New head running issues

aries · Oct 18, 2010

Hi Folks
Many thanks for all your replies. Obviously a wide range of some quite scientific thoughts out there!!. Over the weekend I changed the Needle jet from 106 to a 107 size, and main jet from a 230 to 240 size. This improved things considerably but more tinkering is required somewhere I feel. Get to 70 mph holding the throttle steady at this speed the bike is still slightly lumpy, thouh when opening the throttle though, she takes off and finally breaks that barrier. What should I be doing now to get that sorted Im wondering??.
She idles fine, but had to richen the mixture slightly so she wouldnt get short of breath whilst slowly opening the throttle to increase idle rpm.
Im runnin Iridium plugs and they appeared a little sooty, so maybe my next move is to experiment with needle height??

Yes indeed, the fullauto head is a wonderfull thing and so is the Tri Spark for presenting a solid tickover. Well done Australia. Any carburetor designs on the horizon?

splatt · Oct 18, 2010

Thread hi jacking, I purchased one of the lm2 kit 2nd hand off a young guy at work, broke from trying to keep his bat mobile rotary going, I'm curious about the settings others get, the tool was extremly good as it showed how much and were a change affected the mixture settings, I now see why MIKUNI make such a wide array of needles and jets.
I got around 13-1 at idle, between 10,11-1 through the mid range and about 12-1 on the main jet with about a 24 inch sniffer tube,

comnoz · Oct 18, 2010

Splatt, I usually see best idle at between 13 and 13.5 , I shoot for around 11.5 at full load. Getting any leaner than around 13.8 at cruise speed is asking for trouble.
Most carburetors end up with rich spots that are hard to get rid off without causing dangerous lean spots.
Here is a shot of my target mixtures that I use on my efi bikes.

Note that this is about as lean as you could safely go and you will not be able to safely run this lean with a carb.
Verticle is engine load and horizontal is RPM. Jim

comnoz · Oct 18, 2010

aries said:
Hi Folks
Many thanks for all your replies. Obviously a wide range of some quite scientific thoughts out there!!. Over the weekend I changed the Needle jet from 106 to a 107 size, and main jet from a 230 to 240 size. This improved things considerably but more tinkering is required somewhere I feel. Get to 70 mph holding the throttle steady at this speed the bike is still slightly lumpy, thouh when opening the throttle though, she takes off and finally breaks that barrier. What should I be doing now to get that sorted Im wondering??.
She idles fine, but had to richen the mixture slightly so she wouldnt get short of breath whilst slowly opening the throttle to increase idle rpm.
Im runnin Iridium plugs and they appeared a little sooty, so maybe my next move is to experiment with needle height??

Yes indeed, the fullauto head is a wonderfull thing and so is the Tri Spark for presenting a solid tickover. Well done Australia. Any carburetor designs on the horizon?

Aries, You probably need to go richer yet on the main and maybe a step or 2 richer with the needle. The plugs may get sooty if the bike is misfiring so it is hard to judge by plug color until you are close enough to run smoothly. You may find that once the needle is high enough to give you good 1/2 to 3/4 throttle operation you may be too rich at 1/4 throttle in which case you would have to go to a leaner slide cutaway. Jim

aries · Oct 19, 2010

Thanks comnoz et all. Have ordered a couple of main jets a 250 and 260 . Mick hemmings says same as yourself. So it will get there eventually through experimentation.

New head running issues

aries

splatt

comnoz

comnoz

aries

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