In the home stretch

[Kasea]

hey all new here and looking for advice on my build. I started out with a kesea adventure buggy and stripped it down stretched it, and repowered it and now in the final stages I'm running into problems. To start I cant seem to keep the chain on the sprocket. Now reading up on new chains they can stretch out after the first go, after running it for 20 min i had to take out 1 link of #530 chain. Its tight enough but will still pop off, i attempted to attach a chain tensioner/ guide. But the chain falls off i have made sure the alignment of the sprockets is straight its a head scratcher . I will attach some photos of my progress to better describe my kart and the build .

Photos attached

 

[Budget GoKart]

Hmm thats strange possibly the stock sprocket could be bent put it on jack stands and spin the axle it could be slightly bent

 

[still kikn]

In that last pic it looks like the chain has been through a war. I guess that happened when it got thrown off. I see several spots that are gouged and or mashed. Also the offset link looks kind of weird but hard to tell from the pic. I'm no fan of offset links and that would have been the one I removed if chain needed shortening. Looks like the chain is plenty tight, possibly too tight which can create problems too. If your positive the sprockets are aligned and have no sideways movement, and sprockets aren't warped, I'd loose that half link and while you have the chain off check it over close for any binding, bent or twisted links.

 

[Kasea]

Thanks for the quick responses yeah the chain got pretty chewed up on the jack shaft when I shortened the chain i took the link out that got the worse of it i added a half link or offset link to get the tension just right ill add some additional pictures of the chain

 

[still kikn]

That's some serious damage to that chain. If it were mine I'd double check the sprocket alignments very closely and if everything is square there I think maybe a new chain is in order. I guess the choice of 530 was to match the existing sprockets? I ask that because 530 in not a size that I've come across very often, just in some serious heavy duty applications. That doesn't mean there's anything wrong with it, just wondering if it matches your sprockets, although from the pics it looks fine....

 

[Kasea]

Yea i chose 530 because that is what the original sprocket measured out to. Ive check the alignment and its straight also made sure the pillow block berrings haven't shifted. I had some carborator issues i had to work out yesterday i will take it for a run today and report back .

 

[Kaptain Krunch]

Id replace that chain. Also what size tires? That gear ratio looks wayyy too high.

 

[itsid]

non prestretched 530 chain? is that even a thing?

Anyhow.. that sprocket should really sit butted against a bearing.
those 3/4" shafts are not exactly sturdy, neither is a 1" axle.. a bit of flex is okay alright;
but those two will add up quite dramatically, especially since even the jackshaft runs in axle bearings.

So here's a try.. with the engine off (chain installed),
tie a ratched strap around the axle and jackshaft,
as close to the sprockets and chain as possible.

now tighten it (just like you would tighten load on the bed of your truck but w/o excessive forces)
if you can now take the chain off the jackshaft sprocket easily, you know the culprit.
axle flex..
butt the sprocket against a bearing and it'll stay on.
(I bet even one will suffice so just jackshaft will be okay)

Alternative: you can add another axle bearing close to the saxle sprocket
(but I think that's going to be a bigger hassle tbh)

Yes, those sideplates have seen some torment,
nonetheless that chain is still much stronger than any fresh #40
(oh btw its 219, 420, 428, 525, 530 etc and #25. #35, #40, #41 but never #530 nevermind)

if I'm seeing that correctly that's a 440cc sledengine.. that gear ratio isn't ideal for a high revving engine alright, and for sure that countertorque helps bending the axle when accelerating,
still I think that engine has just enough oomph to deal with that for now.
albeit I agree that I'd check the ratio properly to be sure at one point anyways..
so why not now?
(the original 150cc was heavily gear reduced before it even left the crankcase.. the sled is NOT,
so the original sprocket is NEVER a good idea!)

For now, I'm afraid it's up to redesign the backend, so that you can run the chain and sprockets MUCH closer to a bearing!

'sid

 

[Kasea]

Hey thanks for the input about the jack shaft flexing its a 1 In shaft I will come up with a new design if all else fails ill attach 2 pics of before and after running it for 20 min for a comparison of the chain stretch

 

[itsid]

that is indeed a dramatic amount of stretch.

Never saw something like that on motorcycle chain
I got maybe half a link worth of stretch in a 106link chain after a few weeks
(axle adjusted a few mm only 525 in this case btw)

That in just 20 mins under no load...

frankly that there would spell fatal accident on a motorbike..
(fresh chain kit installed, and dead on the way home because the chain popping off)
that wouldn't be too good of a news paper headline for any chain mfg..

Sooo my assumption was (and since I never actually cared to ask)
that all motorcycle chain is always prestretched.
Hence you see me baffled.
Oh maybe because I never got chain by the foot of course,
but presized chain for the respective bike ..

anyways...
yeah a 1" shaft is better than a 3/4" of course.. still it's not as rigid as one might think.
especially with a good amount of torque on both ends of the chain
the two sprockets might move a measurable distance closer to each other under load.
(that's the exact same force that causes the chain to stretch btw)

'sid

 

[still kikn]

That's very strange.

I'll be watching this thread closely because I'm very curious as to what actually caused this and what the fix will be. Before retiring I maintained dozens of machines with chain drives with all kinds of loads, speeds, and chain sizes, and I never saw anything like that. And that amount of stretch after such a short period of time of running is just crazy. I would think there would have been a ton of chain noise happening long before it actually broke. I suspect it got very hot too, which would have increased the rapid wear.

I'd toss that chain if it were mine to be frank. Besides the obvious damage, the gouges, dings, etc., there has to also be a lot of wear in the pins and rollers themselves. That's where all that "stretch" comes from. If you do decide to run it again, and I hope you don't, make sure you keep it well lubricated.

 

[Kasea]

So quick update I took the kart out for a quick ride this evening and had no issues I only ran the kart for 15 min or so due to limited space and I dont wanna upset the neighborhood however not sure if just a minor tweeking to the alignment of the 2 sprockets was the issue the tension in the chain didn't change ether that being said i didn't get on the kart very hard i didnt want to push it home again. But now I think low end torque is going to be an issue I stopped on a fairly steep hill 6 12 pitch and the kart was having trouble starting out any advice for tackling the torque issues would be appreciated.

 

[karl]

having trouble starting out any advice for tackling the torque issues would be appreciated.

if I'm seeing that correctly that's a 440cc sledengine.. that gear ratio isn't ideal for a high revving engine alright
~
albeit I agree that I'd check the ratio properly to be sure at one point anyways..
so why not now?
(the original 150cc was heavily gear reduced before it even left the crankcase.. the sled is NOT,
so the original sprocket is NEVER a good idea!)

Yup

 

[Kasea]

To be completely honest I have no idea about gear ratios and what would be ideal for my kart the only reason I used the snowmobile engine was because it was laying around in my dads garage for the last 30 years and it was free and still in good working order I got a few ideas for a design and just started to wing it but now the technical side of fine tuning is catching up to my lack of know-how. So if someone could explain in simple terms my next steps such as increasing the teeth in the axle sprockets right now I have a 16 tooth sprocket on the jackshaft and 32 teeth on the wheels

 

[itsid]

well bswan has a similar engine but a different TC
his thread asking about gear ratios and such

your's appears to be the 380cc TC version (pancake style driver with three holes)
but I cannot positively ID it from the pics.

Since your wheels appear to be closer to 20" than 18" in diameter I think it's fair to say
you'd want something closer to 70T on the axle.

'sid