carbs... bloody carbs

[(RIP) pastyman]

Never realised how rough My old Berthas engine was until I had a go on Bubbles PD yesterday. So I decided to try and smooth it out by balancing the carbs which I think is the reason for the roughness. She always starts without fuss and pulls yer arms off when accelerating hard. even trickover is not too bad. Started by stripping the carbs , cleaning and blowing everything through.Then put back, floats checked for level, left one needed adjusting. Started and set tickover to about 1000 reve, screwed right hand mixture screw to fastest tickover then did the same with left hand carb but no amount of screwing in or out made any difference to the tickover, settled for the smoothest I could get and did the rest. Carbtune almost even though one columb slower to react than the other and the engine still does not feel smooth.
seems odd that the mixture screw on the left carb seems u/s but cant think what the prob can be.
Any ideas and/or help gratefully recieved.

 

[BillN]

With Airheads it is just a matter of elimination...........You know all the things to do....just go thru the list

Anyway...just a few easy suggestions from me

do the tappets first, (stone cold)

......make sure that both sides are airtight, (well as airtight as possible).......the WD40 trick......spray it on, (as Henry Cooper used to say), all the black bits........s there any difference?

do the throttle cables open at exactly the same time?, (there should be just a little free play before they move)

are the choke cable nice and free and seating properly?, (again just a little bit of free play before they move)

You have only one adjustment on the carbs

Have you taken the tank off recently removed the petcocks and drain it and cleaned any muck out?

did you check those bloody rubber things, (cannot think of the name), for any holes or damage..diaphragms

Air filter? clean

Take the plugs out and have a look at them

put everything back together carefully......but I would imagine that you know all this

lots of stuff to check anyway before starting the engine

 

[Rob Farmer]

Tony,

That was exactly the problem we had with your right hand carb at Baskerville. The inlet valve was sticking open. As soon as it was adjusted the mixture screw on the carb had an effect.

 

[Steptoe]

then did the same with left hand carb but no amount of screwing in or out made any difference to the tickover,

check the end needle section on the mixture screw hasn't broken off and is stuck in the carb body

 

[(RIP) pastyman]

Tony,

That was exactly the problem we had with your right hand carb at Baskerville. The inlet valve was sticking open. As soon as it was adjusted the mixture screw on the carb had an effect.

Thanks, but ive now checked the valve clearances and they are fine, Im going to try it out tonight and see if iots any better on the road, Let you know the result.

 

[(RIP) pastyman]

check the end needle section on the mixture screw hasn't broken off and is stuck in the carb body

Yup I'll give that a try though when I was cleaning the carbs I did squirt the carb cleaner in all tghe holes and noted that it was shooting out OK. I am begining to think that I may have to fit a reconditioning kit, not sure whether its ever been done and the old girl has covered some miles.

 

[BillN]

If you have adjusted the tappets and checked all the stuff on the fuel/air mixture side, (i.e. cables, the carb diaphragms etc, airtight, air filter and colour of plugs, etc), and then given the Bike a good run and seen no change in the problem, as you think that it is the carb what I do next is to stick a spare carb on the Bike and see if that changes anything.

If not you can then check the ignition side, (plugs, plug leads, coil, trigger, timing and all connections etc.)…..just change the plugs and plug leads over for a start and see if you get any change.

Good luck

 

[(RIP) pastyman]

Thanks for than, So I suppose its off to fleabay again to get a spare carb!!
Did try her out the other night, still a bit off but better, Im really thinking now that its the left hand carb on the mixture side as the screw seems to have no effect on engine speed when screwed in or out, Keep trying

 

[Sean Kelly]

Hi

When the mixture screw on my left carb had no effect a couple of years back, it was 'cos of the build up of oil and rubbish in and around the main jet. You have to take the jet holder (?) out to clean it all properly.

Cheers

Sean

 

[bubbles]

Tony, think I said to you on Sunday how heavy the throttle felt on your bike compared to mine, one of the first things I did when I got mine was to fit a new pair of throttle cables, it certainly made a big difference making it feel much crisper and more responsive, may be worth a try.

 

[Mike Wilkins]

Carb bollix

Mine was fine until recently when tickover was up and 'hunting' similarly when cruising at low rpm. Is this a symptom of knackered diaphragms ?
Cheers
Mike

 

[nud1e]

Mine was fine until recently when tickover was up and 'hunting' similarly when cruising at low rpm. Is this a symptom of knackered diaphragms ?
Cheers
Mike

check that both chokes are returning full to open, on occasions I've found that one or other needed a final push to be full open.
Diaphragms only come in with opening throttle above tickover.

 

[Mike Wilkins]

carbs

Thanks Nud1e
Just the ticket - left hand lock nut loose - choke not closing
Teach me not to look properl;y
Cheers
Mike