Running fine full out but seems to hesitate when going slow and starting - Fuel pump?

[darrylgood]

97 xp

Just re-build the top end and carbs.

I have been using it for the last 2 weekends, but this weekend I had trouble starting it. (takes 3-5 times with full throttle for it to catch) Once it does catch it might die and I start it again. Once im going I then give it a bit of gas and it seems to bog down a bit. It seems like it is not getting enough fuel when touch the throttle. After it hesitating for a couple seconds it seems to get gas and I take off. running it mid to full out there is no issues at all, runs perfect.

I don't believe it is a fuel line or carb issue because running it for long periods of time at 80% of throttle it runs perfect, so the fuel is getting there.

Could it be the fuel pump is weak?

 

[Dr Honda]

Nope... if the fuel pump was weak... it would run out of fuel, in the upper RPM's.

Sounds like...

1) Transition ports are plugged up
2) High speed check valve is bad
3) Pop-off is too high. (What did you set it to?)
4) Idle mix is too lean.

Just because you rebuilt the carbs, doesn't mean they are right.

 

[darrylgood]

Hi Tony,

I believe i had a problem with a lean fuel mix before and that's why I had to re-build my top end. Maybe the problem is still there. What would be the cause of a lean mixture in this case? Any step by step info on testing this would be greatly appreciated.

Thanks Tony, you have been quite helpful

 

[Dr Honda]

Unfortunately... all you can do is to remove the carbs, and double check everything. (no real tests)

BUT... while the carbs are off... you can check the rotary valve to see if you have excessive clearance.

Also... when you did the rebuild... was it an OEM Mikuni kit? Aftermarket kits suck.

Last thing... when you start to give it throttle... and it's stumbling... if you hold the throttle at that point... does it clear out on it's own? Or, do you have to give it more throttle?

I'm thinking it may not be lean... it may be very rich.

Rich mix: Stumbling, missing sound, but normally will clear out.

Lean Mix: sounds fine, but will have no power, or the engine may just shut off.

 

[darrylgood]

No, aftermarket kit

Hmm I believe it may have cleared its self out. One thing I did notice is that I notice the bogging/starting issue when its cold. After driving for a while, I can run quite slow with out it bogging. Does that tell us anything?

also you say the lean mix will have no power, well this does have full power at full throttle.

 

[darrylgood]

Now that I look at the oil reservoir it seems that a lot of oil has been used as well. What is the reason for a rich mixture?

 

[Dr Honda]

Now that I look at the oil reservoir it seems that a lot of oil has been used as well. What is the reason for a rich mixture?

1) Very low pop-off.
2) pilot jet came loose
3) low mix screw open too far, or the tip of the needle is messed up.

 

[darrylgood]

Thank Tony, not to familiar with the low pop off, can you fill me in.

Thanks so much