Bultaco198A Carb Settings

[hencam]

Hi All,

i have been running my 198A for a couple of years but only about 5 or 6 trials a year i have always been content with the carburation, however i do feel it could be better. The bike richens up a little on acceleration and does not really clear, also if i run the smaller pilot jet as the manual states the mixture screw is wound virtually all the way in, hence the move to a 25, which allows mixture screw to be approx 1 turn out.

all components are in very good condition or new, carb is clean and in very good condition, the slide should be a 3 but i found a 3.5 gave smoother running? if i switch back to a 3 then it is quite lumpy low down

am i missing something fundamental or should i just experiment further and not worry the carb is not set to standard etc

current settings

150 MJ

25 PJ

3.5 slide

2b1 needle in middle groove

106 needle jet

Any advice gratefully received please

Edited February 11, 2014 by hencam

[bondy]

hi would start with standard carb jets and slide and needel. ajust the Air screw if its still the same the problem must be some where else. could be points or the timing also the crank seals may need changing. is the carb inlet ruber cracked may be sucking Air in or may be not tight enough all these things can cause problems some times its easy to over look things. carbs do have to be spot on so dose the points and timing.

Edited February 12, 2014 by bondy

[hencam]

hi all, ref Bondy's post (thanks Bondy), i should have said, Motor was rebuilt from top to bottom 2 years ago, all new seals bearings ignition components, carb all new parts as well. timing is set to 2.7BTDC, i am toolmaker/engineer by trade so making a micrometer adjustable timing tool was not a problem.

if i adjust the mixture screw so the bike runs cleaner the slow running is lumpy and jerky, i am sure my carburation is out but not sure where or how. i will try going back to original settings and work from there, any suggestions gratefully received.