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Old 04-24-2019, 08:15 AM
twice99 twice99 is offline
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Default Wet clutch failure advice needed

I bought a new kart with a LIFAN engine and wet clutch. This appears to be a Honda GX160 clone. The kart ran fine for 2-3 minutes then lost all movement. The supplier had me take photos of the clutch interior which had black sludge and debris from the apparent disk deterioration. They also said I should have used 80-90W oil instead of the 10W-30 which was called for in the instructions. They said they would send another clutch, which they never did and would not respond to any subsequent communicate attempts.

I now am deliberating if I should replace just the clutch disks or the entire clutch. Since I am not certain what could cause the disk deterioration, I am hesitant to replace just them when there could be some other cause. It's not a simple task to do either.
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Old 04-24-2019, 09:40 AM
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someone ran that clutch dry for a while...
maybe the shop had the engine tested and forgot to add oil, then shipped it out already nearly broken...
Sounds like you've been screwed over

BUT the good news is: a well maintained wet clutch is nearly bulletproof.
Sure you can cook the oil off with terrible gear ratios and then have it fail on you,
but compared to a std cent clutch it's still a tank

if you buy Honda clutch plates and follow Hondas manual to isntall them (and Hondas recommended oil choice)
I'm almost certain you will not ever regret having made that decision.

'sid

PS what's the chain ratio on the kart.. approx weight and rear wheel size can help us too making a judgement about if that clutch can handle the setup or not.
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Old 04-29-2019, 02:03 PM
twice99 twice99 is offline
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It's possible that damage was done before I received it. I did not open it up, just added oil.

Chain ratio is 15:43. Net weight is 275lbs and is rated at 375lb capacity (2 small youths).
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Old 04-29-2019, 05:38 PM
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Sorry, but that gx160
just doesn't have the power to move the weight with that gear ratio...
yes a 2:1 clutch, still we talk about 5.7:1 overall ratio here
that thing is going nowhere!
and you cannot even compensate much..
so let's hope it's in fact a gx200 clone (if you see a F168... number it's a 196cc engine)

you need to gear _WAY_ lower
(5.5:1 chain ratio perhaps.. hoping you have 15" or smaller rear wheels)

If that kart came like that it's certainly something fishy going on..

Anyways:
fix: replace the sprocket on the clutch with a ten tooth and the axle with at least a 55 Tooth
a freshened up wet clutch should be able to deal with that
(on 15" or smaller rear wheels.. this is important)
a std cent clutch would need roundabout 11.5:1 ratio to reliably move that weight
(58 teeth on the axle)

with larger wheels you also need to compensate again
all with 10 T on the wet clutch:
16" -> 58 Teeth on the axle
18" -> 65 Teeth on the axle
20" -> 73 Teeth on the axle
22" -> 80 Teeth on the axle

And it'll still be hard on the clutch tbh...
I calculated with 6.5horses and a weight of 500 lbs to have my calculator stop screaming;

I think (hope) the wet clutch is able to take the additional abuse...

But with a gear ratio like that.. no, I don't think the clutch was shot when it arrived.

650 lbs with only 4.5 horses and that terrible 5.7 gear ratio
would only move if your rear wheels are less than 6" in diameter (which they clearly are not )

So the chances are it took its damage from the terrible gear ratio instead.

Personally I'd say
maybe you want to swap to series 30 Torque converter instead..
it's relatively cheap (as a clone off ebay)
and instead of 2:1 fixed ratio
it starts at 2.7:1 and ends up at 0.9:1
you'd still need to gear as above but you wouldn't lose any top speed really
(since it'd shift up for you)

'sid
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Old 04-30-2019, 09:15 AM
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To say I'm unsure about the engineering aspects and what to do about it, is a major understatement. I appreciate your comprehensive analysis. Perhaps answers to you questions will narrow the options:

1) The engine is a Lifan 168F-2R, with Lifan Owners manual specs of 196cc and 6.5hp. The gokart manufacturer specs say 200cc.

2) The tires on the driven axle are 16x8-7 and 145/70-6 on the front.

3) Although the capacity is rated by the cart supplier as 375lbs, I cannot conceive of ever carrying that with small youths, probably maxing out at less than 200lbs. The usage however would include some unpaved with a slight grade.
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Old 04-30-2019, 09:24 AM
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Lets see some pics of the whole kart/motor ect, not so zoomed in aswell......
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Old 05-01-2019, 07:07 AM
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Quote:
Originally Posted by twice99 View Post
To say I'm unsure about the engineering aspects and what to do about it, is a major understatement. I appreciate your comprehensive analysis. Perhaps answers to you questions will narrow the options:

1) The engine is a Lifan 168F-2R, with Lifan Owners manual specs of 196cc and 6.5hp. The gokart manufacturer specs say 200cc.

2) The tires on the driven axle are 16x8-7 and 145/70-6 on the front.

3) Although the capacity is rated by the cart supplier as 375lbs, I cannot conceive of ever carrying that with small youths, probably maxing out at less than 200lbs. The usage however would include some unpaved with a slight grade.
Not to worry,
we try our best to answer all your questions and
help you fix your kart,
for you to have some happy kids tearing up your back yard

So,
yes, thank you, having more exact information indeed helps to narrow down onto possible solutions.

So we have a gx200 clone (and a good one at that) with 16" rears
that with the weight is all I need to know at this point

let's take your weight assumption
(275 lbs kart plus 200 lbs worth of passengers)
475 lbs..
6.5 horse 5.73:1 ratio 16" rear wheels

Tha kart calculator takes those infos and calculates the
required wheel torque
(getting to move from a dead stop and climbing up a 5% inclination)
and compares that to the assumed wheeltorque
you get with your engine and gear ratio at 2200 rpm.
(2200 rpm is the speed most clutches fully lock at... thus don't have unwanted slip and do not "burn up" in the process)
and in case it sees an issue
it checks at which point the "available" torque matches or exceeds the "needed torque" to suggest a viable gear ratio.
THAT however is calclated for a drum-shoe dry clutch
of just decent quality, just to make sure even cheaper setups will work.
an with the given values
it spits out this Warning:
Code:

...
PERFORMANCE
Max Wheel Torque: 73.69 Nm | 54.35 ft lbf Top Speed: 48.13 km/h | 29.91 mph
PROBLEMS
You might burn your clutch/belt! Gear ratio too high! Suggested final ratio: at least 11.43:1
11.43:1 that is the Number we care about now..
since you do have a 2:1 reduction wet clutch,
the first and most obvious thing to find your needed chain ratio
is to divide ratio by 2
giving us a rounded 5.72:1

means with the clutch output sprocket fixed,
you'll need a 86Tooth axle sprocket to achieve that.
changing the axle sprocket to 10T a 57T axle sprocket should do

with the owners manual total weight of 650 lbs that suggestion would be 13.43:1 so 6.72:1 chain ratio [clutch to axle] so a 101 tooth axle sprocket with 15T on the clutch or 67T with 10T on the clutch

But not only is it a disc clutch it's also a wet clutch
so it can take quite a bit more abuse..
unfortunately my calculator can't take that into account (thermal capacity of the oil would be one of many factors to make a proper suggestion for example)
Anywhoo..
a working wet clutch should be able to compensate for around 0.3:1
chain ratio mising (this is just a guts value without any scientific calculation or observation backing it)

giving us 5.4:1 with @ 475lbs
or 6.4:1 @ 650 lbs

and that's where the TC came in essentially..

when your kids get older (and therefor bigger) you might need to readjust the gear ratio if we take the numbers close to the weight borders..
And readjusting does two things:
while the kart still moves with the higher weight it naturally gets slowed down when gearing lower

which is odd if you think about it,
the younger version of your kids being less trained in using a kart have a faster kart than the more experienced older versions of themselves.

here's a comparision of a wet clutch (precompensated.. ignore the warning)
against a TC

WETCLUTCH:
KartInfo by kartcalc.net:
Code:

KART
RW diameter: 40.64 cm | 16 in Total weight: 294.84 kg | 650 lbs
ENGINE
Original HP: 6.5 Asummed HP: ~6.5 Torque: 12.86 Nm | 9.48 ft lbf RPM: 3600
TRANSMISSION
Final ratio: 12.8:1
PERFORMANCE
Max Wheel Torque: 164.61 Nm | 121.41 ft lbf Top Speed: 21.54 km/h | 13.39 mph
PROBLEMS
You might burn your clutch/belt! Gear ratio too high! Suggested final ratio: at least 13.4:1
And TC:
KartInfo by kartcalc.net:
Code:

KART
RW diameter: 40.64 cm | 16 in Total weight: 294.84 kg | 650 lbs
ENGINE
Original HP: 6.5 Asummed HP: ~6.5 Torque: 12.86 Nm | 9.48 ft lbf RPM: 3600
TRANSMISSION
Final ratio: 6.6:1 TC type: series 30 6" driven Lowest ratio: 17.82:1 Highest ratio: 5.94:1
PERFORMANCE
Max Wheel Torque: 229.17 Nm | 169.03 ft lbf Min Wheel Torque: 76.39 Nm | 56.34 ft lbf Top Speed: 46.43 km/h | 28.85 mph
As you can see I had to lower the chain ratio a notch (6.6:1 [final ratio] instead of 6.4:1 [*2 for the wet clutch internals] ) since a TC is a dry clutch and belt system.

So as much as I like the wet clutches since they're really reliable and beefy.
in this particular case.. I'm not sure if it's the best way to go.
especially not if -as you can see- the original top speed can almost be met with a TC and would be cut in half with a working setup wet clutch.

'sid

PS Oh and yes there's an adjustable speed limiting weight for the series 30 to slow your kids down at younger ages if want to..
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