What's going on with this setup?

[ArcsandSparks]

I just finished my Speedway widowmaker with a centrifugal clutch setup. I used the original jackshaft and gearing (JS output/tire side). I am using a HF 6.5 clone stock. So my gearing is a 10 tooth on the clutch-10 tooth JS input-8 tooth JS output-60 tooth on the tire. Now I used 2 separate calculators to find my final gear ratio/ estimate speed:
Rawge's Mini Chopper Information Site - Jackshafts
Burris Racing Jackshaft Calculator

My FGR came to be 7.5:1 and top speed is around 19-20 mph with 14'' tires.

Here is the confusing part....After a few passes and having my brother-in-law ride side by side with a quad, I was doing 29-30 mph and that wasn't even WOT...What gives?
What am I not seeing or calculating right?

I've read that some people have bought a HF engine and the governor isn't working so they can achieve higher RPM's, but that would mean I would have to be running 5600 RPM...

Thanks in advance for any input.

 

[ArcsandSparks]

I pulled the clutch off and tested....Governor seems to be working fine, however, I don't have a tach to see actual RPMs...
Anybody know how this could be?

 

[oldyeller]

What brand of atv?..Some of the speedo's are way out of whack..

 

[ArcsandSparks]

What brand of atv?..Some of the speedo's are way out of whack..

Kawasaki prairie 650...I could tell my speeds exceeded 20mph for sure. Weather the atv was accurate at 29 or not that is uncertain, but haven driven many motorized vehicles alike I would say that it was too far off. This question has been baffling me??!!

 

[ArcsandSparks]

I am also having some heavy vibration/banging as I speed up. It goes away after I increase speed. The chains are aligned and there seems to be no wearing on the chain/sprocket. As stated before I'm running
clutch/ JS in/ JS out/ Rear wheel
10 10 8 60 =7.5:1

Is a jackshaft suppose to be run in this manner? Meaning going from a 10 tooth clutch to a 10 tooth JS input?

I am planning on putting a 14 tooth sprocket (JS in) tomorrow to hopefully alleviate the problem, but I will be running close to 10:1...doesn't seem ideal. I don't care if does 40 mph, but I want some hole shot with reasonable top end. Anybody have any insight?

P.s. I have a 40/41 CFC - #40 chain - #40 10T, 8T #420 - #420 chain - #420 60T