HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
Ynahg

Jetting after APJ mod !!HELP!!

25 posts in this topic

Last week I rebuilt the the engine, new piston rings, new distribution chain, valve clearance etc...

I also modified the AP to 0.75 s squirt. Before the mod my settings where : MJ 170 PJ 45 PS 2 turns DXM #4 (DXM #4 = DTM #3).

First tried with the same settings after the mod, but the engine dies when I touch the throttle. :) Raised the needle to clip 5 to compensate the APJ mod, now I have no bog from idle to 1/8 but a big bluuurp from 1/8 to 1/4 or even 1/2. Also tried a 175 at #3 end #4 but dint seem to work ether. I swear I'm trying to stay cool and try to understand what the **** is happening, too rich too lean, but after having dismounted, changed settings etc... for 10 or 15 times i'm loosing my patience. :D

So any input would be appreciated.

Thanks :D

Share this post


Link to post
Share on other sites

The DXM#4=DVM#3=DTM#2.

I don't think you are too rich on the needle yet. The '99 US WR came with DTM#3 or even DTM#4 (DXM#5-6), #45 pilot, 2 1/4 turns, #168 main. Most riders considered the #168 too lean as the YZ used a #175 with open exhaust. The KTM 400/520EXC have #175 mains also.

Try clip DXM#6 , #45, 2 1/4 turns, #175 main.

If the top end is rich, go back to #170, bottom end- adjust the fuel screw.

Hope you are successful,

James

Share this post


Link to post
Share on other sites

:) However by the same token your climate is the same as mine....europe/UK and I found a 170 toooo rich and a 172 blo*dy daft! I run a 168 and I am considering going SMALLER to see what effect it has!,

My symptons were identical to yours with the bigger jets in and the 168 sorted it!

Share this post


Link to post
Share on other sites

Thanks for the added help Guy. Your exhausts are probably the same too. What needle and clip position do you use? (OBDXM?)

Share this post


Link to post
Share on other sites
:) I'm running a DXM clip #6, tried clip#4 and a 170 it didn't like it so 168 DXM clip#6 :D

Share this post


Link to post
Share on other sites

I tried MJ 170 #6 yesterday, it runs better. I will try the 175 for more top end. The only symtom that still bothers me is that the engine needs lots of time to come back to idle, it 's kind of hanging at maybe 2000 or 2500 rpm.

BTW Guy, it's strange you use a 168, this was my stock setting and there was really a lack of top end. My dealer also says the stock jetting is often too lean.

Anyway thanks for your input guys.

[ January 14, 2002: Message edited by: Ynahg ]

[ January 14, 2002: Message edited by: Ynahg ]

Share this post


Link to post
Share on other sites

agree with guy

168 or 170 max MJ

this will allow your lifted needle to work at those low revs and the MJ will stop the richness that sounds like it's killing your mid range.

don't go back to 175 if you can help it. a smaller MAJ woulkd help your top end.

have you got a #75 or a #100 PAJ fitted?

Taffy

Share this post


Link to post
Share on other sites

The PAJ is stock, i think it's a 100. I'll try the 175 MJ to be sure but the the 170 indeed seems to be the best compromise.

About the idle hanging at higher revs.... any idea what this could be. It sounds like a lean spot (like when you run out of gas ?). I have to wait for at least 15 sec till it comes back to idle.

Share this post


Link to post
Share on other sites

the #75PAJ would cure that straight away. yes you do have lean jetting. some say up the PJ but i think you know by now what i think.

i think you've mistaken your needle for the top end MJ.

the MJ is flat out in fifth

the needle is when you whack it in fourth from, say 45mph etc.

your needle is down two clips on guy or me. the reason it's not lean is because the MJ is chucking fuel in. so;

175MJ and DXMc4 (ok mid, rich top)

becomes;

168MJ and DXMc6 (ok mid, ok top)

as i've said before the MJ controls the needle completely.

Taffy

Share this post


Link to post
Share on other sites
Originally posted by Ynahg:

BTW Guy, it's strange you use a 168, this was my stock setting and there was really a lack of top end. My dealer also says the stock jetting is often too lean.

Anyway thanks for your input guys.

[ January 14, 2002: Message edited by: Ynahg ]

with a 168 on clip #4 the top was a little "breathless" but I'm running clip#6 or even #7 which loosened up the top without flooding the bottom!. A 170 was crap,everywhere!

just try it...168 clip#6, 10 mins work and see what you think, you have nothing to loose :)

Share this post


Link to post
Share on other sites

guy i'm sending you a #170 MAJ. you have no choice but to trey it and that's an order!

it'll increase your top end by five mph

Taffy

Share this post


Link to post
Share on other sites
:) OK Taffy, I daren't argue with ya! :D I'll give it a whirl and report my findings on the usual Bat channel! LOL :D I checked, and I'm running the stock #200 MAJ at the mo, You've been "cock on" with everything else :D:D

Share this post


Link to post
Share on other sites
:) Taffy, I'm going to drop the DMM in at clip#4 to start with, does this sound somewhere near my DXM #6? or do I need to be lower...higher... lower, higher hmmnn, I feel that could be a game show somehow! :D

Share this post


Link to post
Share on other sites

guy

the middle suffix is what you go by and there are two letters to each clip change, ok?

so there are ten letters between M and X ok? and that is 5 clip positions. BTW we don't count the letter 'O'.

DXMc6 is the same as DMMc1

so start on the minimum position. clip 1

then try the 170MAJ

then come down ten on the MJ and then you can go up 2 or 3 clips on the needle

don't panic, as long as you take it nice and steady each change will be an improvement and a step in the right direction. look at the missile!

you won't lack for motivation whilst it's going well. just don't try it at 3pm in the afternoon and expect to have valid result in an hour.

Taffy

Share this post


Link to post
Share on other sites

Ok ok I'll try Mj 168 DXM#6 this evening. Just afraid the top end will suffer. Concerning the richer (smaller) MAJ, will this only help the top end or could this cure the hanginhg idle thing ?

I keep the faith :)

Share this post


Link to post
Share on other sites

they are seperate. the MAJ helps get the the curve of fuel at the top end right. the PAJ is there for the bottom end.

at the risk of saying it again and again, you need the amount of fuel to tail off when you get past max torque. if it bleeds lots of air in through a #200MAJ that means the curve of fuel dives down.

with the largest jet-the #200-it dives down the most. now on a piece of paper draw a curve (#1)gently up and then slightly down so that the peak is 3/4 the way along. this is the curve you want.

now starting from the furthest point to the right at the bottom of the "drop-off" you draw (#2) steeply up and then down to the "drop-off" on the left hand end.

why? well your jetting is tested by you for "top speed" and therefore jetted for max revs so it's only right your two lines should join here and it's only right they should start together at the left where the jetting is unaffected,ok?

so you should have one low curve and one high curve with their peaks 3/4 along.

now the big hump in the middle is the fuel you're chucking in at max torque which is 7-9,000 revs to you. it's pouring it in and it dulls the throttle.

SO WHAT YOU DO IS PUT IN A #160MAJ AND THIS BLEEDS IN LESS AIR AT THE TOP. SO NOW YOU GET MORE FUEL. so now i want you to draw a third line (#3). this one follows the upper path to the top of the hump and then stays high exactly the same distance above the lower line and therefore for this purpose looks like a railway track with these two lines (# 1 & 3). ok with that?

what does it mean? well you have been getting too much fuel at max torque and now your getting too much at the red line with the #160MAJ as well and it's rich at max torque and rich at max revs.

so what the phuq i hear you say "what did i do this for?" well what you do now is come down 10-15 on the MJ and the upper line drops neatly onto the lower line and the bike goes like PHUQ.

now i could add more and fry your brain but just try and take that in first ok!

on another subject, definately change the PAJ to #75. but ynahg you're starting to sound like our cousins over there so don't talk-WALK!!!!

Taffy

Share this post


Link to post
Share on other sites

Taff,

Sounds like you should "RoadTrip" to Belgium! Maybe meet Guy, Missle and Ynahg and have some brews and rides Ynahg's bike!

Share this post


Link to post
Share on other sites

:) Ah have seeen the light...... That explains a lot...thanks Taffy, I feel a trip to my Yam shop to order a "Boat load "more jets..he he!

Taff, I'll let you know how I get on, cheers m8 :D

Share this post


Link to post
Share on other sites
:) Ynahg, Have yo tried that 168 clip#4 yet, if so how did it go??? :D

Share this post


Link to post
Share on other sites

I tried 168 #6. It works quiete fine. But still tends to bog after 1/8. Will try 168 #5 and #4. Ordered a 65 SJ and 100 PAJ (to de-octopus the thing) and a 160 MAJ for the top end.

Guy do you still have a stock exhaust ? (Mine is a YZ exhaust with home made spark arrestor for the noise)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0