Accelerator Pump

Ever since rejetting 165main, 48 pilot, pulling snorkle, uni air filter and w/bros headpipe and silencer Ive had high rpm/hard throttle sputter. Last night I went in to diagnose it and think I found the problem. I saw that there is a pin shaped like an allen wrench that goes down into the accelarator pump (the straight part of it), it has a small black boot on it where it goes into a brass fitting on top of the accelarator pump. The boot was not properly in place so I put it in the correct position. At the top part of this allen wrench shaped pin,(the bent, horizontal part) was attached to NOTHING. I looked at it an surmized that it was most likely supposed to be attached to a black hard plastic half moon shaped piece that has a decent size spring attached to it. I managed to get the allen shaped pin into the hole on the black plastic piece as it appeared that is where it should go. By then it was MIDNIGHT so I couldnt ride it around the block but did start it and it sounded and felt good, good throttle response. Is this where that allen shaped pin is supposed to be attached to???? I checked my manual but even then it was hard to tell. I sure hope so, it was a big pain in the ass to get it in there. Sorry if this is too confusing, Im hoping some of you just know from experience what I am talking about..

I don't know for sure what the pin attaches to, but if you turn the throttle and the pin goes down AND results in fuel being squirted in the intake, it's connected properly.

Hope this helps. I'm sure you knew this already, though.

Dr. BillZ, thanks for your reply, I knew I could count on you! Actually, the black plastic piece I refered to pivots UP, I beleive that when throttle is applied hard, it pivots UP, allowing that pin to move UP and perhaps allow more fuel to pour through?? thats my theory at least..

Yep, that 90 degree metal thing coming up from the pump should definitely be attached to that "black hard plastic half moon shaped piece that has a decent size spring attached to it".

I wonder how it got loose in the first place?

It would be interresting to know the difference it will make once you have it reattached, that pump squirts a descent amount of fuel in to the carb (when connected :) ).

Hi Paul,

The accel pump should not give you high RPM sputter. If you rejetted and did mods it may be that you are now making enough power at hi-RPMs to hit the revlimiter.

Good to know that I have attached that pin properly, unfortunately, I took the bike out this weekend and still had high rpm sputter.. I really dont think it is the rev limiter though, I mean sometimes Im not even hitting it that hard and sputters like crazy! It gets worse when it is hot..

Going to a bigger main jet and having a hard throttle sputter that gets worse when the engine is hot, sounds like a rich main jet to me. Try going back to your stock main jet and see if it helps. Do a plug reading with the 165 and see if it shows rich.

Cal, thanks for the response, I did change hte plug and it looked ok, not overly wet but I hadnt been riding it for awhile either. It seems that the bike is running rich though, my next thing IS to lower the main jet and see what happens, thanks again

that black arm pivots clockwise and pushes the inverted 'L' pin down to pump the fuel.

the APJ is a useless piece of **** . but i haven't made my mind up yet!

paul, your bike needs that APJ at low revs only. if your bike was running fine without it, LEAVE IT OFF!!!

become the first DR owner to be able to set his bike up without the confussion of a bucket load of neat fuel being dumped in.

yes your bike is running rich higher up the revs. it sounds like you're not too sure where the different circuits work though. your MJ shouldn't be far off so what i recommend is that you go riding less the rad fanny flaps, one bolt in the seat, one in the tank and do a needle check.

simply ride your bike along the smoothest road you can find flat out. close the throttle for two seconds and then gun it. remember how it felt.

drop the needle and if it's better do it again and again!

eventually you can close the throttle in top gear from flat out and listen to the back popping. if it doesn't happen for 50/100m then your needle is still rich or is now ok. may need to come down one more.

the easiest way is to do it until you get the back popping. this back popping shouldn't be mistaken for the same noise that starts after you closed the throttle back 300m. that's your pilot circuit.

when you do get it, if it's only softly once or twice=lift the needle half a clip. if it's heavy go back up one.

try this test and you'll be sorted. I'm CERTAIN.

check my signiture. you boys have got a lot of work to do. good luck.


[ November 27, 2001: Message edited by: Taffy ]

Just a thought for food here but:

I never had the hi rpm sputter til I put on the yosh or at least I never heard it. We hit the rev limiter yesterday and it is clearly different.

Let me know what you find as it may make it easier for me when I go into battle with the FCR.

Just a quick update for any interested parties.. Spoke to White Bros., they indicate for the headpipe and Pro Meg Silencer I have that a 148 Main Jet is the way to go.. the 165 is apparently too rich. I am going to pick up a 148, put it in and will give an update. Its just strange because it seems EVERYONE says to go 165?? Oh well, I will try the 148 and see what happens.

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

  • Similar Content

    • By BikeChimp
      I'd like to turn my UK 2004 DRZ400S back to stock airbox (snorkel) and jets, needle shim position etc
      When I bought it the PO had fitted a Sigma6 kit and done the 3x3 mod but is doesn't have a tapered needle like the JD and other kits. Took me ages to get it running right, however it still runs rich and I'm fed up of arsing around with it. 
      So I've bought a standard airbox without 3x3 hole, stock exhaust.
      Q1 The Suzuki manual says this Mukuni BSR36 (29FA) carb should have a 142.5 Main Jet but the Clymer manual say its a 135.  In UK everything's from sea level to 1000m. I'm in Sheffield so nothing gets above 500m even in the Peaks (Hills). Any UK owners or anyone else know what the correct jet should be?
      Q2 Says the original needle is a '5DH36-2nd'. The needle has 5 notches on it. Currently set at 2 clip from bottom. The Suzuki reference says needle is 5DH36-2nd, Does the 2nd bit mean 2nd from top or bottom?
      Q3 - Does anyone have a detailed photo of the shim order just in case it was assembled wrong. (mine is attached)
      I know most people on here are going to be horrified I'm taking back to stock but any help on above would be really appreciated.

    • By Bgringo
      I've read a lot of threads about this but still haven't found exactly what I'm looking for.  I'm pulling my 2004 DRZ400S out of storage sometime this week and getting it ready for the season.  I live at 9,000 ft, but my first ride of the year is probably going to be at around 5,000 ft.  I was going to pull the 145 main jet I'm running and put in the 150 adjusting the needle from the 2 clip to the 3rd, then re-jet once I got home.  I already have the extended fuel mixture screw in place so I started thinking that I should just run the 150 jet set up and adjust the fuel screw to compensate for the higher elevation where I'll be doing most of my riding.  I will be going down in elevation for rides until late May or June depending on snowfall, but riding on the street when I'm able.  Are there any disadvantages with this?
      I'm new to posting on this forum, so please forgive me if I didn't get the right search words in and there is already a post about this.
    • By Markl5557
      I am currently running 10w 40 Belray non synthetic and I want to switch to full synthetic amsoil .... is it ok to switch from regular to synthetic? I have read it’s not safe to go from synthetic to regular can someone explain if it’s safe to go from regular to synthetic!? Thanks !
    • By RockyMtnMark
      Good Morning,
        Last night I measured my valve clearances for the very first time (I know...) on my DRZ400S.  It's a 2002 and I've owned is since 2011.  I bought it with t's got about 15,000 miles on it and most of it's miles these days are on dirt.
      Intake specs are 0.10-0.20 mm.  Exhaust specs are 0.20-0.30
      My intake valve clearances are in spec, forgot to write them down.  My exhaust valve clearances are between 0.1778 and 0.2032 which is slightly out of spec.  They are no more than 25 microns out of spec.  My question is, do I really need to shim these?  Will this kind of out-of-spec cause performance, mechanical, or other losses?  As far as I can tell, I'd have to buy a whole shim kit which is like $80.  Thanks!
    • By Zach440
      Selling my 2009 Drz400sm. Been a great bike but it’s time to let go . Not looking for any trades - spring is just around the corner ! Located in northern Virginia . Cash only $4200- willing to negotiate I have some wolfman luggage options available as well. Love to make a package deal for someone 

      -11640 miles . Mild off-road never wrecked.
      -Oil / filter changed every 1500 miles
      -New did chain , brake pads , front sprocket at 10400 miles .
      - valves checked and within spec at 10,000
      - jetted with JD kit and 3x3 mod
      -doubletake mirrors
      -waterproof usb wired and located next to Speedo
      - drc large foot pegs , barkbusters with integrated turn signals . 12oclocklabs tall delete with upgraded circuit board
      -thumpertalk case savers
      -sergeant seat (amazing) and Clarke 3.9 tank (190mile range )
      - fog lights wired in so they shut off with high beams
      -Shorai lithium battery
      -led headlight

      - stock gas tank and seat will be included

      The bike is dirty in photos and I apologize my water is currently disabled outside due to freezing temps . Radiator guards and skid plate NOT included but can be for some extra $$. Rear tire could be replaced but front is fine .