carby jetting

[philipml]

for a 250 n/c can anyone tell me a starting point for the carby jets. had electronic ignition problems that I took as fuel & totally screwed up the carby settings. running a PHBH 28.

[Jordan]

Suggest you go back to the original settings if they worked OK, if you made a note of those.
Then consult a tuning guide:
http://danskkartingcenter.dk/dellorto_m ... _guide.pdf

For a more basic guide, try:
http://amalcarb.co.uk/downloadfiles/ama ... _guide.pdf

as your carb is Amal type, and tuning principle is similar.

[ducwiz]

Just remembered an older thread about PHBH settings: http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=1269&p=8628#p8628. This may help for a starting point.

Hans

[philipml]

no I didn't record my original jetting, I have got it to a point now that idle is a little rich, up to 3K fine, above that very spluttery. I have ordered a new float as trying to get the right level it either floods or no fuel at all. Thanks for the help..

[Jordan]

Sort out the float level before doing anything else, then:
Rather than revs, carb settings are usually adjusted according to throttle position, with idle mixture set between zero and 1/8 full throttle opening.
You have two things to adjust in that range - the pilot jet and the idle mixture screw.
Usually the screw is set to give the correct mixture at 1.5 turns back from fully in (but check for your carb).
So, select a pilot jet to idle nicely at that turn setting. That is, at the highest idle speed at a given throttle stop position.

Next thing to set is the slide cutaway, 1/8 to 1/4 throttle opening.
You have to ride the bike for this and subsequent adjustments, unless you have a rolling road.