Chain pops off when turning.

[Ntv03]

Hello everyone. Just built this kart with my son. #35 chain. Chain pops off the sprocket only when turning. When taking off fast the chain also has a popping noise but does not come off the sprocket. Chain has maybe 1/4 - 1/2 inch slack. And as far as i can tell, everything in aligned. Axle kit is brandnew from BMI. Any ideas?

 

[Ntv03]

 

[Snaker]

Curious to know what would happen if you lifted one of the rear wheels and put it on a 4x4 block, what sort of frame twist you would get.

 

[redflash]

sounds like under stress the axle is slipping right or left. ( when you turn) I don't see any locks beside the bearings holding it tight

 

[Master Hack]

Somerhing is moving. Question for the guys that know this stuff: Is axle flex a common problem with a long span like that rear? I put a center carrier bearing on my junk, but is it unnecessary? I know diameter, material lenght hp yada yada yada. just wondering, rusting minds need to know!
never had much luck with #35 chain.

 

[Master Hack]

A really handy tool, l’ve found , is a go pro camera, mounted watching the offending parts. Takes some of the guessing out of the diagnostic process.
i suppose any video camera and some duct tape would work…

 

[madprofessor]

First of all, kudos for your gray matter being smart enough to build with a hub and split sprocket.
Secondly, I'll tell myself you're just not finished with the build yet. Since that shopping cart could hinder your son from being thrown clear in a rollover (no seatbelt when there's no rollcage), I'll tell myself the rollcage and 4-point safety harness are your next step in the build.
Thirdly, T.Davidson sees the same thing I do, maximum strain from the motor pulling on a sprocket in the middle of a long stretch of unsupported axle, likely flexing it under load. You need another pair of pillow blocks mounted as far to the inside of your frame plates as you can get them. Fourthly, you got it right with the split sprocket, but blew it with the solid locking collars, should have been double-split collars, and NOT just "split collars". You need one on the inside of both existing pillow blocks, and one on each side of both the sprocket hub and the brake disc. Have to pull the bearings off to add more bearings anyway, good time to get rid of those solid collars with the setscrews that are scarring up divots into your axle. Sand those out. Double-splits install in 15 seconds.
Now about that chain skipping teeth when under load.............Usually due to too much slack in the chain, sometimes due to axle flex, motor twist, or frame twist. You can't say a chain has .25 - .50 slack when chain is short as yours, and also when it's as long as my 3-footer, it's different for every length of chain, and I'm betting yours is too slack. Your motor has a solid mounting, minimal squishy pads under the bolts, and a short chain, no problems there. Likely has some axle flex, but you can temporarily tighten the chain enough to stop the skipping of teeth until you get another pair of pillow blocks on it. Check out the links below.................
UCP205-16 Pillow Block Bearing 1" Bore 2 Bolt Solid Base (2PCS) (jeremywellindustry.com)
1" Bore Double Split Shaft Collar Black Oxide Set Screw Style (4 PCS) (jeremywellindustry.com)
Jeremywell Industry (links above) has great parts and service, but you can get that kind of stuff from Amazon or Ebay a little cheaper.
EDIT: Don't forget about the existence of half-links (offset links) for making up chains when a full master link is too much..................
#35 Roller Chain Offset Replacement Links. 35-OL, P/N#76351, FREE SHIPPING | eBay

 

[madprofessor]

T.Davidson is right about the "action camera", I bought mine for that very purpose. Found the long motor mounting plate was flexing downward under load, had to reinforce it. Then used it to verify the shifting of the pulleys on my CVT. Here's the links to what I bought...............
Campark 4K HD 20MP 1080P Waterproof Sport Action Camera WiFi EIS Video as Go Pro | eBay ......NOTE: Lens angle is fixed, not adjustable.
GPCS-S: EVA Hardshell Case for GoPro HD Hero Sport Camera & Accessories | eBay ........Very smart purchase, fits camera and parts perfectly.
....and emergency STOP slap-switch (kill switch). 1PC 22mm Twist Release Emergency Stop Mark Mushroom 40mm Push Button Switch | eBay
....and a very useful and cheap tachometer, Black Digital Tach Hour Meter Tachometer Gauge For Dirt bike ATV UTV Gas Engines | eBay
....and some protection. Funny Go Kart warning sticker Cart decal | eBay

 

[Ntv03]

First of all, kudos for your gray matter being smart enough to build with a hub and split sprocket.
Secondly, I'll tell myself you're just not finished with the build yet. Since that shopping cart could hinder your son from being thrown clear in a rollover (no seatbelt when there's no rollcage), I'll tell myself the rollcage and 4-point safety harness are your next step in the build.
Thirdly, T.Davidson sees the same thing I do, maximum strain from the motor pulling on a sprocket in the middle of a long stretch of unsupported axle, likely flexing it under load. You need another pair of pillow blocks mounted as far to the inside of your frame plates as you can get them. Fourthly, you got it right with the split sprocket, but blew it with the solid locking collars, should have been double-split collars, and NOT just "split collars". You need one on the inside of both existing pillow blocks, and one on each side of both the sprocket hub and the brake disc. Have to pull the bearings off to add more bearings anyway, good time to get rid of those solid collars with the setscrews that are scarring up divots into your axle. Sand those out. Double-splits install in 15 seconds.
Now about that chain skipping teeth when under load.............Usually due to too much slack in the chain, sometimes due to axle flex, motor twist, or frame twist. You can't say a chain has .25 - .50 slack when chain is short as yours, and also when it's as long as my 3-footer, it's different for every length of chain, and I'm betting yours is too slack. Your motor has a solid mounting, minimal squishy pads under the bolts, and a short chain, no problems there. Likely has some axle flex, but you can temporarily tighten the chain enough to stop the skipping of teeth until you get another pair of pillow blocks on it. Check out the links below.................
UCP205-16 Pillow Block Bearing 1" Bore 2 Bolt Solid Base (2PCS) (jeremywellindustry.com)
1" Bore Double Split Shaft Collar Black Oxide Set Screw Style (4 PCS) (jeremywellindustry.com)
Jeremywell Industry (links above) has great parts and service, but you can get that kind of stuff from Amazon or Ebay a little cheaper.
EDIT: Don't forget about the existence of half-links (offset links) for making up chains when a full master link is too much..................
#35 Roller Chain Offset Replacement Links. 35-OL, P/N#76351, FREE SHIPPING | eBay

Thanks, this is my very 1st build of a go kart. I ordered the parts you suggested. Yes, seat belt is coming. Everything was trial and error with this kart. Definitely learning a lot. I had my buddy turn and the axle is not flexing. But does move a tiny bit side to side. My son loves it. Just want to get things in order. And i actually have 2 more pillar blocks sitting in a box in the garage.

 

[Ntv03]

Do you think this would work? Or it would be overkill?

 

[madprofessor]

Do you think this would work? Or it would be overkill?

Take a look at these pics and you'll know I don't care if it's overkill, long as it's over-'n-done. The 1" axle has 4 pillow blocks slung underneath, and the 3/4" jackshaft/swingarm pivots have 6 pillow blocks mounted on top.
Note: The 3-piece jackshaft/swingarm started as a single 44" shaft. It only got cut up into 3 pieces after being mounted on all 6 pillow blocks, keeping the swingarm pivots perfectly in line with the jackshaft so that the secondary chain tension never changes, regardless of the swing of the swingarm. You see that in earliest build pic.
Mount those pillow blocks right where you have them, and I guarantee the axle will never flex.
Note: The closer you can move those wheels in toward the outer bearings the better. Reduces strain on the axle.

 

[Ntv03]

Take a look at these pics and you'll know I don't care if it's overkill, long as it's over-'n-done. The 1" axle has 4 pillow blocks slung underneath, and the 3/4" jackshaft/swingarm pivots have 6 pillow blocks mounted on top.
Note: The 3-piece jackshaft/swingarm started as a single 44" shaft. It only got cut up into 3 pieces after being mounted on all 6 pillow blocks, keeping the swingarm pivots perfectly in line with the jackshaft so that the secondary chain tension never changes, regardless of the swing of the swingarm. You see that in earliest build pic.
Mount those pillow blocks right where you have them, and I guarantee the axle will never flex.
Note: The closer you can move those wheels in toward the outer bearings the better. Reduces strain on the axle.

Im going to rip it apart today and ill keep you updated. The shaft collars come tomorrow along with the half link. Hopefully this fixes it...

 

[Master Hack]

Next you might find the chain stretches. I did with 5hp and maybe a little lighter kart. #35 chain is great for bicycles. Welcome to planet overkill.

 

[Ntv03]

Next you might find the chain stretches. I did with 5hp and maybe a little lighter kart. #35 chain is great for bicycles. Welcome to planet overkill.

My torque converter came with a 35# 12t and 10 tooth sprocket for #41/40/420 chain. Should i just swap the 2 peice #35 sprocket now before anymore issues?

 

[Master Hack]

Well thats up to you. Try it and see what happens. I had the same options. I tried it and was constantly adjusting the chain. After a couple of days l switched to #420 and end of problem. I also found a better quality chain at the motorcycle shop.

 

[madprofessor]

35# 12t and 10 tooth sprocket for #41/40/420

Chains are like a lot of other things, mo' money gets you mo' better. I've gotten the same sprocket choice as you in 2 Chinee CVT kits, but I've used only #35 chains on Predator 212's with those CVT's, one hotrodded to about 12hp. on a minibike (buyer's probably in a hospital) and one hotrodded to 15+hp. on current kart and never broke a #35 chain. Here's how I've chained them up, one on minibike and two on kart.................
#35 Roller Chain 10 FT FEET + Free Connecting / Master Link + Same Day Shipping | eBay.......and.........# 35 Chain Connector Link Qty 10 Spring Connecting Master For Roller Chain 35C/L | eBay..........and..........10Pcs #35 Chain Offset Half Link Roller, 3/8" Pitch Carbon Steel for 06C Chain 782685901505 | eBay.........using this worthless type at first.........Roller Chain Cutter Breaker Detacher Splitter for 25 35 40 41 50 60 420 415 520 | eBay........and then using this proper type.........35 Chain Breaker Tool Racing Chain Press Tool CNC Steel Constructure J3Q4 194724868357 | eBay.
The chain does stretch a little at first, but 1 or 2 adjustments wasn't a problem, and they never stretched further. However, mo' money can buy you pre-stretched and better quality chains..........120 Link #35 RLV Extreme Chain Gold on Gold Racing Go Kart Cart Drift Trike Part | eBay.
My #35 decisions were based mostly on the availability and price of #40, #41, #420 split sprockets, chains, etc. Look at this BMI page from searching "split sprocket" and note the minimal number of split sprockets larger than #35, and their crazy prices from Asuza.
Search Results > split sprocket (bmikarts.com)

Welcome to planet overkill.

I'm a huge fan of overkill on most everything, but needing a .50 cal. Desert Eagle when a .25 cal. Raven is all there is, overkill gets difficult.

 

[Master Hack]

I'm a huge fan of overkill on most everything

AWW Come awn! there is no such thing as overdoing overkill!
Probably doesn't help that the grand brat is s fearless, lead foot maniac!

 

[anderkart]

Not sure if this has allready been suggested, but try standing on your seat while checking chain tension. You might be surprised how much frame flex can alter your chain tension...

 

[Dingocat]

I had one where bad bearings caused play, lifted it up and put the chain on, loose chain would pop off with weight. Clearly not the problem but deffinitly fix the axle walking.

 

[Denny]

Do not put seatbelts in that thing! In a roll over he will break his neck! As it sits now he will just break both legs very badly. Those bars above his legs will not let him safely eject in an accident. He will get hurt. I’m ashamed at you guys for not pointing it out to him sooner! While the kart looks very cool it is unsafe with that shopping kart on there like that! But it can be made safe and still keep the shopping kart.
Now for your other little problem. I prefer spacers over the axle to keep everything centered. Are you sure all your sprockets and chain matches?