pace Posted August 24, 2003 Share Posted August 24, 2003 I note that the Honda microfiche lists a #142 or alternative #140 mainjet. The dynojet kit includes a #136 and #140 mainjet. They [Dynojet] state that the #136 should be used on a bike with stock exhaust, and the #140 with an aftermarket exhaust. This leads me to assume that the stock mainjet as fitted from the factory is the #142. However, what I'm really trying to assertain is the numbering scheme used. Some manufacturers use a larger # to indicate a leaner jet, while others do it vice-versa. Given the information above, am I correct to assume that a smaller # indicates a smaller (leaner) mainjet on this bike? -Pace Quote Link to comment Share on other sites More sharing options...
pace Posted August 24, 2003 Author Share Posted August 24, 2003 Also.. The fiche lists the #140 and #142 part numbers as: 99101-GHB-1420 (#142) 99101-GHB-1400 (#140) So I then went to Ron Ayers and tried the following part # searches: 99101-GHB-1380 [result - mainjet #138] 99101-GHB-1360 [no part found] 99101-GHB-1340 [no part found] 99101-GHB-1320 [result - mainjet #132] 99101-GHB-1300 [result - mainjet #130] I got the same results at servicehonda.com. My hunch is that the #138 is an alternative 'XX part for high altitude owners, and that the #130 and #132 are from a different machine which likely uses the same jet type (for example, 99101-GHB-1200 #120 is the stock CBR900RR main jet). The reason this interest me is that the dynojet kits are painfully overpriced for what you get, as well as being ill-suited for very high altitude riding. If I can source identically sized OEM jets, I'd prefer to go that route. Too bad the #134 and #136 come up with no match. Comments? -Pace Quote Link to comment Share on other sites More sharing options...
tomek Posted August 24, 2003 Share Posted August 24, 2003 Dynojet`s jets have different flow characteristics than Mikuni or Keihin ,well,jets.They can`t be really compared to each other.They are not the some in flow vs pressure or vacum area.I don`t remember but I think Dynojet claims that their mains flow more fuel at part throttle then Keihin or Mikuni with the same number. Quote Link to comment Share on other sites More sharing options...
pace Posted August 24, 2003 Author Share Posted August 24, 2003 Interesting. Thank you! I wonder if that is more indicative of needle design, since technically speaking the main jet is only 100% in control of fueling at wide open throttle (or close to). At partial throttle its a combination of the needle sizing and profile and the mainjet orifice. I note that the Dynojet kit includes a replacement needle.. -Pace Quote Link to comment Share on other sites More sharing options...
Pete in PA Posted August 25, 2003 Share Posted August 25, 2003 Dynojet's # system has no relation to factory #s. A DJ 136 is not the same as a factory (Kehin?) 136. If you had an accurate way to mike the hole size you could get stock jets to match. But to do that you would need a jet kit. :roll: Quote Link to comment Share on other sites More sharing options...
pace Posted August 25, 2003 Author Share Posted August 25, 2003 Thanks, that's good to know and confirms what tomek stated earlier. The plot thickens... www.factorypro.com have some good info on Keihin jets and will supply replacements that use the same numbering scheme. It seems that our bikes come from the factory with two jet sizes; #140 on the outside cylinders and #142 on the inside cylinders. This explains why Honda list both parts in the microfiche. Can anyone just confirm that a smaller number is a leaner jet? If so, I'm going to start by moving to the #138 for all four carbs (since it's readily available from Honda) and then see if I can source a #136 or something close. Bear in mind all my riding is between 5,500 and 9,000ft - my bike is running pig rich with the factory jetting. Secondly, reading the jetting guides at the factorypro site, I come to the conclusion that our carbs use the "393 series, 5x0.75" jet, also referred to as the Keihin "small, round, slotted". Can anyone confirm? TIA. -Pace Quote Link to comment Share on other sites More sharing options...
RodeRash Posted August 25, 2003 Share Posted August 25, 2003 Smaller number is leaner. Most 4 cylinder bikes use one step richer jets for the inside two cylinders, as they tend to run slightly hotter. Try 136's in 1 and 4 and 138's in 2 and 3 for your starting point. Quote Link to comment Share on other sites More sharing options...
RodeRash Posted August 25, 2003 Share Posted August 25, 2003 One other thing, get to know your dealer. I have never had to buy a jet. The local dealerships have been willing to swap jets with me. Quote Link to comment Share on other sites More sharing options...
demon Posted August 25, 2003 Share Posted August 25, 2003 3 words- Fuel Injection Baby self-compensation for air pressure I'll NEVER go back to a carbed bike!! :banghead: Quote Link to comment Share on other sites More sharing options...
pace Posted August 25, 2003 Author Share Posted August 25, 2003 RodeRash - thanks! Demon - :fingers: :wink: -Pace Quote Link to comment Share on other sites More sharing options...
pace Posted August 25, 2003 Author Share Posted August 25, 2003 RodeRash - what needle clip position would you recommend I start at with the stock needle and the jet sizing mentioned? Also... how in the hell does one get the needles out of the diaphram/plastic-retainer??!? -Pace Quote Link to comment Share on other sites More sharing options...
pace Posted August 26, 2003 Author Share Posted August 26, 2003 Well I guess the factory needles do not have a clip (nice going, Honda). Instead I removed the single washer which will drop each needle just a tad. It seems that the available Keihin jets drop from 138 down to 135, and then continue decreasing in increments of 5. I picked up four #138 jets and two #135 jets. For the moment I have just installed the #138 for all four carbs. Not sure whether I want to try dropping the outside two cylinders to the #135. That seems like a big drop right off the bat. Will report butt dyno results later this week. -Pace Quote Link to comment Share on other sites More sharing options...
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