Odd Transmission Issue

MC770
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MC770
Edited Date/Time 1/22/2020 3:22am
Hey all, after doing pages of research on here I haven't really come across my exact issue. I have some weird issue that started happening with my transmission that prematurely ended my race season this past season. Little backstory on the bike it's a 2018 yz250X, has ~150hrs or so on it and it has been raced hard since new (oil changed after every race) in the local woods series. So I had gone to Tennessee for the fall trail ride at Loretta Lynn's ranch and rode the whole weekend with no issues to speak of in the transmission, I did notice that my clutch was worn out (not a huge shock since it is raced weekly) So I got home to NC and had a race the following weekend; Changed my clutch (Friction and Drive plates) After I changed the clutch I went to test ride the bike and adjust the clutch appropriately and found that I had First gear and Neutral but the bike will not shift into 2-5 gear at all. Initially I suspected that somehow something with the clutch or my clutch cable adjustments was playing into it somehow; after getting as far as completely removing the clutch, inner hub, and the whole basket one by one I could still not get past first gear. I looked at the cam and lever on the clutch side of the shift fork and couldn't see any obvious signs that it wasn't working right. Anything I should really be looking at after splitting the cases? Having them opened up on initial inspection I don't see anything crazy obvious and just want to make sure I don't overlook anything
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DynoDan22
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DynoDan22 1/9/2020 6:39am
1/9/2020 6:39am
look at the external shift mechanism (shift drum cam, shift drum cam index lever and shift cam bot that engages into shift drum). All of this can be accessed by removing right side main case cover and the clutch basket. Sounds to me like the mechanism isn't functioning properly and something came loose or is damaged. Also check the shift cam index tension spring. I would start there first. If the problem was with the trans gears and shift forks the bike would be popping out of gear under load. I find it coincidental that you changed a clutch and the issue shows up as well. when inspecting the above, look for debris and proper function of the external shift mechanism. Drain the oil as well and look for anything suspicious. Good luck and keep us posted!
Paw Paw 271
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Paw Paw 271 1/9/2020 10:56am
1/9/2020 10:56am
DynoDan22 wrote:
look at the external shift mechanism (shift drum cam, shift drum cam index lever and shift cam bot that engages into shift drum). All of this...
look at the external shift mechanism (shift drum cam, shift drum cam index lever and shift cam bot that engages into shift drum). All of this can be accessed by removing right side main case cover and the clutch basket. Sounds to me like the mechanism isn't functioning properly and something came loose or is damaged. Also check the shift cam index tension spring. I would start there first. If the problem was with the trans gears and shift forks the bike would be popping out of gear under load. I find it coincidental that you changed a clutch and the issue shows up as well. when inspecting the above, look for debris and proper function of the external shift mechanism. Drain the oil as well and look for anything suspicious. Good luck and keep us posted!
X2

Paw Paw
Tracktor
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Tracktor 1/13/2020 12:33pm
1/13/2020 12:33pm
DynoDan22 wrote:
look at the external shift mechanism (shift drum cam, shift drum cam index lever and shift cam bot that engages into shift drum). All of this...
look at the external shift mechanism (shift drum cam, shift drum cam index lever and shift cam bot that engages into shift drum). All of this can be accessed by removing right side main case cover and the clutch basket. Sounds to me like the mechanism isn't functioning properly and something came loose or is damaged. Also check the shift cam index tension spring. I would start there first. If the problem was with the trans gears and shift forks the bike would be popping out of gear under load. I find it coincidental that you changed a clutch and the issue shows up as well. when inspecting the above, look for debris and proper function of the external shift mechanism. Drain the oil as well and look for anything suspicious. Good luck and keep us posted!
Paw Paw 271 wrote:
X2

Paw Paw
X3. Changes are the shift lever got pushed to the right and isn't indexed correctly behind the clutch basket. Have done this a time or two before when assembly engines in a hurry......
MC770
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MC770 1/16/2020 3:01am
1/16/2020 3:01am
DynoDan22 wrote:
look at the external shift mechanism (shift drum cam, shift drum cam index lever and shift cam bot that engages into shift drum). All of this...
look at the external shift mechanism (shift drum cam, shift drum cam index lever and shift cam bot that engages into shift drum). All of this can be accessed by removing right side main case cover and the clutch basket. Sounds to me like the mechanism isn't functioning properly and something came loose or is damaged. Also check the shift cam index tension spring. I would start there first. If the problem was with the trans gears and shift forks the bike would be popping out of gear under load. I find it coincidental that you changed a clutch and the issue shows up as well. when inspecting the above, look for debris and proper function of the external shift mechanism. Drain the oil as well and look for anything suspicious. Good luck and keep us posted!
When I looked at these parts I didn't see any signs of obvious wear, when I try to shift they all look to be moving correctly just won't go to 2nd gear; anything specifically on those parts that's a suspect area for damage?

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DynoDan22
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DynoDan22 1/16/2020 6:52am
1/16/2020 6:52am
Hmmmm.... let's start with the clutch change. What parts were removed and replaced when you changed the clutch? Did you remove the outermost clutch cover only or did you remove or entire right side cover (with waterpump)??? Was the bike shifting ok before the clutch change??? Any details will help here. Is the shifting problem present even when the bike isn't running? i.e. do you have all gears when the engine is off and the bike is on the stand? You can check this by rocking the rear wheel while shifting up/down. Keep us posted!
MC770
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MC770 1/17/2020 2:57am
1/17/2020 2:57am Edited Date/Time 1/17/2020 2:58am
DynoDan22 wrote:
Hmmmm.... let's start with the clutch change. What parts were removed and replaced when you changed the clutch? Did you remove the outermost clutch cover only...
Hmmmm.... let's start with the clutch change. What parts were removed and replaced when you changed the clutch? Did you remove the outermost clutch cover only or did you remove or entire right side cover (with waterpump)??? Was the bike shifting ok before the clutch change??? Any details will help here. Is the shifting problem present even when the bike isn't running? i.e. do you have all gears when the engine is off and the bike is on the stand? You can check this by rocking the rear wheel while shifting up/down. Keep us posted!
On the clutch change was only the friction and drive plates that were changed nothing else was touched; Only removed the outermost clutch cover. Bike was shifting completely fine the last ride no weird issues that were noticed then outside of the clutch being worn (i.e. all the gears were there and not popping out of gear under load); Shifting problem is present with bike off and on center stand with the wheel being rocked back and forth
DynoDan22
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DynoDan22 1/17/2020 6:32am
1/17/2020 6:32am
OP: OK this rules out a few things (side cover being taken off and shift mechanism being affected). The '18 has the updated shift cam index lever. Thie older models pre '16 had a ball bearing on the end that would shatter and the shifting was affected. In '16 they updated the shift index lever to a solid roller wheel to prevent this failure. The next step would be to pull the right side cover (with waterpump) and clutch basket. From your previous post, you said you looked at the shift mechanism and everything looked ok???? I would take the side cover off, clutch basket, remove shift shaft and shift pawl mechanism and inspect. If all looks ok, take a 12mm T-handle and manually turn the shift cam/shift drum while rocking the rear wheel and holding the clutch shaft and verify the tranny goes through all of the gears. If it does, that means something in the shift mechanism is at fault. If you encounter anything weird while manually shifting the gear by turning the shift cam/drum it's time to split the cases and look deeper.
sandman768
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sandman768 1/17/2020 8:14am
1/17/2020 8:14am Edited Date/Time 1/17/2020 8:15am
Photos worth 1000 words
MC770
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MC770 1/19/2020 8:21am
1/19/2020 8:21am
DynoDan22 wrote:
OP: OK this rules out a few things (side cover being taken off and shift mechanism being affected). The '18 has the updated shift cam index...
OP: OK this rules out a few things (side cover being taken off and shift mechanism being affected). The '18 has the updated shift cam index lever. Thie older models pre '16 had a ball bearing on the end that would shatter and the shifting was affected. In '16 they updated the shift index lever to a solid roller wheel to prevent this failure. The next step would be to pull the right side cover (with waterpump) and clutch basket. From your previous post, you said you looked at the shift mechanism and everything looked ok???? I would take the side cover off, clutch basket, remove shift shaft and shift pawl mechanism and inspect. If all looks ok, take a 12mm T-handle and manually turn the shift cam/shift drum while rocking the rear wheel and holding the clutch shaft and verify the tranny goes through all of the gears. If it does, that means something in the shift mechanism is at fault. If you encounter anything weird while manually shifting the gear by turning the shift cam/drum it's time to split the cases and look deeper.
Okay so still could not get it to shift with the shift mechanism removed from the equation; Split my cases the other day and found no clear signs of issues with the gears, forks, or drum. I did however see a ton of what look to be hairline cracks in the case half that have me very concerned, do these look normal? I did find a couple of bearings that were suspect so I have new transmission bearings on order to replace all of them since there were rough spots in a couple of them







DynoDan22
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DynoDan22 1/19/2020 8:53am
1/19/2020 8:53am
Most of those cracks are normal casting "checks" from the mold being hot. Many a Yamaha have freaked out over them but I wouldn't worry about it. Shift forks look ok and no signs of abnormal thrust (wear marks on forks) from worn gear dogs. I do see on small chip in second gear driven on the countershaft but nothing major. Please take a few pics of the external shift mechanism (shift cam, pawl assembly with little springs etc.).
harescrambled
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harescrambled 1/19/2020 9:29am
1/19/2020 9:29am Edited Date/Time 1/19/2020 9:29am
From the pic you provided of your shift forks, it looks like your R shift fork has a small amount of wear on it (would indicate it's slightly bent). Also, the shift fork marked C10 looks like it has a wear groove in it on the left tip as shown. Does it have a groove in it, or is that just a trick of the light?
sandman768
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sandman768 1/19/2020 12:37pm
1/19/2020 12:37pm
That oil drain bolt is not interfering with shift drum is it? Does not look like a stock drain bolt.
Jeremy_Brown 1/20/2020 4:48am
1/20/2020 4:48am
What kind of oil were you using. Did you place each metal clutch piece 60 degrees. I think that’s what’s required. I just was talking to my buddy who had the same issue and he said it was the oil. Try using T4 because it’s slicker and the clutch problem and shifting problem went away for him. Idk
Jeremy_Brown 1/20/2020 4:50am
1/20/2020 4:50am
Those little cracks are very normal just leave them alone you will be fine. It’s how it is and there not really cracks it’s a descrepency in the aluminum. I didn’t spell that right oh well.
Jeremy_Brown 1/20/2020 4:55am
1/20/2020 4:55am
He said that his bike wouldn’t shift at all and that’s when he switched the oil to the t4 and no problem after that. Weird shit. It’s worth a try
Jeremy_Brown 1/20/2020 5:30am
1/20/2020 5:30am
Or I would try the yamalube 10/40. It’s crazy but what happens is with wet clutches the tend to stick and need a slicker type of oil in order to work properly. Good idea changing the oil every race

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DynoDan22
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DynoDan22 1/20/2020 6:27am
1/20/2020 6:27am
Sandman768: good catch on the oil drain plug. OP: is that the stock oil drain plug? Could it have been rubbing the shift drum???
Jeremy_Brown 1/20/2020 6:56am
1/20/2020 6:56am
DynoDan22 wrote:
Sandman768: good catch on the oil drain plug. OP: is that the stock oil drain plug? Could it have been rubbing the shift drum???
It could be
Jeremy_Brown 1/20/2020 7:10am
1/20/2020 7:10am
Since you have the cases split I would check to make sure your trans sprockets aren’t missing any washers. That’s what don’t make sense because if you were missing mashers it would lock up
MC770
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MC770 1/22/2020 2:51am
1/22/2020 2:51am
Okay to answer some of the questions I've gotten; It is a yz250x with the wide ratio transmission so the gears have those little grooves or whatever in them for whatever reason, as for the parts on the gears that look like something got wedged between the gears I believe that is a trick of the light in the photo, I took every gear off of the shaft one by one and inspected every tooth and saw nothing but the factory little grooves. The drain plug is an aftermarket magnetic drain plug and it was my first suspect as well, While it was close it was not touching anywhere on the shift drum and there was no evidence that it was rubbing at any point in the past (no damage to the drum) The oil I use in the clutches is the recommended oil from the factory service manual (I think it was 10w40) and was changed after every ride, this was the third clutch in the bike all the same brand plates using the same brand oil and this was the first time I had any issues with the transmission so I don't believe that is the issue, and I do soak the plates for at least 2 days usually before they get installed. As far as the shift forks C10 is a trick of the light as well there wasn't as dramatic of a wear spot in it as what it looks like in the picture, I'd have to look at the one marked R again to verify but I think it was fine. I will try and get some good pictures of the shift linkage (cam, pawls, etc.) tonight after I get home from work
sandman768
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sandman768 1/22/2020 3:17am
1/22/2020 3:17am
process of elimination....photos of the clutch side of engine will help....
Jeremy_Brown 1/22/2020 3:22am
1/22/2020 3:22am
I wonder if you could be putting the gears in the wrong direction. I wonder what those grooves are for
Jeremy_Brown 1/22/2020 3:38am
1/22/2020 3:38am Edited Date/Time 1/22/2020 3:44am
I think it’s your right shift fork

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