Help :(

[Jean]

If the diaphragms weren't replaced, that's the second thing to do. The first is check for free flowing fuel.
Later, you might want to see about replacing the spark plug wires, the caps and finally the coils.
Used mufflers are available and new ones can be had from numerous vendors.
Knocking out the baffles only makes noise. These engines like some back pressure (it's a tuning thing) and unless you are changing the carbs and making a race bike, the stock exhaust is fine.
IF you get the urge to do ANY performance enhancements...ONLY CHANGE ONE THING AT A TIME.

Did you get the roll of tools with the bike?
FIVE hundred $$ for what got done means YOU need to find out really fast how to do some mechanicing. Nothing you listed is out of reason for you to do in a couple of hours!

As I mentioned in another post, join the Airheads and participate in one of their Saturday tech sessions...Both good for the bike and for YOU as you will learn a lot more than you could by yourself.
There are lots of Airheads in the LA area.
www.Airheads.org

[daz]

Jean, I'm with you on the free flowing fuel. The mechanic could quickly get it up to 70 before it ran short of fuel. The owner says at 50 it begins to stumble. Two different scenarios. I also agree that the owner should be able to diagnose this problem. Quickest way would be to remove the float bowls, put containers under each carb and turn on the fuel. There should be steady continuous streams.

[Jean]

WE think the owner "should" be able to diagnose the problem....That's not a sure thing now-days.
I've observed many under 40 who really (And I do mean REALLY!) don't have a clue about how a simple engine opertes.
Bike shop young mechnaics think a carburetor is totally mysterious, and cannot fathom how it could work.
They only know fuel Injection.
Same with points, capacitor and coil..."Duh?" "How's that work, anyhow??"
On the other hand, a $500 job should have resulted in a lot more parts replaced and a bike that would GO-GO-GO.
I'd be willing to bet the deep-insides of the main jets are still filled with gunk, and, NOT installing new diaphragms...get real!! I suspect the cleaning was a dunking in some cleaner and now the outsides are shiny.
West-coasters, Ya gotta FIND this fellow.....
The only thing at the moment that goes is the stuff in the wallet.

[SteveD]

Bike shop young mechnaics think a carburetor is totally mysterious, and cannot fathom how it could work.
They only know fuel Injection.

I parked next to a HP gs type thing a few years back. The owner wandered over and had a look at my bike (same roundel!!!) and pointed to the carbs and asked "what are these things?"!

[SteveD]

deleted double post

[Deleted User 287]

Bike shop young mechnaics think a carburetor is totally mysterious, and cannot fathom how it could work.
They only know fuel Injection.

I parked next to a HP gs type thing a few years back. The owner wandered over and had a look at my bike (same roundel!!!) and pointed to the carbs and asked "what are these things?"!

Did you say "Well, they mix the fuel with the air so it will burn and get me down the road!"?

[Ken in Oklahoma]

WE think the owner "should" be able to diagnose the problem....That's not a sure thing now-days.
I've observed many under 40 who really (And I do mean REALLY!) don't have a clue about how a simple engine opertes.
Bike shop young mechnaics think a carburetor is totally mysterious, and cannot fathom how it could work.
They only know fuel Injection.
Same with points, capacitor and coil..."Duh?" "How's that work, anyhow??"
On the other hand, a $500 job should have resulted in a lot more parts replaced and a bike that would GO-GO-GO.
I'd be willing to bet the deep-insides of the main jets are still filled with gunk, and, NOT installing new diaphragms...get real!! I suspect the cleaning was a dunking in some cleaner and now the outsides are shiny.
West-coasters, Ya gotta FIND this fellow.....
The only thing at the moment that goes is the stuff in the wallet.

Good points, Jean. Since I'm immersed in the culture, so to speak, I tend to miss them when reading of problems. I particularly like your point about not dunking the carbs in a vat of carb cleaner and then just putting them back on the bike. When I'm cleaning carbs I make it a point to know where each passageway comes from and where it goes--and then make sure that spray can carb cleaner can be shot through the passageway. That and new rubbers where needed goes a long way to curing carb ills.

That point was reinforced to me when years ago my Dad asked me to clean the carb on his farm truck. It was a 4 barrel IIRC which seemed to be a strange thing to have on a farm truck. Anyhow, I'm looking at the carb kit and looking at the carb and wondering how the hell I was going to get his truck going. (By then I knew the limited success liklihood by simply dunking the carb in cleaner and installing a new kit.)

So I looked at the carb, looking at the casting for drilled passageway lumps and drill hole plugs after the drilling, and then made sure I could spray cleaner through them.

I was actually surprised when the carb was back together and the truck ran just fine! My dad, of course, knew I could do it all along.


Ken

[Jean]

Wonder where the Original poster went?
Hope he's not gone back to this $500 mechanic...

[ibjman]

My guess would be restricted fuel supply due to deteriorated or "twisted" "corks" in the fuel petcocks. These are the rubber gaskets between the rotational part of the petcock and the petcock body. If the bike has been in storage or unused for a period of time, these "rotational passageways tend to become stuck to the bodies. When you turn the petcock, the "cork" gets twisted up, blocking the passageway across the petcock.
Regards, Ibjman

[Deleted User 287]

My guess would be restricted fuel supply due to deteriorated or "twisted" "corks" in the fuel petcocks. These are the rubber gaskets between the rotational part of the petcock and the petcock body. If the bike has been in storage or unused for a period of time, these "rotational passageways tend to become stuck to the bodies. When you turn the petcock, the "cork" gets twisted up, blocking the passageway across the petcock.
Regards, Ibjman

Lookout Zombie Master - there is a new boy in town!

(ZM got his handle for digging up old threads.)