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Messages - blackeagles
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31
« on: July 17, 2020, 01:35:41 PM »
ok thanks. mine are different - pd42b - but i have found what believe is them and if i get a pic of the location i will put it up.
this is a pd42a but it shows the bit i'm talking about:
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left side of carb 1 has one but its a blank, the right side of 4 has none, the two facing each other on the right/left of 1/2 and the right/left for 3/4 have what looks like a blank in the hole but a bit of probing with a calor gas pricker found a hole in the centre of which one was blocked and the other 3 clear.
32
« on: July 17, 2020, 12:20:48 PM »
There's a small air vent in the side of the carb bodies, if one or more is blocked it's impossible to get even running. The vent is hard to see and cannot be cleaned with carbs assembled. Also, I have never seen that vent mentioned in any manual.
My F2 runs spot on after the second carb rebuild to clean the vents, where previously it would not balance up at all. And don't forget, the air screws work in the opposite direction to earlier 750's.
ok, something i didn't clean when they are off. can you indicate where the 'vent(s) are ?
33
« on: July 16, 2020, 01:25:24 PM »
while you have the bowl off you need to check the brass pipe inside the bowl for any split
34
« on: July 15, 2020, 02:59:11 PM »
it comes to us all!!
35
« on: July 15, 2020, 01:30:51 PM »
ah, i should have known that!
36
« on: July 15, 2020, 10:40:20 AM »
There should be a non return valve in the accelerator pump body (the removable cap) that prevents fuel flow until the diaphragm is pumped, could that possibly be stuck slightly open. They are still available from CMS. https://www.cmsnl.com/honda-cb750f2-super-sport-england_model14689/diaphragm-pump_16021393004/#.Xw6z8puSmUl
There are no restrictors as such in mine just small bore brass tubes inside rubber tubes (I assume to prevent the rubber tubes collapsing). There's a small air vent in the side of the carb bodies, if one or more is blocked it's impossible to get even running. The vent is hard to see and cannot be cleaned with carbs assembled. Also, I have never seen that vent mentioned in any manual.
My F2 runs spot on after the second carb rebuild to clean the vents, where previously it would not balance up at all. And don't forget, the air screws work in the opposite direction to earlier 750's.
as far as i can see the acc. pump non return valve is ok. you say "just small bore brass tubes inside rubber tubes" if you are talking about the 3 rubber tubes connecting the acc. pump supply to each carb then i don't have any of these bass tubes in my rubber tubes and these may be the 'parts' i saw mentioned. they do not show in any diagrams i have seen - are they likely to allow too much fuel into the carb each time the acc.pump works??
37
« on: July 14, 2020, 02:06:07 PM »
part no 16123300004 ebay 401385919944 but you could try using another spring or reducing the existing one
38
« on: July 14, 2020, 01:48:44 PM »
so your saying with the engine off they snap shut but with it running thye shut slowly if slightly activated but ok at a larger movement of the throttle. presumably with cable on and off and if you press them down either running or not they close 'correctly'. only thing i can think of if everything is running freely it could be the vacuum pressure in the venturi acting against the return spring - is the spring the correct poundage for this carb?
39
« on: July 14, 2020, 01:16:31 PM »
40
« on: July 14, 2020, 12:17:17 PM »
i don't think it had a pic, just a requote from a post you did earlier but it still hold good today and something i will try.
bike is not fully insured so can not run it down the bypass to test out the changes, or go to the local garage, although i don't think i am that far away as things stand. i am going to reset the gauges by using one cylinder so they should all show the same afterwards (i did do the bench set but it ran badly so may have screwed that up) and anyway i guess they only need to be close not necessarily spot on - i may see if i can borrow carbtune pro or such if i feel it will help.
41
« on: July 14, 2020, 11:55:16 AM »
The only thing I can think of is an air leak in the inlet rubbers but when I had the carbs off I inspected them all and they all looked good??
Don’t really want to start throwing money at it when I don’t know what the exact problem is?
Any more help would be appreciated if you guys/girls have any ideas??
Thanks
Alan
this is what i said when i was having the initial problems with my pd42a carb setting (not quite sorted yet). even spraying carb cleaner/ether on them didn't raise the revs (but took the paint off the brace) but k2-k6 suggested i get my wallet out and i replaced the lot (i didn't realise the 'stacks' in the cleaner are tapered so act a velocity stacks) anyway at least it now runs and when, like you, i sort out the sync and pilot setting it should be all good.
42
« on: July 14, 2020, 10:38:21 AM »
an interesting idea and i assume my 'local' has a gas tester although i have not seen one when there.
i just read a post you did back in 2017 where you were quoting 'honda manual' about syncing then adjusting slow running no 2 screw to max rev then back 100rpm, readjust and then do the others likewise. i cant say i have tried this, just set them all the same setting so maybe i will try although i have got to get the syncing right/checked first and find an electronic rev counter to do the final adjusting as i doubt the bike one is accurate enough (or maybe it is goo enought as i'm not looking for the last bhp!)
43
« on: July 13, 2020, 06:34:27 PM »
i have had another close look at a number of diagrams online and the 3 acc. pump rubber hoses between the carbs do not seem to show a restrictor to fit into them.
i got the idea they may need such a restrictor(s) as i came across a post on this site that mentioned there were "3 brass restrictors per pipe" and i am guessing that if they actually exist they will be unobtainable or, of course, i may have misread the post (not that i can find it again anyway).
44
« on: July 12, 2020, 01:24:10 PM »
following on from my earlier post about drive chain noise and syncing the carb to help....i have been having a little trouble setting them up and i just noticed, looking at an illustration of the pd42 carb, that the 3 pipes that connect the acc. pump to each carb seem to have a restrictor in each (is it part number 16026-393-004 or maybe that is what joins the carbs fuel supply together). no surprise when i took the old pipes off they didn't have such a restrictor so i have not used one....is that likely to cause an issue with setting the sync or the slow running?  bearing in mind they cannot be obtained (as far as i know)
45
« on: July 11, 2020, 10:20:04 AM »
ok, thanks all.
k2-k6. i did start at 1 3/4 out as per your suggestion in an earlier post but i was under the impression that with these carbs you then went in or out until you had the fastest tickover (rather like most carbs) then went back weaker by maybe a 1/8 turn. doing this i get about 2 turns out! so maybe since its 'hunting' a bit i need to go back in another 1/8 turn and reset the tickover - i have to say i have tried this and to my befuddled mind the engine seemed to run rough rather than 'hunting' but that may just be me (since my hearing is not what it was)!!!! .
i will give it one more go so may be in touch (this is really driving me mad)!!
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