Carb question - Page 2

Weldangrind · 03-04-2012, 07:07 PM

Quote:

Originally Posted by Plukey

Weldangrind,
I keep reading that the weather makes a difference, Hot air Vs cold air when I did these changes it was around 40 degrees.. When it hits 70 & above in the upcoming months here in Virginia will it run richer? What are your thoughts?

Exactly right. As the weather gets colder, the air becomes more dense, so more fuel is required to compensate. You might be able to just trim the pilot screw to adjust as necessary when the weather warms up, without actually changing jets again.

Glad to hear that you got it dialed in!

I've wondered if a fatter slow jet would help, and you just confirmed it. I have some on order at the local Yamaha dealer, but they haven't arrived yet. I'm going to fatten the slow jet on my 200 atv, and from there I'll decide how to jet my son's 230. Thanks for the follow-up.

Azriel_Strife · 03-07-2012, 10:59 AM

Hi there, not sure if you got this resolved yet, but you said you hit something resembling a rev limiter. I had the exact same problem with a 130 main jet.

it's far too big for these bikes, you should be in the 110-115 area max on that mikuni. As for the slow jet, 30 might be a bit big too, from what iv'e seen in my search for jetting 25 seems to be about right.

All the sizes I am quoting are at sea level, if you are at higher elevations you'll need leaner jets.

Frog · 03-07-2012, 12:27 PM

Hi

I'm on a 25 slow 110 main set up and the first 2/3rd of the carb operation are spot on. So I am happy with the 25 jet.

The last third is the issue - I have just lifted the needle to its highest point but yet to test on the road. I suspect a 115 main may be needed but we shall see.

Frog

Frog · 03-31-2012, 06:39 AM

Quote:

Originally Posted by Plukey

Gentlemen,

Please keep us posted on any break thru's you may have.

Hi Plukey

my issue which sounded exactly the same as yours was down to float heights - they came slightly too low from the factory. See my recent thread re: 30mm Mikuni.

Cheers

Frog

kzcarb · 06-16-2012, 12:06 PM

Hi everyone,

I wanted to bring up a question about these mikuni 30mm carbs that I haven't seen discussed yet. The question is about mid range tuning. I purchased one of these carbs and so far the 1/8 to 1/2 throttle position is very lean. Pilot and main jets are easy enough to find, and after some jet changing, the power seems good up to 1/8th and over 1/2. But the mid range still has a very lean condition. So, my question is about changing the throttle slide, needle, and needle jet. Now, these parts are not so easy to find! Does anyone have experience or information on matching these parts to Mikuni parts that are currently in the catalog?

The question has been raised on whether these carbs are "knock-offs" or genuine Mikuni, and so far I have not been able to tell. But it seems that the mikuni catalog does not support these carbs. Regardless, they have a good reputation and seem to please their owners when tuned well. Any help will be greatly appreciated!

Weldangrind · 06-17-2012, 04:26 PM

Welcome!

For midrange tuning, I simply try different clip settings on the jet needle until it runs properly. I really don't care if these carbs are genuine or not; they make me happy.

06-17-2012, 04:26 PM	#21
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Welcome! For midrange tuning, I simply try different clip settings on the jet needle until it runs properly. I really don't care if these carbs are genuine or not; they make me happy. __________________ 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
	0

03-07-2012, 10:59 AM	#17
Azriel_Strife Join Date: Mar 2012 Location: Chilliwack BC, Canada Posts: 32	Hi there, not sure if you got this resolved yet, but you said you hit something resembling a rev limiter. I had the exact same problem with a 130 main jet. it's far too big for these bikes, you should be in the 110-115 area max on that mikuni. As for the slow jet, 30 might be a bit big too, from what iv'e seen in my search for jetting 25 seems to be about right. All the sizes I am quoting are at sea level, if you are at higher elevations you'll need leaner jets.
	0

03-07-2012, 12:27 PM	#18
Frog Join Date: May 2008 Location: Hampshire England Posts: 191	Hi I'm on a 25 slow 110 main set up and the first 2/3rd of the carb operation are spot on. So I am happy with the 25 jet. The last third is the issue - I have just lifted the needle to its highest point but yet to test on the road. I suspect a 115 main may be needed but we shall see. Frog
	0

06-16-2012, 12:06 PM	#20
kzcarb Join Date: Jun 2012 Posts: 1	Hi everyone, I wanted to bring up a question about these mikuni 30mm carbs that I haven't seen discussed yet. The question is about mid range tuning. I purchased one of these carbs and so far the 1/8 to 1/2 throttle position is very lean. Pilot and main jets are easy enough to find, and after some jet changing, the power seems good up to 1/8th and over 1/2. But the mid range still has a very lean condition. So, my question is about changing the throttle slide, needle, and needle jet. Now, these parts are not so easy to find! Does anyone have experience or information on matching these parts to Mikuni parts that are currently in the catalog? The question has been raised on whether these carbs are "knock-offs" or genuine Mikuni, and so far I have not been able to tell. But it seems that the mikuni catalog does not support these carbs. Regardless, they have a good reputation and seem to please their owners when tuned well. Any help will be greatly appreciated!
	0