DMM Trials and Results

7 replies to this topic
  • Tim_in_WA

Posted April 10, 2002 - 12:56 PM


OK, here ya go Taffy and James: I know it's a lot of info, but I know a lot of us are (or will be) trying the DMM needle, so I'd appreciate some interpretation and feedback on the following results. This might help others to avoid my mistrials.

The Bike: 2000 WR400, WR Timing, Vortip, Open airbox, BK Mod., stock air jets (200 MAJ, 75 PAJ), 60 degrees F, 1000' elev.

Jetting before trying DMM needle: Stock DRQ #4, 172/45PJ/FS 1.75

Test #1: DMM #3/170MJ/45PJ/FS .75 turns:
Pulls hard from low rpm, but has minor stumbling between 1/8 to 1/4 throttle. Top end smooth and continous- no hits. Very slight backfire on hard deceleration (felt lean). Bike runs with fuel screw all the way in.

Test #2: DMM #2/172MJ/42PJ/FS 1.25 turns:
I know, I made too many changes on this one. Felt lean on the low end with the 42 PJ. Low end bog noticeable, especially when whacking throttle open from idle. Still minor stumbling at 1/8 throttle at high, constant rpm. No backfire on deceleration. Bike still runs with fuel screw all the way in (???).

Test #3: DMM #2/172MJ/45PJ/FS .5 turns
Best so far. Still very minor stumbling at 1/8 throttle at high rpms. Also minor stumbling at constant high rpm (1/8 throttle) in neutral. Still bogs a little if whacking throttle open from idle, but when riding, no bog whatsoever. Pulls hard all the way through the powerband. Still runs with fuel screw all the way in. Checked plug after running at 1/8 throttle (and while stumbling): plug look good, slightly tan, but may be a hair on rich side.

Test #4: DMM #1/172/45/1 turn
Even better yet. Still minor bog when throttle whacked open at idle. Wheelie monster on low end. Still extremely minor stumbling at around 1/8 throttle, but hardly noticeable. RPM's just start to increase when fuel screw turned all the way in, but gets rich at about 1.25 to 1.5 turns. Ran best at .75 to 1 turn. Top end smooth and continous, but feels a little flat from 3/4 throttle and up.

I'm thinking that I'm still running a little rich on the low circuit, but the bike seems to run better with the 45 PJ. I haven't messed with the pilot air screws because: a) I didn't order any, and :) because all of this so far has been kind of a pain, and I hate the idea of adding more variables into the equation. But at this point, I'm definitely open to suggestions.

I'm thinking about trying the DRN needle, as it looks from JD's jetting program that it will be just a tad bit leaner at 0-1/8 throttle. I may also go back and try a 42 PJ with the last trial jetting, just to see, but it seems like it would be on the lean side, especially with the needle at clip #1. The stumbling at 1/8 throttle seemed to decrease with the 45 PJ. I would also like to be able to have the fuel screw set at about 1.5 turns so that in the warmer weather months and higher altitude riding, I can lean it out a bit to compensate. Am I way off base here? Comments??? Ideas??? Flames???

[ April 10, 2002: Message edited by: Tim in WA ]

  • bman

Posted April 10, 2002 - 05:52 PM


I also just switched to the DMM.
Settings= 160mj 160maj, 38pj 50 paj, 2 turns out, needle on pos 1. I tried other lower clip positions on needle but had the stumble you have. Has clean low end and does pull the front up better from just above idle. Very smooth power and also rev's faster. My Wr ran very good before. I even beat a KTM 520 SX in a fire road drag race before dmm change. Ok it was very dry and I hooked better than he did. Hey, I still beat him. Only road for a hour last Saturday but it felt better than before. Maybe 25% better down low and about the same power as before. Remember my bike ran really good before. Seems odd that I can make the same or better hp on less fuel. My old setup= dvp pos 4,172 mj 200 maj, 50 pj 100 paj. Thanks to Taffy for his help. It's kinda cool that a guy on just about the other side of the planet helped make my motorcycle run better.
PS you need to tell us what air jets you are running.

  • Taffy

Posted April 10, 2002 - 09:08 PM


the reason you had a low end stumble is because the 45/75 pilot ratio on your bike works. the trouble is that as a pair they're too rich. then when you go to 42PJ you're ratio is too lean and you get the stumble.

you need to go to 60PAJ with that 42 and you'll be ok. try them as a pair and then do the old snap wheelie tests with your kouba in hand.

what's your APJ setting, do you know?

i make no apology for the fact that i didn't know yam make a DRM and DRN needle. i recommend this needle above the DMM as you will be working on the middle clip.

but DMMc1 is still good as long as the MJ is low enough. 148/150 quiet pipe and 155/158 open pipe.

that will get rid of your stumble.


good luck :)


  • Tim_in_WA

Posted April 11, 2002 - 05:23 AM


Thanks for the suggestions Taffy. My APJ is set at about .5 sec squirt, and the stream just misses the throttle plate when opened. I'll order up a 60 PAJ and try that. As for your MJ recommendations, can I go down that low on the MJ while still using the stock #200 MAJ, even with the vortip and stock (US) exhaust? Or will I also have to drop the MAJ?

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  • Taffy

Posted April 11, 2002 - 07:25 AM


those jetting #'s are for 160MAJ. if you go with 200MAJ you are just about right if your pipe is open.


  • James_Dean

Posted April 13, 2002 - 08:41 PM


Tim and bman,

Thanks for sharing the results. The DMM top clip position was unexpected. This gets close to a stock '99 DTM#4 setting. The smaller pilot jet or leaner needle diameter help with running a richer clip position along with reduced APJ. DMN#3 is becoming popular with a few of the KTM riders using reduced pump stroke and a #45 pilot/#170 main.


  • bman

Posted April 13, 2002 - 08:56 PM


Went to a 158 mj. Runs better. Just got a call from Sudco to let me know my emm is in. I also had them send a 35 pilot (they sent the wrong pj's last time). Taffy, what would be the clip pos for emm if my dmm is on #1 ?. Should get it on Monday. Sudco is 1/2 hr drive from my home. It takes the US mail 2 days to get here. Go figure.


  • Taffy

Posted April 14, 2002 - 01:56 AM


about clip 4 will do for the EMM needle. the MJ can come down to 155 with that needle.

so it's
155MJ and EMM c4.



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