Minibike lost 10mph

[Dk@t]

My minibike has lost 10mph off its top speed (previously 50 now 45) it’s cvt driven and I’m at my whits end on this issue. I have tested and confirmed it is properly tuned and right now back to the stock carburetor setup still only pushing 40 (previously 47). I believe it’s the cvt but I have cleaned and lubricated the clutch (haven’t touched the driven) any recommendations of what I should do or check would be very helpful since soon I am going to be leaving right his bike and not have all my tools available.

 

[Hellion]

Where do you ride? Looks dirty and gritty. All other concerns aside, the piston rings may be toast because that is not a good air filter (it’s for “clean” street use in the tuner/ricer frame of mind)...

Show us pics of the CVT and belt (we have guys here with trained eyeballs). Nice overall shot of the bike though, looks totally “no nonsense”.

 

[Dk@t]

I ride pure dirt and otherwise that picture was after I went down and broke the air filter, engine is new and when I checked how well that filter was working I didn’t see any dust on the adapter, I make sure to wash the bike well and carefully but I can’t always do it well and the belt is brand new other than sitting in a bag for a month or 2

 

[Dk@t]

After getting better looks and touching the belt it left black marks on my hands from the inside and is peeling somewhat from the outside, I only have most likely 2 hours on this belt at most.

 

[Dk@t]

Where do you ride? Looks dirty and gritty. All other concerns aside, the piston rings may be toast because that is not a good air filter (it’s for “clean” street use in the tuner/ricer frame of mind)...

Show us pics of the CVT and belt (we have guys here with trained eyeballs). Nice overall shot of the bike though, looks totally “no nonsense”.

I was able to compression test the engine and get it to 60 by hand and 70 by drill, but I do know there is a compression release so this might have been a pointless test

 

[Denny]

That’s not a GENUINE COMET BELT is it?

 

[Dk@t]

That’s not a GENUINE COMET BELT is it?

No it is a replacement off Amazon

 

[Denny]

There’s your problem!!!

 

[Dk@t]

There’s your problem!!!

I’ve hit 50 and had a fine time with this last belt from the same pack but maybe I’m having bad luck with this one I’ll swap to my last belt I have and see how that goes

 

[Whitetrashrocker]

Comet or rotary belts.

The cheap yak hair and grease ones last exactly 2 hours.

 

[Dk@t]

Comet or rotary belts.

The cheap yak hair and grease ones last exactly 2 hours.

View attachment 163212

So if I go out and spend $30 for one good comet belt will it guarantee my top speed gets fixed?

 

[Whitetrashrocker]

Its been proven over and over that the cheap belts just dont last. Some make it longer than others but all fail at some point.
The good belts will last. BUT, the cvt needs to be smooth and lube properly and aligned.

Ive never seen my belts get sticky goo. Thats the "rubber" breaking down.

When the belt slips or gets narrowed from missing material it will not fully engage the cvt. This leads to loss of power across the power band.

Compare the belts together. Im curious to see what they look like.
Can you get some more pics? Maybe turn on a light too, its hard to see.

 

[Dk@t]

New belt vs newer belt seems the new one stretch out quicker I’ve also included what the clutch looked like before lubrication and the newer ones pictures are before it was rode (not the same 2 belts)

 

[Whitetrashrocker]

Much better. Thank you for the light.

This edge looks like the top of the belt is making a shelf. The inner ribbed part looks worn thin. This should be a flat bevel all the way around.
The belt should be uniform thickness too. Any hourglassing is bad.



In this pic you can see the uneven wearing on the cording between layers.



And on this side its real bad.

 

[Dk@t]

I see that now thanks for pointing that out I’ll take the newer belt off and send you pictures of what that looks like since it only has 30 minutes on it. I found a good looking rotary belt for sale on omb warehouse would that work or should I get comet?

 

[Whitetrashrocker]

Ive had luck with rotary belts.
Denny will vouch for the comets.

 

[Dk@t]

Here’s pictures of that newer belt with 30 minutes. I also know a guy who rides around with a big block 420 and he recommended black horse belts to me do you know anything about those?

 

[panchothedog]

Get the rotary or comet belt. Also please post a picture from above of your driver and the driven ( also from the rear ) so we can see the alignment of the two clutches. On the 30 series, alignment has to be almost perfect. Misaligned clutches causes premature belt wear on an awful lot of karts and bikes. Kind of just like you are experiencing.

 

[panchothedog]

Post the picture with the belt removed. That part is important.

 

[Edwin Spangler]

Much better. Thank you for the light.

This edge looks like the top of the belt is making a shelf. The inner ribbed part looks worn thin. This should be a flat bevel all the way around.
The belt should be uniform thickness too. Any hourglassing is bad.

View attachment 163219

In this pic you can see the uneven wearing on the cording between layers.

View attachment 163220

And on this side its real bad.

View attachment 163221

Ive gotten the cheap belts that look like this brand new, with the cords partially showing...