How tight are you getting the engine stop bolt(s)? Sometimes with a rubber stopper hand tight isn’t enough. You may be able to keep better tension on the motor if you use a wrench to eliminate the last little bit of play between the bolt and the motor mount.
This was my next question
Axle doesn’t appear to be shifting side to side, but I did recently notice it seems like my axle bearings might have some play in them like I feel a small play if I pick up on the axle. Not sure how much should be considered normal there or not. When I get the dial indicator stand I’ll measure that as well.
Axle bearings shouldn’t give enough lateral play to be doing this, tap your axle laterally left then right to see is it moving. It’s quite strange I’m a bit foxed, any progress?
The chain isn’t to tight prior to running is it? I would have that problem with my 420 but never with a 206. I could tell when it was to tight though as the kart would have a bad push. If you find nothing else run with more slack in the chain.
Hey Ron, I’d say I’ve gravitated to having the tension tighter as I’ve gone on this year. I initially thought the tension was too loose and causing the issue. Again I’ve got a direct comparison to Andy who’s using the same chassis, motor mount, motor, etc and his was typically tighter than mine. Coming from KT100s where we ran the chains on the verge of too loose to make sure there was no drag I’d say KAs definitely seem to normally be tighter, but I suppose I could try loose again.
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I didn’t get a lot of time in the garage tonight, but played around with the new dial indicator stand. Some measurements and observations I was able to take:
Axle run-out/variation where the sprocket mounts was 0.007". closer to the end where the wheel would be I’m getting more like 0.011". I’m not sure what’s normal or acceptable there. Any ideas?
I could also get 0.004"-0.005" of bearing up/down play so I guess if you combine that with the axle run-out under load it could be upwards of 0.012" at the sprocket. Anyone know if the bearings should have that play or not?
I could not get any measurable side to side axle movement.
I also have ZERO idea how much the axle flexes during normal use so all of that may be moot if the thing is typically flexing more than that.
The sprocket itself isn’t completely flat/true, but I also have noticed that for every single sprocket/carrier I’ve had in the past. Measuring from the side as close to the teeth on the axle (outer diameter) sprocket as i could I got 0.013" of variation throughout one rotation.
I checked again axle sprocket to front sprocket alignment using the laser and while it would vary a bit around different areas on the sprocket (likely due to the above noted variability), it would never move enough to not be lined up with the small flat end of the front sprocket (about 0.1" wide).
I also spun the front sprocket while keeping the laser on it and couldn’t see any discernible movement which would tell me that the front sprocket isn’t spinning at an angle away from the rear sprocket, unless someone has a better way to test that.
Also to note, I’m currently on a borrowed motor which means I’ve tried and had this issue while using a completely different motor, clutch, and OTK magnesium motor mount. I’ve also tried different bottom mount clamps without noticing any difference. I’m still quite perplexed as to the issue.
My proposed next steps are:
- Fit new axle bearings
- Fit new axle and compare run-out of both the axles and bearings
- Rebuild the brake caliper with fresh seals, fluid, and a bleed to make sure it’s not sticking after being released.
- Try a different chain lube.
- Be more careful when driving to make sure I’m not using the gas and brakes at the same time.
While I’d love to test these independently to try to narrow down the single issue, I have neither the time or patience to do that, nor the desire to keep sacrificing chains and sprockets in the name of the scientific method.
The axle runout is high to me. Combine that with the bearing play and that seems like quite a bit of movement.
Chris – What chain lube are you using and what is your brother using?
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I’ve gone through a myriad of lube strategies. When we raced Yamaha I used chain wax exclusively. The chain would get completely cleaned and then dipped in molten speedwax. One chains waxed like that would last an entire race weekend with no additional maintenance needed and cleanup was easy.
With the KA I found the wax could only last one session which created a need for updated strategy. Initially I was still doing the full dip and then supplementing after each session with squirt liquid wax. Then when I experienced these issues I went back to Xeramic which I had used in the past, but I still stretched a chain so I didn’t continue with it. I also tried Bel Ray Super Clean with similar results. Recently I tired the Squirt wax made for e-bikes that’s supposed to have more friction modifiers in it.
Meanwhile my brother uses the standard squirt wax, no full dip. He cleans the chain, applies a couple coats to dry before race day, then one after each session and no issues. I’d also note I follow this regimen for my sons kart just fine but isn’t quite as apples to apples on his mini Swift.
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You may have to remove any clutch/chain cover to do this, but I find it a more accurate measure of alignment. Resting one end of the straight edge on the side of the driven sprocket and the other on the side of the drive sprocket so that its over front and rear ends. Do you see any variations in the contact surface between the straight edge and the sprocket? You should check at several degrees of rotation for each. You may also want to check the lateral crank run out in case the crank is shifting slightly. If it is, you can try to split the difference with the laser.
Yeap thanks Greg that’s exactly what I was eluding to. This is how I set mine up - if the driver or driven sprockets are off kilter in regards to their plane of rotation, it’ll eat chains for breakfast - this method will identify where a laser cannot.
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Yes, centerline of rotation of the axle and the engine may not be parallel. Look at the drive sprocket and see if that has excessive wear. Chain reliability should be a no brainer with LO or 100cc. I use Bel Ray Chain Lubrication for years (10?) and oil the inside of the chain and get many races/practices out of one chain but there are some chain oils that do not work.
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Personally, I just think it’s because the kart is bogged down due to a mid corner slide. Once it bogs down you’re putting a lot of stress on the chain. Try doing a session (or two) of just rolling corners and not trying to throw it in so hard.
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Does your brother has the same weight as you?
The chassis tends to bend just in front of the bearing carrier,so if he is a heavy guy
and the track is bumpy than there is a lot of movement and bending.
Normally when you get in a kart the chain gets more slack.
We run the same class and are typically within 5lbs of each other. I’m slightly taller so carry my weight a bit higher.
Still didn’t get to the bottom of it?
Testing today and race this weekend, we will have more data next week.
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Still not sure on the solution. I ran the chain loose enough that it popped off during the last session of practice yesterday. Haven’t had a chance to see if that’s cause the chain stretched or just from flex as it was in the highest load area of the track and over bumps.
Have you considered the chassis could be out of alignment?
Is the chain tension the same before and after a session?
Another solution would be to purchase a set of new front and rear gears, an O-ring chain and an O-Ring chain lubricant.