2020 YZ250f "Lurching" on heavy acceleration

BeachMX wrote:

Hey everyone,
I have a 2020 YZ250f with about 60 hrs on it, and it began "lurching" upon heavy acceleration this week. It seems fine in the upper revs, but the low end torque makes it "Slip-catch-slip-catch". Does this sound like a clutch issue? I replaced the clutch with a tusk comp clutch about 20 hrs ago (didn't really need it) so I am wondering if that's it. I am thinking about just ordering a OEM clutch setup with new springs, but wanted your experiences and advice first.

I also use fully synthetic yamalube oil, so could that be it? I am a vet guy, and don't got too hard on the clutch or engine.

Good afternoon, I have found in my experience that Tusk clutches last a few rides at most. I am really hard on clutches period but can usually get 10-15 out of the stock clutch, however I barley got 2 out of the Tusk. Go back stock or go Hinson, Barnett, or Rekluse. That will fix your issue unless the basket is grooved.
Ryan

BeachMX wrote:

Hey everyone,
I have a 2020 YZ250f with about 60 hrs on it, and it began "lurching" upon heavy acceleration this week. It seems fine in the upper revs, but the low end torque makes it "Slip-catch-slip-catch". Does this sound like a clutch issue? I replaced the clutch with a tusk comp clutch about 20 hrs ago (didn't really need it) so I am wondering if that's it. I am thinking about just ordering a OEM clutch setup with new springs, but wanted your experiences and advice first.

I also use fully synthetic yamalube oil, so could that be it? I am a vet guy, and don't got too hard on the clutch or engine.

GoYamaha wrote:

Good afternoon, I have found in my experience that Tusk clutches last a few rides at most. I am really hard on clutches period but can usually get 10-15 out of the stock clutch, however I barley got 2 out of the Tusk. Go back stock or go Hinson, Barnett, or Rekluse. That will fix your issue unless the basket is grooved.
Ryan

Thanks for the reply!

Basket is cool.. I'm just surprised that the tusk clutch only lasted 15-20 hours at best, and I'm not a clutch abuser. I have heard of some issues with the gearbox on this year, so I am hoping that it is the clutch!

I will probably just go back to stock with new springs.

Thanks again!

Matt

Order a complete OEM kit, I believe it comes with springs too. Yamaha OEM clutch kits are usually pretty inexpensive too. Something like $100 for an OEM steel/fiber/springs kits I’d get for my YZ250F.

JB500 wrote:

Order a complete OEM kit, I believe it comes with springs too. Yamaha OEM clutch kits are usually pretty inexpensive too. Something like $100 for an OEM steel/fiber/springs kits I’d get for my YZ250F.

Thats exactly what I'm going to do!

Buy OEM yamaha for everything my dude.

Lurching can also be a sign of a chipped tranny gear. I'm hoping this isn't the case.

DynoDan22 wrote:

Lurching can also be a sign of a chipped tranny gear. I'm hoping this isn't the case.

Me too!! It is happening in 3rd and 4th... mainly when I quick shift up under heavy torque. It doesn't happen all the time, just when the back wheel hooks up good.

Well, I put in new compete OEM clutch plates and fibers in, as well as new springs, and its still doing it...

Any ideas? The best way to describe it is it "on-off-on off"... it feels like my rear tire is spinning on the rim or something(it's not... I checked).

Runs perfect, starts right away, revs out great in neutral on the stand..

Tranny

Split the cases and look

You've replaced the clutch and the basket is ok...so I would guess that you've got an issue with one or more of your transmission gears. That will make it feel like the clutch is slipping. I wouldn't ride it until you've stripped it down and checked, you may make it worse by doing so.

Any news on what this issue is? I’m interested to hear what you find.

JB500 wrote:

Any news on what this issue is? I’m interested to hear what you find.

Major Update:

It was definitely the transmission... 2 shift forks and 4 gears(dogs).

Stripped it down myself (first time ever doing a bottom end) replaced 2 shift forks and 4 gears (bad gear dogs).
I decided to do a top end while apart as well (piston, rings, cam chain) .... also my first time in a 4 stroke top end.

I just go done today, and it fired right up once back together. I took it for a little putt on the street, and all gears are working properly.

I'm going to the track in the morning for a light break-in/gearing check, so I will report back!

Matt

JB500 wrote:

Any news on what this issue is? I’m interested to hear what you find.

BeachMX wrote:

Major Update:

It was definitely the transmission... 2 shift forks and 4 gears(dogs).

Stripped it down myself (first time ever doing a bottom end) replaced 2 shift forks and 4 gears (bad gear dogs).
I decided to do a top end while apart as well (piston, rings, cam chain) .... also my first time in a 4 stroke top end.

I just go done today, and it fired right up once back together. I took it for a little putt on the street, and all gears are working properly.

I'm going to the track in the morning for a light break-in/gearing check, so I will report back!

Matt

WOW! I don't believe I ever seen a YZ Tranny do that. You don't drag your foot on the shift lever do you? Double check a good blow up diagram with what you took apart to make sure nothing was missing from the factory? I would measure all clearances, and double check the drive and driven shafts. I have 381 hours on my 2017 YZ250F and nothing ever looks like that when I pull it apart. I regularly inspect all of the parts. I overhaul at 35 hours, crank and bearings at 70. And I'm way hard on my bike. PS built a 270 along the way, what a blast to ride.

Truckdriver wrote:

WOW! I don't believe I ever seen a YZ Tranny do that. You don't drag your foot on the shift lever do you? Double check a good blow up diagram with what you took apart to make sure nothing was missing from the factory? I would measure all clearances, and double check the drive and driven shafts. I have 381 hours on my 2017 YZ250F and nothing ever looks like that when I pull it apart. I regularly inspect all of the parts. I overhaul at 35 hours, crank and bearings at 70. And I'm way hard on my bike. PS built a 270 along the way, what a blast to ride.

Nope, no foot drag. This seems to be an issue with some of the 19-20's.. I'm not hard on my bike at all.

All parts were there from factory. I am hoping that these will last awhile (60-70hrs) before I have to replace again.. all and all about 500 bucks in parts.

I have heard of some people switching to the 2015 tranny in this bike... maybe I'll look into that.

Truckdriver wrote:

WOW! I don't believe I ever seen a YZ Tranny do that. You don't drag your foot on the shift lever do you? Double check a good blow up diagram with what you took apart to make sure nothing was missing from the factory? I would measure all clearances, and double check the drive and driven shafts. I have 381 hours on my 2017 YZ250F and nothing ever looks like that when I pull it apart. I regularly inspect all of the parts. I overhaul at 35 hours, crank and bearings at 70. And I'm way hard on my bike. PS built a 270 along the way, what a blast to ride.

What oil are you using?

Skerby wrote:

Buy OEM yamaha for everything my dude.

Is this the way to go? Also for piston, timing chain etc? I just replaced mine with OEM. But keep wondering if there is not a stronger timing chain as the Yamaha one seems to be a weak spot.

BeachMX wrote:

Nope, no foot drag. This seems to be an issue with some of the 19-20's.. I'm not hard on my bike at all.

All parts were there from factory. I am hoping that these will last awhile (60-70hrs) before I have to replace again.. all and all about 500 bucks in parts.

I have heard of some people switching to the 2015 tranny in this bike... maybe I'll look into that.

I'll be looking out for this on my 19. Just got it at 62hrs, hope I won't have the same. I went away from my RM250 '10 as I I had to change the tranny once every year.

Skerby wrote:

Buy OEM yamaha for everything my dude.

Thedirtyrider wrote:

Is this the way to go? Also for piston, timing chain etc? I just replaced mine with OEM. But keep wondering if there is not a stronger timing chain as the Yamaha one seems to be a weak spot.

I went OEM on everything.. I know that that is the way to go for reliability/durability.

Update:

Rode the bike today for the first time since the new gears/top end/timing chain/valve adjustment, and all seems good! I took it very easy, but no slipping that I could feel(I wasn't pushing it though due to breaking in the new piston).

will keep you posted!