Newbie with a question about my SU carb...

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Throttle Junkie
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Newbie with a question about my SU carb...

#1

Post by Throttle Junkie » Tue May 18, 2010 6:03 pm

I recently had my 64 pan's top end done. I am a carb novice to say the least. Well my bike was running great then it died like it ran out of fuel. I can pump the tickler about 5-6 times, twist the throttle a few times and it will fire on the first or second kick. It proceeds to fire each cylinder once or twice then dies like it's not getting anymore fuel. I can see fuel when I pump the tickler but no other time. Is the carb plugged up somewhere? Any thoughts would be appreciated.



Bosheff
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Re: Newbie with a question about my SU carb...

#2

Post by Bosheff » Tue May 18, 2010 8:43 pm

1st check the obvious. Got fuel? Is it gettin to the carb? Twisting the throttle when the engine is not running does not introduce fuel to the venturi as the S.U. doesn't have an accelerator pump. Make sure you have a very efficient fuel filter. No, 2 fuel filters are better as S.U.'s are known to turn to shit with only a few grains of dirt. I am on my way to work right now, but will post up the basics of the S.U. when I get home. Make sure yer not suckin air as the S.U. doesn't like that either. I realize these probably aren't directly attributed to yer fuel starvation problem, but ya need the preliminaries covered first. Pull the bottom off the carb being very careful not to spill the fuel it contains. Check for tiny grains of dirt in the bottom. What kind of air filter are you running. The stock foam type supplied by Rivera is junk. Will get back with ya later....bosheff

Throttle Junkie
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Re: Newbie with a question about my SU carb...

#3

Post by Throttle Junkie » Tue May 18, 2010 8:51 pm

There is fuel in the bowl, I have not checked for debris yet though. It has the stock SU filter on it. I have a cheap glass fuel filter assembly on it right now. Thanks for any info...

Robert Luland
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Re: Newbie with a question about my SU carb...

#4

Post by Robert Luland » Wed May 19, 2010 12:59 am

Sounds like you got something stuck in something some were. Pull the bowl off and clean the sucker. I mean if ya got fuel at the inlet to the carb. You found your problem. If you need an instrution sheet for the carb I can scan and e-mail it to you. I stock all the parts for that puppy. Bob L

Bosheff
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Re: Newbie with a question about my SU carb...

#5

Post by Bosheff » Wed May 19, 2010 4:50 pm

I will assume you are running an S.U. marketed by Rivera Engineering made especially for H-D's. The earlier versions had a conventional needle/seat combo with a Viton tip on the needle. This was later superceded by by what Rivera called a "Gross Jet". This essentially was a small glass ball wrapped up in a brass body. These were introduced in the mid to late 80's. The 1st ones had a tendency to stick in the closed position so that you would run out of fuel a block or two after ya left the driveway or bar. Sittin idlein, you were O.K. I damn near went nuts tryin to figure this out. If you remove the "Gross Jet" and give it a physical inspection, it appears to be alright as the glass orb moves freely in the brass body, but upside down in the carb it didn't do its job correctly. This is the only fuel starvation problem I have ever encountered with an S.U. If yer runnin a stock or close to stock pan use the BBX needle, .100 pick-up tube, and the "Silver" spring and ya should be good to go. Get rid of the stock air filter because after a while the filtering material used will decompose and be sucked back into the carb. No one I know of makes a good filter unit so you may have to fabricate. The time spent fabricating is time well spent as it will pay off in the long run as S.U.'s must be filtered exceptionally well to function properly. The same goes for the fuel filtering. If a little is good and more is better, than to much is just enough. Hope this helps ya out....bosheff

Throttle Junkie
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Re: Newbie with a question about my SU carb...

#6

Post by Throttle Junkie » Wed May 26, 2010 11:40 pm

Thanks everybody. I found that the jet needle guide had fallen due to the set screw loosening. It started up today like normal. I haven't got to take it for a ride yet due to crappy weather. I'll keep ya posted.

Any air filter suggestions or pics?

Throttle Junkie
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Location: Central Illinois

Re: Newbie with a question about my SU carb...

#7

Post by Throttle Junkie » Thu May 27, 2010 10:55 pm

Well she left me stranded. She was running really well so I took her out for a plug read. I noticed that the rear plug was sooty and the front plug looked pretty good. I leaned it out a little and tried it again. I noticed the bike start to cut out slightly, I then richened it back up. The cutting out continued to get worse. So I headed for home. The bike made it a few miles before cutting out and backfiring. I found a shady spot to pull it over. I am now thinking it has something to do with the wires or magneto...After it cooled off it started up but still was cutting out a little.

Sir_Rat
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Re: Newbie with a question about my SU carb...

#8

Post by Sir_Rat » Fri May 28, 2010 11:06 am

PLUGS??????

Throttle Junkie
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Re: Newbie with a question about my SU carb...

#9

Post by Throttle Junkie » Fri May 28, 2010 3:16 pm

Autolite 4275's.

Bosheff
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Re: Newbie with a question about my SU carb...

#10

Post by Bosheff » Fri May 28, 2010 6:15 pm

If one plug is readin o.k. and the other is sooty you maybe be suckin air, have a bad plug or plug wire. Rotate plugs and take it for a ride and read plugs. If the same plug fouls ya probably got a plug issue, If the same cylinder fouls a plug, it could be a plug wire or the cylinder itself. If ya can't tune it at an idle yer probably suckin air. Start out at 4 turns out and go from there.. If you have to go more than 2 turns either way from the 4 turn starting point you got problems somewhere else. This may also be an ignition issue....bosheff

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