Jet size needed

Jeffh

New Member
Aug 6, 2020
6
1
25
27
Hello everyone I am running a fmf gold series expansion chamber with a stock silencer and a uni filter with no air box (previous owner cut the air box out) I am currently running a 230 main jet in my mikuni carb that I do not know where it came from but it is not oem, what size of jet does everyone recommend? I have a amazon carb that came with the bike when I got it that has a bigger jet in it, you can tell by sticking a drill bit/pick in the jet, when I try to use that carb it gets too much fuel and will not move under its own power, I have tried adjusting the needle and I have also tried adjusting the float height to see if that was causing the problem but nothing worked, the only thing I have gotten to work is a 230 main jet size, I am still spitting out minimal smoke out of the tail pipe, I have rode it like this a few times now I am able to move through all of the gears just fine but with the other carb with the bigger jet that idk the size of I can’t even make it out of 1st gear
 

Attachments

  • 5FD1D57E-96AB-4C86-B5F5-8573F68939A9.jpeg
    5FD1D57E-96AB-4C86-B5F5-8573F68939A9.jpeg
    1.9 MB · Views: 306
Second picture of carb
 

Attachments

  • BD181695-6D16-4E4E-8588-5A34CF197E1E.jpeg
    BD181695-6D16-4E4E-8588-5A34CF197E1E.jpeg
    1.9 MB · Views: 244
stick with the stock carb, the 230 main is the stock size and will fry your engine with an FMF pipe and airbox mods
you need to buy 270 thru 310 mains, a six pack of B8ES plugs, start large and plug chop down until you get a nice dark brown smoke ring, follow the plug chop DIY letter for letter..........
https://www.blasterforum.com/threads/how-to-plug-chop.53237/
 
stick with the stock carb, the 230 main is the stock size and will fry your engine with an FMF pipe and airbox mods
you need to buy 270 thru 310 mains, a six pack of B8ES plugs, start large and plug chop down until you get a nice dark brown smoke ring, follow the plug chop DIY letter for letter..........
https://www.blasterforum.com/threads/how-to-plug-chop.53237/


All I have for a carb is the one pictured, looks like it might be a 28 mm mikuni carb I put a 260 jet in it and it bogged at WOT but was fine until 1/2 maybe 3/4 but there is absolutely no top end and I can’t get out of 3rd gear
 
Oh, there's a multitude of things wrong with non stock carbs, starting with wrong pilot, needle, slide and main jet, could all be wrong :(
check this thread and see if anyone else reported jetting for a 28mm Mik ?
https://www.blasterforum.com/threads/what-jets-are-you-using.28981/

as for your specific description right now,
if it starts easily and gets past 1/4 throttle, the pilot and airscrew must be close ?
1/2 to 3/4 throttle is all needle jetting, and it must be close too if it pulls good to 3/4 throttle, I'd still drop the clip one spot at a time until it bogs rich, then back up one slot to be safe
your full throttle bog is all main jetting and with your mods I'd say you still need to go up, try a larger jet for 1 full throttle pull, like 290/300, and see if it responds better, if it does, plug chop that main and see where you stand.
 
Oh, there's a multitude of things wrong with non stock carbs, starting with wrong pilot, needle, slide and main jet, could all be wrong :(
check this thread and see if anyone else reported jetting for a 28mm Mik ?
https://www.blasterforum.com/threads/what-jets-are-you-using.28981/

as for your specific description right now,
if it starts easily and gets past 1/4 throttle, the pilot and airscrew must be close ?
1/2 to 3/4 throttle is all needle jetting, and it must be close too if it pulls good to 3/4 throttle, I'd still drop the clip one spot at a time until it bogs rich, then back up one slot to be safe
your full throttle bog is all main jetting and with your mods I'd say you still need to go up, try a larger jet for 1 full throttle pull, like 290/300, and see if it responds better, if it does, plug chop that main and see where you stand.


So I’m not able to find any used oem carbs online whatsoever cause I was going to try and just get a different carb, do you have any recommendations on a carb? I was told vm26-606 won’t work but other than that carb I’m looking at cheap Chinese crap
 
  • Like
Reactions: tuffluckbmx
shoot sorry guys I forgot to update, I did pick up a true oem Mikuni for 100 I’m at a 290 jet with absolutely no smoke coming out of the tail pipe, not enough room to perform a proper plug chop either
You can ride the brake alittle if a longer distance is Not available.The idea is to have a load on the engine