Trailmaster MB200-2 with Tillotson 212 and TAV

[onionfmr]

Looking for some advice, pointing in a direction. I've been working on this build for approximately a year. Getting close, but kind of hit a wall in terms of performance. Here's the general information of the build:
Tillotson 212 Hemi.
Billet flywheel and rod.
.010 head gasket.
CS 265 cam, 7000 max RPM.
26# valve springs.
Mikuni VM22-133 with 20 pilot and 140 main jets.
Chinese TAV with 146 gram weights, white garter springs. Driven spring in 3rd hole.
10 tooth jackshaft sprocket and 50 tooth rear sprocket.

Engine will hit a top RPM now of 5,500 RPMs at full throttle and then fall back to around 5,200 RPMs if the throttle is help open. Top speed at approximately 550 feet on a GPS is 45 MPH. RPMs top at 5,500. That's it. I'm guessing that I might pick up a little RPMs and top speed if I held the throttle open over a longer distance. Based on the feel of the engine, it isn't pulling hard at this point. Kind of flat.

I would like increase my top speed to around 51 MPH over this distance. I'm thinking of changing to the blue/silver garter springs and to yellow spring in the driven unit. Realizing that I can change gearing to accomplish more top end, but will lose on the low end. I would like to get more RPM out of this engine maintaining my existing gearing. Here's the question. Would swapping to a different cam, head work, etc.., allow me to build more RPMs or am I stuck because of the TAV and the gearing and need to change gearing (60 tooth rear sprocket) to get more out of this engine package? Thanks in advance for any comments and suggestions.

 

[Davis]

Head work does wonders. And your gearing seems way to high. How tall are your tires?

 

[onionfmr]

Head work does wonders. And your gearing seems way to high. How tall are your tires?

Tires are 19".

 

[Davis]

Tires are 19".

I would definitely try the 60t sprocket.

 

[massacre]

I feel like the load and OD of a TAV will keep the revs lower than with a centrifugal clutch.

When I ran a centrifugal clutch on my drag bike, I was turning the motor 9350 RPM.
But with the Polar clutch I run even faster but the engine is only at 7800-8000 RPM.

Noticed the same thing with my modded MTD, bike was going faster but RPMs were lower, I think it is because the TAV is going into OD and keeping the revs down. So my motor is supposed to be able to turn over 5000 RPM but I never see that on the tach because of the OD, usually get close to 4000 RPM

 

[onionfmr]

Appreciate the replies. I leaning to trying the 60 tooth rear sprocket. Why I've been hesitant to try it is because on the Trailmaster bikes, I've heard of chain interference issues using a 60 tooth sprocket and swing arm frame.

I've talked to individuals at two well known mini bike shops indicating that they are seeing 6,500 RPMs running Trailmaster mini bikes with built 212 engines and TAVs. They claim to be getting into 40-45 MPH range easily with Stage 1 engines. Some say they are running 60 tooth rear sprockets, other says 36/38 tooth rear sprockets. One claim was with a Predator 212 and a Stage 4 engine build, TAV with 146 gram weights and white garter springs, 36/38 tooth rear sprocket and 240 lbs. rider, they are seeing 6,500 RPMs and 64 MPH. I'm not disputing anyone's claims. I'm just trying to make sense of it based on my actual testing results.