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Dynojet Kit install – with AFR meter

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My Dynojet kit from ProCycle was waiting for me in the mail when I got home from a business trip a couple of weeks ago. :lol: The kit is installed and tuned now and the results are outstanding. :lol::banana:There is a significant increase in performance (2nd gear power wheelies, and 50 + MPG). All good. :ride: However there are some issues with the installation that surfaced and the AFR meter continues to teach me lesions in humility. Once again, the facts revealed by the broadband O2 sensor and AFR meter were not exactly what I expected.:smirk:

The bike I am experimenting on is my 2008 DR650 that has a basically stock motor except for a ground out header weld. It has an Innovate AFR meter installed with the O2 sensor in the header. The best setup with the stock needle for this bike is with the snorkel removed, stock jet, and no shims on the needle. This set up gave very good AFR readings and increased performance (easy first gear wheelies) over the stock configuration that had the snorkel installed. (Many report that they need a .030 shim to run well in this configuration but not my bike)

There are 4, 1” holes drilled in top of the air box that I can tape over or uncover to help with tuning.


But as I discovered in the post below, the stock needle will not support a more open air box. If it is shimmed enough to give good mid range readings, it gets way too rich at just off idle. I had resisted going to the DJ needle because I expected that it would be way too rich in the ½ to ¾ range due to the radical taper as compared to the other needles. Also I have seen a lot of posts about poor gas mileage with this needle. Turns out this is all wrong! I am now convinced that these poor mileage problems are directly related to the installation issues.

The first issue is the “D” shelf problem. This is not big news as it has come up several times before on this forum, but for anyone new it is sure to cause problems. MX_Rob did a great job of describing this issue in this old post::lol:


09-24-2010, 08:31 PM

Bottom of the slide... right at the hole where the needle goes through the slide. The open face of the clip should face the D shelf to prevent it from binding on the side and to allow it to center itself properly in the needle jet. It is a poor set up as far as retaining the needle goes. The plastic spring guide is supposed to hold the needle firmly in place in the bottom of the slide. But the D-shelf prevents the guide from sitting flush against the clip. In DJ's instructions they tell you to place the washer that comes in the kit on top of the clip. It's an attempt to make up for the D shelf but poorly executed. The washer itself is actually too big and binds on the side of the D-shelf... beside that it is not thick enough to make up for the height of the shelf anyway. In either case the spring guide sits cocked to one side. I did a mod to my spring guide in the Needle Comparison thread for this reason.

So if you follow the DJ instructions you will have a mess. The needle clip and washed will bind with unknown alignment. Rob did an elegant fix by making an improved spring guide but I am more of a hack so I just made a fat shim to replace the washer that came with the kit and ground one side off of it to clear the shelf. ( A “D” shaped spacer to clear the “D” shelf if you will)


The shelf is .080” high so I made my spacer about .0075” so when sitting on top of the clip, it is just proud of the shelf. It is not critical but if it is too high it will not allow the hole in the spring guide to go over the top of the needle. I used fiberglass tubing I happened to have but any stiff plastic or aluminum tubing should work. My spacer is easier to make but a bit more of a pain to get all aligned when installing than Rob’s solution.

The second big issue has also come up several times before but the jetting guidelines that come with the kit are way too rich. The bike will run OK but mileage will suffer. A lot. :prof:

I started off with snorkel removed and the 4 1” holes drilled in the top all uncovered. I like the holes approach because I can recover and run different experiments by covering and uncovering the holes with duct tape. To start, I selected the DJ 155 Main jet and set the clip in the 4th slot. This was way too rich in the mid range. So I dropped the needle by moving the clip to the third slot. Much better. WFO gave high 12’s to low 13’s and cruise at most speeds in the low to mid 13th’s. The bike felt good and I can now reliably get the front wheel up in second gear with a little bounce and pull on the handle bars. Lacking a dyno (the right tool!) my best method to gauge power is by how easy it is to wheelie. Fun too! :smirk:

So I dropped the needle one more slot to the second position from the top. This gave leaner readings as expected but still a bit richer than stock. Low 14’s during cruise. This should give very good MPG ratings but I didn’t keep it there long and went back to the 3rd clip position but with a .020 washer (ground off on one side to clear the “D” shelf) to split the difference..

I did test MPG there over 4 fill ups and got around 50 MPG average. Best was 56 MPG but I was hypermileing just to see how much I could get. Worst was 46 when I was performance testing, one 49 and one 52. I am happy with that.:lol:

So where was the surprise? I expected the radical taper to cause the readings to go richer as I gave it more opened throttle. i.e. cruise speeds in 5th gear increasing 40, 45, 50, 55. . . and so on. NOT!:lol: What I saw was the exact opposite. Just as with the stock needle when running with an opened air box, it got leaner as speed increased until the main jet started kicking in at higher speeds. But not near as much as the stock needle. It actually could use MORE taper to flatten out the response.:lol: But it is about tapered as it can be now. At least on my bike it works that way. YMMD.

More experiments;

DJ recommends a 160 main jet for opened air box (they say take the side cover off) . This time it did get exactly what I expected, it was way too rich. So I drilled 3 holes (¾” D) in the side cover.


This helped a little for WOT but no impact on mid range. The interesting thing to me is that I could cover and uncover these holes while I was riding and watch the AFR meter in real time.

As A final test of the 160 main jet, I pulled off the side cover. So with the side cover off and the 4 holes in the top opened, I think the air box was as wide opened as you can get. It was still a little too rich on the 160 but not too bad. I think it is a little stronger but is so not a big difference if any on the wheelie meter. But too much noise! :eek:I went back to the 4 hole open, side cover on (side cove holes covered) configuration and the 155 main. The needle is at third clip and a .020 washer is under the clip. That is where I am going to stay for now. (until I think of a new experiment or the next mod:D)

I feel even more strongly now that the opening of the air box yields it’s best results with the first small increases (like removing the snorkel) and you get diminishing returns after that but more noise. With the snorkel out and the 4 1” holes, I have almost 4 times the intake area as compared to stock. (5,87 Sq” verses 1.5 Sq”) After that, increasing the area will continue to flow more air as you open it more but not much. YMMV

I totally confirm what ProCycle said, that this DJ needle is about the best available for the BST carb and the opened air box. It is still not a pumper carb or EFI but a big improvement over stock. If you want to go with the DJ needle, I think I would go with the ProCycle complete kit, that comes with the correct screws that you will want to replace and other goodies. In my case I already had all that so just ordered the DJ kit.

Have to go now my brain hurts.:lol:


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