Yamaha Bear Tracker 250 Runs but doesn’t drive

[TimothyLindblom]

Hi everyone, I’m new here and new to 4 wheelers. Just got a Yamaha bear tracker 250 and joined here to see if I could get some help.

The motor runs and it drives if it up on jackstands but if you get on and try to ride it, it starts to drive but then quits after a foot or two and dies out and won’t drive. The guy I got it from said he was running and using it shifting through all the gears great and he started it up the next day and it started this.
He told me he thought it was the U joint on the driveshaft. He said it was probably worn and needed to be replaced.

I just finished pulling the swing arm and rear end assembly to check out the U joint and there’s no play in it. It’s tight and not nearly enough play to be loose enough to not catch and go.

Any ideas on what it could actually be?

Thanks

Timothy

[Mech]

"after a foot or two and dies out and won’t drive. ". The engine isn't dieing is it ? It's just the drive stops happening and the engine revs freely ? Yes ?

If it is that, then it will be one of the two clutches it has. They are probably accessible with the engine in place. You can test which one is slipping by putting it in a forwards gear and trying to push the bike forwards. If it's hard to push and tries to turn the engine over then the worn clutch is the centrifugal clutch, but if it pushes easily and doesn't turn the engine over it's the plate clutch that's slipping.

[Mech]

Better mention.. before you rip it apart.. haha.. The plate clutch can be adjusted. You should check the adjustment if the push test does indicate it's that playing up.

There's no adjustment on the centrifugal clutch.

[TimothyLindblom]

7 hours ago, Mech said:

"after a foot or two and dies out and won’t drive. ". The engine isn't dieing is it ? It's just the drive stops happening and the engine revs freely ? Yes ?

If it is that, then it will be one of the two clutches it has. They are probably accessible with the engine in place. You can test which one is slipping by putting it in a forwards gear and trying to push the bike forwards. If it's hard to push and tries to turn the engine over then the worn clutch is the centrifugal clutch, but if it pushes easily and doesn't turn the engine over it's the plate clutch that's slipping.

No it's stalling out the engine like if something is locking it up and keeping it from turning. 

[Gwbarm]

It sounds like the engine is stalling under a load . Plate clutch may be stuck.

[Mech]

Oh ok. So you need to figure out where in the engine, gears, driveshafts, wheels the problem is..

So.. You are saying it can be operated if it's jacked up ? But locks up when you try to drive it ? Right ?

And so can it be operated in all the gears when it's jacked up ?

When it locks up, does it grind to a halt over the foot or two, or does it come to an abrupt stop ? It'd be good to decide if it's something grinding to a seize, or a chunk of metal getting stuck in a gear.

Does it always move the same distance before stopping, or can you get it to go further by driving with less throttle, or in a different gear ?

Have you checked the oil for signs of metal, either steel flakes or dust ?

I'm assuming that you have tried turning the driveshaft and rear diff, wheels while/when you were working on the driveshaft.. 

[Mech]

And..  this bear tracker..  Is this four wheel drive or only two.

If you give us the year, and model designation suffix, I could have a look in a service manual so I know what I'm dealing with.. I'm not familiar with yamaha.

[Mech]

And in relation to Gw's suggestion, I don't think the bike coming to a stop should cause the engine to stop abruptly because once the engine revs drop as the bike stops moving the centrifugal clutch should start slipping.

So, do you think it's killing the engine because there's a wire somewhere that's seizing out because you are sitting on it, perhaps a wire shorting under the seat say, or because the bike moving causes a wire to short out ? Does it feel like the engine stops then stops the bike moving, or does the bike stop moving and then than engine stops because of that ? You should be able to detect that by the sound of the engine, whether it stops firing in a single firing, or whether the bike stops moving and as it's happening the engine sounds like it's labouring.

And, after it's come to a stop, does it restart ? After it's stopped, can you push the bike forwards or backwards (try both directions) ?

[Gwbarm]

Just a thought since it runs on jack stands if it was clutch it should die as soon as you put it in gear.

[TimothyLindblom]

1 hour ago, Mech said:

And..  this bear tracker..  Is this four wheel drive or only two.

If you give us the year, and model designation suffix, I could have a look in a service manual so I know what I'm dealing with.. I'm not familiar with yamaha.

Will do that when I get home Sunday. Thanks everyone for chiming in 

59 minutes ago, Mech said:

And in relation to Gw's suggestion, I don't think the bike coming to a stop should cause the engine to stop abruptly because once the engine revs drop as the bike stops moving the centrifugal clutch should start slipping.

So, do you think it's killing the engine because there's a wire somewhere that's seizing out because you are sitting on it, perhaps a wire shorting under the seat say, or because the bike moving causes a wire to short out ? Does it feel like the engine stops then stops the bike moving, or does the bike stop moving and then than engine stops because of that ? You should be able to detect that by the sound of the engine, whether it stops firing in a single firing, or whether the bike stops moving and as it's happening the engine sounds like it's labouring.

And, after it's come to a stop, does it restart ? After it's stopped, can you push the bike forwards or backwards (try both directions) ?

It isn’t a wiring short, it sounds like the bike is stopping and forcing the engine to stop as well. Once I get back in neutral it fires right back up. 

1 hour ago, Mech said:

Oh ok. So you need to figure out where in the engine, gears, driveshafts, wheels the problem is..

So.. You are saying it can be operated if it's jacked up ? But locks up when you try to drive it ? Right ?

And so can it be operated in all the gears when it's jacked up ?

When it locks up, does it grind to a halt over the foot or two, or does it come to an abrupt stop ? It'd be good to decide if it's something grinding to a seize, or a chunk of metal getting stuck in a gear.

Does it always move the same distance before stopping, or can you get it to go further by driving with less throttle, or in a different gear ?

Have you checked the oil for signs of metal, either steel flakes or dust ?

I'm assuming that you have tried turning the driveshaft and rear diff, wheels while/when you were working on the driveshaft.. 

it’s hard to describe. Maybe Sunday when I get home I can put the rear end back in and try to get a video of it happening. It acts as if it’s bogging down because of too much load. I haven’t personally shifted it through the gears on jackstands but I was able to drive it from the front to the back yard in first gear just fine while walking alongside it. But then when I got on it and tried to drive it, it tries to go but acts forced to shut off. 
The neighbor I bought it from said when it worked he was able to go through all the gears without an issue and didn’t think it was a clutch problem. 

[Mech]

"It acts as if it’s bogging down because of too much load. I haven’t personally shifted it through the gears on jackstands but I was able to drive it from the front to the back yard in first gear just fine while walking alongside it. But then when I got on it and tried to drive it, it tries to go but acts forced to shut off".

Ok. That's interesting, and telling. Not sure what it's telling us just yet but it's going to be an important clue I think..

I wonder if there's something wrong with a brake cable or suspension part that's causing the brakes to come on and lock on when your weight puts the suspension down. I've seen brake shoes systems jam the brakes on because the backing plate was loose or the wheel could move backwards pulling the brakes on..

Normally if you got the brakes on so hard that it slowed the bike right to a stop the engine would have slowed to it's idle speed and the centrifugal clutch would have started slipping.. perhaps though if the brakes get jammed fully on fast enough the centrifugal clutch doesn't have time to let off..

Couple of things..

Try sitting on it and waddling/getting pushed forwards to see if the brakes jamb on.

The plate clutch is connected to the shift lever and it gets disengaged when you push the lever up or down(to help gear changes when the centrifugal is locked up), so you can use the shift lever as a clutch lever if you only press down a little. If it's adjusted right it will slip the clutch before it changes the gear. You could use that feature to experiment a bit and try to see if the lockup is in the engine or in the gearbox.. Hopefully you will have eliminated brakes/suspension as a cause before then.

[TimothyLindblom]

Sorry to disappear on everyone after asking for help. I haven't had much time to work on it at all and have been tied up with other projects. I did get it back together and hope to mess with it more soon and will report back when I do. Thanks to everyone who chimed in

[bellarmine]

Thought I'd chime in with an idea, what about the sticky throttle cable VARS / VATS safety protection system operating on limiting the engine speed / stalling the engine?  Perhaps, when it's on jacks in runs fine because it needs very little throttle, but on the ground under load, it needs more gas and/or you pull the throttle cable more and the sticky throttle protection system then kicks in and stalls the engine?

Get the manual and wiring diagram and try temporarily shorting out the throttle safety system system (make sure the throttle actually does move freely first!...:o)

Just an idea.  Robert

[Mech]

I think you are over estimating the sophistication of this old beast Bellarmine. It doesn't have any of those systems..

 

"It acts as if it’s bogging down because of too much load. I haven’t personally shifted it through the gears on jackstands but I was able to drive it from the front to the back yard in first gear just fine while walking alongside it. But then when I got on it and tried to drive it, it tries to go but acts forced to shut off".

I reckon the fact it drives without weight on it is going to be the vital clue here..

[TimothyLindblom]

Turns out the issue was much easier than I expected. The rubber piece was ripped nearly all the way off on the intake manifold boot. New one off amazon for about 10 bucks fixed it and it's got plenty of power now. Still a project that needs brakes and tires and some carb adjustment but I think the main issue is fixed for now

[bellarmine]

Good news you got it fixed!  It is amazing how it tends to be the more obvious stuff that normally you take for granted and don't think to check at first, stuff that normally never goes (until it does..:o)

Thanks for the reply Mech.  I'm working on a friends 1989 Yamaha Exciter sled and it as a throttle protection system in it, just 2 switches on each end of the cable that tell the CDI if the throttle cable is operating properly and not sticking.  I don't know what year Timothy's 250 is (I thought I heard 2000?), but I was feeling  pretty sure it has something like that, unless you know better than me then no argument I stand corrected......:o).  Feels so good when you actually find something wrong and turns out to the the problem.

Cheers!~  Bellarmine

[Mech]

Good one..

Glad it was so simple.