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What needle/air filter do i have? + jetting Q

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Heya,

A while ago i bought a used DRZ 400 SM, previous owner told me there was a dynojetkit installed and a k&n airfilter.

Today i went for a free Dyno run as a general checkup of the motor and the guy told me the bike was jetted way to lean, he advised me to rejet.

so now i removed my carb from my bike in order to rejet, but i'm wondering how i can see if my needle (and spring) are dynojet built?

i also removed the air filter, but there was no K&N sign on it, so i was wondering if someone knows if there should be a sign on it if its a K&N filter.

then my final question, what jets etc. should i use? (currently running a 155 main)

Mikuni BSR36

Std. exhaust header with Rino slip-on

3x3 mod

dynojet kit (?)

Somewhat below sealevel

Std. airscrew

Greetings Richard

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If it's a dj needle , it will have grooves for needle height.

Kn-filter is very different from oem , usually orange on the lip going against the airbox.

SU-4000.jpg

Oem filter is a foam ,easy to see the difference.

the dj kit suggests 155 main on an complete exhausts or "high-flowing baffle"

Can't understand you are running lean , but check if the needle is in groove #2 from top .

Which rpm's was lean ?

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If it's a dj needle , it will have grooves for needle height.

Kn-filter is very different from oem , usually orange on the lip going against the airbox.

SU-4000.jpg

Oem filter is a foam ,easy to see the difference.

the dj kit suggests 155 main on an complete exhausts or "high-flowing baffle"

Can't understand you are running lean , but check if the needle is in groove #2 from top .

Which rpm's was lean ?

thanks for your reply, guess i have an oem airfilter then, because i have the foamy one.

every RPM was too lean, didn't quite understand it either, because i did have 38 rwhp and it said 78.5nm torque (which seems a bit too much to me)

what i did notice was that the origional float bowl screws were still installed and they weren't really tight, perhaps it has some air leaks and thats whats messing it up.

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Top of the needle will be painted red of blue. When you buy a jet kit, that is how they tell you which is the cold/low altittude one from the hot/high altitude one. If it is unpainted and has a series of letters stamped on the side, it is an OEM needle..

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the dj needle has no paint.

guessing does no good.you will need to acutaly find out what jetting it has.

ok, thanks, im quite sure i have the DJ needle + origional air filter, just read the bills from the previous owner and somewhere it says a dynojet kit is installed, but nowhere i read about a K&N filter.

bike was jetted as follows:

main jet 155

pilot jet * will check tomorrow

needle clip on the 4th groove from top (think i got like 6 grooves

air screw was 2.75 turns out

also got a testrun from the previous owner which looks ok, if i get my camera i will post a pic and upload it. air fuel ratio is somehwere around 12.5 and max hp is 36.6@8k rpm

this puzzles me a bit, and i've been thinking, got 2 possible explanations

- difference in temperature between the run from the previous owner and my run today is 20 degrees celcius (previous owner had it running @77fahrenheit, today i ran at 41 fahrenheit) but i don't know if this causes such a big difference

- the float boal was installed using the damaged origional bolts and it wasn't tight at all (thank god :thumbsup:) But this could be a problem... can it cause the carburetor to have air leaks because it was not tightened enough? (screws were not loose, but certainly not handtight) or would this cause other problems?

- one of the two tests i did was not executed correctly which caused readings to be off. what i don't understand is how a bike thats jetted too lean can still produce 38 hp (with my setup, which is close to standard). i would think jetting has a great influence on the performance of an engine, or am i wrong?

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saw the difference in air pressure between the two measurements was about 40 millibar, could this explain the difference? any way to solve this? like installing a bigger main jet during the winter (low air pressure) and a smaller one in the summer (high air pressure)

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ok, thanks, im quite sure i have the DJ needle + origional air filter, just read the bills from the previous owner and somewhere it says a dynojet kit is installed, but nowhere i read about a K&N filter.

bike was jetted as follows:

main jet 155

pilot jet * will check tomorrow

needle clip on the 4th groove from top (think i got like 6 grooves

air screw was 2.75 turns out

also got a testrun from the previous owner which looks ok, if i get my camera i will post a pic and upload it. air fuel ratio is somehwere around 12.5 and max hp is 36.6@8k rpm

this puzzles me a bit, and i've been thinking, got 2 possible explanations

- difference in temperature between the run from the previous owner and my run today is 20 degrees celcius (previous owner had it running @77fahrenheit, today i ran at 41 fahrenheit) but i don't know if this causes such a big difference

- the float boal was installed using the damaged origional bolts and it wasn't tight at all (thank god :thumbsup:) But this could be a problem... can it cause the carburetor to have air leaks because it was not tightened enough? (screws were not loose, but certainly not handtight) or would this cause other problems?

- one of the two tests i did was not executed correctly which caused readings to be off. what i don't understand is how a bike thats jetted too lean can still produce 38 hp (with my setup, which is close to standard). i would think jetting has a great influence on the performance of an engine, or am i wrong?

If the bowl screws were loose enough to "suck air" it would be pouring out fuel also. You are wondering how it could be lean and still have more power then stock? The stock carb jetting is really really lean from the factory. Your bike has been jetted richer it seems but maybe not enough. Get some new bowl screws and write down exactly what your current jets are and find out exactly what needle/clip postion and somebody here will let you know how you should jet it.:ride:

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If the bowl screws were loose enough to "suck air" it would be pouring out fuel also. You are wondering how it could be lean and still have more power then stock? The stock carb jetting is really really lean from the factory. Your bike has been jetted richer it seems but maybe not enough. Get some new bowl screws and write down exactly what your current jets are and find out exactly what needle/clip postion and somebody here will let you know how you should jet it.:thumbsup:

they weren't that loose, i'm beginning to think its the low air pressure thats caused the "problem"

current jetting seems to be ok looking at other people with approx. the same setup.

155 main

22.5 pilot

air screw 2.75 out

dj needle on 4th position from the top.

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the wideband on the dyno porbably wasnt getting a good reading.

the pumps and sensors need constant care which most dyno operators severely neglect.

what is part number of the kit in your paper work?

if its on 4th clip that would indicate you have a S model dj kit.

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the dj needle has no paint.

guessing does no good.you will need to acutaly find out what jetting it has.

Thanks for the correction. I take it means that DJ kits only have one needle? And there are no markings at all on it?

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the wideband on the dyno porbably wasnt getting a good reading.

the pumps and sensors need constant care which most dyno operators severely neglect.

what is part number of the kit in your paper work?

if its on 4th clip that would indicate you have a S model dj kit.

seems like a good explanation to me, tho the guy has a good reputation when it comes to tuning engines, measuring errors happen everywhere.

but what do you think of my other hypothesis, 40 millibar difference in air pressure, could that be it?

i can't find any numbers in my paperwork, what i've got is a print from 2 dyno runs, and to me, it looks ok (but i'm by no means an expert :ride:):

30kyijm.jpg

its in dutch, but i think the figures speak for themselves.

on the bottom parts with notes it says:

Dynojetkit Jet=155

Rino slip on

"Quick" (:thumbsup:) Cams

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It doesn't say much of use..

Looks like he's got the afr a bit better, but the rest of the paper doesn't say much.

Looks like he has pulled through all gears , instead of taking a run in 4th.

The nm is way off ,both in value ,and where max is.

The run is made in din ,which reads a bit higher than sae.

The operator doesn't state which jet and position of needle in run 1 ...

Learned a new word today; "Nokkenassen", can be useful sometime :thumbsup:

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just ordered the fmf power up kit for drz400s and was highly disappointed, the biggest main jet in the kit was a 136 and only 1 needle, does FMF number their jets diffrent? if so, what would a 136 be?, i haven't installed it yet because the main i have now is a 147 and its still lean.......:banana:....???

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they are close enough to mikuni jets that they interchange.

need more info than "its still lean". lean where? symptom?

i know my pilot is too big at 27.5, but when i full on then back off and hit again there is a big dead spot, trying to get the figureing right before i tear it apart again

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