carb jetting instructions

mizke · 08-08-2010, 11:59 PM

came across this in my research into jetting my carb in the next few weeks.. pmed a mod was told it was ok to post it up.. hopefully it gets a sticky for other people to find it easly

http://www.atvriders.com/articles/jetting.html

SpudRider · 08-09-2010, 03:54 AM

Thank you for posting the good link, Mike. I am sure this information will help many members of these forums.

Spud

mizke · 08-09-2010, 04:19 AM

no problem spud

like i said in the pm's in the very near future when i rejet for my fmf pipe and intake. i will do a write up with pictures for every step from removing the carb, to putting it back on and testing/checking the plug for the correct jet.

mizke · 08-11-2010, 04:15 PM

ok need to order jets but i need some advice..

went to a place called tj's and bought 2 jets.. first off my main jet was an 88.. so i bought a 90 and a 92.5

are those sizes going to be larger enough to handle the fmf pipe and a intake ?

thing is i need to order another set from rmatv, cuz the jets i bought today are a different style.. so now is the time to get some advice on should i order a jet larger then a 92.5 ?

they dont thread all the way up to the head of the jet.. where as the jet in my carb that came in the carb does.. im going to try running theirs for awhile.. but i want to order correct parts.. tj's only charged me a dollar per jet.. they did not have the pilot jet neither does rc so i dunno about that one..

Weldangrind · 08-11-2010, 07:32 PM

mizke, I presume this is the thread you PM'd me about.

Those jets sound awfully small, but that is when compared with a Mikuni or Keihin. Your carb might use some arbitrary number that doesn't correspond with metric.

Run 'em. See what happens and watch the plug carefully. If the plug turns white, they're too small.

mizke · 08-11-2010, 07:40 PM

they are mikuni jets... mikuni make the 92.5

with keihin the next jet up from an even 92 is 98

to be honest when looking through the 92.5 jet and my stock 88 jet the hole does not seem to be any larger..

what sizes do you run ? i know you told me at one point.. but i cant find the thread..

and yes i pmed you about this thread cuz i need to get these ordered.. i also lowered the needle valve.. funny story the clip shot off the hemostats i had it clamped in when trying to put the clip back on the needle.. shot across my garage.. though crap that one is lost.. turns out it landed on my welders magnet that was 10ft away..

Weldangrind · 08-11-2010, 07:42 PM

Go buy a lottery ticket. Most people never find that clip.

I installed a 110 main and a 22.5 pilot in TurboT's Beast, and that's at sea level. The stockers were 100 and 20.

mizke · 08-11-2010, 07:46 PM

lol i should go buy a ticket, cuz the clip landed on the welders magnet found it sticking to the magnet about 45 minutes later...

i have some rather small cleaning rods, all are sized.. going to try and see if there is a difference between the 88 and the 92.5

mizke · 08-11-2010, 08:18 PM

ok just did a test ride using the 90 main, dropping the needle one notch seems to have cleared up the hesitation in the mid range, but it still hesitates pretty bad on the top end side of it.. not as bad as the 88 main..

going to go ahead and order up a 110 and a intake..

also the exhaust is smoking the 1200 temp paint..

rockymountainatv rocks big time.. 7 bucks for 3 day shipping should have my jets monday..

went ahead and took a big jump ordered up a 98, 110 main jets.. once i find one that works i will be doing a write up on how to jet your carb

TurboT · 08-11-2010, 08:45 PM

Quote:

Originally Posted by Weldangrind

I installed a 110 main and a 22.5 pilot in TurboT's Beast, and that's at sea level. The stockers were 100 and 20.

Runs like a million bucks too. Starts on half a crank from the starter button, barely needs choke in the warm weather.

mizke · 08-11-2010, 08:59 PM

well the 92.5 main i bought today at tj's appears to be the same size as the 88 main that came in the carb..

its odd tho cuz the 88 main is a keihin and the 92.5 is a mikuni.. so there is clearly a difference in sizes.. altho the thread pitch is exactly the same.. the mikuni 90 main screwed in perfectly just the threads stop before reach the underside of the top of it.. so it does not seat fully, other wise mikuni's would work with the keihin and vice versa..

and holy crap is the fmf pipe LOUD.. deff going to repack very soon..

waynev · 08-11-2010, 10:04 PM

As W&G has also stated, my 200cc beast with the free flowing exhaust and the mikuni carb with the UNI air filter seems to like the 110 main jet and 25 pilot jet.
Normally when modding an engine, the free flowing exhaust is usually good for a main increase of 2 jet sizes as well as a better flowing air filter is usually good for increasing 2 jet sizes, i did both and 4 sizes bigger than stock is working great for me.
Also remember jetting a tad on the rich side is always better as under most conditions a temperature change of 7 degrees C means you need to change 1 main jet size to be safe, ie. if you were perfectly jetted to 110 at 25 deg C, then when the temperature falls to 18 deg C then you would need to goto a 112.5 main ( next size up ) to be perfectly jetted, humidty also plays a factor so being on the richer side will burn a bit more fuel but your engine will thank you for it.

mizke · 08-12-2010, 09:20 AM

can you post a picture of your carbs intake tube ? trying to see if switching to a mikuni pz30 will be a smiple bolt on install to a intake manifold...

my pilot jet in the kihein is different then any pilot jet the guys at tj's have seen before.. also going to make it easier to tune since every one else runs them.. i see to be the odd man out with the kihein pz30..

also will my cable choke bracket bolt right up to the mikuni pz30 ? cuz i dont want to give up the cable choke, and cannot find any cable choked mikuni pz30's..

waynev · 08-12-2010, 09:32 AM

My X31 came with the Kehien PZ30 carb, like you i found the jets to be oddballs so i ended up using the GIO upgrade mikuni carb, it bolted right on, i will check the measurements tonight so you can see if it will fit yours, but it should, as for the cable choke, the mikuni i put on my beast needed a few parts from the stocker to use the cable, if the carb you have now is a cable choke you can just remove the parts you need and use them on the new carb to use the cable choke.

mizke · 08-12-2010, 09:50 AM

sweet thanks, and yes mine has a cable choke.

just pulled my plug and its black, so that means its running rich, but yet i get back firing and hesitation when going wot..

whats the part number on the gio upgrade carb ? i looked on giobikes.com an hour or so ago and they have several carbs...really dont want to order one off ebay from japan, 14day shipping, woo hoo 2 weeks with a atv with a problem is going to really bad.. i have ocd over motorized toys not running correctly

im just back to being confused that it acts lean on the top end wot side, but the plug is black.. last night when i fired it up for the last time.. the motor was warmed up.. i revved it up to full throttle and then turned it off at the key with out letting off the throttle to check the plug today.. but i just installed the 92.5 main jet i got yesterday (bought 2 jets 90 and a 92.5) so once it gets to be about noon here i will fire her up and check again..

08-08-2010, 11:59 PM	#1
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	carb jetting instructions came across this in my research into jetting my carb in the next few weeks.. pmed a mod was told it was ok to post it up.. hopefully it gets a sticky for other people to find it easly http://www.atvriders.com/articles/jetting.html
	0

08-09-2010, 03:54 AM	#2
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	Thank you for posting the good link, Mike. I am sure this information will help many members of these forums. Spud __________________ Spud "Never argue with an idiot. He will drag you down to his level, and beat you with experience." Mark Twain 2015 Zongshen ZS250GY-3 (RX3) 2006 Zongshen ZS200GY-2 (Sierra 200) 2005 Honda XR650L 2004 Honda CRF250X 1998 Kawasaki KDX220 Mods made to my Zongshen ZS200GY-2: http://www.chinariders.net/showthread.php?t=6894
	0

08-11-2010, 07:32 PM	#5
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	mizke, I presume this is the thread you PM'd me about. Those jets sound awfully small, but that is when compared with a Mikuni or Keihin. Your carb might use some arbitrary number that doesn't correspond with metric. Run 'em. See what happens and watch the plug carefully. If the plug turns white, they're too small. __________________ 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

08-11-2010, 07:42 PM	#7
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Go buy a lottery ticket. Most people never find that clip. I installed a 110 main and a 22.5 pilot in TurboT's Beast, and that's at sea level. The stockers were 100 and 20. __________________ 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

08-09-2010, 04:19 AM	#3
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	no problem spud like i said in the pm's in the very near future when i rejet for my fmf pipe and intake. i will do a write up with pictures for every step from removing the carb, to putting it back on and testing/checking the plug for the correct jet.
	0

08-11-2010, 04:15 PM	#4
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	ok need to order jets but i need some advice.. went to a place called tj's and bought 2 jets.. first off my main jet was an 88.. so i bought a 90 and a 92.5 are those sizes going to be larger enough to handle the fmf pipe and a intake ? thing is i need to order another set from rmatv, cuz the jets i bought today are a different style.. so now is the time to get some advice on should i order a jet larger then a 92.5 ? they dont thread all the way up to the head of the jet.. where as the jet in my carb that came in the carb does.. im going to try running theirs for awhile.. but i want to order correct parts.. tj's only charged me a dollar per jet.. they did not have the pilot jet neither does rc so i dunno about that one..
	0

08-11-2010, 07:40 PM	#6
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	they are mikuni jets... mikuni make the 92.5 with keihin the next jet up from an even 92 is 98 to be honest when looking through the 92.5 jet and my stock 88 jet the hole does not seem to be any larger.. what sizes do you run ? i know you told me at one point.. but i cant find the thread.. and yes i pmed you about this thread cuz i need to get these ordered.. i also lowered the needle valve.. funny story the clip shot off the hemostats i had it clamped in when trying to put the clip back on the needle.. shot across my garage.. though crap that one is lost.. turns out it landed on my welders magnet that was 10ft away..
	0

08-11-2010, 07:46 PM	#8
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	lol i should go buy a ticket, cuz the clip landed on the welders magnet found it sticking to the magnet about 45 minutes later... i have some rather small cleaning rods, all are sized.. going to try and see if there is a difference between the 88 and the 92.5
	0

08-11-2010, 08:18 PM	#9
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	ok just did a test ride using the 90 main, dropping the needle one notch seems to have cleared up the hesitation in the mid range, but it still hesitates pretty bad on the top end side of it.. not as bad as the 88 main.. going to go ahead and order up a 110 and a intake.. also the exhaust is smoking the 1200 temp paint.. rockymountainatv rocks big time.. 7 bucks for 3 day shipping should have my jets monday.. went ahead and took a big jump ordered up a 98, 110 main jets.. once i find one that works i will be doing a write up on how to jet your carb
	0

08-11-2010, 08:59 PM	#11
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	well the 92.5 main i bought today at tj's appears to be the same size as the 88 main that came in the carb.. its odd tho cuz the 88 main is a keihin and the 92.5 is a mikuni.. so there is clearly a difference in sizes.. altho the thread pitch is exactly the same.. the mikuni 90 main screwed in perfectly just the threads stop before reach the underside of the top of it.. so it does not seat fully, other wise mikuni's would work with the keihin and vice versa.. and holy crap is the fmf pipe LOUD.. deff going to repack very soon..
	0

08-11-2010, 10:04 PM	#12
waynev Join Date: Aug 2009 Location: London, Ontario Posts: 1,097	As W&G has also stated, my 200cc beast with the free flowing exhaust and the mikuni carb with the UNI air filter seems to like the 110 main jet and 25 pilot jet. Normally when modding an engine, the free flowing exhaust is usually good for a main increase of 2 jet sizes as well as a better flowing air filter is usually good for increasing 2 jet sizes, i did both and 4 sizes bigger than stock is working great for me. Also remember jetting a tad on the rich side is always better as under most conditions a temperature change of 7 degrees C means you need to change 1 main jet size to be safe, ie. if you were perfectly jetted to 110 at 25 deg C, then when the temperature falls to 18 deg C then you would need to goto a 112.5 main ( next size up ) to be perfectly jetted, humidty also plays a factor so being on the richer side will burn a bit more fuel but your engine will thank you for it.
	0

08-12-2010, 09:20 AM	#13
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	can you post a picture of your carbs intake tube ? trying to see if switching to a mikuni pz30 will be a smiple bolt on install to a intake manifold... my pilot jet in the kihein is different then any pilot jet the guys at tj's have seen before.. also going to make it easier to tune since every one else runs them.. i see to be the odd man out with the kihein pz30.. also will my cable choke bracket bolt right up to the mikuni pz30 ? cuz i dont want to give up the cable choke, and cannot find any cable choked mikuni pz30's..
	0

08-12-2010, 09:32 AM	#14
waynev Join Date: Aug 2009 Location: London, Ontario Posts: 1,097	My X31 came with the Kehien PZ30 carb, like you i found the jets to be oddballs so i ended up using the GIO upgrade mikuni carb, it bolted right on, i will check the measurements tonight so you can see if it will fit yours, but it should, as for the cable choke, the mikuni i put on my beast needed a few parts from the stocker to use the cable, if the carb you have now is a cable choke you can just remove the parts you need and use them on the new carb to use the cable choke.
	0

08-12-2010, 09:50 AM	#15
mizke Join Date: Aug 2010 Location: austin, tx Posts: 1,452	sweet thanks, and yes mine has a cable choke. just pulled my plug and its black, so that means its running rich, but yet i get back firing and hesitation when going wot.. whats the part number on the gio upgrade carb ? i looked on giobikes.com an hour or so ago and they have several carbs...really dont want to order one off ebay from japan, 14day shipping, woo hoo 2 weeks with a atv with a problem is going to really bad.. i have ocd over motorized toys not running correctly im just back to being confused that it acts lean on the top end wot side, but the plug is black.. last night when i fired it up for the last time.. the motor was warmed up.. i revved it up to full throttle and then turned it off at the key with out letting off the throttle to check the plug today.. but i just installed the 92.5 main jet i got yesterday (bought 2 jets 90 and a 92.5) so once it gets to be about noon here i will fire her up and check again..
	0