YZ250wr Wont Start, Desperate

[robbieisurfriend]

ALright guys I just had my local shop go through my bike because it will not start for some strange reason. It is a 1989 YZ 250wr with 175+lb compression and new crank seals (leakdown test great.)

Got freezing rain on it and hasn't started since. Might or might not be the cause though because I was having random hard starts since I bought it. I was also going through plugs more than I should. Sometimes I would spend an hour trying to start it and sometimes it would start first kick. Now all it does is backfire if kicked and occasionally spudder for a second or two when you push it. Figured gas froze in the carb, went through it two times and my local shop went through it two times, clean as can be. Theres fuel and air, and compression, three of the four things it needs to run. All that leaves is spark.

Nows where the REAL ISSUE lies. . .
What electrical component is it? My shop guessed stator from his experience but said it was a coin toss. He tested the spark at the plug and it would jump a gap fine. The resistance in the stator was off but he assured me that almost all bikes/ manuals are wrong when the leave the dealer floor. All connections are good, the cdi box is not cracked and looks sealed well and the stator looks about the same. Kill switch is fine. The only reason he guessed stator was because he has only seen 2 bad cdi boxs in 30yrs and hundreds of stators, especially on yamahas like mine. I was thinking it was the cdi box because it got wet, its on the bars, and it back fires but wont run. He then told me that timing can be thrown off by weak spark also.

All I know to do is throw parts at it till it runs. I really just need some help with guessing. I have little experience and just know what Ive been told and a little bit of common sense. Coil, stator, or cdi box? I can get both the stator and cdi box for about $200 a piece :(. Makes me hesitant to throw cash at it. I also found that I can buy the stator coils for a 1991 WR 250(which is the replacement for the stator in my bike. Part numbers a different by a couple of numbers but on my bike the part number for the one that replaces the original is the same as the stator on the WR. Is it a safe $100 assumtion that the coils will fit on my original stator alright. I cant even put into words how bewildered and frustated I am with it right now. :bang: I spent less than $500 on it and it still needs the tranny fixed so parting it is still a possibility. I like the bike though and would love to keep it. Any thing you guys have for me will be greatly appreciated. Thanks, Rob.

 

[docgonzo]

I would guess the cdi box is bad. I had a similar issue a few years back, I had fuel , compression and spark and still could not get it started. It turned out the box still sort of worked and was causing it to spark at the wrong time, it was stuck on full advance. You should be able to get one at a boneyard or online at a reasonabe price.

 

[ckassen]

I have seen some really funny things with CDI boxes. I know very little about the yamaha. On a 00R1(sport bike) the CDI was bad and would fire on 2 cylinders and not fire on 2(a short in the wiring harness). A friend on of mine has a 89CR125, and it will run fine until the CDI gets hot, then when you shut the bike off, it will not start until the CDI is allowed to cool off(still dont know why the CDI keeps on going bad). On my own Triumph, I went through 3 CDI boxes and that was because of a bad ground(when a box would go bad, I would get a weak, completely random spark-along with other things)....

As I said, I know little about the yamaha 2-stroke, but I do know that the CDI controls spark/ignition. I dont think that it is possible for the stator to go bad and still have some kink of spark since it is pretty much just an alternator....

 

[robbieisurfriend]

Well thanks for the input. My shop owner claimed it could easily be the cdi but he had no experience with them going bad, especially in this manner, in all his 30yrs of motorcycle work. I have read several cases similar to mine and from what I see it could easily be either, or both. I guess I will go with you guys and buy the cdi box. I can only find it one place and that is mrcycles.com and it is $140. Anybody know of a better source? Thanks for your time.

 

[mox69]

1. If your strapped for $$ watch EvilBay (remove the "vil").

2. You may want to consider parting this bad boy out and starting over. You may end up fixing the problem, or you may end up throwing $400 at a 25 year old bike. If you really like this bike, pickup another old WR250 , then you will have a lot of spare parts :).

 

[zoommx]

I'm gonna guess the ignition coil. Make sure it is well grounded. I had a very similar problem on my '98. Could kind of correlate with the rain; causing a little more rust. Try cleaning it up and testing resistance.

Good luck, Roger MOVMX #491

 

[Beuford]

A couple more things to try that wont cost anything.
1. Un-plug the kill switch,"just to be sure". The switch does its job by grounding, so un-hooking both wires will take it out of the pitchure.
2. Since you had crank seals replaced check two things, first pull the flywheel off and make sure the woodruff key is good and keeping the flywheel where it should be and second is make sure the stator plate screws are tight and the plate,"timing", has not moved.
At this point it couldn't hurt to mark the plate and then move it differant ways to see if it starts."you have nothing to lose but time".

 

[dirt bike dave]

FYI, cracked or warped reeds can make a cold two stroke nearly impossible to start. I would check the reeds before you throw lots of money at electronics.

If the reeds look god, definietely check the woodruff key as previously mentioned.

 

[robbieisurfriend]

He checked the reeds and stator assembly and they all looked good visually. As far as the actual timing goes it is marked and the line lines up right. It is obviously a timing problem though. Just need to figure out if it is the stators weak power causing the cdi to be wrong or the cdi itself being the problem. I checked all connections and so did the shop owner. Can a source coil cause something like this? I hear that they usually fail completely and not partly.

Reasons I have myself convinced its the cdi:

The bike would occasionally act just like it does now for no reason but would start perfectly most of the time. In my head it would make sense that the timing in the cdi is getting "stuck" to where it should be at high rpms occasionally and is now stuck for good. I admit I have no idea how a cdi works or if that is even possible but it seems logical to me.

If the bike was not in as good as shape as it is I would have given up on it already but it is my first real bike and I like it. It is also a good one to learn how to work on things myself with. I have pretty much decided that it is worth keeping. When I have the cash to buy a newer bike I will probably keep it as a backup because it is a blast to ride. I have ridden newer bikes and honestly do not think they are worth the cost for someone like me. The slight difference in performance is not as significant as the difference in cost if you ask me. Especially because I could spend a few grand on a newer bike and it grenade just the same. If I take this thing down and go through it completely I will know exactly what I have. Hmmm, if only it ran. . .

 

[Matt Fisher]

Have you tried pull starting it with another vehicle? If the CDI is stuck in the full advanced postion for high rpms, then getting the motor to those high rpms might allow it to run.

 

[dirt bike dave]

Good luck getting it sorted out. Those old YZ/WR's run very strong once you get it started.

In my experience, stator failure on an old bike is more common than CDI failure.

Over time, the stator wiring can break down, but still look fine from the exterior and still have some continuity. While the bike can generate a spark whicih you can see when you lay a plug on the side of the motor and kick it over, the spark may be too weak to fire in the cylinder.

Stator re-winding is not terribly expensive (maybe $100 - $150), and might be worth a try before you buy a new CDI.

While the reeds may have passed visual inspection, they may have lost their tension. It happens, and can really make for hard cold starting.

Have you tried using staring fluid just to see if it will run? If it will start with starting fluid, I'd suspect a weak stator or reeds. If no go even with a blast of starting fluid, a new plug and fresh fuel, it would seem more like a CDI or woodruff key problem.

 

[robbieisurfriend]

Good luck getting it sorted out. Those old YZ/WR's run very strong once you get it started.

In my experience, stator failure on an old bike is more common than CDI failure.

Over time, the stator wiring can break down, but still look fine from the exterior and still have some continuity. While the bike can generate a spark whicih you can see when you lay a plug on the side of the motor and kick it over, the spark may be too weak to fire in the cylinder.

Stator re-winding is not terribly expensive (maybe $100 - $150), and might be worth a try before you buy a new CDI.

While the reeds may have passed visual inspection, they may have lost their tension. It happens, and can really make for hard cold starting.

Have you tried using staring fluid just to see if it will run? If it will start with starting fluid, I'd suspect a weak stator or reeds. If no go even with a blast of starting fluid, a new plug and fresh fuel, it would seem more like a CDI or woodruff key problem.

Thanks for the information. I tried starting fluid first thing. It makes no difference. Im 100% convinced it is a spark related problem. I am also know that it has weak spark, but it backfires and spudders just fine and looks like a decent spark to me. If I didn't have it tested I would say it was a good good spark. I am very 99% confident it is a timing problem. But still don't know whether it is a bad cdi or a bad stator/coil making the cdi not work properly. The woodruff key looks fine and the flywheel was marked and lines up right so I really doubt there is a problem there. How about this, can you guys agree that I can atleast rule out the source coil? Stator is $230 and much harder to change and a cdi is $130 and I can change it myself in a few minutes. This is another reason im telling myself it is the cdi. Guess ill have to break open the pocketbook to find out . . .

 

[robbieisurfriend]

Have you tried pull starting it with another vehicle? If the CDI is stuck in the full advanced postion for high rpms, then getting the motor to those high rpms might allow it to run.

Thank you for reminding me, I had a friend pull me around his pasture with his jeep and it would try to run but still not. It would run for couple of seconds with no response and then die. Pinging misfiring mess I might add. Thanks again for reminding me because this was another reason I was considering the cdi. Although it would make sense that the RPMs help with the stator also if not more so. :(

 

[KDX175MMI]

I am having the same problem with my KDX, Did you ever try the cdi box or stator?? I am thinking of picking up a cdi box and trying it..

 

[dirt bike dave]

FWIW, stator failure is quite common on old KDX's. Happened to my '84 and several others I know. Even though the stator would test in spec using the manual, rewinding the stator fixed it 100%.

On mine, the bike started out stalling when hot, then being hard to start warm. Over a few rides, it would be harder to start cold, then would die sooner when it got hot and take even longer to restart. Eventually, it would just not start at all. Basically, the problem came on somewhat gradually; it was not a case of one day the bike just would not work at all when the previous day everything was fine. Real PITA to identify, too.

 

[ojasia]

Hmmm. I just did full seals all new gaskets, crank, crank bearings, PV bearing, Cleaned PV, new jug, new top end kit, and I still am having some hard starting issues. Maybe this could be something to do with it although my reeds visually look just a little bit chisseled. I figured after doing everything I just did would clear up the hard starts. when its warm/hot it starts right up though when its cold I usually just say Ef it and pop it first try starts. other then replacing the reeds in the near future im just gonna bash on it for a little I think I deserve it after everything I have done :)

 

[ojasia]

Another input on the Re-winding of stators. Talk to some people you might actually know a electrician or two. the 100 to 150 the other guy was talking about is marked way up especially for the parts that you would actually need. I know a guy that makes his own electric guitar foot pedals gets the parts for $40 bucks and makes pedals that are 180-300 in the magazines. Just need to do some research tear it down and start winding :) an a lil sodering as well. You prolly end up spending $100 for the tools and hardware to do it but you'll gain knowledge and a trade. And thats way more then ya had when you just dropped it off and paid to get it re-winded.