keihin / dynojet conversion myths

[dave07ex]

I'm certain that I'm not the first person to have done this but, in the process of junking the dynojet main jet that had originally used to tune the carb, I decided to take a look at how the dynojet and keihin jets matched up. I determined that the main was probably one step too small so I bought some Keihins and figured i'd start over with genuine merchandise. According to the conversion chart that's been posted on this board a number of times, a DJ #150 (which was too small) should be equal to a K #165. Being that I have no scientific way to measure the actual size of the opening, I opted to use the tapering of a needle jet to eyeball the sizes. To my amazement, the DJ #150 that I had been most recently using had an opening that appeared to be noticeably smaller than a K #162. The DJ #155 appeared to be very close in size to a K #158. As I said, this was a visual measurement of how far up the needle taper the jet would go, by no means scientific. Am I a nutcase or could this possibly be a reason that some people have trouble tuning with the DJ jets?.....
Got the K #162 in there now, gotta do some testing.

[JOHNDOE83]

you can use small drill bits to figure size better, and even drill jets to jet...lol.

also on www.jetsrus.com there is a conversion chart.

[CJM]

I firmly believe it isnt so much the jetting numbers when it comes to DJ vs whatever else-but the way the fuel is delivered thru the jet.

Buddy of mine just got an 09 450R and they threw in the HRC kit and FMF pipe/jet kit. The FMF jets look exactly like DJ and he now has a low down bog. Warranty be damned, Id throw out the jets and start over. I had the same exact problem till I put keihin jets in mine too. Low down bog that goes away after half throttle.

[dave07ex]

CJM, i hear ya there. As of now I have a REAL 162 main and I need to do more testing to determine if i'm where I need to be or not.

[CarGuy7a]

I really never had any problems with DJ jets. Now you can run into problems if you try to run a DJ main jet with the OEM Keihin needle as the tapers between the Keihin needle and DJ needle are different.

Now I did also notice an orifice size difference between DJ jets and Keihin jets. I can't remember how much of a difference there was as I went through this process a long long time ago. I do remember cross referencing the conversion chart though that is floating around and it wasn't quite correct.

As far as a difference between how a DJ jet and a Keihin jet actually runs in the quad. I couldn't tell any difference.

[dave07ex]

The adjustable needle that i'm using is a honda (keihin) needle, as far as i know. I got it from my neighbor who is the lead tech at the local honda/yamaha shop. The DJ kit that I was using was left over from my previous quad.

[400exrider707]

Originally posted by dave07ex
Being that I have no scientific way to measure the actual size of the opening


Originally posted by dave07ex
As I said, this was a visual measurement of how far up the needle taper the jet would go, by no means scientific.

Sounds like you answered your own question there...