Cryoed - yukons - back cutting oh my !

[jonpiper]

The first time I blew second gear out of my ESR 330 pv powered R I shrugged it off as bad luck and old gears.

The second time after being replaced with another stock gear set, I have decided it is time to pull the trigger on a stronger setup.

I have searched the forum and read this and that but it doesn't seem there is a direct answer to "what is the strongest tranny"

I have narrowed it down to 3 choices and I would like a little help making my choice.

(1) replace broken gears with oem having them cryoed and back cut

(2) replace with oem clutch side gears and yukons

(3)all new oem clutch side gears, yukons all back cut and cryoed.

The over achiever in me really wants to go with option 3 but after my searching I have no found a single person running a set up like that.

[Trix r for kids]

Im building a 350 non pv and im in the process of doin number 3 just shop around for the yukons u can find them on ebay for way cheap most places want 350-500 dollars for tem i picked mine up for 270 plus shipping i started a thread last week or so about this same subject take a look at it i might have some info ur lookin for

[Trix r for kids]

i had also spoke with dave from dave moore racing and he told me dont bother buying the oem gears just have urs glass beaded and if there are any cracks oil will start seapin out but he also said the gears that came in the 250r are hard as hell so they dont really crack if they crack they explode he told me just to use the stock drive side gears and go with the yukon drivin side gears and have them all cryoed just make sure u have ur tranny mod done to the gears b4 u have them cryod or just send it to these guys they know there stuff http://www.w-c-r.com/index.htm

[86 Quad R]

Originally posted by Trix r for kids
i had also spoke with dave from dave moore racing and he told me dont bother buying the oem gears just have urs glass beaded and if there are any cracks oil will start seapin out but he also said the gears that came in the 250r are hard as hell so they dont really crack if they crack they explode he told me just to use the stock drive side gears and go with the yukon drivin side gears and have them all cryoed just make sure u have ur tranny mod done to the gears b4 u have them cryod or just send it to these guys they know there stuff http://www.w-c-r.com/index.htm

cant see where you'd go wrong there. that cryo-ing does awesum things with those trannies. :cool:

[Burns310r]

Why couldnt you just cryo the entire oem tranny? Wouldnt that be more than tough enough?

[rustyATV]

The stock 250R tranny meets its limits on motors in the 310cc range. Larger than that and aftermarket gears are really needed.

[jas250r]

my ct 350pv has the yukon and stockers cryoed not back cut. i also have a spare stock motor that is just cryoed. going to buld another bottom the same as the ct 350. should be a stout setup.

[jonpiper]

Originally posted by Trix r for kids
i had also spoke with dave from dave moore racing and he told me dont bother buying the oem gears just have urs glass beaded and if there are any cracks oil will start seapin out but he also said the gears that came in the 250r are hard as hell so they dont really crack if they crack they explode he told me just to use the stock drive side gears and go with the yukon drivin side gears and have them all cryoed just make sure u have ur tranny mod done to the gears b4 u have them cryod or just send it to these guys they know there stuff http://www.w-c-r.com/index.htm

trix,

when you spoke to dave did he suggest having them back cut ?

[kev440]

this might be a dumb question but im new to the 250r engine biulding what do you mean by cryoed gears

[derby]

Originally posted by jonpiper
trix,

when you spoke to dave did he suggest having them back cut ?

My puma blew out the stock trans in the first 2 hours of ride time. I went to wcr for the cryo and they backcut 1-4. It shifts much smoother than a non-backcut. You can cryo and be fine with most transmissions especially on a 350. I would say if you are building a 400+cc motor or something that puts out 75 +hp then backcut 1-4. For smaller motors it is probably a waist unless you trans damage is rider error.

Just curious jonpiper what gear or shift were you in when you damaged the trans?

[jonpiper]

Derby,
both times I was in 2nd gear.

First time: I was climbing a hill at a local spot (west point, Tn) got maybe waist high air and on the landing the small clutch side 2nd gear came out the bottom of the case

2nd time: I was on a super cross track ... on the down hill side of a double and when the tires hit the large counter shaft 2nd gear came out the top side of the case.

On the rider error end of things I would love it if someone could tell me that I did something wrong. However, I have been on quads and dirt bikes for about 16 years also supermoto's and drag racing sport bikes. Im typically not hard on parts like trannys etc but hey I'm always up for some knowledge :)

[derby]

Originally posted by jonpiper
Derby,
both times I was in 2nd gear.

First time: I was climbing a hill at a local spot (west point, Tn) got maybe waist high air and on the landing the small clutch side 2nd gear came out the bottom of the case

2nd time: I was on a super cross track ... on the down hill side of a double and when the tires hit the large counter shaft 2nd gear came out the top side of the case.

On the rider error end of things I would love it if someone could tell me that I did something wrong. However, I have been on quads and dirt bikes for about 16 years also supermoto's and drag racing sport bikes. Im typically not hard on parts like trannys etc but hey I'm always up for some knowledge :)


Exactly what I thought. 2nd gear is the worst. With the yukons the larger 2nd gear will not break like the stock one. I shattered the small second gear on the opposite shaft from the yukon. Rider error.... now that I think about the situation it may or may not be rider error. Once you get some wear on the transmission may be the problem. What I have noticed with both 2nd gear failures I have had. It was 1st to 2nd gear shift that did not quite get to 2nd gear. One was at wide open the other was shifting up a hill. But half shifting is something I consider rider error in my situation. Your situation sounds a little different.

If it were me I would get the yukons and have them cryo treated @ WCR in florida. I would not backcut them....once you do that you may only get 600-800 shifts out of 1-4.

[jonpiper]

Heck I was hoping there was an ultra secret part throttle, clutch, fingers crossed, voodoo and chicken bone rider preparation for jumping a 250r that I didn't know about LOL

Thank you for some insight and info !

Can anyone post a picture or describe what the back cut gears look like?

Thanks!

[Aceman]

Originally posted by jonpiper
Heck I was hoping there was an ultra secret part throttle, clutch, fingers crossed, voodoo and chicken bone rider preparation for jumping a 250r that I didn't know about LOL

Thank you for some insight and info !

I've believe I've heard guys that run sandrails mention they clutch it right before they land a jump to save their trannies. Too much stress on the transmission if the wheels are spinning a different speed in the air than what the landing calls for. That sudden speed change when the tires hook up grenades them.

[latheboy]

the circled area is the undercut

The stock Honda gears already are cut back, your picture shows the cut back to be more pronounced or cut down further; is this correct?

[Trix r for kids]

i havnt done much research on back cutting but putting all that power on those small dog is enough strain but then grinding them down some more makes them weaker i would think now if someone were to build that contact area up to where there is more material then backcut them after that it would seem to me not only would it make the dog stronger but it would also distribute the stress much more evenly throughout the gear rather than the small area they have on the gear making it break and destroy everything in the way the only big problem would be if it would still shift and shift good

[jonpiper]

can anyone with yukons post up what the physical differences are ? Maybe a picture ?

I ordered my yukons tonight from everett powersports (i believe) on ebay. 299 shipped.

This week I will have the engine out and see just how bad this blow up was. see what clutch side gears I need make a parts list...

sigh

[destey]

why backcut? To keep it from slipping out of gear?

[gandgracing]

When you gas it and then let off the gears try to seperate from each other. Getting them backcut will keep them together. When I blew my second gear I was coming to the top of a breaker, clutched it and then hammered it. Didnt feel or hear anything but it was like it was in neutral. Looked down and half of my left case was gone. No more problems after the backcut and cryo treatment with yukons.

[latheboy]

What do you all think about just adding the yukons? No cryro, or backcutting?

[derby]

Originally posted by latheboy
What do you all think about just adding the yukons? No cryro, or backcutting?

Depends on what your setup is. If it is a puma backcut, cryo and yukons no doubt about it. Every puma that I know with a non override trans built with in the past year has blown. I never blew a trans on a 350 cant speak for my 370 because it has an override. Puma must have all 3.

[jonpiper]

Originally posted by latheboy
What do you all think about just adding the yukons? No cryro, or backcutting?

but what is another $300 for the added protection ?

[86 Quad R]

Originally posted by jonpiper
but what is another $300 for the added protection ?

right on!!!! :D

[derby]

Originally posted by 86 Quad R
right on!!!! :D

I beleive the backcut is $25 per gear and the cryo is $75. So $175 is almost half of what you are thinking.(without the yukons)

[latheboy]

Thanks for the opinions. I am building a 350pv, have the yukons in hand, not installed yet.....

[red88r]

We installed the Yukons in my ol man's 340pv...brother and I mx'd this quad pretty hard in A and B classes with no problems...yet anyways.

[jonpiper]

well apparently the yukons come with a 4* back cut ... when you send a gear set out to be cut what degree back cut is machined ?

[derby]

Originally posted by jonpiper
well apparently the yukons come with a 4* back cut ... when you send a gear set out to be cut what degree back cut is machined ?

Backcut set came back with 45 degree cuts.

[Allison55ex'er]

Anyone know anything about the ISF gear coating from CV-4. I think I saw somethin about that in the 450 section

[Trix r for kids]

http://www.osro-superfinishing.com/en/technology/the-isf-process

this will answer some Q's

[Allison55ex'er]

So I geuss its not really a coating but more polishing seems like a pretty cool process it would be interesting to see a price. If its not bad you could do all the transmission stuff. so maybe there should be a option D.Yukons that are Cryoed, backcut, and ISF. haha thats alot but it seems like it would be indestructible if everthing worked together.

[Trix r for kids]

yea im gonna do it to every gear in my entire engine i got the yukons a brand new transmission and almost every gear besides the kickstarter and counterbalencer those r the only ones i couldn't find new hopefully my trans will be unstopable atleast for a while ive put so much money in my setup i dont want it to break