More jetting problems!

[eff]

My bike has a tiny sputter, but I only notice it on road sections at a certain rpm (low throttle opening). Other than that it is running great now.

I've decided that is the way it is.

[jeffd]

FYI - You can have your existing slide "cut" (machined) without having to spend the money for a new one. Me, I would go #8, but think about dialing in the squish to get it running more cleanly first. I noticed that "loosenut" went back to a #7 slide after having the "squish mod" done by RBD.

The bike doesn't run cleanly or as efficiently as it should with the squish set up as loose as it is in stock form. Some guys tighten it up the squish spec and boost compression by simply using a thinner base gasket. But to get the ideal setting - you need to have the head machined by a competent tuner. (RB-Designs here in the U.S. - not sure who you would want to use in the U.K.)

jeff

[juzzasmith]

Originally Posted by eff

My bike has a tiny sputter, but I only notice it on road sections at a certain rpm (low throttle opening). Other than that it is running great now.

I've decided that is the way it is.

Kind of thinking the same way now! Been spending so much time time trying to iron out that little sputter that I think I've kind of forgotten to ride the thing the way it should be ridden. On the dirt and on the pipe!

[GMP]

Eff has a 250. Probably a #7 slide. I think a #8 may be too lean in a 250, but works to clean up the 300s. If its a #6 then yes, try a #7. I just did this to my old '03 that had a #6 and it cleaned it up a lot. When I had it the #6 was fine, but riding styles differ and the carb nozzles wear also.

2-strokes don't seem to run right at a partial steady throttle unless there under a slight load, so maybe thats the issue. Off idle throttle coasting on a flat road mine will do the same. Add a slight hill and it clean and sharp.

I'm going to do the head but maybe for once the tolerances worked in my favor, as the bike runs very clean and pulls hard as is.

[eff]

GMP is right, mine is a 250.

LTR Needle middle clip
48 pilot
178 main
2.5 out on the screw.

[Eric K]

For straight taper needles, including LTR, I have found that the 1/8 throttle richness can be addressed by going with a larger straight diameter needle. The appropriate size straight diameter cleans up the 1/8 throttle richness. When it gets quite warm I increase the straight diameter an additional step.

As a note, I primarily trail ride. The engine has a nice linear response. It will run smooth for extended periods at all low throttle settings. It also improves fuel mileage.

Please note that "your mileage may differ" and you may get different results depending on many other factors. I have the RB Designs head mod.

[juzzasmith]

Originally Posted by eff

GMP is right, mine is a 250.

LTR Needle middle clip
48 pilot
178 main
2.5 out on the screw.

Just curious to know whether your jetting is the same as the baseline jetting given with the LTR kit?

[eff]

Yes. I'm in New England at just about sea level, base temp 60ºF.