Need help in identifying main jet type

Vlad87 · 06-08-2023, 09:16 PM

Some time ago i bought chinese knock-off of Mikuni VM24 carb, and today i tried to disassemble and check it out. Well, i'm kinda puzzled. Pilot jet is not marked at all, and what is supposed to be Main Jet is of a very strange design, and i can't find any relevant information on the internet. I suspect that it's not even a mikuni type of jet. Anyone have ideas about what it is? Compatible carb models? It has 97.5 marking on it.

Would be really glad for any help.

**JerryHawk250** · 06-09-2023, 09:07 AM

Quote:

Originally Posted by jeffrey

That looks like the jet holder and the main jet. Put a wrench on the lower part and see if the jet unscrews,it should. Hope that helps.

What Jeffrey said.

dirtbkr188 · 06-09-2023, 10:31 AM

Once you have it removed, measure and see if it matches the specs of the Mikuni main jet shown below

Vlad87 · 06-09-2023, 10:51 AM

Quote:

Originally Posted by jeffrey

That looks like the jet holder and the main jet. Put a wrench on the lower part and see if the jet unscrews,it should. Hope that helps.

Thanks for your help, Jeffrey, you're right, that is a jet holder.

Guys, i'm not sure if i should create a new thread for that, and i understand that this is more of a trial-and-error thing, but what would be your recommendations on correct jet sizes for stock 164fml - 200cc CG engine (no head decking or porting), with a twin exhaust manifold.

dirtbkr188 · 06-11-2023, 03:06 PM

Did you ever get around to taking some measurements of the main jet you have?

Vlad87 · 06-11-2023, 08:50 PM

Quote:

Originally Posted by dirtbkr188

Did you ever get around to taking some measurements of the main jet you have?

Hey, dirtbkr188, huge thanks for providing the reference. That 97.5 main jet corresponds to mikuni measurements on the pic you've attached. The mystery of the default jet is solved ) However, i'm still a bit puzzled - i have a set of main jets that i ordered from Aliexpress, that are supposed to be Mikuni-type. They are of the same 9mm length and compatible threading, but have larger head of 8mm... If i understand correctly, that's another Mikuni standard. Do they have the same sizing numbering system as those with smaller heads?

dirtbkr188 · 06-11-2023, 09:34 PM

Yes, the main jet sizes between Mikuni jets are the same, the bigger head main jet size range can be found right HERE.

The thread size and pitch are the same for both the little head and big head round jets

06-09-2023, 10:31 AM	#3
dirtbkr188 Join Date: Aug 2009 Posts: 577	Once you have it removed, measure and see if it matches the specs of the Mikuni main jet shown below
	2

06-11-2023, 03:06 PM	#5
dirtbkr188 Join Date: Aug 2009 Posts: 577	Did you ever get around to taking some measurements of the main jet you have?
	1

06-11-2023, 09:34 PM	#7
dirtbkr188 Join Date: Aug 2009 Posts: 577	Yes, the main jet sizes between Mikuni jets are the same, the bigger head main jet size range can be found right *HERE*. The thread size and pitch are the same for both the little head and big head round jets
	1