PW80 Problem

[RHarper]

I purchased my 6yo a new PW80 back in May. He took to it pretty fast. We've made a few modifications to it since then.

The bike seems to run great for the first 10 or 15 minutes of riding. Then it seems to loose 75% of it's power for a while. It just seems to become unresponsive. Then out of no where all the power comes back, and it runs well.

Modifications done

1. Removed the restictor in the mouth of the exhuast. Then drilled out two other restrictors in the mouth that condensed the opening. Also removed that cone shaped thing in the silencer.

2. Boysen Power reeds

3. Leaned the needle Jet 1 position

4. Changed the main jet from .125 to .115

5. K&N Filter

6. Open up the Air box using some small one inch Uni Filters

7. Changed the front sprocket to one tooth smaller.

Next thing I want to do: Remove the premix system, and start mixing my own.

This problem only started happening in the last week. It ran well for about a month since the last modification I did.

The plug looks healthy when it looses power, and I've even replaced the plug when it starts loosing power to no avail.
I thought at first the carb was getting dirt in it, but it's clean.
Any advice would really help.
TIA

 

[Studboy]

Rharper,

Is the bike getting hot or losing lubrication?

I found that the stock bike would sputter a lot because the jetting was WAYYY fat. I leaned out the main and needle as you have and it improved the bike tremendously. I also threw away the stock airbox and put a K&N clamp-on with pre-filter on the bike.

I've found that the bike seems to run much better with the cone in the silencer. When I took it out it not only made the bike much louder, the power went down.

I also dropped a tooth on the front sprocket, stock the bike has about a 60 MPH top speed but can't get out of 1st gear in the sand! (It's got a WIDE ratio 3-speed).

Your problem is strange indeed... my PW80 does smoke a bit with the injector system but it still runs fine.

 

[xr100ider]

I also dropped a tooth on the front sprocket, stock the bike has about a 60 MPH top speed but can't get out of 1st gear in the sand! (It's got a WIDE ratio 3-speed).

are you sure about that?

 

[Studboy]

I GPS'd the bike at 58 MPH, with my 160 Lb butt on board!!! My bike is an 84 so I'm not sure if the gearing has changed with the newer models.

 

[2dayinc]

I purchased my 6yo a new PW80 back in May. He took to it pretty fast. We've made a few modifications to it since then.

The bike seems to run great for the first 10 or 15 minutes of riding. Then it seems to loose 75% of it's power for a while. It just seems to become unresponsive. Then out of no where all the power comes back, and it runs well.

Modifications done

1. Removed the restictor in the mouth of the exhuast. Then drilled out two other restrictors in the mouth that condensed the opening. Also removed that cone shaped thing in the silencer.

2. Boysen Power reeds

3. Leaned the needle Jet 1 position

4. Changed the main jet from .125 to .115

5. K&N Filter

6. Open up the Air box using some small one inch Uni Filters

7. Changed the front sprocket to one tooth smaller.

Next thing I want to do: Remove the premix system, and start mixing my own.

This problem only started happening in the last week. It ran well for about a month since the last modification I did.

The plug looks healthy when it looses power, and I've even replaced the plug when it starts loosing power to no avail.
I thought at first the carb was getting dirt in it, but it's clean.
Any advice would really help.
TIA

Check out www.x-tender.com for yout Yamaha PW80 & TTR90 needs. They have stuff for the suspension and a triple clamp. :)