Jump to content
Gary_01YZ250

Engine Rebuild Help Needed YZ250

Recommended Posts

I just rebuilt my 2001 YZ250 2 stroke and I am having issues. The bike wont start and I can't get it into neutral. Any suggestions on how I can start troubleshooting this would be greatly appreciated.

I installed a Hot Cams bottom end and a Namura top end.

I didn't take the transmission out when I split the cases so I am guessing the neutral shifting issue has something to do with the gears on the opposite side of the engine. It seems to shift through the gears just not into neutral.

I also plan to pressure test the engine to see if that can tell me something but I don't have a gauge yet.

Share this post


Link to post
Share on other sites

You didn't take tranny out not even to clean cases oh boy lol. Did you take the segment off? Shift paws out?  Ive never left a tranny in seems it would get knocked around taking crank bearings out and in. Yikes 

Share this post


Link to post
Share on other sites

Nah, I used some wood to lift the casing off the bench when doing one side. The other side didn't have any issue.

I tried removing the trans gears but the screws holding it in would turn. I couldn't reach them with the impact driver, breakaway didn't work, and I tried heat as well.

Share this post


Link to post
Share on other sites
29 minutes ago, Gary_01YZ250 said:

Nah, I used some wood to lift the casing off the bench when doing one side. The other side didn't have any issue.

I tried removing the trans gears but the screws holding it in would turn. I couldn't reach them with the impact driver, breakaway didn't work, and I tried heat as well.

There's no screws holding trans gears 😀

Share this post


Link to post
Share on other sites

I used the Rocky Mountain ATV video as a guide while I disassembled the engine. After I removed the case cover the transmission didn't fall out of the engine case. I noticed three screws to the left of the transmission, seated against the rear wall of the case. I tried removing them but they wouldn't budge. I assumed they were retraining the transmission. Since I know the connecting rod seized and slightly gouged the bottom of the case, my plan was just to replace the main bearings, piston, and bottom.

I can take a picture, but I have to take the casing off again.

Share this post


Link to post
Share on other sites

Yeah.... maybe ask around the local riding club and find someone who knows what they're doing...

Share this post


Link to post
Share on other sites

Yeah, I watched and followed all three. I just didn't pull the transmission. You can actually see one of the three screws I reference in that picture.

Share this post


Link to post
Share on other sites

Might want to take it apart just to replace the Namura piston.  Its a piece of shit.

  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites

Grab a Beer (maybe two) and read the service manual. They are available free online if you need one. the manual is loaded with tips and tricks on how to overhaul.

 

Share this post


Link to post
Share on other sites

I have the manual and videos, but clearly something went wrong somewhere during the reassembly. I was hoping for some direction to a particular area. Anyone have any idea on where to start looking considering it doesn't start or shift into neutral? My first guess is the shift lever(rod?) that goes through the engine.

C'mon guys, no one has a clue? Really?

People come to this site to share advice and experience. If all we ever do is say "read the manual" you are not really helping. I can always take it back apart and put it back together and hope for the best. Waste some gaskets along the way. But I know some of you have done this before and learned some lessons. No clues?

Share this post


Link to post
Share on other sites
26 minutes ago, Gary_01YZ250 said:

I have the manual and videos, but clearly something went wrong somewhere during the reassembly. I was hoping for some direction to a particular area. Anyone have any idea on where to start looking considering it doesn't start or shift into neutral? My first guess is the shift lever(rod?) that goes through the engine.

C'mon guys, no one has a clue? Really?

People come to this site to share advice and experience. If all we ever do is say "read the manual" you are not really helping. I can always take it back apart and put it back together and hope for the best. Waste some gaskets along the way. But I know some of you have done this before and learned some lessons. No clues?

First, go read the manual.  If you have any questions past then, ask them here.  

My guess is that you butchered the assembly and put something back the wrong way.  No amount of internet whining will save you from the fact that you need to start disassembly again.

This time test the transmission before you finish assmebly...

  • Haha 1

Share this post


Link to post
Share on other sites

Are you getting spark?

Did you clean all the electrical connectors when reassembled?

Did you use dielectric grease, and contact cleaner?

Is the timing marks set up and aligned?

Did you get the woodruff key in?

Did you remove the shift pawls, segment and shift stop when you cracked the case?

When you left the transmission in while doing this work, are you sure it didn't get jostled around?

HotRods not hot cams you mean?

Do you have a dog, wife, or children?

How old is our POTUS and are you for or against him?

Did you vote?

Do you watch Football or Soccer? 

Are you a Spear carrier?

Some questions may be irrelevant, but it will answer some of a deeper issue than just your bike problems. 

:smirk:

All in fun, don't get uptight. That will be another session with the DOC.

 

 

3 minutes ago, bikedude987 said:

First, go read the manual.  If you have any questions past then, ask them here.  

My guess is that you butchered the assembly and put something back the wrong way.  No amount of internet whining will save you from the fact that you need to start disassembly again.

This time test the transmission before you finish assmebly...

See post.. LOL

Edited by 2 STROKE YZ DOC
  • Like 1

Share this post


Link to post
Share on other sites

Yes, I have spark.

No, I didn't clean the electrical connectors.

Yes, spent quite a bit of time on these to ensure .0007" BTDC was perfect.

Yes, the key is back in.

Yes, I removed them and hopefully reinstalled correctly. Those damn small springs were a challenge and I am a bit suspicious now that it wont go into neutral.

That damn thing wouldn't move for nothing. Spins nicely, but not coming loose.

Sorry, Hot Cams, yes.

Dogs and chickens. I don't collect humans.

Always vote and believe everyone should.

Neither now. Never watched soccer.

Rifle

I know I butchered the reassembly and put stuff back wrong. Otherwise it would work. Troubleshooting this issue is the real challenge. If I took the engine completely apart this weekend and put it back together and everything worked, I would not learned anything. Because I don't know what I did wrong. So looking at the manual wont help. It would be a bunch of "yes I did that" and "yes I remember that".

I tried to sound encouraging and not whinny in my last post, but clearly it didn't come across that way.

The trans spun fine before I put the case cover back on.

I will post some photos after the weekend and see whats what.

Share this post


Link to post
Share on other sites

Obviously you didn't get the Spear reference Gary, that's ok. And you voted but for who? 

Collecting humans can be fun. Dogs, chickens, goats, been there done that.

Pulling apart and reassembling it can be therapeutic  and you will see what you did wrong.

So, when you pulled it apart and reassembled, did you put the correct locating dowels in between the case, and the outer right case? 

Had a guy on here with kind of same problem bring me his engine, we spent an hour or so tearing it down and putting it back together. He had a wrong dowel in between mains and it didn't align transmission correctly and shifting was a problem. Another happy patient from the DOC shop.

Your starting problem? Compression from the Namura crappy piston feel solid? 

Electrical not connected from stator to CDI, could be s few things. 

  • Like 1

Share this post


Link to post
Share on other sites
3 hours ago, Gary_01YZ250 said:

I have the manual and videos, but clearly something went wrong somewhere during the reassembly. I was hoping for some direction to a particular area. Anyone have any idea on where to start looking considering it doesn't start or shift into neutral? My first guess is the shift lever(rod?) that goes through the engine.

C'mon guys, no one has a clue? Really?

People come to this site to share advice and experience. If all we ever do is say "read the manual" you are not really helping. I can always take it back apart and put it back together and hope for the best. Waste some gaskets along the way. But I know some of you have done this before and learned some lessons. No clues?

Did you check shift mechanism, segment at all? Take stuff back apart post pics and stuff we can help you out better. But you should take trannies all way out to clean case and inspect everything.  Yz250 tranny is known for slipping its good to check few gears and replace before its 7 gears and couple forks like last time killed one 😂 800 just in gears and 2  forks

Share this post


Link to post
Share on other sites
4 minutes ago, Motox367 said:

Did you check shift mechanism, segment at all? Take stuff back apart post pics and stuff we can help you out better. But you should take trannies all way out to clean case and inspect everything.  Yz250 tranny is known for slipping its good to check few gears and replace before its 7 gears and couple forks like last time killed one 😂 800 just in gears and 2  forks

What, you shop at the expensive store just to pad the price? :smirk:

I'm thinking maybe the shift pawls, stopper, or segment has issues. There is the slight possibility of the wrong dowel in the center cases tho. I found the extra one in the rear of the case belonging to the outer right and it created a bind as it was longer than the blind holes and bubbled out not allowing the case to completely come together.

Share this post


Link to post
Share on other sites
27 minutes ago, 2 STROKE YZ DOC said:

What, you shop at the expensive store just to pad the price? :smirk:

I'm thinking maybe the shift pawls, stopper, or segment has issues. There is the slight possibility of the wrong dowel in the center cases tho. I found the extra one in the rear of the case belonging to the outer right and it created a bind as it was longer than the blind holes and bubbled out not allowing the case to completely come together.

😂😂😂 something like that.  Gears add up man 

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×