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Buy just 1 Accelerator pump and Boot. They wear out fast.

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I rebuilt the Hitachi 4 years ago and seems i need a new accelerator pump and boot replaced every 6 months. Ive had the same damaged pump and boot on for 2 years now. This last one does work good beat up but now i just want to buy another pump and boot. Not from a whole kit anymore.


Only place i see to buy just what i need without the whole kit is from Carbs Unlimited.

Seems there is only 1 available... Accelerator pump part #866F and Boot part #862F  ..from Carbs Unlimited.


Anyone else notice the fast turnaround with these parts or is there another source...maybe a better heavy duty pump/boot available somewhere.


BTW yea im starting to want the Weber.  I want a Weber carb. ...and get rid of the vac hoses, looks like theres better air flow and gain some performance... but need to wait til spring. Thank you.

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I replied this am but mustatook too long and the reply didnt stick again. doing 4 things at once. and  make sure to sign in even when looks like signed in already.


Every time i take the air house off i notice the boot is bad or missing and dirt n gas residue there.   tired of buying a $30 kit for just a pump and boot,

ACTUALLY ITS JUST THE BOOT THAT GOES MISSING... so i just replace the pump too. I need to find a exploded view of these parts at carb to see if im missing a gasket or something...its just a flat oval like metal washer that holds the pump in place.. maybe a little rtv might help it out..


  Think the boot is rubber and black color and the pump is rubber or so in blue or black.  i wouldnt think to check the bore but definantly will. if theres a burr to fix thatd be good. i imagine gas vapor is causing the boot to deteriorate too fast or just cheap replacements available. wonder if performance is lost and i dont notice it since its slowly deteriorating over a 6 month period.  could replace them ev 6-12 months as it goes. this last boots been missing for nearly 2 years but it runs fine still.  just didnt want to buy another $30 kit.


Last night i found individual boot-pump available at www.carburation.com.  its carbs unlimited inc in Auburn Wa. with ?/info line at 253 833 4105 or order by phone at 800 994 2277.

Cant believe i didnt order one today i had the day off but goofed off napped thru movies nice lazy afternoon.  ive been back to work since last post and have rent ready and more. its booming here gonna be an awesome next year got my eye on a single cab across town in good original shape with 135 k  just sitting there (broke down?) gone find out. AND an 84 KC too ..here in MY neighborhood.    they prob just need the oil pump dist lined up correctly...hahahahaha  when i get $1000 or more im going to go knock on that door with cash ready.

ive got the best looking KC wish i could post pic figure it out later. it has the stripe still from front to back and curls up to the top tailgate like i remember the new ones had back in the 80's. with ST wheels tint  all original except 225 size tires.    about to put 205s in the front though. 205 front w/225 in back should ride better, look good and go 75-80 mph without so many rpms .


if Weber carbs need replacing too is good news i guess.  they just go bad soon.

seems to be a good idea to apply a bit of rtv over the flat oval washer or so.  ill study that and if possible apply at next replacement time and try for increased boot life. 

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Its just the boot thats the problem. i have the original air filter assembly so the boot isnt noticeable until the assembly is removed (about every 6-12 months for some reason or another).    By then it is completely missing.  except once it was split and barely hanging on.  The pump neoprene is usually ok but once way back i think it was cracked a bit when i tried to put it back in and realized its bad and needs replaced.  ill order a new boot and pump today and reply how the old pump neoprene looks. id guess its just in OK condition  as its only about  2 years old but will replace it in a few days and post condition. ill try to post some pics of old/new pump and my truck.   

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Oh yea i remember there is an adjustment. There are holes on top of the pump...i placed the set up right in my mind that made sense....like to make sure the pump travels far enough to provide the engine plenty of gas upon full throttle.. but it may be bottoming out then ruining it?

I dont even know what the accelerator pump is for really..i havent needed to know the order of routes the gas goes thru the carb. ...

guessing the jets allow more or less gas down to the motor depending on throttle position?  

How do you know what hole to set the pump at...do i just push the pump all the way down then back it up a bit then hook it up..so it doesnt bottom out at full throttle or something like that?


Hey what air filter do yall use?   id spend money for the best. k&n? 

i went to Autozone late last night and got a new air filter and the only one they had was an stp so i got it for now

..Ive only been using fram or stp air filters forever.   does it matter with air filters?.

Thank you.


I worked late again so i may have to wait til Monday to order the new pump and boot.  Tomorrows Saturday im going to see where the lever is set to the pump. i have to adjust the choke..its set itself revn too high somehow...... it has held right for 4 years tho. 

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My thinking is have the accelerator pump move as little as possible, then drive it, if it falls on its face then move it to the next hole that moves it a little farther(adds more gas) when you push on the pedal, do this till it doesn't fall on its face when you give it the pedal deeply.


The photo above is of a carb that sat out in the weather/elements, the rubber piece has deteriorated because of this and normal wear/time.

That carbs accelerator pump is not adjustable, it only goes together one way, it is an 86 carb.


What an accelerator pump does is squirt fuel in the engine when you step on the pedal, if it didn't squirt fuel the engine would hesitate/fall on its face, when you hold the pedal steady the accelerator pump does absolutely nothing.

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When you step on the gas the throttle opens but the engine isn't spinning fast enough to move enough air through the venturi. Without fast moving air there is no vacuum produced to drag fuel in to mix with it and the mixture suddenly goes super lean. The idle circuit will run the engine at idle but quickly runs out of gas much above idle. If you drive away slowly there is time for the engine to rev and make vacuum but this isn't feasible in the real world. To offset this large hole in the transition from idle to primary fuel delivery, an accelerator pump is used to add raw gas in.  If you drive around a corner in second gear in town near idle and then step on the gas and the engine bogs, this is caused by a poor delivery of fuel from the accelerator pump.


The accelerator pump is just a plunger in a cylinder like a syringe, with an one way valve on the inlet from the float chamber allowing gas in when the plunger rises, but blocks flow out when it goes down.  The outlet to the primary barrel also has a one way valve that lets fuel out as the plunger goes down pushing gas out, but closes to prevent sucking air in when the plunger rises. Both one way valves are just a spring with a BB covering the hole. The inlet one way valve is designed with a slight leakage in it. When stepping down fast on the plunger all the gas is forced into the outlet and very little back flushes into the float chamber. If you step down slowly on the gas, like when driving on the highway, most of the fuel has time to go back into the float chamber. Thus the amount of fuel delivered is proportional to how fast you step on the gas. In town is a higher demand at slower speeds while out on the highway an accelerator pump isn't needed at all. Webers pump the same measured amount even when not needed.

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  • 3 weeks later...

Now another problem.  

I finally put the new accelerator pump in...i couldnt buy a boot seperate so the old is still there and works fine i guess.

 i took the carb off to replace acc pump and clean and adjust the cam from touching anything  as i dont like high idle when cold and choke working.  ( now im thinking ive had a bit of problem with it idling too high with choke/cam working til warm up)  After spraying carb cleaner in the jet ports and from venturi ports backwards and everywhere else i could.... i put the carb back on. i had to make and use  2 cork gaskets....material i had lying around instead of the thin gaskets from a kit for the (2)carb bases'...put all back together and cranked it up.

 NOW it idles high and eventually dies....theres too much gas dripping down from the venturi and i noticed the snorkle part of air cleaner where the heat riser tube meets it..that diaphram there with a vac hose from (port b at air cleaner-fastboats vac diagram..nicoclub)  that stays closed for the warm exhaust air til engine warmed....well that diaphram stays closed even when engine fully hot... and buzzes.   


i think i messed up a bb or something when carb cleaner spraying.   allowing too much gas to venturi somehow.   I checked the spring and bb at bottom of the accel pump and its perfect...the new acc pump works fine as i drove it 7 miles so far.  it just tries to die especially on hard braking and have to pump the petal a bit


does this cali feedback carb have 2 bb's to worry about?  and i messed one up spraying carb cleaner evrywhere?


this carb looks just like a dfp384.   my carb id print is missing.


So ive read as much as i can and hope to get a few suggestions to right this thing.

 i even tried to idle it real high and smother the carb with a towel to try to dislodge something but it still runs...actually just fine and smooth with a towel smothering it to death.,,,sign of a hell of a vac leak ???


oh BTWAY my float chamber is at mid level and working fine i guess but somehow i suspect it is dumping fuel to the venturi ANYWAYS. 


tomorrow am ill-

1st.    read ratsun for better ideas..    why is this happening to MEEEEE LOL.

1.   redo the gaskets maybe its sucking air  or obstructing airflow?

2. figure why the snorkel diaphram is staying closed and bzzing.

3. put cam back as before

4. disect this carb and look for a problem..then buy thin gasket material to put it back together.



thank you.

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Gas dripping is usually the float chamber flooding. Look on the front where the glass bull's eye is... gas level should be at the dot.


You need a slightly fast idle when warming because the choke is on. The choke forces a rich mixture that won't burn, just make black smoke. It needs added air and it will rev up. The intent is to hasten the warm up and the engine will run much better during this time


Snorkel flap is controlled by a temperature sensitive air bleed in line with the vacuum hose that operates it. Engine off the flap is open. When cold, the vacuum is passed to the snorkel and the flap is pulled closed and warmed air is pulled from around the hot exhaust. As the temp under the hood rises the sensor slowly opens a bleed and vacuum is reduced opening the snorkel to blend cold and warmed air at about 100F, roughly. With this arrangement full throttle and low intake vacuum  the snorkel will will open fully for best performance.     

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I should of put the heat riser tube on and put the extra spring back....see  Ive been using an extra spring for years...that goes down about 10 inches and i hook it to a gas line i think.

well  this makes my carb idle return fast and somehow i get a consistent idle with the extra tension spring.  it idles way down but i adjust the idle screw til i get 800 rpm.


without the xtra spring on..(i didnt think it would make a difference) but sure does big time....without it the motor rpms go to 1400-1500rpm and is a bit eratic and then there goes all of the gas dripping from venturi. i believe the throttle shaft gets too much air without that extra spring and over the years somehow it just makes the carb great..consistent.   i also can change gears fast (Without clutch 2-3-4- 5 th gears if not in a hurry. and bcdd   etc   set right.


I had to go give an estimate this morning..after that i pulled over to put my bcdd right again  and decided to put the xtra spring on and whaaalaaa theres my girl!!   makes sense now.   i noticed also when the heat riser tube wasnt on straight at exhaust    the snorkel was closed....put that right and now it stays open like it should.  

enjoyed a great trip back home in my 720 like all the times before..running like new.


Thanks for being there  Happy New Year.

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