running issue. its got me beaten

since i have been running my totally rebuilt engine in my 75 i have been plagued with a niggling running problem. when ridden at a steady speed and steady throttle, it hesitates and surges. now, all i have read up on concerning this , points to running lean.
here is a list of the things i have done to try to find this annoying :sensored: problem.

tank drained and dried, fresh fuel added . half a cup of metho added and sloshed round.

fuel filter replaced ( brass sinter type )and checked for flow.

fuel pump replaced, original had slightly perished diaphram.

carbs stripped and cleaned excessively. all rubber replaced, new air cut off valve, new Honda float valves. floats were floated in a jar of petrol to make sure they didnt sink. every nook and cranny in the carb bodies cleaned and blown out with air.
slides polished to within an inch of their lives. floats set at exactly 21 mil.

ignition ( C5 ) checked over for good connections and earths. new iridium plugs switched for new NGK stock type. ( resistor type as specified ) New NGK plug caps, run with and without the built in resistors.

to rule out the possibility of an ignition fault, i re installed the Dyna gear. coils and points replacement modules. still ran the same. worse actually.......
put the C5 back on.

switched the carb rack with the original set. still did it. put the rebuilt carbs back on.

in desperation, i switched the camshafts over. the ones in the new engine were a new pair i bought off ebay. i thought maybe they were mismatched. nope, still ran the same.

and then busted the :sensored: right hand side cover. :sensored:

it is driving me mad............... i am missing some thing. this most annoying, as i dont make mistakes.... :rant: :smilie_happy:

Describe better what it's doing.

Does it do this in all gears, when is it most noticeable.

it is most noticeable between 2,000 and 3,000 revs. seems to be at its worst in third gear at 50 klms per hour. with the throttle steady it hesitates and sort of surges.
ber ber ber berber ber ber, twist the throttle and it takes a second or so and off she goes and pulls strongly.
at first i thought it may have been an ignition advance thing, but changing the whole ignition ruled that out.

I am not trying to insult your intelligence as it seems like you have a pretty good handle on this thing. I am just trying to rule out the obvious stuff. When you rebuilt the carbs are you sure that the jets ended up in the right spots? The Clymer manual has them reversed (I bet you already knew that though) which can make the bikes do some crazy stuff, but it will idle just fine. Since the ignition is running a C5 its probably not that. Really sounds like a carb related issue, I'm just not sure what yet. :Awe: There has to be some sort of obvious explanation. Something simple that we are missing here. Carb sync?....

Dan, this seems like the guy who was having the problem with his starter and you figured out it was spinning backwards. Would have never thought that would have been the issue. This may be something crazy like that too. Probably some magic smoke somewhere that needs to be circulated....

Wish I could be more help. Ill keep thinkin on it

ok .....seems there isnt much left the same with all the switching......try resyncing the carbs at the 3000rpm instead of idle ....its acting like it is lean ...i did this once on a bike that had clean but worn carbs and in shafts and stuff maybe leaking air some ...the result was it ran well where it hesitated and surged before and overall ran better after ....

Have you done the flat spot mod?

i am rather sure after reading your last post that resnycing the carbs at the higher rpm.... will work for you.... the stock racks were all set lean from get go ...being cv carb they tend to be late and lean by nature ....if you dont have sync stuff to work with add a 1/4 turn to each sync screw this will also make it go richer and show results

True that about syncing different at rpm than idle.
The linkage could be pulling the throttle shafts at that point creating a vacuum leak. Was the case on mine. It never would sync at rpm after syncing at idle but syncing at rpm made it idle rough.
A trade off is the best I could get.

I'd check carefully with ether spray nozzle for any vacuum leaks at all the joints too.

Is your air filter box on tight with good filter? CV carbs need a little vacuum in the filter box to lift the slides. Have you reset the air fuel mix screws?

+1 on all the above, especially vacuum leaks. Throttle shafts, plenum gaskets... Also, is the fuel tank cap venting?

I didn't notice anyone suggesting the fuel cap. Could it be something as simple as that? Crack the cap and see what happens.

My 2 cents is possible float level. I assume that you have set both racks exactly the same. With aftermarket jetting kits they advise adjusting float levels to get optimum performance for the mods. I do think throttle shaft air leaks more likely but wouldn't expect both racks to be the same.

Just thinking here...Since there seemed to be an improvement when using the C5 it is possible that the C5 being better at burning unspent fuel is burning excess fuel, then I would look for possible fuel leaking into the cylinders either one or more.
I suppose you filled your carb rack with fuel before installing, I would always suggest that you do, the float stop tab contacts the float post, make sure your float setting is contacting the float needle and not the post and that there is plenty of room between the tab and post.
I suppose a fast check of the float level could be done without pulling the rack by just center standing the bike and running it a few seconds then draining the float bowls one at a time and measuring the fuel in each bowl. Thinking it was 50CC`s but better to double check the manual.
I really think it is an excess fuel problem, not so much air.

Pull the spark plugs. You'll know if it's rich or lean.

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=132111#p132111:9u8hc7a3 said:

Steve83 » Thu Sep 25, 2014 8:17 am[/url]":9u8hc7a3]
Pull the spark plugs. You'll know if it's rich or lean.

Click to expand...

That C5 should make them look lean with all those extra sparks.

i'm done with it. it can do what it wants. not going to look at it for at least six weeks. i got others i can use. over it. :fishin:

but thank you all for your comments and replies. :thanks:
i will try to answer all the topics raised.
the jets are all in the correct places. i was aware of the clymer mix up.
the jets were all soaked in carb cleaner, had guitar string pulled thru them and then blown out with compressed air. bodies also spotless.
a word on these carbs. i bought them from a fellow in Scotland. he came across them ( along with a matching engine) in a Tech School. never been in a bike and had never been run.
they have about 30,000 klms on them. so, in as new condition.
the " flat spot mod " ? there are two that i know of. one is changing the air jet, the other is lifting the needle with a thin washer .( for the 77 i think ) have not done either.
all the air/fuel idle mix screws affect the engine when screwed in and are now set at two turns out. the stock setting for these carbs is one and three eighth turns.
air filter is new and fitted right,
fuel cap was an early suspect and was swapped with one , with a wee hole drilled in it. just to rule it out.
yesterday, i set the carbs up with the bowls off and tested the float valves . they all shut off properly, and at the right height. and now it runs worse. i am done.
i really am over this thing. i will not touch it again for a while. i will use my LTD for a planned trip this weekend . :moped:

Sometimes it's best to walk away for a while. Later, you'll approach it with a different mind set and probably find the problem right away. Hopefully... Maybe... :Awe:

Use the 75 for the weekend Maurice :yes: :good: :salute:

it is a completely different world when you actually use a real user friendly carb system on a oldwing ...i am of the opinion the the stock racks are about 80% to coming close to performing as a good strait system can do ... i also know that a lot want to stay original ...but i comes at a severe performance loss on there best day they could ever have ....

personally i thought oldwings were just not made good enough ...or in a way that the motor could perform well .....and when i went to the single close my ears to all bs discounts and bs how to do it people ... and only collaborated with people who were trying help ...i eventually got to where it was clear the oldwing motors can really perform ... and the stock carbs were the biggest flaw to the performance problems ...and now have a oldwing that runs fast and is much more reliable than before ....did a 300 mile trip i dont think it missed on lick on the road the whole time ...

it all in what one wants to me this is what i want ....ive ridden with several people now ...no stock oldwings are even close to running like hooch ... what i have found is the flat 4 is the perfect smooth running power bike if almost no vibration what so ever.......with your bike running the c5 ...its obvious the carbs are failing this bike performance big time...