YZ 250 trans issues

ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400
Edited Date/Time 12/17/2015 12:17pm
Hey guys I am kinda at whits end, I have a 2014 Yz 250, 45 hours on it and have lost 3rd gear for the 2nd time. I have had other yz 250's '06 to present and never had a single issue. I know 3rd gear is a weak link but other then cryo gear treatment is there anything else aftermarket gear wise to beef these up?
|
scooter5002
Profile picture for user scooter5002
Posts
4748
Joined
6/6/2010
Location
Nanton Alberta, CA
scooter5002 12/6/2015 5:51pm
12/6/2015 5:51pm
Hey ese, what's up? Can't help you with the trans, just thought I'd let you know I'm back on this side of the continent. Still have your # programmed in my cel. Good luck with the Piano.
xnationalwrench 12/6/2015 6:04pm
12/6/2015 6:04pm Edited Date/Time 12/6/2015 6:05pm
What exactly failed the 1st time? Take it down and see if its the same problem. Coatings don't usually stop a gear failure but can help with shifting and less drag. You might consider changing your final drive gearing to stay out of that gear as much.
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/6/2015 6:06pm
12/6/2015 6:06pm
scooter5002 wrote:
Hey ese, what's up? Can't help you with the trans, just thought I'd let you know I'm back on this side of the continent. Still have...
Hey ese, what's up? Can't help you with the trans, just thought I'd let you know I'm back on this side of the continent. Still have your # programmed in my cel. Good luck with the Piano.
Hey buddy, I am doing well, in Louisville for work for a bit. Need to meet up at Baja someday.
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/6/2015 6:07pm
12/6/2015 6:07pm
xnationalwrench wrote:
What exactly failed the 1st time? Take it down and see if its the same problem. Coatings don't usually stop a gear failure but can help...
What exactly failed the 1st time? Take it down and see if its the same problem. Coatings don't usually stop a gear failure but can help with shifting and less drag. You might consider changing your final drive gearing to stay out of that gear as much.
3rd gear broke. Common issue, I know coatings will make them shift better, I just wanted to know what else people have done to combat this.

The Shop

See All »
scooter5002
Profile picture for user scooter5002
Posts
4748
Joined
6/6/2010
Location
Nanton Alberta, CA
scooter5002 12/6/2015 6:19pm
12/6/2015 6:19pm
scooter5002 wrote:
Hey ese, what's up? Can't help you with the trans, just thought I'd let you know I'm back on this side of the continent. Still have...
Hey ese, what's up? Can't help you with the trans, just thought I'd let you know I'm back on this side of the continent. Still have your # programmed in my cel. Good luck with the Piano.
ehr400 wrote:
Hey buddy, I am doing well, in Louisville for work for a bit. Need to meet up at Baja someday.
Haven't been there in a while, but I could do Log Road as well. See how it goes once we hit springtime. Have a long time friend from north of the Motor I need to hook up with too. Need to catch up on some riding, been pretty skinny the last 4 years.
Joko
Profile picture for user Joko
Posts
1555
Joined
1/2/2011
Location
Haddam, CT, USA
Fantasy
127th
Joko 12/6/2015 8:14pm
12/6/2015 8:14pm
What do you mean by losing 3rd gear? Are the teeth or dogs sheared off? Can you show a pic?
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/7/2015 7:54am
12/7/2015 7:54am
Chunk of tooth the first time, I havent got the cases split yet but it appears as it happened again.
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/7/2015 8:04am
12/7/2015 8:04am


xnationalwrench 12/7/2015 8:41am
12/7/2015 8:41am
Maybe find a shop that does Magnaflux and send the gears there to be checked/inspected. Like I said before change the final gearing to stay away from using that gear as much.
mxtech1
Profile picture for user mxtech1
Posts
1968
Joined
7/21/2011
Location
Galesburg, IL, USA
mxtech1 12/7/2015 10:08am
12/7/2015 10:08am
Despite what you might think, I would say this isn't a "common" problem. Yes, the YZ250 transmissions aren't the smoothest or most bulletproof of the bunch, but they are not weak to the point of what you are seeing.

Are you sure you have all of the shims in the correct places?

IMO, the fact that you have had this happen twice points directly back to whoever is building the bottom end. Something is wrong with the process of building the bottom end, not the gear. The chances of you getting 2 bad gears with defects is probably slim to none.
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/7/2015 11:00am
12/7/2015 11:00am
First time was original never been apart. I have had 2 other YZ 250's with over 100 hours each that have been apart with no issues. I verified shims and thrust washers when repairing first time. I don't power shift this thing either. Kinda stumped.

This motor has been ported, not stock HP.

If shims were incorrect from the factory, which they werent, i would expect to see side loads on the gears or burrs. Nothing was there. The gear was in great shape minus the tooth broke off. I put die penetrant on the gear and there was a crack near the dog as well.
DuroTools
Profile picture for user DuroTools
Posts
755
Joined
9/9/2015
Location
Middletown, CT, USA
DuroTools 12/7/2015 1:31pm
12/7/2015 1:31pm Edited Date/Time 12/7/2015 1:45pm
Ya like MXtech1 said it seems like it is something else that is causing that, it is too much of a coincidence to break the same part twice. Simply replacing even with a stronger one somehow seems like a bandaid or then different adjoining gear will break instead. Does it sound like it is abruptly going into gear when you shift or is it smooth and normal? maybe just get a used tranny off ebay and swap it out rather than chasing it part by part.You can probably get one super cheap. I've swapped out parts that have looked identical and it has fixed shifting issues so rather than splitting the cases a bunch of times I'd say do one clean sweep and replace the bearings too!
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/7/2015 1:39pm
12/7/2015 1:39pm
I have thought about that.

No warning signs, no missed or hard shifts. First time sand track feathered the clutch in 3rd gear and i felt it give.

Second time, landed from jump got on the gas and crunch.

I am about to talk to the guys who have made gears for my buddies pulling tractors and see if they can make something will work.
DuroTools
Profile picture for user DuroTools
Posts
755
Joined
9/9/2015
Location
Middletown, CT, USA
DuroTools 12/7/2015 1:55pm
12/7/2015 1:55pm
Strange, maybe the gears are misaligning and not meshing properly when shifting. Is the bearing that holds the shaft or spindle of gears worn so there is excessive play or wobble side to side? If one side is straight and the other crooked maybe it won't be able to spin once they are moved to each other and so it would just shear off?
floridaflash
Profile picture for user floridaflash
Posts
149
Joined
4/1/2008
Location
Melbourne, FL, USA
floridaflash 12/8/2015 9:04am
12/8/2015 9:04am
are you landing from jumps with your toe on the shifter, that will do it
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/8/2015 9:56am
12/8/2015 9:56am
Nothing different then I have done the last 25 years of riding. I guess when i get this thing torn down i will check alignment and see what if any issues are going on with the bearings or backlash. Could be poor casting quality control or final machining. Or bad batch of gear material. Who knows.
FGR01
Profile picture for user FGR01
Posts
6159
Joined
10/1/2006
Location
USA
Fantasy
910th
FGR01 12/8/2015 11:16am
12/8/2015 11:16am
xnationalwrench wrote:
Maybe find a shop that does Magnaflux and send the gears there to be checked/inspected. Like I said before change the final gearing to stay away...
Maybe find a shop that does Magnaflux and send the gears there to be checked/inspected. Like I said before change the final gearing to stay away from using that gear as much.
We're talking 3rd gear here. Right in the middle of your spread. The most used gear in motocross. I don't think you're gonna do anything with your sprockets that's going to keep you in 1/2 or 4/5 all/most of the time.

This is a fairly well known prob with the YZ250. It seems to increase with the guys that do the 285/295 big bores and put a higher load on the tranny. Thankfully, I have not had any probs with my 2006 yet, knock on wood. I use only Bel-Ray Gear Saver and change it about every 6 rides.
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/8/2015 11:21am
12/8/2015 11:21am
xnationalwrench wrote:
Maybe find a shop that does Magnaflux and send the gears there to be checked/inspected. Like I said before change the final gearing to stay away...
Maybe find a shop that does Magnaflux and send the gears there to be checked/inspected. Like I said before change the final gearing to stay away from using that gear as much.
FGR01 wrote:
We're talking 3rd gear here. Right in the middle of your spread. The most used gear in motocross. I don't think you're gonna do anything with...
We're talking 3rd gear here. Right in the middle of your spread. The most used gear in motocross. I don't think you're gonna do anything with your sprockets that's going to keep you in 1/2 or 4/5 all/most of the time.

This is a fairly well known prob with the YZ250. It seems to increase with the guys that do the 285/295 big bores and put a higher load on the tranny. Thankfully, I have not had any probs with my 2006 yet, knock on wood. I use only Bel-Ray Gear Saver and change it about every 6 rides.
Weird thing is I had a 295 BB kit on my last one over 100 hours on it 0 issues.

I had this motor done by Derek Harris and still is a 250, obviously more hp but shit, not many hours and I am a Vet B rider for god sake. Lol. I have been using Lucas gear oil.

Pit Row

See All »
sandman768
Profile picture for user sandman768
Posts
8270
Joined
3/21/2014
Location
Saratoga Springs, NY, USA
sandman768 12/8/2015 12:39pm
12/8/2015 12:39pm
There are other threads on the yz gear problems. Back in 2005, me & 2 of my riding buddies all had new YZ250"s, I raced the most, my tranny went first, a few months later both my buddies trannies went, all the same problem, worn engagement surfaces on the gears... Ours did not break teeth on the gears... I loved my Yamahas, but after 3 new YZ"s & they all had the same tranny issues, I moved back to Honda"s, I figured I rather have bad forks vs bad trannies!
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/9/2015 4:23am
12/9/2015 4:23am
sandman768 wrote:
There are other threads on the yz gear problems. Back in 2005, me & 2 of my riding buddies all had new YZ250"s, I raced the...
There are other threads on the yz gear problems. Back in 2005, me & 2 of my riding buddies all had new YZ250"s, I raced the most, my tranny went first, a few months later both my buddies trannies went, all the same problem, worn engagement surfaces on the gears... Ours did not break teeth on the gears... I loved my Yamahas, but after 3 new YZ"s & they all had the same tranny issues, I moved back to Honda"s, I figured I rather have bad forks vs bad trannies!
I was trying to find that thread. I remember reading that. My buddy and I had '06's one with a BB and the other ported race gas motor with over a 100 hours on each with zero trans issues.
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/17/2015 3:30am
12/17/2015 3:30am Edited Date/Time 12/17/2015 4:11am






You can see where the one teeth sheared off again, however this time it broke a second also and then clashed the 3-4 ones causing the lockup.
sandman768
Profile picture for user sandman768
Posts
8270
Joined
3/21/2014
Location
Saratoga Springs, NY, USA
sandman768 12/17/2015 5:35am
12/17/2015 5:35am
I would replace every gear, shaft, shim ect in that gear box, I became very frustrated with my last YZ 250 in 08 due to tranny gear issues & cracked cases. The YZ"a are great bikes but I question the metallurgy, had a 2006 yz450f, first year the bike was great, approx 50 hrs, very well maintained, 2nd season....not so great, Ti Shock spring snapped, wiped out shock assy. Then 5th gear grenaded going through a whoop section, taking out everything in the gearbox! 3rd & 5th gear were on national b/order..then when I finally got it back together, 10 hrs later on the hr meter, the piston wrist pin snapped! After all that, I went & bought the 08 YZ 2 stroke mentioned above. I have to say, before these duds, I had 2 yz250f"s & they were 2 of the best bikes I ever owned! Both had well over 100 hrs of MX, Gncc & hard sand motos, with not even a single valve adjustment!
ehr400
Profile picture for user ehr400
Posts
2630
Joined
4/1/2008
Location
Britton, MI, USA
ehr400 12/17/2015 12:17pm
12/17/2015 12:17pm
I agree very frustrating considering second time it has happened in less then 45 hours. Same exact mode of failure. I also have thought possibly shaft deflection due to it being hollow for the clutch pushrod and 3rd gear being in the middle of the shaft. I know the day before it grenaded I was jumping a triple into a roller section and when i landed i was pinned 3rd and seatbouncing out so i wonder if the extreme load like that would cause it but thats bs because i have done way worse with other bikes.

Post a reply to: YZ 250 trans issues