Slow speed woes

[JayDub]

I'm having problems with tuning which I just can't get right, I'm hoping some of you with more steamer experience may be able to help...
The engine is not smooth, its a kind of erratic surging which makes the bike difficult to control, the problem seems to be most evident when in slow traffic mostly in 1st but also 2nd gear from slightly above idle speed to approx 2000rpm - although its there in 3rd slightly too,
It seems Ok other than that (maybe slightly flat at the very bottom of the rev range when under load) it really is a problem especially with such a heavy, tall bike and two up its very unpleasant.
I have replaced the:
- carb to head rubbers,
- jet needles, + stripped/cleaned carbs, checked seals and diaphragms and run through some Profi-fuel max.
- cracked carb tops,
- plugs,
- crank pick-up sensor,
- air filter, + sealed the airbox and auxiliaries, cleaned drain etc.
fuel air mix OK, valve clearances checked, carbs balanced, cleaned/replaced fuel filters, the jetting is standard and needles are in the middle notch, and checked for air leaks, checked coils, leads and ignition connections.
The only two things I think could pos cause this are... The needle jets (tubes) could be worn, and the exhaust cans have been messed about with and look like they may be straight through, would either of these cause those symptoms?
I've spent too much on the bike since I bought it in December so I'm reluctant to throw anymore cash at it.
If I could be sure that it could be the needle jet tubes I would spend another 65 quid (the needles themselves were replaced as they looked quite worn) and I was thinking of maybe repairing/blocking the bottom of the exhaust baffles where they have been 'poked through'
Any ideas, suggestions, magic spells anyone?

[Mustang]

need more info ..........................
when it comes out of the flat spot stumble , does it run like a scalded dog right up to redline ?
how do you know your coils are good ? are they Gill's or PVL's or nologys ?
are the carbs Mikunis or Keihins , I'm guessing Mik's ?
where are the pilot screws set at ?
have the o-rings been replaced on the float assemblies ? ( assuming they are Mik's)
have the carbs been synched ?

[JayDub]

Thanks Mustang, was hoping you were around... :icon_wink:
1, No, not really a flat spot - it just grunts a bit and smoothly picks up - a bit like being in too low a gear.
2, Stock coils, I think PVL.  Assumtion really as its fine other than that.  not sure how to test with a meter ie which Ohms range and where to connect 
3, Mikuni's.
4, Pilots approx 1.5 turns.
5, No, I didn't disturb the O rings.
6, Carbs synched.

[Mustang]

what gearing .......
std is 18 / 48
anything lower sucks the life right out of her , coming off idle .
have you tried simply turning the idle up to just below 1500 rpm
say 1300-1400 rpm .
it responds so much better on the bottom end when you do

[ram33]

if you stripped and cleaned the carbs properly you would have disturbed orings by removing floats. it would be a good idea to change the rings as if they are leaking maybe they could be causing a rich mixture at low revs. also did you check the float heights? do you know the balance was done correctly?

[JayDub]

The gearing is standard now, when I got the bike it was 19/42! I keep the idle speed down to 1050/1100 due to the loud pipes... I like my neighbours.
I'll try it higher but I think the problem lies deeper. do you think it could be the needle tubes? would any wear/ovaling affect this area of the rev range, it seems to be as it goes off pilot onto main jets.

[JayDub]

if you stripped and cleaned the carbs properly you would have disturbed orings by removing floats. it would be a good idea to change the rings as if they are leaking maybe they could be causing a rich mixture at low revs. also did you check the float heights? do you know the balance was done correctly?

with the luck I was having at the time I decided that if I tried to remove the float assembly it WOULD break, so I tried blowing them through with the valves closed, - no leaks. I checked the float heights were OK, I balanced the carbs and they are spot-on.

[Mustang]

The gearing is standard now, when I got the bike it was 19/42! I keep the idle speed down to 1050/1100 due to the loud pipes... I like my neighbours.
I'll try it higher but I think the problem lies deeper. do you think it could be the needle tubes? would any wear/ovaling affect this area of the rev range, it seems to be as it goes off pilot onto main jets.

too low of an idle get it up to around 1250 when it's warm .

[JayDub]

Tried it at 1250 and the problem is still there, still surging from tick-over to 1800-2000 rpm what do you think about it being the needle tubes then?

[Mustang]

would need to be there physically to diagnose the problem .
how many miles on bike?

[JayDub]

only 39k, and I saw some blue silicone gasket inside when I did the crank sensor so suspect some major overhaul in the past.  I think I may talk myself into replacing the needle jets, I think these bikes have that effect - they feel so good to ride that we fall in love with them so quickly, they need too much attention... suck too much out of my bank account... too heavy... too big... too comfortable... too nice 
I'm going for a ride, thanks fella  .............later!

[Hodabode]

I have the same problem.
Anyone I asked said it was due to the modern ethanol added fuel and cleaning the carbs seamed to cure the problem for a while.
As the issue is only in the 1/4 throttle range I changed the pilot jets and all was well for about a month.
To cut a long story short I Have now changed all jets and needles including the emulsion tubes and fitted new coils but It has gone bad again.
The only things I haven't changed are the O rings and float needles which I have ordered today so I hope this is the final cure.
I will update this thread when I have done this, Let me know if you cure yours.

[JayDub]

I have the same problem.
Anyone I asked said it was due to the modern ethanol added fuel and cleaning the carbs seamed to cure the problem for a while.
As the issue is only in the 1/4 throttle range I changed the pilot jets and all was well for about a month.
To cut a long story short I Have now changed all jets and needles including the emulsion tubes and fitted new coils but It has gone bad again.
The only things I haven't changed are the O rings and float needles which I have ordered today so I hope this is the final cure.
I will update this thread when I have done this, Let me know if you cure yours.

I did all that too, the only thing left to pin my hopes on are the exhaust cans, they've been made straight through by a PO, I have another set of standard ones on the way which I managed to get for 48 quid via fleabay so watch this space.....

[motoOzarks]

you guys just need to go faster.

walaa problem solved

[JayDub]

Ours is just a small city but it still has traffic problems and there are 30 mph limits in all the surrounding villages, no avoiding those but away from such restraints the problem isn't that noticeable.