Carb?

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Mar 4, 2012 | 11:35 PM

Sho71vel

Thread Starter

Stage II

Joined: Mar 2012

Posts: 2

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From: Port Orange, FL

Carb?

I have a 71 Shovelhead and could use some advice.

Bike has SuperB carb and when it runs will 'puff' through carb a couple of times before dying. Or if it doesn't die right away it will idle high and then idle down and repeat this on its own several times before dying. If bike does stay running for a few minutes the front exhaust will glow red.
Thanks.

Mar 5, 2012 | 08:02 AM

junker73hd

Road Captain

Joined: May 2010

Posts: 502

Likes: 2

An intake leak will cause sporadic and inconsistent problems such as hesitation,erratic idling,a lean A/F mix,overheating,that cherry red glow radiating from your exhaust pipes,etc,etc.While dry or cracked intake manifold seals are often to blame,this is not always the case.Leaks can be due to improper manifold to cyl head alignment,improper mounting and/or insufficient support of the carb and air cleaner assembly(the carb should never be supported by the intake manifold clamps alone)support bracket selection and fitment is crucial and is determined by year of production and model designation.Leaks can be caused by worn throttle shafts,cracked or dry vac lines and/or hoses on VOES equipped models.The easiest way to check for and pinpoint any leaks is to do the following:
Start the mc and while holding the throttle bring engine speed to approx 2000 rpm.More important is that you hold the throttle at a steady rpm.Using an aerosol lubricant or cleaner spray every point at which a leak could originate from ONE AT A TIME.Any change in rpm level indicates a leak that must be addressed before moving on.If problems persist after all points have been addressed repeat the procedure from the beginning to ensure that nothing was overlooked.Keep in mind that spitting or backfiring thru the carb at operating speed should not be confused with the same symptoms that occur while at idle speed....Good luck my friend,hope this info helps...Junker.

Mar 5, 2012 | 12:04 PM

Sho71vel

Thread Starter

Stage II

Joined: Mar 2012

Posts: 2

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From: Port Orange, FL

Thank you very much for the info. Seems like for every problem I've fixed since I got this bike another one takes its place. Will check it out later. Thought I had all leaks covered but maybe not.

Mar 5, 2012 | 09:32 PM

TwiZted Biker

Club Member

Joined: Mar 2009

Posts: 66,106

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From: Niles Canyon Ca.

Too much advanced timing will do that to you and take a good look at the flyweights 4 out 5 shovels I see they are bad .

Mar 16, 2012 | 10:02 PM

msgtarmor

Tourer

Joined: Sep 2007

Posts: 272

Likes: 1

From: Salem, Oregon

Quote:

Originally Posted by Sho71vel

If all the above is OK then i would suspect the carb throttle shaft is worn. Super B's will leak air where the throttle shaft fits into the carb body after several thousand miles of use. It's easier to check with the carb off the bike. Just see if you can move the throttle shaft forward or backward (toward manifold then aircleaner) or up or down. If it has significant play you can get a rebuild kit which comes with a new throttle shaft, among alot of other parts. It also has a coupla bushings that you can have a machine shop or carb repair shop install if the holes are really bad. I've found that just replacing the shaft was enough to fix mine 2 different times as the shaft was what had worn.
Good luck!
jim

Mar 20, 2012 | 02:47 PM

ARBY

Advanced

Joined: Apr 2008

Posts: 94

Likes: 2

From: CT

Yep, check for intake leak, worn throttle shaft AND timing. Also, how do the plugs look? Could be lean. Intake leaks will cause that. I change my intake clamps every 18 months or so just in case.

Last edited by ARBY; Mar 23, 2012 at 06:58 PM.