple places after rotating rear wheel. I push the chain "up" with little effort till it stops and count that measurement as 0mm and then let chain rest. Once chain stops in resting position i take measurement. i adjust chain until chain pins measure between range of 20mm-30mm. Is this correct? Or do I push then chain up and down forcing it with much effort till it stops? Note: when torquing rear wheel nut, I do stick screwdriver between chain and rear sprocket then rotate wheel till stops so that wheel lines up straight and forced towards front of bike.

I watched countless "youtube" videos and they say 1in - 1.5in chain slack.

Thanks for your help and sorry for noob question.

 

[DJK1505]

Put the bike in neutral, at the longest point on the bottom side of the chain, kinda right behind the swing arm pivot point, you should have no more than two inches total play. That means two inches max, from the highest point you can pull it up, to the lowest point you can push it down.

DJ

 

[DJK1505]

do not put a ton of force on it, just pull it up, and push it down and see how much slack you have.

Why are you sticking a screwdriver anywhere around the rear of the bike? Your rear axle nut is flat sided so you can torque it and the axle will not rotate on you.

DJ

 

[JSP]

Like DJ said. Push up and THEN down but not with a lot of force. Just an easy up and down. Do this where there is the most slack to begin with, towards the middle of the chain.

Different bikes have different slack specs. Your swing arm and owners manual will have correct specs.

 

[n8kdfz8]

Put the bike in neutral, at the longest point on the bottom side of the chain, kinda right behind the swing arm pivot point, you should have no more than two inches total play. That means two inches max, from the highest point you can pull it up, to the lowest point you can push it down.

DJ

Ok so, use "bottom" of chain for all measurments? Two inches huh? That sounds like a lot. So in a sense my factory 20-30mm i've been using has been to tight? If it is tight that wouldn't cause a chain slap then right? Chain slap is due to a loose chain not tight?

Thanks for ur help!!!

 

[DJK1505]

20-30mm is about 1-1.25 inch. I use 2 inch as a max. Just a general measurement I use as I work/ own several different model of bikes. Go by the book. To tight of a chain will damage/ bend your output shaft before it snaps a chain.

DJ

 

[JSP]

Ok so, use "bottom" of chain for all measurments? Two inches huh? That sounds like a lot. So in a sense my factory 20-30mm i've been using has been to tight? If it is tight that wouldn't cause a chain slap then right? Chain slap is due to a loose chain not tight?

Thanks for ur help!!!

Too tight can eat up your output shaft bearing which is a no no. Must remove engine and split case to replace that.

Make sure you have proper slack and the wheel is aligned correctly.

What are you thinking is chain slap? Are you hearing something? Seeing something? Chains move while riding. They make some noise.

 

[DJK1505]

get your bike up to about 6K, let off the throttle and twist it pretty hard. Dont pull the front end up, but this will torque the hell out of your chain. If you hear metal smack something your chain is way too loose. Its just as easy to get off the bike, and pick it up and down,2 inch is about the length of your index finger from your middle knuckle to the end of your finger. Hold chain up, put middle knuckle up to chain, drop chain, if it goes past your finger, tighten up your chain.

DJ

 

[n8kdfz8]

do not put a ton of force on it, just pull it up, and push it down and see how much slack you have.

Why are you sticking a screwdriver anywhere around the rear of the bike? Your rear axle nut is flat sided so you can torque it and the axle will not rotate on you.

DJ

Well i watched on acouple videos that "AFTER" all adjustments r made, u put the shaft of the screwdriver between the top of rear sprocket and under the top chain, rotate tire backwards,this pulls the chain tight and and the rear tire foward then torque rear axle nut. If it doesn't need to be done like that because of our flat sided axle nut like u said then i definetly wont do that anymore.

Thanks again for ur help!

 

[n8kdfz8]

Too tight can eat up your output shaft bearing which is a no no. Must remove engine and split case to replace that.

Make sure you have proper slack and the wheel is aligned correctly.

What are you thinking is chain slap? Are you hearing something? Seeing something? Chains move while riding. They make some noise.

I think i have slightly tight chain slack. because when i last checked it couple days ago i pushed the chain up with little effort (to 0mm using top of chain) and pushed down to (about 26mm using bottom of chain). but when i get home tonight ill check 0-2 inches using only bottom of chain like "DJK1505" advised me to.

As to ur question about what i think is chain slap. I thought its described as a loud metal slap of the chain when decelerating / shifting. And if i heard anything abnormal?....no i didn't notice anything abnormal. My buddy asked if my chain slack correct cause he felt like he heard the chain slapping. my buddy was the second person to say that to me. so thats why im asking for ur guys help if im adjusting chain correctly. i personally dont feel i have any chain slap occuring. but i just want to be cautious because after u described repairs of tight chain i dont want that to happen.

I appreciate all your help, thank you!

 

[rug_burn]

You just want some slack, but about as litle as possible. The point is not to put a load on bearings or chain continuously. 1 inch total is good. You can tell by the fact that they specify a large range that this is not a precision adjustment. You just want some slack, not tight.
Rapid accel/decel throttle controls that jerk on the chain will stretch it out like nothing else- those are what you want to avoid.

 

[n8kdfz8]

get your bike up to about 6K, let off the throttle and twist it pretty hard. Dont pull the front end up, but this will torque the hell out of your chain. If you hear metal smack something your chain is way too loose. Its just as easy to get off the bike, and pick it up and down,2 inch is about the length of your index finger from your middle knuckle to the end of your finger. Hold chain up, put middle knuckle up to chain, drop chain, if it goes past your finger, tighten up your chain.

DJ

Well good news I checked my chain slack before adjusting again and found that it was exactly 20mm. So even though it was technically ok i re-adjusted it anyways to 1.25mm. then i tried your test of getting bike up to 6k rpm then let off throttle and twist it hard and no metal smack noise. thanks for all your help! It was extremely useful!