Kart vibrates like crazy before taking off from stop

[jmandawg]

Hi all. Have a predator 212 and max torque clutch. For some reason when I'm stopped and I floor the gas it vibrates like crazy before finally taking off. Any ideas what it could be?

Only happens on take off. Once it's going it's fine. I did cut the back bumper bar off. Maybe that messed up the stability of the frame.

 

[Hellion]

Hmm, my 212cc also vibrates like crazy, just idling still.

It's not exactly a refined design, these single cylinder engines despite the counterweights on the crankshaft. However, can you please elaborate more on vibrates like crazy???

Is the engine firmly bolted down?

I rarely floor the gas pedal from a dead stop--I moderately accelerate until the clutch is fully engaged and then I go all out.

 

[sefishy]

if i run a 212cc on my bench at idle it will bounce around like crazy. However, rev it a little and it settles down nice and smooth.

 

[mckutzy]

They aparently cannot be fully balanced due to the design of the engine...

The big block does have a balance shaft... As I recall that takes the lower rev vibes to a more managed level for the motor itself and equipment it is mounted to...

As for your ride, what is your gear ratio?.... I'm going to guess that the shudder is related to the motor/clutch trying to overcome the friction of the stationary mass/driver...

 

[Hellion]

...
As for your ride, what is your gear ratio?.... I'm going to guess that the shudder is related to the motor/clutch trying to overcome the friction of the stationary mass/driver...

This.

Sort of like trying to accelerate a standard transmission car from a dead stop in 3rd gear...or worse (5th, etc.)

 

[jmandawg]

My gear ratio is 12:65 teeth, whatever that equates to. By vibrate I mean it shakes my head like crazy, maybe I shouldn't be flooring it from a stop.

I just cut off the rear bumper today and remounted the engine. I had a really bad experience with my ratcheting wrench getting stuck on one of the engine mount bolt. So I should probably double check all the bolts are tight, but I think they are.

---------- Post added at 06:33 PM ---------- Previous post was at 06:30 PM ----------

This.

Sort of like trying to accelerate a standard transmission car from a dead stop in 3rd gear...or worse (5th, etc.)

I guess your right, but I see some guys popping wheelies, so I was trying to see if mine could.

 

[mckutzy]

As I suspected, your at 5.416:1 ... You might if you can, offset that by using a rear 72t, to at least bring it to a 6:1, or might work in a jackshaft.....But the latter is a bit more work....

A rolling throttle start can mitigate this a bit, but your ratio is a little off, the clutch will begin to unnecessarily heat up.

What size of tires, OD?

 

[Hellion]

He could get an 11 tooth clutch, right? 65/11 = 5.909...

I guess your right, but I see some guys popping wheelies, so I was trying to see if mine could.

Get a manual clutch. Search 3D Manual Clutch. It's cable operated with a lever and you can rev the engine up, dump the clutch and get some skid marks.

 

[mckutzy]

If that clutch drum is retro-fittable, then maybe ya 11t will help...

 

[jmandawg]

As I suspected, your at 5.416:1 ... You might if you can, offset that by using a rear 72t, to at least bring it to a 6:1, or might work in a jackshaft.....But the latter is a bit more work....

A rolling throttle start can mitigate this a bit, but your ratio is a little off, the clutch will begin to unnecessarily heat up.

What size of tires, OD?

OD (from floor to top of tire) is 12". Thanks for the clutch suggestions, the manual clutch looks cool, but it's expensive. I'll tinker around some more and report back tomorrow.

 

[Bbqjoe]

Hi all. Have a predator 212 and max torque clutch. For some reason when I'm stopped and I floor the gas it vibrates like crazy before finally taking off. Any ideas what it could be?

Only happens on take off. Once it's going it's fine. I did cut the back bumper bar off. Maybe that messed up the stability of the frame.

Doctor, it hurts when I do this!

Well, then don't do that!!!!

 

[Hellion]

Doctor, it hurts when I do this!

Well, then don't do that!!!!

You're such a benefit to the forum, spouting useful wisdom left and right.

The wise old hermit...

 

[sefishy]

as another option, since you cut the back off there is plenty of room to run a torque converter. plus this will allow you to pick the sproket size you need

 

[jmandawg]

I have another of the same kart with the original 79cc engine (with governor removed) and i tested it out and it does the same thing, just not as bad as the one with the predator. Maybe it's just how the kart is made or the clutch trying to engage under load. No clue, but if i gradually give it gas it goes fine. I guess i'm not going to worry about it.

Torque converter sounds like a pretty good idea though.

 

[mckutzy]

Those 79's are really underpowered motors for machines like these... But none the less... It's still most likely gear ratio...

 

[jmandawg]

Those 79's are really underpowered motors for machines like these... But none the less... It's still most likely gear ratio...

Do you think i should go with the 72t sprocket or 11t clutch?

 

[mckutzy]

If you have a clutch with12t, get a rear sprocket with 72t.

 

[jmandawg]

Here is a slow motion video of the clutch during acceleration. Does the chain look too loose. I think maybe the clutch just slips during initial acceleration. It seems to wobble a little too.

https://youtu.be/EPHhEw1GalE

 

[Panhead5496]

I second the torque converter idea!!

 

[BigMark408]

Is your engine mounted properly? Looks to be flopping around in video but that could YouTube trying to stabilize the upload.

And yes your chain is loose. I would tighten or install tensioner. But adjustment is easier than buying parts.... I also agree with Torque converter upgrade

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