Dirt Bike help!

[n_schulenburg]

I've got an old dirtbike that needed a new carb after replacing the carb it starts and idles fine but once you put it in gear it has no power and bogs down. any help would be appreciated.

 

[jimfsr]

CHeck compression first, then let us know...

 

[n_schulenburg]

compression was 110psi

 

[jimfsr]

What year, make, model and cc is it, 110 is pretty low unless your on a 500. I would consider that minimum for a small bore single cyl. 2 stroke to even run, let alone make any power.

 

[n_schulenburg]

Its a 1990 yamaha rt 100 has been stored inside but not riden since 2007

 

[fish633]

does it die when you put the bike in gear or when you ease the clutch out?

 

[n_schulenburg]

It dies after easing the clutch out

 

[fish633]

Have you changed the trans oil?

 

[n_schulenburg]

no i have not.

 

[vic_junior]

Warm it up and change oil. If that doesn't help, your clutch plates could be sticking together due to being wore out. Also, adjust your clutch cable.

 

[n_schulenburg]

Thanks i will try that

 

[fish633]

Vic is spot on.Have you tried a new plug,check fuel flow from petcock,remove spark arrestor from muffler wire brush the carbon off of it,check for mouse nests in pipe.The rt's are low comp to begin with so 110psi aint that far off.Let us know if you get it sorted out.

 

[dofo1]

Also make sure to clean the fuel tank , filter/screen in petcock and put fresh gas in tank.

Might think about changing spark plug cap.

 

[jimfsr]

Its a 1990 yamaha rt 100 has been stored inside but not riden since 2007

I didn't find any info on a 1990. 1992 was the first year I have info for but... since you installed a new carb, I don't know if it was the OEM one from Yamaha, or a chinese copy of that carb. which are out there. Make sure the jetting is correct-Main is 140, pilot is 17.5, clip in middle. airscrew 1 1/2 turns out to start with. Also visually check the reed petals, they were steel from the factory and were prone to breaking.

The way you describe it running, with 110 lbs (assuming the reading was accurate) it sound like the idle circuit is close, but the main fuel supply (main jet/clip position) is way off, offering only enough fuel to idle, but not enough to make power. If the plug color is black, but dry/powdery, it could be way lean, eventhough lean is usually white tip on the plug. Wet and black is too rich. Timing is another issue, that model has an adjustable stator plate I believe. Need a timing light (automotive type) to check it. retarded too much, it will start, but no power.