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Old 04-01-2019, 12:20 AM
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Default Someone please help me lol *** my kart keeps throwing it's chain

Ok brand new member here, first kart I've ever modified. And I'm running into some issues. To make this easier let me just describe everything about the kart

Old Birell chassis. got a 300cc snowblower engine, removed governer, and all the winter engine BS . Slapped it on the kart, using a mounting plate thing that is removable/adjustable. Has a one inch drive with a centrifugal clutch rated for 420cc. Got a #35 chain. all new 56 tooth sprocket. The one that comes off in 2 peices. Brand new #35 chain. With one master link. Hooked it all up, kart runs and drives.

Ok went to make my first test drive, made it down the driveway no problem, pulled into the road and gave it full throttle, let off and started to turn, threw the chaiin.. rolled it back into the garage, re-adjusted tension on chain, re-alligned sprockets, all seems to be good, made another trip down the road, threw the chain under load again, re-adjusted and tensioned chain 4 times and the kart threw it under load each time. Really hoping someone can help me out here with a solution .
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Old 04-01-2019, 04:51 AM
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itsid itsid is offline
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Hi and welcome!
and before we begin: Please do not start duplicate threads regarding the same question,
that's why I deleted the other one.

easier would be PICTURES of the drivetrain..
but okay, let's start with what we have.

clutches are torque/hp rated not by displacement but I think it's fair to assume it'll work
at least for a while.
Not for long though, since your gear ratio is sub par for longevity
(1" #35.. we talk 17T or such... a 3.3:1 gear ratio is not going to work very well! more on that later)

The engine mounting plate is adjustable you say,
but is it rigidly enough mounted (bolted down),
so that the engine has zero play in regard to the chassis?
especially lateral movement will throw your chain

Are you sure the two halves of your split sprocket are perfectly aligned as well?
jack up the rear and turn the wheels..
you should not be able to hear the transition over the gap, if you do, you will need to fix that.
an ever so slightly binding -or worse catching- chain at slow (chain-) speeds
means you might throw your chain at high (chain-) speeds.

The master link itself is hopefully installed the right way round
(closed side of the clip points in direction of (chain-) travel)

the clutch bell can have (and should have) minimal lateral play,
~0.5mm or such if it's too much and there is the slightest imbalance
that again means you might throw your chain because of it.

The chain itself stretches when new and again when wearing down,
but since it's new it will have to..
have you pre stretched it before installing or bought pre stretched chain?
If not, you will have to retension the chain a couple more times until it settles in.
Just take it off,
put some heavy zip ties at each end of the then open chain strand,
attach convenient handles to the ties and yank the chain as hard as you can (manually!)
to pre stretch it... it's likely not enough,
but at least saves you the chain jumping a three or four times

Since you jerk the chain quite aggressively with the terrible gear ratio you have.
it will still stretch a bit more and jump because of that on the kart.

I know you wanted more speed and opted for that instead of a reliable setup..
I mean a Birel is meant to be raced for a reason .. I get that.
but 3.3:1 or thereabouts is terrible, especially for #35 chain

While you say it has the power for takeoff (amazing.. hard to believe even, but alright)
the clutch is likely engaging in the 1800rpm range and locking at 2200 rpm (maybe 2500)

@2200 rpm with 11" wheels you will need to travel at ~22mph for the clutch to be able to lock down.. (25mph for a locking speed of 2500 rpm)
slower and the clutch will slip (thus heat up and burn out eventually in very short order)
And every speed below 22mph will add stress and heat to the clutch and wear it out prematurely..
every start, every corner chips a severe amount of lifetime off your clutch;
be aware of that!
Racing clutches can handle that for a while but since those cost upwards of 100 bucks,
I have the funny feeling that's not what we're dealing with here

Personally, I'd ditch the #35 chain entirely for a kart and mostly engine like that.
Birels use 219 chain (way smaller.. WAAAY heavier duty) for good reasons
finding a 219 sprocket is easy and you can also find 219 race clutches for 1" shaft engines (but truth is.. we likely talk about 100++ bucks for the clutch)

OR maybe you just have enough room to go the "fun kart" route and install a TC instead (50-70 bucks for a series30 off ebay should suffice I guess)
it's technically rated for 8horses and below, but it withstands quite abit more;
modded 212 upwards of 10horses are not much of an issue for it at least.

that would remove the sudden jerk when taking off and accellerate even quicker than a std clutch and could give you the ability to just cruise down the alley if you so choose
(with your clutch again the minimum speed will be 22 or 25mph or you'll destroy your clutch)

'sid
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Old 04-01-2019, 08:40 AM
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Jeez sid you had some time lol
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Old 04-01-2019, 09:13 AM
300kart 300kart is offline
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Quote:
Originally Posted by itsid View Post
Hi and welcome!
and before we begin: Please do not start duplicate threads regarding the same question,
that's why I deleted the other one.

easier would be PICTURES of the drivetrain..
but okay, let's start with what we have.

clutches are torque/hp rated not by displacement but I think it's fair to assume it'll work
at least for a while.
Not for long though, since your gear ratio is sub par for longevity
(1" #35.. we talk 17T or such... a 3.3:1 gear ratio is not going to work very well! more on that later)

The engine mounting plate is adjustable you say,
but is it rigidly enough mounted (bolted down),
so that the engine has zero play in regard to the chassis?
especially lateral movement will throw your chain

Are you sure the two halves of your split sprocket are perfectly aligned as well?
jack up the rear and turn the wheels..
you should not be able to hear the transition over the gap, if you do, you will need to fix that.
an ever so slightly binding -or worse catching- chain at slow (chain-) speeds
means you might throw your chain at high (chain-) speeds.

The master link itself is hopefully installed the right way round
(closed side of the clip points in direction of (chain-) travel)

the clutch bell can have (and should have) minimal lateral play,
~0.5mm or such if it's too much and there is the slightest imbalance
that again means you might throw your chain because of it.

The chain itself stretches when new and again when wearing down,
but since it's new it will have to..
have you pre stretched it before installing or bought pre stretched chain?
If not, you will have to retension the chain a couple more times until it settles in.
Just take it off,
put some heavy zip ties at each end of the then open chain strand,
attach convenient handles to the ties and yank the chain as hard as you can (manually!)
to pre stretch it... it's likely not enough,
but at least saves you the chain jumping a three or four times

Since you jerk the chain quite aggressively with the terrible gear ratio you have.
it will still stretch a bit more and jump because of that on the kart.

I know you wanted more speed and opted for that instead of a reliable setup..
I mean a Birel is meant to be raced for a reason .. I get that.
but 3.3:1 or thereabouts is terrible, especially for #35 chain

While you say it has the power for takeoff (amazing.. hard to believe even, but alright)
the clutch is likely engaging in the 1800rpm range and locking at 2200 rpm (maybe 2500)

@2200 rpm with 11" wheels you will need to travel at ~22mph for the clutch to be able to lock down.. (25mph for a locking speed of 2500 rpm)
slower and the clutch will slip (thus heat up and burn out eventually in very short order)
And every speed below 22mph will add stress and heat to the clutch and wear it out prematurely..
every start, every corner chips a severe amount of lifetime off your clutch;
be aware of that!
Racing clutches can handle that for a while but since those cost upwards of 100 bucks,
I have the funny feeling that's not what we're dealing with here

Personally, I'd ditch the #35 chain entirely for a kart and mostly engine like that.
Birels use 219 chain (way smaller.. WAAAY heavier duty) for good reasons
finding a 219 sprocket is easy and you can also find 219 race clutches for 1" shaft engines (but truth is.. we likely talk about 100++ bucks for the clutch)

OR maybe you just have enough room to go the "fun kart" route and install a TC instead (50-70 bucks for a series30 off ebay should suffice I guess)
it's technically rated for 8horses and below, but it withstands quite abit more;
modded 212 upwards of 10horses are not much of an issue for it at least.

that would remove the sudden jerk when taking off and accellerate even quicker than a std clutch and could give you the ability to just cruise down the alley if you so choose
(with your clutch again the minimum speed will be 22 or 25mph or you'll destroy your clutch)

'sid

Thanks for that very informative answer, I really appreciate it. the issues you stated are pretty much what was going through my mind also, I know that the engine is pretty big so the flexing could definately be an issue. I feel like the mounting plate is not rigid enough, do you think maybe adding a few spars would change the issue. ?

Also you mentioned the clutch burning out, I also was told about getting a torque converter but opted to try a clutch first, and it was cheaper too. when I bought the clutch the box had a cc rating of 400cc on it, so I figured it would be ok. The clutch has 19 teeth on it, so my ration might be even worse then yu think lol but the kart really does have alot of power.. it takes off really good and even breaks the tires loose when I floor it.


I will go and try to stiffen up the frame a bit, do you think getting a sprocket guard would help keep the chain on it ?
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Old 04-01-2019, 09:50 AM
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itsid itsid is offline
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unfortunately the chassis MUST flex, it is designed to do so..
(to ensure lifting the inner wheel in tight corners for improved steering)

depends on what axle you run..
I have the feeling you have a 1" axle, which I'm afraid is the equivalent of a rubber band compared to what the kart is designed for

Most flex is with a 30mm axle (smallest european size for adult race karts)
which is considered 'rain setup' (slippy road need more flex to lift the wheel)
dry road setups are 50mm axles (~2") to stiffen the chassis a bit more

IIRC for most Birels there are stiffening crossbars so you might get away adding one of those.
chances are depending on the tube size and distance you might find one such stiffener from another mfg race kart that fits in case there's no Birel part available.

The engine mount has to be specifically designed for the tube size and rail distance.
one incorrect value and you're screwed I'm afraid.

Show us a pic of it, maybe we can see a way to improve, but if it's the wrong size for the chassis there is only so much you could do..
applying more clamping force IS NOT a solution
(in fact you could ruin the chassis folding the tube and still have a floppy engine mount)

cc rating on clutches smell chinese ..
Again if you feel comfortable with it as it is now.. great..
but frankly I wouldn't suspect it to live for very long..
with a 19T clutch
minimum speed increased from 22->24.5mph [2200rpm full lock]
or 25->27.7mph [2500rpm full lock] in order to NOT BURN the clutch..
nothing I'm particularly fond of tbh...
if you can break traction at least the engine has the torque for such ratoi
(great.. but only half the problem )
But sure.. burning rubber instead of sintered clutch lining is a way to keep the clutch alive
(you'd spend more on new tyres every other week than for a clutch I guess.. but hey
.. you play your game like you want to )

A sprocket guard helps keeping chain and sprocket alive if you fear it ever touching the ground,
it won't help much keeping the chain on the sprocket if it wants to jump off
small hiccups sure, but it wont prevent all mishaps if there's something wrong with the drivetrain.

Show us the kart, engine mount, from everal angles and we try to see what you got and what can be done to improve your issue.

'sid
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Old 04-01-2019, 10:11 AM
300kart 300kart is offline
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Quote:
Originally Posted by itsid View Post
unfortunately the chassis MUST flex, it is designed to do so..
(to ensure lifting the inner wheel in tight corners for improved steering)

depends on what axle you run..
I have the feeling you have a 1" axle, which I'm afraid is the equivalent of a rubber band compared to what the kart is designed for

Most flex is with a 30mm axle (smallest european size for adult race karts)
which is considered 'rain setup' (slippy road need more flex to lift the wheel)
dry road setups are 50mm axles (~2") to stiffen the chassis a bit more

IIRC for most Birels there are stiffening crossbars so you might get away adding one of those.
chances are depending on the tube size and distance you might find one such stiffener from another mfg race kart that fits in case there's no Birel part available.

The engine mount has to be specifically designed for the tube size and rail distance.
one incorrect value and you're screwed I'm afraid.

Show us a pic of it, maybe we can see a way to improve, but if it's the wrong size for the chassis there is only so much you could do..
applying more clamping force IS NOT a solution
(in fact you could ruin the chassis folding the tube and still have a floppy engine mount)

cc rating on clutches smell chinese ..
Again if you feel comfortable with it as it is now.. great..
but frankly I wouldn't suspect it to live for very long..
with a 19T clutch
minimum speed increased from 22->24.5mph [2200rpm full lock]
or 25->27.7mph [2500rpm full lock] in order to NOT BURN the clutch..
nothing I'm particularly fond of tbh...
if you can break traction at least the engine has the torque for such ratoi
(great.. but only half the problem )
But sure.. burning rubber instead of sintered clutch lining is a way to keep the clutch alive
(you'd spend more on new tyres every other week than for a clutch I guess.. but hey
.. you play your game like you want to )

A sprocket guard helps keeping chain and sprocket alive if you fear it ever touching the ground,
it won't help much keeping the chain on the sprocket if it wants to jump off
small hiccups sure, but it wont prevent all mishaps if there's something wrong with the drivetrain.

Show us the kart, engine mount, from everal angles and we try to see what you got and what can be done to improve your issue.

'sid
Thanks for the prompt reply, yes I believe that flex while turning is what causes it to throw the chain now that I think of it.

Lol it may be a Chinese clutch but I won't be using the kart for racing or anything just a fun toy on the weekends to take to a empty parking lot n have fun with the boys, so reliability isn't really that much of an issue. However I would like to get the thing to run for more then 1 minute without throwing the **** chain

The axle I have came with the kart and it's pretty big but not sure of the exact size, looks like 40 or 50 mm . However I will get some pics in a few hours when I get into the garage and post them up for you,

Once you see what I'm working with hopefully you can give me a starting point as to what I should do next

Again thanks for the help, should have the pics up in a few hours
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Old 04-01-2019, 11:21 AM
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itsid itsid is offline
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Quote:
Originally Posted by 300kart View Post
Lol it may be a Chinese clutch but I won't be using the kart for racing or anything just a fun toy on the weekends to take to a empty parking lot n have fun with the boys, so reliability isn't really that much of an issue. However I would like to get the thing to run for more then 1 minute without throwing the **** chain
See, that's the problem
When racing you take off ONCE and then stay above such nasty minimum speed for all day (well you WANT to at least)
so the abuse is short and more bearable..
Having fun in the parking lot is different,
you take off from a dead stop every other minute, you take much slower corners (since you likely have to on a parking lot)
and in general have to slow down occasionally below said min speed...
and thus the abuse to the clutch will be MUCH WORSE.

Just because racing clutches can take more abuse
doesn't mean racing causes more abuse to the clutch


good.. 40 or 50mm axles either of which should do for a fixed crossbar chassis..
a detachable crossbar chassis now can only be stabilized with the crossbar in place.
I wonder if you can add a secondary (detachable) crossbar to a fixed crossbar chassis *headscratch*

Oh hang on... you have the rear bumper mounted, haven't you?
It too is an integral part of the rigidity of a race kart chassis
(looks better without, drives better with!)

'sid
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Old 04-01-2019, 01:54 PM
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Need some pics!
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Old 04-01-2019, 02:12 PM
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Quote:
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Need some pics!
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Old 04-01-2019, 04:39 PM
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Quote:
Originally Posted by itsid View Post
See, that's the problem
When racing you take off ONCE and then stay above such nasty minimum speed for all day (well you WANT to at least)
so the abuse is short and more bearable..
Having fun in the parking lot is different,
you take off from a dead stop every other minute, you take much slower corners (since you likely have to on a parking lot)
and in general have to slow down occasionally below said min speed...
and thus the abuse to the clutch will be MUCH WORSE.

Just because racing clutches can take more abuse
doesn't mean racing causes more abuse to the clutch


good.. 40 or 50mm axles either of which should do for a fixed crossbar chassis..
a detachable crossbar chassis now can only be stabilized with the crossbar in place.
I wonder if you can add a secondary (detachable) crossbar to a fixed crossbar chassis *headscratch*

Oh hang on... you have the rear bumper mounted, haven't you?
It too is an integral part of the rigidity of a race kart chassis
(looks better without, drives better with!)

'sid
U made a very valid point there, I didn't think of it like that but so true. Well I'm gonna definately look into torque converters untill this clutch blows lol. I'm not into the kart for very much ATM and it's gonna be a summer project. Hopefully I'll get all the bugs figured out.

So the update is I got the chain to stay on, built some spars and braced the motor on offset sides, chain stayed on under hard exelleration and most turns, took one really hard turn n it popped off again. But for the most part stayed on


I took pics n tried to upload em but I didn't figure it out, weird cuz I'm not super old or anything I'm 25 ... I think I'm just not tech savvy


But anyway thank-you for the help I really appreciate it, I will be adding more supports and readjusting the chain

Gonna try to upload the pics too from my computer instead.
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Old 04-01-2019, 08:18 PM
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Here is how on the pics....
http://www.diygokarts.com/vb/showthread.php?t=737
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