Author Topic: pd41 carb problem  (Read 245 times)

Offline legin101

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pd41 carb problem
« on: May 13, 2020, 03:34:30 PM »
Hi all can anyone tell me what i have done wrong she starts good idles reasonably well and picks up speed through the gears, not as quickly as i feel she should but when i ask it to go past 5 or 6 thou it bogs down. the carbs have been in the ultrasonic bath so reasonably clean, but what i have noticed is the pump isnt although ive had it to bits and cleaned it. any ideas, at a stand still it revs really well and returns to idle it timed to the "F" at around 1000 rpm.

nigel >:(       
nigel
Current Bikes:-
GT750L 1974
gsx750ET 1980
CB750F2 1979
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Online K2-K6

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Re: pd41 carb problem
« Reply #1 on: May 13, 2020, 09:04:08 PM »
Do you mean that the accelerator pump has no output? as I didn't quite understand the bit about cleaning it.

Offline legin101

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Re: pd41 carb problem
« Reply #2 on: May 14, 2020, 08:47:00 AM »
i do have a feeling it still after cleaning the pump its top and lower ball valves etc still not squirting fuel, so i don't think they are working i think they are coming off i must have missed something. getting to the output of those pump outlets is a nightmare, do they push out?

cheers

nigel 
nigel
Current Bikes:-
GT750L 1974
gsx750ET 1980
CB750F2 1979
MT10 2017

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Re: pd41 carb problem
« Reply #3 on: May 14, 2020, 09:08:36 AM »
http://forums.sohc4.net/index.php/topic,146893.0.html

Above Link may help on the USA site if you've not seen it already.

It definitely needs the pump to make it GO! The "static" jetting on these is close to optimum for clean running and power,  but the addition made by the pump in acceleration phase is fundamental to their strategy. 
Non pumped carbs just do this by running excess mixture generally, in effect slightly too rich.

Offline legin101

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Re: pd41 carb problem
« Reply #4 on: May 14, 2020, 11:25:00 AM »
Thank you i am about to strip them down. see how i get on what is your take on pods ? do i need to ut the damn box back on?

nigel
nigel
Current Bikes:-
GT750L 1974
gsx750ET 1980
CB750F2 1979
MT10 2017

Offline legin101

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Re: pd41 carb problem
« Reply #5 on: May 14, 2020, 12:40:47 PM »
How far should the top of the diaphragm shaft actually move as mine move only a small amount maybe a millimeter.

nigel
nigel
Current Bikes:-
GT750L 1974
gsx750ET 1980
CB750F2 1979
MT10 2017

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Re: pd41 carb problem
« Reply #6 on: May 14, 2020, 02:18:15 PM »
How far should the top of the diaphragm shaft actually move as mine move only a small amount maybe a millimeter.

nigel

I'm not sure but think it's more than that usually,  though it doesn't travel far as the diaphragm would limit it. There's set up information in the manual that gives clearance at two points but it has no absolute movement specified.

If you need the manual page that details the above I'll have to get a photo of it to post,  just shout if you've not got it.

Offline SumpMagnet

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Re: pd41 carb problem
« Reply #7 on: May 14, 2020, 05:40:39 PM »
Pods?

Suffice it to say, the first thing I bought for my F2 rebuild was an airbox.

Pod filters can work well to give good power....but usually only in a certain poart of the rev range...and never everywhere. Jet for full power, and it's rich at idle, and horrid on the over-run ... get teh mid range right, and it won't pick up or rev out. It's always a compromise.

Only bike I owned that ran well on pods was an 850 LeMans. 36mm DelOrto pumper carbs like firemans hoses, pouring buckets of fuel down the inlet. Lumpy tickover was normal....so it was all good. As a bonus...the space I had where the airbox used to be was perfect for carrying the large toolkit I needed......
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline legin101

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Re: pd41 carb problem
« Reply #8 on: May 14, 2020, 06:30:10 PM »
Sent for new pump diaphragm and a new filter for air box one way or another i will beat it, the existing diaphragm did seem stiff in the material so in for a penny as they say.
nigel
Current Bikes:-
GT750L 1974
gsx750ET 1980
CB750F2 1979
MT10 2017

Offline chrisbmxr

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Re: pd41 carb problem
« Reply #9 on: May 14, 2020, 10:35:56 PM »
I've just rebuilt the accel pump on my F2. I was unsure how much the diaphragm should move as well. Mine was moving a mil or so … new one moves several mil and feels spring loaded. This results in a positive 'squirt'. I checked by assembling the pump and the no.2 bowl. Fil it with water, and press on the shaft. Trust me, you'll know if it works properly. I ended up with a face full of water! The it can be fitted to the carbs. Then check you get an 'accel squirt' on all 4 carbs before refitting.

Don't let carb cleaner get anywhere near the diaphragm though as apparently it destroys them.

Offline legin101

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Re: pd41 carb problem
« Reply #10 on: May 16, 2020, 10:42:14 AM »
thanks for your help and suggestions i am waiting on parts so will let you know how things go

nigel
nigel
Current Bikes:-
GT750L 1974
gsx750ET 1980
CB750F2 1979
MT10 2017

Offline legin101

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Re: pd41 carb problem
« Reply #11 on: May 21, 2020, 09:09:44 AM »
Well new parts fitted has made a massive difference the diaphragm now moves in the region of 3 plus mm making the pump now work really well so with fully working carbs i bit the bullet and re fitted the air box which isn't such a fiddle if you half it before fitting by taking the bottom off, now it runs like billy bollox i cannot fault it, i maybe will fiddle with pods again in the future but for now its sorted.

nigel 
nigel
Current Bikes:-
GT750L 1974
gsx750ET 1980
CB750F2 1979
MT10 2017

 

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