5500 and up stumble

[rhpaw]

Well I'm still fighting this bike on my main driveabillity issue 5.5k and up the damn thing just will not pull. Today as I was popping around the neighborhood it occurred to me what it feels like for you guys. - it's just like running out of gas before you switch to reseve tank. Only it is everywhere in the rev range, at any application of throttle.
Hold the throttle open and EVENTUALLY the bike reach 9k, but it's a lot of work. Stuttering all the way with some 1k intervals that actually feel like they're doing what they should. (with zero load, the bike will rev cleanly all the time)

I have been playing around ith sync and the mix screws for quite a few weeks now and although I can "F" my idle and low speed perfornce pretty well, I can't get rid iof this high RPM bog.
Right now,
the bike starts good, cold or hot,
idles fine-ish (some days it's good, others it's high) -but I think that's because I'm screwing with the mix screws.
1500- 5000 perfornce seems good. What I would expect a 550 twin to do.

Really is this just an issue of my pouring a full bottle of berrymans in the tank and doing a steady 7.5k highway run? (Itallian style)
I have a big bottle of berrymans B12 (1 litre?) When people on here say "pour a bottle of berryman's in the tank" is THAT the bottle size they're talking about?

[Night Vision]

Today as I was popping around the neighborhood it occurred to me what it feels like for you guys.....

hmmm.... both mine pull hard to redline, no stumbles

you must still have dirty carbs. it takes a couple of cleans for some folks.

[rhpaw]

lots of berrymans and an angry road?

[Night Vision]

mechanic in a can does not work cleaning Vision carbs that have sat... they need to be stripped and dipped.

the fuel pilots, air pilots, and main jets all have to come out.... the pilot screws and orings too

I don't recall reading that you did a teardown.... pardon me if you did

[rhpaw]

Yeah, I did.. I stripped and rebuild them a few months ago with a kit from sirrus. The bike hadn't run in ages before we found it.

The carbs if dirty are MOSTLY clean, the only problem is the 5.5k and up bog. Below that the bike behaves as I "imagine" it should.

here's a video of a drive, does it sound ok?
http://www.youtube.com/watch?v=CPyH0nDXo0Q

[Tiger]

 :) IMHO...the carbs need to come off again for another "bath"...

                8).......TIGER....... 8)

[Night Vision]

stripped but not dipped?

there are lots of small passage ways... both carbs have tiny holes below the butterflies that alot of people miss for example. I used guitar string to chase the routes.

these are downdraft carbs and it's vital that all the passageways are spotless in order for the draft to pull the fuel out of them...

after 4k-5k the high speed main jets (the ones on the side of the carb) overtake the low speed fuel pilot jets (the ones under the carbs).... the pilot screws mostly affect the low speed performance.

one reason you can't get to redline readily might be it's starving for fuel...... the fact that you can rev it fine and ride around the block, but under load it bogs.... kinda points to that...

[rhpaw]

No, not dipped. just the usual wires and carbcleaner route. As starting and low speed duty are good, I was figuring that I could get by without pulling the carbs again.

Not the case, eh?

Damn, if I didn't just have those carbs off last week for the intake boot swap. :(

[Rick G]

I rebuild Vision carbs, if your interested PM me. I also include  a monometer to sync the carbs , which is also very important.
Just spraying them won't do it , they need to be dipped. a 5 gal bucket of  carb dip is up to 250.00. You need at least a gallon and tha's over 50.00

[rhpaw]

thanks Rick, I'm ok. I have all the stuff here.

[Rick G]

Just don't leave them in the dip too long , it will damage the butterfly shaft seals. Don't try to remove the butterflys either, the risk is too great.

[xswheels]

When i dip carbs i strategically place them in the basket so the butterfly valve is above the solution. 90% of the carb is submerged so i use spray cleaner/compressed air on the other 10%. I also apply silicone spray on the butterfly shaft to treat the rubber seals.

[YellowJacket!]

Check your fuel line to make sure it does not have a big bend in it that gets squeezed together when it warms up and cuts off the fuel.  Happened to me and was a bugger to find out.  Once fixed, everything was good.

David

[Kid Jedi]

i had a similar problem. there is a capped off vacuum port on one of the intake boots. make sure the cap hasn't rotted off.

[rhpaw]

running a full can of berrymans' at 7.5k has really done wonders...