an under cut tranny keeps the trany from jumping out of gear under extream use and pressure do to the added horse power.

I found this and it explanes it beter than I can:
APE TRANSMISSIONS

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Transmission Undercutting

Undercutting a transmission involves machining angles on the engagement dogs and slots to prevent the transmission from jumping out of gear under load. There are three types of undercuts available

Racecut...
This cut is performed on the side of the dogs that are loaded on acceleration. Recommended for hot street bikes and drag racers, dwarf cars, etc.

Up and down cut....
Both sides of the dog are cut to also prevent jumping out of gear on down shifts. Recommended for road racing.


Up and down cut....
Both sides of the dog are cut to also prevent jumping out of gear on down shifts. Recommended for road racing.

What exactly is undercutting?

The transmission gears lock together with a series of "dogs' or "dogs and slots" several of the dogs engaged together so that both gears turn together. Under hard use, the gears can began to separate until the dogs become disengaged, this causes the transmission to jump out of gear. They both have angles cut on them where they meet. This causes them to lock together. They cannot separate without first backing up to unload the angles. This is an undercut. Road race "up and down" cuts have angles machined on both sides of the dog so it works the same way under acceleration load and deceleration load.

 

Here are more info with correction:

> Lakota 300 and Bayou 300 have exactly the SAME engine as following:
76.0 mm bore x 64.0 mm stroke w/ 8.6:1 comp ratio w/ same Keihin CVK 32 carb but with different main jet size due to freer air intake system on Lakota. Also, Lakota has higher rev limit setting in the igniter resulting in slight higer power output, 21.5 hp @7000 rpm vs. 19.4 hp @6500 rpm.

> Lakota lasted 8 years from 1995 to 2002. Earlier (95~2000?) Lakota came with front & rear cargo racks and dual headlights giving more of ute impression, then (2001?-2002) Lakota had no racks at all and a center mounted single headlight giving sportier look.

> MSRP ranged from $4100 to $4800 depending on years (2002 was the lowest).

> It's almost bullet proof engine except it's got a plastic oil pump gear which can disintegrate into pieces or melt away in extremely overheated oil condition. If you drive properly and keep healthy amount of engine oil, it will last forever.

 

They are the same motors BUT thier are diferences like you said. The jetting in the carb is defferent and the rev. limiter is defferent.

Also dont forget, the CAMS (lift, duration) are different in the lakota than the bayou resulting in a little more agressave power delivery.

 

The Lakota does have a hotter cam than the Bayou , I remember that also.

 

YEP.

That is what I was talking about when I said:''And no, the bayou motor and the lakota motor are not the same. The lakota motor is tuned more aggressivly than the one in the bayou.''

Thanks TLC

 

Great info guys! Can't wait to tear into it. I go pick it up tomorrow if everthing goes as planned.

One question.... Why don't all atvs come with undercut trannies? What's the downside?

Since this one will need rings at the least,,, I will go ahead and bore it and see if a high comp piston is available. 8.6 is kinda low.

 

Nope. Looks like no high comp piston is made by wiseco. Anybody else make them?

I'll probably end up milling the head and jug then....

 

It is very expensive and a verry precise thing to under cut a transmision and most 4-wheelers have a transmision that is more than enough to handle what ever you put them throu. It is only when you increase the horse power on a motor so much that the tranny starts to slip, this becomes useful. Also a good majority of 4-wheelers and dirt bikes are undercut to a certian point.

Look up cycle works for a piston. They can probably help you.

 

Thanks! I'll check into that.

Does the lakota pop out of gear a lot? My bayou does maybe 1 out of 100 shifts and that is only when I dont get a good stroke in on the shifter.

My quadsport has oodles of power (for a 1/4 liter) and it has never popped out of gear.... I do hit neutral sometimes in between 1st n 2nd, lol.

 

Sometimes popping out of the gear problem can be remedied by adjusting the shift linkage (tie-rod) just below the hi-lo shift lever. Turn the adjusting nut about 2 turns at a time and test ride. Trying making it shorter first, if worse, go the other way.