XT won't start

[JimmyJay]

Gents, I need some suggestions to try and fix my issue, as I'm stumped right now. I have the XT, stock motor with a jetpro side mount and the baja air filter. I'm running a walboro 990 with inclined shredstack with the ada teflon gaskets. I have also vented the tank, and am running a Killer Bee.


The issue started a few days ago where I was running around the track great and about 15 minutes in, the motor bogged out and stalled, now I can not get it running again. I took apart the carb, cleaned it all out and reset the needles then reinstalled - still won't start. Switched to a new 668 and it still won't start.


I am getting a nice blue spark and the plug is coming out wet after yanking the pull start a dozen times. The motor doesn't even sound like it wants to start!


Now, I did install a new cylinder base gasket about 3 or 4 weeks ago and I have about 3 tanks through since the new gasket was installed. It still looks like it is in good shape.


I figure I'll be pulling the head off tonight to inspect the piston and cylinder walls to make sure they're in decent shape.


Any suggestions to try or to look for so I can get up and running again?


Thanks

 

[stalker77]

I had a starting problem on my Baja last year. It turned out to be a blown head gasket. I would check that or the kill switch first.

 

[andyken]

Gents, I need some suggestions to try and fix my issue, as I'm stumped right now. I have the XT, stock motor with a jetpro side mount and the baja air filter. I'm running a walboro 990 with inclined shredstack with the ada teflon gaskets. I have also vented the tank, and am running a Killer Bee. The issue started a few days ago where I was running around the track great and about 15 minutes in, the motor bogged out and stalled, now I can not get it running again. I took apart the carb, cleaned it all out and reset the needles then reinstalled - still won't start. Switched to a new 668 and it still won't start.

I am getting a nice blue spark and the plug is coming out wet after yanking the pull start a dozen times. The motor doesn't even sound like it wants to start!

Now, I did install a new cylinder base gasket about 3 or 4 weeks ago and I have about 3 tanks through since the new gasket was installed. It still looks like it is in good shape.

I figure I'll be pulling the head off tonight to inspect the piston and cylinder walls to make sure they're in decent shape.

Any suggestions to try or to look for so I can get up and running again?

Thanks

I just got a used xb, it bogged down and died...first was a gas cap vent.

Then later it bogged down and wouldn't start, it would cough a little at full throttle but not run.

I got it running by leaning the low needle A LOT.

I'm not sure if the prev owner overtightened the needles?

The low is like 3/4 turn out....but runs well.

 

[Guest]

If you have a wet plug you are flooded. I know that doesn't explain the stalling out, but it will never fire once it gets wet with fuel.

 

[cordy]

When the plug is wet your running to rich. Reset your needles. 11/2=high speed,11/4=lowspeed.Also check for air leaks around your intake,make shure your carb bolts are tight and your intake manifold is not worped.Have you checked the squish on your head?Make shure your head bolts are torqued down 5lbs.Hope this helps.

 

[JimmyJay]

Thanks for all the suggestions guys, I'm gonna start checking things out some more. I'll let you know what I come up with. Before the issue, I also had the low needle set to 3/4 out cuz that's where it seemed to like it the most.

 

[Deluge]

Try cleaning the plug with some carb cleaner. Could just be dirty. And let it sit for a bit without the plug, sounds like you were flooding it.

 

[SWD]

First check for blown/leaky gaskets and check to see if you have any up/down play in the crank.

Have you tried something as simple as a new plug? I've had them produce spark and still not run. You could be running a tad rich and have a fouled plug. When they start to foul up the internal resistance becomes high and they burn out.

Also check the gap between the flywheel and the coil. The coil can come loose and the slightest increase in gap on a roll over can still produce a visible spark but not intense enough to run correctly.

Hope this helps.

 

[JimmyJay]

I found the issue. Looks like the piston and cylinder are done.

What I think may have happened is a tiny piece of the cylinder wall broke off (last picture) and was bouncing around on top of the piston causing all sorts of damage. There is also a chunk missing off the piston, and the sides of it are gauged bad. You can see how badly pitted the piston is as well as the top of the cylinder. The ring is stuck is an off centre position so I'm not getting a good seal..not enough compression.

I guess it's time to do some shopping.

 

[SWD]

What I think may have happened is a tiny piece of the cylinder wall broke off (last picture) and was bouncing around on top of the piston causing all sorts of damage. There is also a chunk missing off the piston, and the sides of it are gauged bad. You can see how badly pitted the piston is as well as the top of the cylinder. The ring is stuck is an off centre position so I'm not getting a good seal.

The ring shouldn't be off centered from it's normal position. There's a centering pin on the intake side of the piston that's supposed to prevent it from rotating/moving.

Is the centering pin still in the piston or did it break free and take out the top end???

 

[Guest]

Ouch. That sux.

 

[Deluge]

Looks like the pin popped out and got caught between the head and the piston. Oh, well. Now you have an excuse to upgrade. If you're just going to rebuild it, do a complete rebuild. Replace the bearings, seals, etc. You need to clean out the crank case and make sure the pin is gone before you throw a new head and piston on there.

 

[JimmyJay]

Thanks for the advice, after I rebuild the bottom end, will this top end bolt right on?

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.8795/.f

 

[Deluge]

It'll bolt up, but it'll drop the displacement to 29cc. If you want to stick with a 30.5cc, you'll need a 36mm kit.

 

[JimmyJay]

Thanks. Just to be sure before I order, can you tell me if which of these is the correct one? If none of these are correct can you link to one that is?

Option 1

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4166/.f

Option 2

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4170/.f

Option 3

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.1099/.f

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.1102/.f

Thanks!

 

[SWD]

Thanks for the advice, after I rebuild the bottom end, will this top end bolt right on?http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.8795/.f

Stay as far away from the 35mm kits as possible. They are well known for plating issues. Been there done that.

Thanks. Just to be sure before I order, can you tell me if which of these is the correct one? If none of these are correct can you link to one that is?Option 1

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4166/.f

Option 2

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4170/.f

Option 3

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.1099/.f

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.1102/.f

Thanks!

Out of the 3 I would go with the ESP kit (option 2). I personally run a couple ESP 30.5 Championship ported motors in a couple bajas and they go like a raped ape.

 

[Deluge]

Just built an ESP 30.5 Champ port. It's awesome.

ESP Mod/ESP CHAMPIONSHIP PORTED GP290 36mm kit

 

[JimmyJay]

Thanks for your help guys! I was pretty discouraged when I saw the damage and was almost ready to just put the XT away for awhile, but now I'm looking forward to getting up and running again!

So here is my shopping list:

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4168/.f

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.1275/.f

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4153/.f

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.1112/.f

 

[Guest]

Have fun.

You will see a nice performance gain.

 

[Deluge]

Anytime, dude. You'll have a beastly engine.