Mikuni carb tuning suggestions

bucannon · 02-05-2014, 06:50 PM

after sitting for over a year, i rebuilt my Mikuni 30mm carb. i have bigger jets in it now since my exhaust is gutted. I am having trouble getting it to idle right by adjusting the air/fuel and the other screw on the side.

any suggestions on tuning?

is there a troubleshooting guide for mikuni carbs available?

zingshoen · 02-05-2014, 07:31 PM

how big are the new jets?

1.5 turns out from seated give you a starting point. adjust by a quarter turn.
in case you haven t considered it: rough idling could be due to other problems, such as air leaks (intake boot) or sth electrical (spark plug etc). try to get her to idle as good as you can for now and inspect for other problems if you haven t.

if you do a search for mikuni on this site you ll find heaps of info

bucannon · 02-05-2014, 08:32 PM

I cant remember the sizes now but there's a thread somewhere on here about it.

Im going to check on my intake to see if that cap on the side is dryrotted...

Im getting a slight backfire out the carb also

Weldangrind · 02-06-2014, 10:52 AM

It sounds a little lean. Perhaps you need to fatten the mixture at your specific elevation.

For me, a 200cc four stroke at sea level with a 30mm Mikuni, pod filter and free-breathing exhaust will run on a 110 main and 25 slow in the summer. In the winter, it likes more fuel and is happier with a 112 and 30.

02-05-2014, 06:50 PM	#1
bucannon Join Date: Nov 2011 Location: Galveston, TX Posts: 63	Mikuni carb tuning suggestions after sitting for over a year, i rebuilt my Mikuni 30mm carb. i have bigger jets in it now since my exhaust is gutted. I am having trouble getting it to idle right by adjusting the air/fuel and the other screw on the side. any suggestions on tuning? is there a troubleshooting guide for mikuni carbs available? __________________ 2008 200cc dirtbike
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02-05-2014, 07:31 PM	#2
zingshoen Join Date: Jun 2009 Location: Brisbane, Queensland, Australia Posts: 648	how big are the new jets? 1.5 turns out from seated give you a starting point. adjust by a quarter turn. in case you haven t considered it: rough idling could be due to other problems, such as air leaks (intake boot) or sth electrical (spark plug etc). try to get her to idle as good as you can for now and inspect for other problems if you haven t. if you do a search for mikuni on this site you ll find heaps of info __________________ 1971 Garelli Gulp 50cc with open ports and 16 mm Bing Carbie + 1980 Honda XL 223 ZS + 2007 Zongshen LZX200G + DR400SM
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02-05-2014, 08:32 PM	#3
bucannon Join Date: Nov 2011 Location: Galveston, TX Posts: 63	I cant remember the sizes now but there's a thread somewhere on here about it. Im going to check on my intake to see if that cap on the side is dryrotted... Im getting a slight backfire out the carb also __________________ 2008 200cc dirtbike
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02-06-2014, 10:52 AM	#4
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	It sounds a little lean. Perhaps you need to fatten the mixture at your specific elevation. For me, a 200cc four stroke at sea level with a 30mm Mikuni, pod filter and free-breathing exhaust will run on a 110 main and 25 slow in the summer. In the winter, it likes more fuel and is happier with a 112 and 30. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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