Hello,
I have a 1983 Shovel 5 speed FLT. The motor is stock with a fresh top end and a mild street cam. I am running fishtail mufflers that are baffled. I have a super B carb and upon reassembling the bike after painting it idles fine and under load/throttle runs like crazy, however at a constant cruising speeds it spits, sputters and coughs. I have done nothing to the engine or fuel system any different than before I took it apart for paint other than changing the faulty petcock out with a brass on/off type.
My fuel/air mixture screw was adjusted the same as before tear-down but was running so rich i was fowling plugs and blowing black smoke out the tailpipes along with fire......I turned the fuel input down and the needle is basically out only a half to 3/4 turn only...... it idles and picks up on the road okay but at a constant cruising speed or getting going from a dead stop it sputters, etc. I spent an hour trying to adjust and ride the bike to overcome the issue, but became exhausted and disgusted.
Is there anyone that may have some pertinent info that may help me with this problem?

Any advice would be greatly appreciated. Thanks in advance.

 

The only thing that can cause a steady throttle spiting back like you have is the low speed jet might be clogged, dirty -- from the carb not being held in an upright location when it was off for the top end work soooo remove it and clean it - if you need an explain what one it is and or the location just ask - jz

 

jz,
Thanks for the reply. I did have the carb off and cleaned the carb as well......I removed and blew out the jets, too. They seemed really clean. I will remove the secondary again and soak it and blow it out with compressed air again.
If this is not the issue, could it be possibe my secondary is too small?......but how could that be if it picks up under load?
confusing stuff

 

No usually not the main jet with your spitting the 72 / 74 you might have --- but if the 295 or 31 is the low speed -- some of the cams that are on the market have very poor VE ( volumetric efficiency ) and as such jetting becomes a thing, just if you try to re jet it go one at a time dont go up 2 or 3 sizes as that will end up the other way wrong --

sometimes you cant clean a jet like some think we just replace it than we know for sure whats up with what is going on -- jz

 

When you clean your carb. make sure all the transfer ports are cleaned out.
If any of them are plugged, you will wish they weren't.

 

How long are the fishtails ? The Super B does not get along well with long pipes . Here's a few of the common problems , there's a small vent port on the side of the carb that tends to plug when it does they start sucking more gas hence the false rich characteristics at speed . Second is the throttle shaft that holds the butterfly tends to wear and they suck air , B's are very prone to this one . At an idle while warm take a can of brake cleaner and give a small shot or two around the shafts and at the intake clamp's she drops off you've got leaks .

 

good advice. if not super b, what carb _does_ go with long pipes?

 

Is everything set up the same now, except for the new cam, as before the top end? I would bet that tweaking your secondary jet will help. Sounds like it needs to be just a little fatter.

 

Did you paint it black? Everyone knows black bikes are faster, so they need more gas. haha good luck I wish I could help...