Manco 386B-17 Issue

[Missile]

Hello,

I just purchased a Manco 6.5HP off road kart. Replaced the Subaru/Robin engine with a Predator 212cc Hemi (stock so far). Purchased a new 30 series asym drive pulley and belt. The tires and jackshaft spin freely (no binding). The belt and chain are aligned and the frame is in great shape.

When I accelerate from a dead start, the back end vibrates something fierce until you get going. It happens with the Robin engine as well. Is this normal? I'm 6' 1" 245 lbs, could my weight be the reason? I'm new to go karts and I don't think this is normal.

Thanks,

Gary

 

[950speed]

Mine does sometimes, it’s a 606b model, an off-road kart. Make sure your belt is the correct one, I learned this on the forum that these clone TAVs done always have the correct belt. Top notch would be to search for a “comet tav2 belt”

 

[landuse]

Welcome!!

Have a look at this chart for the correct belt. If you bought a knock off TC, then don't use the chinese belt that came with it

https://www.gokartsupply.com/tcbelts.htm

Also, what is the gearing on your kart and how tall are the rear tyres? Gearing being the sprocket tooth counts

 

[mckutzy]

What is the gear ratio??? and What is the OD of the rear tires?...

 

[Hellion]

...I'm 6' 1" 245 lbs, could my weight be the reason?

I bet you're quite the 'missile' once you get going though, right?

WHOOOOSH! Unstoppable.

 

[Missile]

Welcome!!

Have a look at this chart for the correct belt. If you bought a knock off TC, then don't use the chinese belt that came with it

https://www.gokartsupply.com/tcbelts.htm

Also, what is the gearing on your kart and how tall are the rear tyres? Gearing being the sprocket tooth counts

The belt that the Manco parts diagram list is a 5959 which was too short, the old drive pulley was symmetrical (the 7" driven pulley is asym). After ordering a few belts, I found the correct fitting belt.

The rear tires are AT 22x11-8 though the parts diagram list the rear tire size of 18x9.5 (stock?). Might this be a problem?

I need to count the teeth on the sprockets and will post.

 

[950speed]

Wait in the first post you said you purchased a “30 series drive pully” never mentioning if you have a driven pully for the 30 series. And you said the old drive pully “was symmetrical” meaning it’s pribably a comet 20 series.

Meaning, from what you have told us, you have a 20 series symmetrical drive and a 30series driven asymmetrical, which you cannot do. It will chew belts like crazy and cause vibrations

Correct me if I’m wrong but that’s what I’m getting from what you said

 

[Karttekk]

Double check the chain too, make sure there aren't any binding links.

 

[Missile]

Wait in the first post you said you purchased a “30 series drive pully” never mentioning if you have a driven pully for the 30 series. And you said the old drive pully “was symmetrical” meaning it’s pribably a comet 20 series.

Meaning, from what you have told us, you have a 20 series symmetrical drive and a 30series driven asymmetrical, which you cannot do. It will chew belts like crazy and cause vibrations

Correct me if I’m wrong but that’s what I’m getting from what you said

The driven pulley (jackshaft) which came with the kart is a 7" asym pulley and was not replaced. The old engine drive pulley that I replaced is symmetrical. I purchased a 30 series asym drive pulley to match pulleys, so I thought.

Should a 20 series torque converter driven pulley be symmetrical because the one that's on there as purchased is asym? Do I need to purchase a 30 series asym driven pulley?

Thanks for the feedback!

 

[landuse]

Have a look at this link

https://www.gokartsupply.com/identify.htm

Asymmetric has one flat sheave and one angles sheave on both driven and drive pulley. You cannot mix asymmetric and symmetric (ie. 20 and 30 series) pulleys.

The larger tyres you have compared to the stock 18" that usually come with the kart (if the manual is correct) would not help your gear ratio much and you might find that you are now geared too high. This will eat belts up faster than if it was geared perfectly. We will need tooth count to see what your gearing is like though

 

[950speed]

You currently have a 30 series driver pulley, either replace it with a 20 series or replace the driven with a 30 series driven

 

[Missile]

I bet you're quite the 'missile' once you get going though, right?

WHOOOOSH! Unstoppable.

 

[Missile]

The driven pulley is a comet stamped 20 and is asymmetrical with a 9 tooth sprocket.
The axle sprocket is 52 teeth, (the parts diagram call for a 54 tooth sprocket).
The rear tires are AT 22x11-8, (the parts diagram lists a 18x9.5 rear tire.)
The dive pulley is a new 30 series asymmetrical.

I assume I still need to purchase a 30 series asymmetrical driven pulley?
Looking forward to your analysis for the gearing, larger driven pulley? Looking for torque over top end.

Thanks,

Gary

 

[950speed]

So your saying you have a 20 series asymmetrical comet driven? As far as I know that didn’t exist ever. Even so still you must NOT combine a 20 and 30 series clutches, and make sure to measure the correct belt using the chart Somone posted a few posts ago.

Do you have a 30 or 20 series driven?

 

[Missile]

So your saying you have a 20 series asymmetrical comet driven? As far as I know that didn’t exist ever. Even so still you must NOT combine a 20 and 30 series clutches, and make sure to measure the correct belt using the chart Somone posted a few posts ago.

Do you have a 30 or 20 series driven?

I'll purchase a known 30 series driven and be done with it. I'm not exactly sure what's on there at this point, It's definitely asymmetrical though.
I'm confident I have the correct asymmetrical belt, did the belt chart through GPS.

What are your thoughts on the gearing? The combination of the larger tires and smaller axle gear could be an issue I'm assuming? How do you go about determining the gearing setup?

 

[Missile]

I'll purchase a known 30 series driven and be done with it. I'm not exactly sure what's on there at this point, It's definitely asymmetrical though.
I'm confident I have the correct asymmetrical belt, did the belt chart through GPS.

What are your thoughts on the gearing? The combination of the larger tires and smaller axle gear could be an issue I'm assuming? How do you go about determining the gearing setup?

I'm finding only 6" driven pulleys available instead of the 7" that's on there now. Would it be advisable to use the 6" driven pulley? I would just need a smaller belt and shorten the chain? I'm going to hold off on buying anything until I get more direction, feel like I'm chasing my tail .

 

[Tpdingo]

I'm finding only 6" driven pulleys available instead of the 7" that's on there now. Would it be advisable to use the 6" driven pulley? I would just need a smaller belt and shorten the chain? I'm going to hold off on buying anything until I get more direction, feel like I'm chasing my tail .

No shorter chain, just a smaller belt.

 

[Denny]

Just because the driven has 20 on it does not mean it is a 20 series. It sounds like you have both 30 series driver and driven now on there, so that's good. Just make sure the driven's cam buttons are not worn out and the spring is in good shape. If I was you I would go to a 60 tooth axle sprocket and 18 inch tires in the rear.


Denny

 

[Missile]

Just because the driven has 20 on it does not mean it is a 20 series. It sounds like you have both 30 series driver and driven now on there, so that's good. Just make sure the driven's cam buttons are not worn out and the spring is in good shape. If I was you I would go to a 60 tooth axle sprocket and 18 inch tires in the rear.


Denny

Thank you Denny, I was reaching the same conclusion after further investigation. There's a 62 tooth sprocket available that I'm going to try. What do you think of going to a 6" 30 series driven pulley, maybe instead of a tire swap (just bought the rears)? Some of the cam buttons cam out while I was messing with the driven pulley, not sure if I want to rebuild it or just get another one. I keep telling myself I'm having fun...…..

 

[itsid]

the seven inch driven is only providing you with a tad more wheeltorque..
that's okay no need to purchase anything but a driven spring IMHO.

Since yours look rather busted to me (coating cracked.. steel rusted ...)
Full Driven maintenance is due I'd say..
cleaning the sheaves to babybutt smoothness, new spring, and you'll be good.

Now initial issue:
chances are the jackshaft bearings are worn out..
remove the belt and wiggle on your driven unit..
if there is any play, you can be sure it's causing vibrations when running.
Also make sure the Jackshaft is 100% parallel to the PTO of your engine,

so also remove the driver pulley from the engine for a moment.
Get a tailors tape measure out and wrap it around both shafts as if it were a drive belt
twice: first snugly at the PTO output bearing. (take exact note!)
then at the very end of the pto shaft (again take exact note!)
and if the two numbers are not identical,
chances are the two shafts are not parallel.

Once the shafts are parallel with the jackshaft bearings in good condition and a freshly maintained TC,
there shouldn't be no excessive vibration (no other than engine vibration actually)

'sid