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Good chart on Keihin vs. Mikuni jet sizes...

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63K views 25 replies 9 participants last post by  buckoz  
#1 ·
Width------Keihin # -- DynoJet # -- Mikuni #
0,0350---- 92,5--------- 92----------- 86,3
0,0360---- 95----------- 94----------- 88,1
0,0370---- 97,5--------- 96----------- 90,0
0,0380---- 100---------- 98----------- 91,9
0,0390---- 102,5------- 100---------- 93,8
0,0400---- 105--------- 102---------- 95,6
0,0410---- 107,5------- 104---------- 97,5
0,0420---- 110--------- 106---------- 99,4
0,0430---- 112,5------- 108--------- 101,3
0,0440---- 115--------- 110--------- 103,1
0,0450---- 117,5------- 112--------- 105,0
0,0460---- 120--------- 114--------- 106,9
0,0470---- 122,5------- 116--------- 108,8
0,0480---- 125--------- 118--------- 110,6
0,0490---- 127,5------- 120--------- 112,5
0,0500---- 130--------- 122--------- 114,4
0,0510---- 132,5------- 124--------- 116,3
0,0520---- 135--------- 126--------- 118,1
0,0530---- 137,5------- 128--------- 120,0
0,0540---- 140--------- 130--------- 121,9
0,0550---- 142,5------- 132--------- 123,8
0,0560---- 145--------- 134--------- 125,6
0,0570---- 147,5------- 136--------- 127,5
0,0580---- 150--------- 138--------- 129,4
0,0590---- 152,5------- 140--------- 131,3
0,0600---- 155--------- 142--------- 133,1
0,0610---- 157,5------- 144--------- 135,0
0,0620---- 160--------- 146--------- 136,9
0,0630---- 162,5------- 148--------- 138,8
0,0640---- 165--------- 150--------- 140,6
0,0650---- 167,5------- 152--------- 142,5
0,0660---- 170--------- 154--------- 144,4
0,0670---- 172,5------- 156--------- 146,3
0,0680---- 175--------- 158--------- 148,1
0,0690---- 177,5------- 160--------- 150,0
0,0700---- 180--------- 162--------- 151,9
0,0710---- 182,5------- 164--------- 153,8
0,0720---- 185--------- 166--------- 155,6
0,0730---- 187,5------- 168--------- 157,5
0,0740---- 190--------- 170--------- 159,4
0,0750---- 192,5------- 172--------- 161,3
0,0760---- 195--------- 174--------- 163,1
0,0770---- 197,5------- 176--------- 165,0
0,0780---- 200--------- 178--------- 166,9
0,0790---- 202,5------- 180--------- 168,8
0,0800---- 205--------- 182--------- 170,6
0,0810---- 207,5------- 184--------- 172,5
0,0820---- 210--------- 186--------- 174,4
0,0830---- 212,5------- 188--------- 176,3
0,0840---- 215--------- 190--------- 178,1
0,0850---- 217,5------- 192--------- 180,0
0,0860---- 220--------- 194--------- 181,9
0,0870---- 222,5------- 196--------- 183,7
0,0880---- 225--------- 198--------- 185,6
0,0890---- 227,5------- 200--------- 187,5
 
#9 ·
Yep, that appears to be so. I have always known that Keihin jet sizes were larger than Mikuni, just never have seen it quantified.

And, orifice size does not 100% equate across carbs, as has already been pointed out. Other geometry also comes into play.

Scot
 
#3 ·
Now I'm starting to worry slightly - I run 132.5 Dynojet on the outside and 127.5 centre. According to that chart, I'm actually running 119.4 and 124.2 jets, which is slightly smaller than stock for the Daytona :eek: And it's still too rich :confused: This suggests that it's either not getting enough air or the exhaust system is too restrictive - or both.
 
#5 ·
I just realised that I do NOT have a Dynojet kit, but Factory. And they claim to use a numbering system identical to Mikuni. Judging how my engine runs, I am inclined to believe them on their claim.

Regarding Mikuni vs. Keihin - the information I have is ancient (from a Cycle World article back to 1983), but the claim was that one brand use tapered holes that flow better than their actual number would suggest. Hence, if you take a Kehin jet size 100 and replace it with a Mikuni jet of the same size, you will run rich - even though the hole may be identical in size at its narrowest point.
 
M
#14 · (Edited)
Factory Pro uses Keihin dimensional sizing on their K Series jets

faffi said:
I just realized that I do NOT have a Dynojet kit, but Factory. And they claim to use a numbering system identical to Mikuni. Judging how my engine runs, I am inclined to believe them on their claim.

Regarding Mikuni vs. Keihin - the information I have is ancient (from a Cycle World article back to 1983), but the claim was that one brand use tapered holes that flow better than their actual number would suggest. Hence, if you take a Kehin jet size 100 and replace it with a Mikuni jet of the same size, you will run rich - even though the hole may be identical in size at its narrowest point.
Click to expand...
How could you forget Factory?? :)

After a year, I'm sure you already figured it out, but, Factory Pro uses Keihin style "K Series" sizing for Keihin carb apps (like the Triumphs) and different Mikuni style "M Series" sizing for our Mikuni carb kits apps.

Good sleuthing on the Cycle World article - sadly, I think they were told that, but never understood the scale of the differences. Dynojet actually explained why they had a different lead-in angle, but it didn't really make much sense, to me, anyway.

After work, I've had the discussion with other tuners and we pretty much agreed that whatever the dj difference was (or wasn't), it made little difference and because the hole size was different - you just didn't swap dj for any other jet - unless you were vacating dynojet jet use from now on.

Thanks -
Marc Salvisberg
Factory Pro
................
"Honey, do these posts make my head look big?"
 
#6 ·
Apples 'n Pears........

Hi,

From what I have seen elsewhere, all three use a different coding method, based upon the following:
- Mikuni jets are marked with their flow rate - ie: 150 = a rating of 150 cc of fuel per minute.
- Dynojet jets are marked with the diameter of the hole in the jet - ie: DJ150 = 150mm hole.
- Keihin, well, I haven't seen a good rationale for these?

Geoff
 
#7 ·
GeoffE said:
Hi,

From what I have seen elsewhere, all three use a different coding method, based upon the following:
- Mikuni jets are marked with their flow rate - ie: 150 = a rating of 150 cc of fuel per minute.
- Dynojet jets are marked with the diameter of the hole in the jet - ie: DJ150 = 150mm hole.
- Keihin, well, I haven't seen a good rationale for these?

Geoff
Click to expand...
That is probably more accurate than my memory from something I read 25 years ago ;) Maybe I need to dig out that old article and see if it says anything about Keihin...
 
M
#12 · (Edited)
Keihin jet/ FactPro=dimension sized, dj=supposed to be but isn't, Mik ref is off

Width---Keihin 393#---DynoJet #-----Mikuni #
0,0350---- 92,5--------- 92----------- 86,3
0,0360---- 95----------- 94----------- 88,1
0,0370---- 97,5--------- 96----------- 90,0
0,0380---- 100---------- 98----------- 91,9
0,0390---- 102,5------- 100---------- 93,8
~~~
0,0860---- 220--------- 194--------- 181,9
0,0870---- 222,5------- 196--------- 183,7
0,0880---- 225--------- 198--------- 185,6
0,0890---- 227,5------- 200--------- 187,5
Click to expand...
Keihin "393" series:
The Keihin sizing is pretty close to right (ish). Close enough for hand drilling a jet when you don't have what you need. A 150 is 1.50mm in diameter.

Factory Pro "393 K Series":
The Factory Pro "K Series" jets are also dimensionally sized, just like the Keihin jets.
Example: a "150" Keihin or "K Series" main jet is usually 1.50mm in diameter.

Dynojet:
According to dynojet, http://planetminis.com/f21/finally-f...ets-52984.htmlthe dynojets are supposed to be sized the same as Keihin (dimensionally)- but I've never found that to be true.

As far as different lead-in angles and such, I'm guessing that that difference is more that metric manufactured K and M jets tend to have a std metric 90 degree included lead-in included angle and USA manufactured jets tend to be 82 degree included angle. I could be wrong on the lead-in angle, but I remember that that dj is different. It was 20+ years ago that we started making Keihin and Mikuni style jets.

Mikuni N102221 (small round slotted jets)
That part of the chart is wrong. The gist is right, but, the holes sizes are wrong.
You have to take a selection of jets, across the entire range, measure and create a curve for them to be correct.

Summation -
If you have a pile of a certain brand of jet and you want to use them, it's up to you. I've seen and tuned Keihin carbs jetted with Mikuni jets that "squeak" that last 1/2 turn (the threads are .05mm pitch different) and vice versa. Heck - I've even used dynojet jets if that's what's available.

SO.....If you are using a particular brand of jet, don't swap brands of jets using this dj and Mikuni cross reference chart.

If you are drilling jets (reaming is preferred, btw) then, you'll likely find that a Keihin, dj and Mikuni jet, with the same orifice sizes, flow very similarly.

If you take the decimal inch size and multiply by 25.4, you'll get the metric dimension and the Keihin / Factory Pro jet sizes.

Example: .0390" hole x 25.4mm = .9906mm hole (or essentially a "100" Keihin or Factory Pro "393 K Series" 100 main jet.

Thanks -

Marc Salvisberg
Factory Pro Tuning
 
#16 ·
Marc, the reason I was confused about the brand was that I got the bike from my brother and hadn't checked anything :eek:

I'd like to ask about an actual jetting issue I have with my bike, but topic hi-jacking is not viewed with keen eyes here.

Would you mind if I PM'd you? PS! I will not hold it against you if you object, so do not be afraid to tell me to mind my own business if you have better things to do that chat with frustrated triple owners ;)
 
#17 ·
i recently bought some Emgo Shorty Megs, though i haven't even received them yet i'm starting to figure out that i'll have to re-jet the bike for it to run properly with them installed. if i buy the Factory Pro jet kit for the Legend, is there some type of directions or recommendation for the set up i should use? i know we have a proven set-ups thread but this is rather specific to a brand so i figured i'd ask. i enjoy tinkering with my bike but don't want to needlessly waste time pulling the carbs more than once or twice
 
M
#19 · (Edited)
The end result of any jetting job depends on either work or luck.

If you grab whatever somebody else does and it works perfectly for your bike in your part of the world -- That's good luck.

If you try your luck, and you don't get optimal results, then, you revert back to word (we call that "bad luck")

The dynojet and Factory Pro jet kits were both designed differently - one with whatever works best on uncontrolled "8 second / 4th gear" wacks and the other, with a combination of stable steady state tests, backed up with controlled rate sweeps using a 4/5 gas EGA to help guide tuning, which makes sure that things aren't too rich. (hmm... guess which one's ours)

There are slight (generally a main or so, a clip or so and a 1/2 turn or so) differences in different exhaust systems.

The biggest difference is what one does to the intake side - air filters, snorkels and extra holes will (not "might", but will) affect the optimal main, needle height, float height. I'm guessing that there's someplace here where that's listed.

http://www.factorypro.com/tech/carbtun.html

That link describes a decent procedure for proper fine tuning.

If someone wants to copy this into a new thread, that's ok -

Thanks,

Marc
 
#20 ·
thanks for the quick reply, i'll be picking up a set from you guys by the end of the week!

pathunderbird said:
Last week I installed a Factory Pro UK jet kit or as they call it carburator recalibration kit. It came with 40 pilots, 5 clip needles, 100,102,and 105 main. My bike is 01 Tbird with Kehlin Carbs. My only trouble came as I set the carb height wrong, cutting off fuel to the middle carb. Set the float height correctly, put the carbs back on the bike. Used 40 pilots, second clip on needles, 105 mains, and 3 turns out on pilot screws. Took the snorkle off, tie wrapped the side cover on. The bike warms up much faster, pulls stronger in all gears, and no back firing under de-acceleration. Bought the kit on Ebay for $43. Called Factory tech and they were very helpful. Anyone out there wanting to jet thier TBird, this is a great place to start. Im very pleased with the way the bike runs and pulls now.
Click to expand...
probably use that set up as a base line though i'll be running a K&N in-box filter with Emgo Shorty Megs...will keep you guys posted when i start the project in a week or two. i'll make sure to take video in case hilarity ensues :cool:
 
M
#21 · (Edited)
Legend JJ said:
thanks for the quick reply, i'll be picking up a set from you guys by the end of the week!
probably use that set up as a base line though i'll be running a K&N in-box filter with Emgo Shorty Megs...will keep you guys posted when i start the project in a week or two. i'll make sure to take video in case hilarity ensues :cool:
Click to expand...
Buy from one of the site sponsors - see if you can get a clue as to what jets you might need extra if you mod your airbox - get them at the same time. If a site sponsor can't help.......

One of the first rules of relaxed tuning - "Just assume that whatever you put in the carbs the first time... Will be wrong."
So - get it over with. <wink!>

http://70.141.63.105:8080/image1

Funny what a live dyno cam will pick up. I was doing a Benelli Amazona with Tuneboy over the weekend -
 
M
#24 ·
What?? The BEST jet kit in the world for a Triumph and no site sponsors sell them?? :)

Why... I oughta......
be a site sponsor......

I'm sure that there are site rules about sellers soliciting sales - but you want a TD09 kit -

Star can get it for you - Call and ask -

Marc Salvisberg
 
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