Chain problem-

[JAGUARMAVEN]

Hello,

I just finished {or so I thought} a full restoration of a 1970's era Margay Cheetah:

media blasted frame, new OHV 6.5 motor {Harbor Freight special $109.00}, custom rear disc brake, throttle and brake cables, axle, axle bearings, sprocket, wheels, tires, clutch etc etc etc.

Anyway, on it's maiden voyage yesterday {in the rain} it ran great EXCEPT every time we would take a hard left or right turn the chain would pop off the sprocket. After the 5th time it continued to do this, I had to pull the plug on riding.

The axle sprocet and clutch seem to be in a perfect linear alignment. When I installed the motor I clamped a metal straight edge to the sprocket and aligned it with the teeth on the clutch so I don't think that the alignment is a problem there.

The new solid rear 1" axle in held in place by 4 axle bearings:

2 on the frame itself and 2 more axle bearings that are part of the swing arm engine mount.

Any ideas why this keeps happening? I have about less than 1" delflection on the new chain so I don't think that it is too loose.

Thanks for any advice.


Regards,

Dan Siegel

 

[GreyhoundOfYerfDogs]

I'm not sure what you mean about the two bearings that are part of the swing arm mount. The axle and engine should be mounted on their own rigid subframe so the chain is unaffected by suspension travel.

The axle is probably "walking" left and right on turns. Make sure your collars are tight and that the bearings are installed correctly (left and right bilateral asymmetry, thrust face and collar both facing each other. Make sure the bearing hangers cannot flex on turns.

 

[Russ2251]

I am very familiar with the Azusa swing mounts you speak of. Excellent product.
I use 2 of them for my twin engines.
Slack in chain is probably the culprit.
Should be much less than 1", but never tight.

The axle sprocet and clutch seem to be in a perfect linear alignment. When I installed the motor I clamped a metal straight edge to the sprocket and aligned it with the teeth on the clutch so I don't think that the alignment is a problem there.

I use a plumb bob as opposed to a straight edge.
I had some chain probs early on, but are non-existent now.

 

[anderkart]

Make sure your sitting in the kart (or at least standing on the seat) while you check your chain tension. Depending on the kart and how much you weigh, side-engine race kart frames can flex quite a bit and cause the chain to be much looser than you think while your riding.

I usually go for somewhere around a 1/2" of freeplay while sitting in the kart, but block the rear wheels up off the ground (and while standing on the seat) spin a tire to make sure the chain rolls freely so you know its not too tight and binding.

Something else to consider is even though you used a straight edge to line up your sprockets, Its possible your rear axle and motor mount may not be perfectly square to each other causing the chain to come off. If their not perfectly square, sometimes sliding the rear sprocket over just a little bit is an easy way to compensate and help keep that chain on. (of course having a high quality chain and sprockets in good condition helps a bunch too)

 

[JAGUARMAVEN]

Thanks for all of your imput. I'll see if I can post some pics later today. I'll check the alignment again re the engine and the gears.
I was thinking of installing an idler gear. I can weld up a mount with an adjustable rod so I can simply screw the idler up a bit higher each time I need to remove slack. Has anyone done that mod? Seems like an easy enough solution to chain slack.

Regards,

Dan Siegel

1950 Ford F2 pickup
1971 Jaguar E Type
1973 Margay Cheetah
1974 Jaguar E Type
2006 Mustang GT Conv

 

[anderkart]

A couple things Dirt Oval kart racers use is sprocket savers or chain guides to help keep their chains on because their frames are designed to flex so much this sometimes causes alignment issues and their chains tend to fly off while hitting bumps, turning and contact with other karts on the track.

The most commonly used on Dirt oval are Sprocket Savers. Their just basically a couple aluminum or hard plastic disks that bolt on either side of the sprocket and act as a guide keeping the chain from rolling off the rear sprocket. They also keep the chain/sprocket from digging in the ground while hitting big bumps and driving over berms and stuff. They're available starting around $20 and bolt right up to any standard race hub.

That's what I use on my kart shown here:
(you could also substitute a couple old used/wore out sprockets instead of buying these)

Here's a link to a roller guide some dirt oval racers use instead of sprocket savers: http://ultramaxracing.com/cart/index.php?l=product_images&p=133

Here's a video of a spring loaded chain guide in action:

http://www.youtube.com/watch?v=jP7BXihi8eU

 

[JAGUARMAVEN]

Thank you for that video.

Do you happen to know where I could purchase the Sprocket Savers? And could they also used used on the clutch side?


Regards,

Dan

 

[Russ2251]

Here's one. There are many more suppliers:
http://www.mfgsupply.com/GoMiniSprocketsGuards.html/mv_session_id=KUrzSmnr

 

[anderkart]

Here.s some more: http://www.out2win.com/catalog/sprkt_acc.html

I dont know of any similar products for your clutch/driver gear but you dont need one there anyway. There's pretty much always a higher tendency for the chain to roll off the larger sized gear.

 

[JAGUARMAVEN]

Thank you both for those links re the Sprocket Guard.



Regards,

Dan