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#Post#: 9316--------------------------------------------------
HELP Please! - Transmission Problem.
By: Max Venturi Date: September 7, 2023, 3:43 pm
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Just when I thought I was making some progress in getting the
'kart drivable for Sywell I've hit a problem I can't see a
solution to.
I've repositioned the engine to where I want it and got the
chain tension just right but when I lift off the accelerator and
hit the brake the chain jumps off the axel sprocket. My best
guess is that what ever is supposed to protect the chain driven
part of transmission from sudden changes in torque input is not
working.
The photo shows the spring loaded clutch on the driven shaft -
does this look right?
Any other suggestions or ideas please.
#Post#: 9317--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: Jimr1999 Date: September 8, 2023, 12:58 am
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Looks fine Max, veiwed from the TAV30 side of the engine, the
outer dog should be to the left (anticlockwise) side of the
plastic puck...
I would look to your engine mounts first.
#Post#: 9319--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: NewbieNick Date: September 8, 2023, 1:49 am
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Hi Max answered under chain tensioner, sorry in the wrong place
again. Have you checked your chain alignments?
Cheers Nick
#Post#: 9320--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: Max Venturi Date: September 8, 2023, 2:37 am
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Chain alignment and tension is OK.
Funnily enough the engine was on a plywood block before I
swapped to the rubber spacers. The chain was way too slack then
so I was never able to test it to see if the chain jumped.
I'll swap back to a thicker solid mount then and see what
happens.
I take it the spring loaded clutch assembly looks correct then?
Thanks
Joe
#Post#: 9323--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: Mark Under Date: September 8, 2023, 6:04 am
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I would think it’s the rubber mounts. They will move quite a
bit under power and make the chain jump off.
Honda recommend NOT using any rubber mounts on the GX engines,
it over stresses the crankcase. Honda want the engines bolted
down to a 3mm steel plate.
Any thicker than 3mm can distort the engine if it’s got a slight
warp in the mounting plate causing engine issues.
If you are going to use a chain tensioner system based on a
third sprocket on the slack side you will need a lot of force on
the idler to maintain correct tension under acceleration.
#Post#: 9324--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: Max Venturi Date: September 8, 2023, 6:06 am
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Thanks for that info. [emoji106]
#Post#: 9325--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: Jimr1999 Date: September 8, 2023, 6:22 am
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To add to Marks chain tensioner bit, the straighter the chain is
to start with, the less force you need to apply to keep tension.
This obeys a hyperbolic cosine rule. Basically, any hanging
(catenary) chain rope or wire is impossible to pull to a
straight line as its self weight is acted upon by gravity. The
nearer you get to a straight line, the harder you have to pull
to overcome the forces of gravity and the calculation moves
towards an infinite force the nearer straight you get.
Working this backwards (Your tensioner wants to deflect the
chain) the straighter it is to start with, the less force you
need to achieve tension.
HTML https://en.wikipedia.org/wiki/Catenary
JimR
#Post#: 9334--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: Max Venturi Date: September 10, 2023, 9:59 am
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You are all correct; the rubber mount was the problem. No more
jumping off but the chain is now too slack again. I'm going to
have to find a way of raising the motor a little bit by packing
out the mounting plate a bit more.
Something like this
HTML https://www.wdscomponents.com/en-gb/sandwich-bolt-down-anti-vibration-mount?vatslider=1&gad=1&gclid=EAIaIQobChMIrqGQgaOggQMVUvHtCh02gATEEAQYCCABEgI4ifD_BwE
but thinner, denser and the full size of the crankcase base
would be ideal.
Thanks for the advice.
#Post#: 9335--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: NewbieNick Date: September 10, 2023, 10:27 am
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Hi Max, can't you just shorten the chain by 1 link?
Cheers Nick
#Post#: 9336--------------------------------------------------
Re: HELP Please! - Transmission Problem.
By: Max Venturi Date: September 10, 2023, 10:30 am
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I've tried that. Regardless of where I mount the motor the chain
is always either 1 1/2 links too long or too short. In my
motorbiking youth it was possible to get a 1 1/2 link but I can
find them now.
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