Fuel pump change -> hunting idle? - Page 2

ABuck99 · 03-06-2013, 12:56 PM

I feel your pain, & dont envy pulling the top end apart just to check the carbs over

.

You mentioned that the new pump cycles on longer than the old one when you turn the ignition on, which means the pump is taking longer to build pressure ( old one was building pressure faster and shutting of sooner?) - So its possible there is a leak of some kind- air seeping in through a fuel line- a float sticking open- or maybe that "new" pump is not the right one or not so new?- Double check the pump by inspecting the points beneath the cover. You can pull the cover off the old one and check those points against your "new" pump.

In a perfect world when you turn the ignition on the pump should only take a second or two build pressure and shut off. Also If your pump cycles on every time you switch the ignition on- say even after 15-30 minutes there is probably a leak somewhere.

If the new pump is bad for some reason you can check it. If you want to experiment- take the points off the new pump and install them on the old pump re-install pump- test- what happens?

here is a how to on that process

"Dont replace your fuel pump- FIX IT."
http://www.advrider.com/forums/showthread.php?t=611799

bloc · 03-06-2013, 01:20 PM

Interesting.

Found a few of the air jets partially clogged and cleaned.. cleaned the bowls, double checked slide diaphragms, etc. Idle hunted really bad. Couple spits through the rear carb while warming up.

THEN,
I gravity fed the carbs from a fuel container and the idle is rock solid, goes right back where it should after revving..

Gonna try the new points on the old pump and see what happens. Or maybe a facet.

Edit: side question.. should we be able to see fuel flowing out of the orifice around the slide needle at idle? It is idling awesome while gravity fed, but it sure seems like a ton of fuel. Needles on middle clip groove.

Second edit: Yeah, the pump cycles more.. but I was assuming this one was operating at a higher pressure or something as opposed to the old one, thereby stroking more. It does only take a second or two.. but whereas the SOP for the old pump was one "click" upon turning the ignition on, maybe two.. this one goes 5 or 6.

ABuck99 · 03-06-2013, 02:55 PM

Im hooked now so keep us posted what you find- good luck

bloc · 03-06-2013, 04:51 PM

Well, I want to put more miles on it than the quick trip to get food that I just did, but so far so good. The idle seems to run up maybe 100 rpm every once in a while, but no crazy surging like before and it settles right down when you chop the throttle. I'm not sure if it was the screws, the clogged air jets, or the needle clip being too high.. but it picked up a significant amount of midrange punch as well. It wants to pull the front off the ground by itself in second gear now.. didn't do that before.

So to recap...

It appears it was the new fuel pump all along. I harvested the points out of the new pump and soldered them into the old pump housing (the old points were TRASHED) and things are going great.

I think I also figured out why the new pump was stroking more times than the old one. The points were so worn down each stroke went substantially further than in the new pump.. so it would have taken more strokes with less throw each to equal the amount of fuel. 3-5 times as much? who knows.

So yeah.. if you do something as simple as change the fuel pump and it immediately starts acting funny.. dont suspect a bunch of other crap.. suspect the pump. Even if it's brand new.

03-06-2013, 12:56 PM	#16
ABuck99 0.0 Joined: Feb 2009 Location: Georgia Oddometer: 261	I feel your pain, & dont envy pulling the top end apart just to check the carbs over . You mentioned that the new pump cycles on longer than the old one when you turn the ignition on, which means the pump is taking longer to build pressure ( old one was building pressure faster and shutting of sooner?) - So its possible there is a leak of some kind- air seeping in through a fuel line- a float sticking open- or maybe that "new" pump is not the right one or not so new?- Double check the pump by inspecting the points beneath the cover. You can pull the cover off the old one and check those points against your "new" pump. In a perfect world when you turn the ignition on the pump should only take a second or two build pressure and shut off. Also If your pump cycles on every time you switch the ignition on- say even after 15-30 minutes there is probably a leak somewhere. If the new pump is bad for some reason you can check it. If you want to experiment- take the points off the new pump and install them on the old pump re-install pump- test- what happens? here is a how to on that process "Dont replace your fuel pump- FIX IT." http://www.advrider.com/forums/showthread.php?t=611799 __________________ KTM: 06 KTM950S & 10 KTM450EXC (690E sold) BMW: 08 R1200GSA & 74 BMW R90/6 Ducati: 08 S2R1000 MONTESSA: 82 COTA 349 "The White Wonder"

03-06-2013, 01:20 PM	#17
bloc ^OP Gnarly Adventurer Joined: Apr 2012 Location: Austin, TX Oddometer: 158	Interesting. Found a few of the air jets partially clogged and cleaned.. cleaned the bowls, double checked slide diaphragms, etc. Idle hunted really bad. Couple spits through the rear carb while warming up. THEN, I gravity fed the carbs from a fuel container and the idle is rock solid, goes right back where it should after revving.. Gonna try the new points on the old pump and see what happens. Or maybe a facet. Edit: side question.. should we be able to see fuel flowing out of the orifice around the slide needle at idle? It is idling awesome while gravity fed, but it sure seems like a ton of fuel. Needles on middle clip groove. Second edit: Yeah, the pump cycles more.. but I was assuming this one was operating at a higher pressure or something as opposed to the old one, thereby stroking more. It does only take a second or two.. but whereas the SOP for the old pump was one "click" upon turning the ignition on, maybe two.. this one goes 5 or 6. bloc screwed with this post 03-06-2013 at 01:27 PM

03-06-2013, 02:55 PM	#18
ABuck99 0.0 Joined: Feb 2009 Location: Georgia Oddometer: 261	Im hooked now so keep us posted what you find- good luck __________________ KTM: 06 KTM950S & 10 KTM450EXC (690E sold) BMW: 08 R1200GSA & 74 BMW R90/6 Ducati: 08 S2R1000 MONTESSA: 82 COTA 349 "The White Wonder"

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03-06-2013, 04:51 PM	#19
bloc ^OP Gnarly Adventurer Joined: Apr 2012 Location: Austin, TX Oddometer: 158	Well, I want to put more miles on it than the quick trip to get food that I just did, but so far so good. The idle seems to run up maybe 100 rpm every once in a while, but no crazy surging like before and it settles right down when you chop the throttle. I'm not sure if it was the screws, the clogged air jets, or the needle clip being too high.. but it picked up a significant amount of midrange punch as well. It wants to pull the front off the ground by itself in second gear now.. didn't do that before. So to recap... It appears it was the new fuel pump all along. I harvested the points out of the new pump and soldered them into the old pump housing (the old points were TRASHED) and things are going great. I think I also figured out why the new pump was stroking more times than the old one. The points were so worn down each stroke went substantially further than in the new pump.. so it would have taken more strokes with less throw each to equal the amount of fuel. 3-5 times as much? who knows. So yeah.. if you do something as simple as change the fuel pump and it immediately starts acting funny.. dont suspect a bunch of other crap.. suspect the pump. Even if it's brand new.