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Parts for Motovox / MBX 10

Parts for Motovox / MBX 10

Oct 5th 2020

I have is a minibike. It does have a torque converter with 11 tooth sprocket. I did have a 24 tooth on the rear with 15" tires. Yes it will pass cars on the highway running at 4000 rpm lol. It's a motovox but they are now called mbx 10. However since installing new upgrades I want it to tach out more so I switched to 13" tires on the rear and 30 tooth sprocket but still wouldn't tach out only slowed down my top end speed. Now I put a 36 tooth on the rear. It should definitely tach out but wont. Has so much low end power it will wheelie and smoke tire just wont go higher than 4100 rpm. I did have to make a custom exhaust with some sharp angles to fit because I had to raise the engine mounting plate in order to fit the torque converter. I had a hunch it is either that exhaust or the main jet but I'm probably totally wrong idk. The main jet is the gx390 that came with stage 2 kit. I have a predator 212 hemi. The hemi has stage two but without the 8 degree timing advance because my flywheel has a 32 degree advance. I have also added 18# valve springs and a cam with pretty wide lobes. Oh and heavier push rods. A racing spark plug and billet rod. What are your thoughts why wont this engine get it?

The driven unit of the TAV is opening too soon and the engine will "nose over" and does not have the ability to pull the ratio I did a quick drawing. The spring in the driven is in the center hole. If you move that spring over to the left hole by the red arrow, that will hold the driven unit closed longer and allow the engine to rev higher

The stock spring may not be heavy enough and you may want to upgrade that spring to this. This spring is heavy enough that you can install this in the stock center position in the driven hub

We can also use this spring set in the driver to allow a higher rpm engagement of the belt 

I don't think it is the engine... I believe all these issues are related to the torque converter