Sprocket / chain issue

[joeyballz]

Good afternoon everyone. Soas I dive more and more into the project, the more issues I come up with. I cut off the crappy welded plate and bought the Burris 15degree into motor mount. (Very nice item). So for starters I measured my axle and it's 1.5in. I picked up a brand new chain today. The clutch is a 13tooth stand 3/4 piece. The issue is the axle sprocket. It is a 2piece design which I guess the orginally owner installed to make swapping easy. However the chain was not sitting right on it and skipped off the sprocket each revolution around. I took the sproket pieces off and it's warped slightly. It is a 53 tooth. Question is...what size should I replace it with. (Predator 212cc) and I'm 240lbs. Keep split design? Sorry for length for question but I wanted to be detailed.

 

[anderkart]

Split sprockets work fine, you just need to buy a high quality brand and instal them correctly.
I always had good luck running Horstman brand split sprockets on my racekarts.

One side of each sprocket half will be labeled with a tooth count,
You need to instal both half's with this label pointing away from the sprocket hub.

Then instead of immediately tightening all the nuts/bolts, start with just barely snugging them up;
Instal your engine, clutch and chain, with the chain tension adjusted fairly tight,
Then jack up the back of your kart, and spin the axle around serveral times. This will allow the sprocket halves to better center themselves to each other & the hub before you do the final tightening.

Then as you tighten these bolts, take your time working your way around the 6 bolts and just gradually tighten each one just a little bit at a time until they're all fully tight. (but don't over-tighten these 6 bolts to the point of deforming things, just get-em snug and use a new set of lock-nuts so they won't loosen!)

Then spin the axle again to see if the sprocket halves are running true & perfectly aligned with each other or not, If not, loosen the 6 bolts and repeat this whole process again until you get it perfect !!!

Horstman split sprockets are available at most any racekart shop, including here:
http://out2win.com/catalog/sprkt_axle.html

Installing a sprocket guard on each side of the sprocket is a good Idea to help the chain stay on, they also help protect your chain and and axle sprockets making them last longer...
The "Part# 'KM 1081' Sprocket Guards 9" OD Nylon - 2 Sides" at this link works very good for reasonable price: http://out2win.com/catalog/sprkt_acc.html
But you might need to buy 6 longer bolts when installing sprocket guards.

You can check out the pics on my old racekart thread to see what sprocket guards look like when installed, you'll find my pics at this link: http://www.diygokarts.com/vb/showthread.php?t=6364
______________

Is your 13-tooth clutch made for the #35 pitch chain size?

If so, I'd suggest you start out with an axle sprocket somewhere in the 73 tooth range for a 245lb driver with a 13-tooth clutch and 11" tall rear tires. Most guys with racekarts end up owning serveral different sets of split sprockets, so they can change their gearing to better match wherever they'll be riding or racing...

Investing in a Chain Breaker tool makes it easy to shorten or lengthen your chain if necessary when swapping to different sized axle sprockets...

______________

PS:
Before you do the final alignment/tightening of your split sprockets:
You'll first need to make sure your axle sprocket and clutch are perfectly aligned with each other.

You can use a straight edge across the two sprockets.

Or, I think an even more accurate method is to start out by not installing (or tightening) your clutch retaining bolt: Then, (with the chain adjusted to around a 1/2" of slack, and the back of the kart jacked up), If you simply spin the axle you'll be able to easily see if they align with each other or not, by watching if the spinning axle sprocket & chain moves the clutch inward or outward on the engine. You'll want to align the axle sprocket hub and possibly also possibly your engine & motor mount in a way that spinning the axle moves the clutch (in or out) to the exact position that It'll need to stay when all the retaining bolts are fully tightened up.

Of course your clutch needs to easily slide (in and out) on your engine for this chain alignment method to work.

If your clutch doesnt have set screws, and only uses a retaining bolt/washer at the end of your engines output shaft, you might also discover you'll need to instal shims on the inside or outside of your clutch, so it will remain in the correct alignment to your axle sprocket... Some clutches need shims, and some don't...


________________

PPS:
I've never heard of a 1.5" diameter axle sprocket on a racekart.
I've got a feeling your axle is actually a 40 millimeter metric-sized diameter, that's a very common size

 

[joeyballz]

Wow thank you so much for all the good information. I am going to try reinstalling the old sprocket following your directions until the new one comes. I ordered up a new 55 sprocket but after reading your post i am going to order a bigger one. I eventually would like to go up to a mildly modifed 420 predator to assist with my size but down the road. Couple people told me to get a comet 30 series TC for my preadtor 212 as it would make a world of a difference.

 

[anderkart]

Your welcome. Your gonna end up with a fairly tall gear ratio with 13/55 gearing, don't be surprised if the clutch overheats and burns up from constantly slipping. Although you can help the clutch out by immediately getting the kart up to the speed where you can hear/feel the clutch is locked-in and no longer slipping.

What brand and model of 13-tooth clutch do you have now for your Predator 212cc ?

TC's are cool, you'd definitely get a lot better acceleration, but you'd discover they're quite a bit wider than a centrifugal clutch. You'd probably need to either mod the motor mount to position the engine further right, or move the seat further left, or you'd possibly need to do both to free up enough space for a TC on a side-engine racekart like yours...

Your 55 tooth axle sprocket would be a pretty good gearing combination with a 420cc big block and a 13-tooth, racing clutch like the 1" bore Noram Star model.

 

[joeyballz]

I have a Burris adjustable motor mount so I can move my engine left and right etc. I will check the make on the clutch and get back to you.