Doesn't like throttle when cold !

[Mustang]

while the tank is off
have a look see what the brand name on the coils are
If they are Gill's (which would be OEM on a 98) 

we'll discuss that in a bit ....................

[Sparky]

I drained the tank through the fuel petcock with the gas cap closed and the flow never slowed, opened the cap halfway through and flow did not change.  Removed the petcock and the screens are clean.

Coils are Nology Pro Fire.

Does this fuel line routing look correct between carb 2 and 3 ?

Does this hose with the 90 on the end vent to atmosphere ?

These red washers under the needle heads do not look factory to me, has someone added shims ?  Maybe 102.5 jets and shims are too much ?

I'm going to remove the red washers and take it for a road test.

[Mustang]

I drained the tank through the fuel petcock with the gas cap closed and the flow never slowed, opened the cap halfway through and flow did not change.  Removed the petcock and the screens are clean.

Coils are Nology Pro Fire.

Does this fuel line routing look correct between carb 2 and 3 ?

Does this hose with the 90 on the end vent to atmosphere ?

These red washers under the needle heads do not look factory to me, has someone added shims ?  Maybe 102.5 jets and shims are too much ?

I'm going to remove the red washers and take it for a road test.

the coils are a reAL GOOD THING means someone already had the gills fail
my solo steamer runs 105 mains with shims under the needles that likely isn't your problem

*cough* ahem  lose that filter and run your fuel line like OEM , cuz everything other than that is good !
3/4 throttle is over a hundred mph on my steamer BTW  how often do you bounce this thing off the rev limiter.................?

[Sparky]

Came back from a quick ride no change still stumbles doesn't feel any better or any worse.

I had the gas cap open for a short time with no change.

I'm going again without the fuel filter. I was taught only one change at a time when troubleshooting.

What's the oem fuel line 1/4" or 5/16" ?

It can be 3/4 throttle at 20mph in first gear or 3/4 throttle at 60mph in top gear as soon as you get past 3/4 it stops pulling and starts stumbling.

[Mustang]

does it quit stumbling if you roll the throttle back a touch ?

[Sparky]

does it quit stumbling if you roll the throttle back a touch ?

First off Thanks for the assistance with this it is much appreciated.

Yes if you roll into full throttle it stumbles if you back off to about 3/4 throttle it stops stumbling and starts to pull, feels a bit like a two stroke hitting the power band except I'm backing off the throttle.

Tried with no fuel filter and still no change.

Because it's so throttle position specific I'm thinking carburation more specifically the high speed circuit.  Trying to decide whether to go leaner or richer and see what happens.  If you are running 105 jets with needle shims then maybe I need to go bigger on the main jets.

[Sin_Tiger]

It sounds awful like a problem I had with a car carb,  the throttle mechanism was interlinked with the choke which was operating at high openings. This can't happen with the Steamer arrangement but it has go me 

It's there any chance you can get a mate to follow you and note if they see darker exhaust when it bogs?

[Sparky]

Where would I find the stock jetting specs, main, pilot and needle ?  Online parts only list the main as a 98 no numbers given for the pilot and needle.

Carbs are coming off again and I want to check installed jetting vs factory specs.

[Sparky]

More info.

Went for another ride today and did not change anything except halfway through I removed the snorkel and cap from the air box intakes and it made the bike run worse.  Not sure if this helps anything just throwing it out there.

Pic below is the plugs 1,2,3 left to right.  These were new about 200 miles ago.

Took the carbs off again, getting good at this, main jets are 102.5, pilots are 40, needles are N3RF with 40 thou shims.  As far as I can tell the only changes from stock is an increase in main jet size and the shims under the needles.

Previously I had removed the shims from under the needles I reinstalled these and will try it again tomorrow.

[Mustang]

try bigger mains .....seriously

you are too lean at WOT ...............

OEM is .98 main
            #40 pilot
            n3rf needles

the shims are for the mid range lean ness or flat spot  that 98 tigers have from about 3800-5k rpm
bigger mains fix the fall on your face dead spot that happens at WOT

a #59 drill bit twisted thru the main jets will make them 104's but there is no going back 

[Sparky]

Good news got it sorted out and it now runs great.

Found some 105 main jets locally and installed those filled up with fresh 94, half a bottle of Seafoam in the tank and went for a ride.  Off idle throttle is nice and clean mid range is strong and it just keeps pulling right to redline 

Before I reinstalled the carbs I checked the slides by lifting them and letting them drop, one of them did not feel the same as the other two it felt stickier in the top half of the travel and was slow to close compared to the other two.  I used a fine 3M pad and gently cleaned all the slides and reinstalled.  I think the running problem after the initial carb cleaning may have been one slide not fully opening.  This might explain why it was so throttle position specific.

When I bought the bike it felt a little soft from 5K and up under throttle nothing significant just a feeling it wasn't running it's best.  I planned on riding it through the summer and doing a carb clean over the winter with Mustangs recommendations on the jetting and an early carb cleaning it now runs great.     

  Many thanks to Mustang who PM'd me his number and ran through a few things with me on the phone 

[JayDub]

Well done, we must be sharing that feeling of elation. We should make the most of our joy and go and ride the tits off it - before it goes wrong again   

[Sin_Tiger]

Great news  Mustang hits the spot again