Well I just cleaned my carbs.
Now the revs die for a second when I open the throttle then they pick up.
This is bad enough that it occasionally kills the engine when revving up from idle.

So, I'm open to theories as to what is going on.

Oh and my bike just failed it's MOT, but not because of the engine problems.
(MOT is UK annual  bike saftey test)
It failed due to leaking fork seals, which I've just changed.
Guess i ballsed it up.
Also the head bearings are notchy. meh.

Do you have the airbox etc on it when you are trying to rev it up?

Did you  change anything while in the carbs?

Too lean. When you open the butterfly valve it administers too much air, the carburetor temporarily looses (decent) vacuum and can't suck enough fuel to keep running (as opposed to bogging, or too much fuel/flooding).

Did you use the plastic sandwich bag over the forkleg when sliding the fork seal on?

Sorry to hear the steering head is notchy.

Hope things get better for you.

Jared:
Air box was on when reving, I was riding the bike when I discovered the problem.
While I was in the carbs I sprayed all the holes through with carb cleaner.
I also moved the needle up one notch so that should make things richer.
And I cleaned the air filter.

I'm running standared jetting for a UK bike wich is pretty close to srinath's recommended setup
Pilot Jet    : 40
Needle jet: 0-2
Main Jet   :125
Needle clip : 3rd from top (currently 4th from top)


My valves are close to their lower clearance limits.
I'm about to fix the valve shims, so I'll see what that does for me.


Scratch:
Thanks.
What is the sandwich bag trick?
Hmm, too lean? umm, dunno how

Well, I take a plastic sandwich bag (do you have these in Scotland?), or I suppose you could use some Saranwrap/plastic wrap for food, and place it over the top of the fork tube before you slide the fork seal on, and rub some fork oil on the outside of the bag, too. What this does is keeps the sharp edges (they're sharp to the seal) from ripping/tearing or folding back the inside lips of the seal, as you slide the seal over the top of the tube and cap.

Did I explain this allright?

Quote from: red_philJared....My valves are close to their lower clearance limits....

The valves are a common cause of this problem - not as common as a vacum leak.  Vacum leaks have the greatest effect at lower RPM.  Could be the carbs are not entirely seated in the boots, the clamps are loose, a missing cap on the vacum port on one or both carbs, failure to get the little rubber o-rings under the carb top back in properly when reassembling, a cracked hose to the vacum side of the petcock (although that should leave you without gas)

Hmm, now onto the carbs...

You stated that you sprayed carb cleaner through all the little holes. Did you know that carb cleaner causes rubber to swell? While this may seal up better in certain areas for the better, it may be too tight in other areas restricting movement or flow. Also, it deteriorates the rubber quicker. When in areas of movement (i.e.: mixture screw), the movement may cause the rubber to tear...allowing a leak.

Carb synch is the only other thing that I can think of. Did you synch the butterflies visually?

Scratch:
Thanks for the bag tip, I'll try that with the next set.
Lets see if I can get them on without tearing them up.


MjM:
Hopefully the valve job will make things better but they can't be the cause
as they are just like they were before I did this work and things were ok (Ish) then, certainly not having this rev dip when applying throttle.
I'm hoping it might be a leak around the carb boors or similar.
I think I got the little o-rings back in ok, dunno.


Scratch mkII:
The carb cleaner I used "claimed" to be rubber safe, dunno how much I believe that though.
I did visually synch the carbs but i have a vacum guages and was planning on synching with that once I have the valves done.


Plan is to fix the valves and inspect the carb seating and the diaphragm end of th carbs.

Hmmmm....

I've never fooled with anything but stock (stock works ok ...plus I'm usually selling the bikes I fix..).....but...

It kind  sounds like the slides are opening just a little too quick.... The bike runs strong after it gets going?? idles good or anything odd before returning to idle (hanging rpms at idle = lean..) ?

You may want to go back up a notch on the needles.... if you need a little in between use those tiny washers....

You saw daylight through the pilots after cleaning them? (I'll assume yes because it idles...)

What's the idle set at by the way ( rpms)?

I'd just double check everything else before making any changes tho... Make sure the diaphragms are good and seated...the o-rings are all good...eyeball the throttle plates  ( eyeball synch em..) ...and so on....

Hard to diagnose from the keyboard sometimes....