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.

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