250GS -81 Jetting issue

[dirtbike]

As you have seen, my 250 is up running. The thing is that for the first time ever I think that I have a small jetting problem.

The idle and just off idle seems perfect but from there on and up to about 1/3 throttle it four strokes. When I twist the throttle up to 1/2 it hooks up crisp and clean, and hey.. the engine is explosive and a lot faster than I expected. I really don't think that my Honda CR 250 -86 can hang on, really!!!

According to the manual this is supposed to be taken care of by the needle position and needle jet. The needle is in it's lowermost position so there is nothing to do there. The throttle doesn't show much sign of wear, nor do the needle. The choke slide goes all the way up too. The manual says that my needle jet is supposed to be 276.
I haven't taken it out yet but I have another one that looks free from wear that is 2.80-2- whatever that is supposed to mean. My main jet is supposed to be 175 and I only have a 180 spare.

The other thing that I have noticed is that turning the air screw doesn't do anything. I can twist it back and fourth with no changes in RPM or anything. Maybe the problem is there? Could the air channel be blocked somewhere so it doesn't play it's role?

I live close to sea level up here in sweden so it's not overly hot outside.

But I really wan't to point out again, oh man the engine comes on really strong..It's the last one without reeds and if the -81 495 is like this but that much bigger, it must be a plain brute!

Thanx in advance
//B

[firstturn]

dirtbike,
  First I am not a expert on carburetion, but with that said I have resolved a lot of problems by eliminating the obvious.  What you said about the air screw not having any effect is something that needs to be addressed.  Per your comment:

The other thing that I have noticed is that turning the air screw doesn't do anything. I can twist it back and fourth with no changes in RPM or anything. Maybe the problem is there? Could the air channel be blocked somewhere so it doesn't play it's role?

I will tell you what I would do to resolve the problem quickly (sorry if other people disagree).  I would unscrew the needle screw and be sure to get the spring, o-ring and small washer (if there is one-old racers moment).  I would the try blowing the the circuit with compressed air.  Before you do this let's hear what the experts have to say.
  My approach is first things first:).




Ron Carbaugh

[dirtbike]

It's fixed!
The problem indeed was the float level. And/or the throttle since I switched that too....

Like I said, I was fooled because the tickler didn't engage letting more fuel in. So I assumed without thinking that I needed to adjust the level so the tickler worked. As it turned out the tickler wasn't seated into position. It's held in place just with friction pressed into place. Mine had to be pressed down som 3-4mm further. As it turned out, I could lower the fuel level by approximately 5 mm (0.2").
This solved the problem and it only four-strokes on low gear and slow forward motion with hardly any throttle. As it's supposed to be according to me.

For other carb issues here, I can testify that the float level is real important. Small changes seems to make quite a difference.

All fine now!

[dirtbike]

It's fixed!
The problem indeed was the float level. And/or the throttle since I switched that too....

Like I said, I was fooled because the tickler didn't engage letting more fuel in. So I assumed without thinking that I needed to adjust the level so the tickler worked. As it turned out the tickler wasn't seated into position. It's held in place just with friction pressed into place. Mine had to be pressed down som 3-4mm further. As it turned out, I could lower the fuel level by approximately 5 mm (0.2").
This solved the problem and it only four-strokes on low gear and slow forward motion with hardly any throttle. As it's supposed to be according to me.

For other carb issues here, I can testify that the float level is real important. Small changes seems to make quite a difference.

All fine now!