Pro mx problems need help

[chadbarger18]

Well my stepbrother got a pro mx about a month ago and saturday was his second race in the stock appering class but this thing is just a turd we changed to a uni filter a 35 tooth back spocket and moved the niddle to the middle notch with the air screw about 1 turn out and and the stock honda 90s will out run it off the gate it will finally hit the powerband about 100yds out but none of the tracks are that big so i was wondering how to make it alot faster but keep the motor stock

[riding4fun]

OK,

You will have to make one change at a time. I am guessing this is a 90

Here are some things that might help.

18t front sprocket. If you have more turns than straightaways.

Don't know what the roller weights are but a good starting point is around 4.7 (may have to mix 4.5 and 5.0)

Torque spring may be too stiff to where it keeping the belt in the slow gear.

Is there a rev limiter on the cdi box?

Hope that helps.
Darrell

[wrhracing]

Advance the timing from stock, then maybe something around 4.5 gram rollers.

[nordic quad]

Ok we had problems with my sons pro mxr 70 too,we had to adjust the carb first found it to be running ritch,dropped the needle to the bottom and changed the main jet from 115 to 108 and airscrew 1 turn out and remowed every other rollerweigth.We still get some bogs uot of the corners when it gets hot but when it runs like it shold no other stock mini can touch it.Just got a dynotested pipe and cutch kit from Lakes Motorsport to get rid of the last bogs,have some metrakit parts to but wont play with these before it runs like it shold.My advise is to adjust the carb first to do this you need to shut the egine off at max rpm ,then read the sparkplug it should bee ligth brown ,if it is dark brown or black its running ritch, if its grey.white its running lean.When you get the carb right look at the roller weights and drive spring koso 2000 shold be rigth for a 90 i think.
The tracks we race has a lot of turns and jumps and not to many long straigts.
Stein A

[chadbarger18]

yeah its a 90 how would you advance the stock timing with a rev box
im new to these little quads

[ecmini1]

Pull water pump cover off , then you will see the stator plate has 2 the same size hex bolts just loosen and barley move counter clock wise about 1/8 inch. Due note to check to see if the stator plate is all the way counter clock ways 1st as this may be your problem to much timing advance. I have seen them from the factory advanced all the way. Hope this helps

[chadbarger18]

thanks ill try that

[qcitytile]

I have a polaris 90 and I noticed the stator was drilled out and advanced just a little but it was clockwise any body know why this is.

[wrhracing]

Your plate has been rotated counter clockwise placing the bolt in the right hand portion of the top slot. Quickly looking, this diludes to thinking the "Plate " has been rotated clockwise. when in fact the plate itself had been rotated counter clockwise placing the bolt in the top slot farther to the right .

[qcitytile]

The plate has been drilled out to make it slotted and the top hole was slotted to the left and the bottom was slotted to the right. Thats if your looking at it on the quad. What does rotating the stator either way do. Sorry to invade on this post but I was reading the comments and got curious. Thanks