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52 pan coughs while crusing

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james
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52 pan coughs while crusing

#1

Post by james » Fri Jun 12, 2009 5:40 pm

I've been running a newly restored 52 panhead close to home to work out any bugs.
The engine is completely rebuilt including the heads, solid pushrods, sifton lifters,
Andrews J grind cam, carb (linkert 74) gone over 3 times with Cotten float, has electronic ignition 2000 beyond, everything is super clean, valves adjusted twice, carb adjusted several times, new plugs, battery good, new gas @ 2 gallons in tanks, runs strong now that I have the timing set and the starting procedure in order.
My problem is after about 2 miles the engine will cough as if it's starving for gas or like the gas level is low and you pull up on the gas reserve. It will stop coughing and move on but I fear it will leave me stranded. It didn't die out yet so I didn't have a chance to see if wacking the carb would help.
Im thinking fuel starvation of some sort, any ideas?

jim



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Re: 52 pan coughs while crusing

#2

Post by LittleAl » Fri Jun 12, 2009 6:19 pm

float level in carb?

"older" Cotton float? I remeber reading recently about the very newest gas not necessarily being compatible and swelling causing the float to rub inside the bowl

but pulling up on the rod solving the problem when it happens leads me to believe it's most likely the fuel valve. test it by opening it (not rod up in reserve) and see how much gas it flows and for how long. I'm sure someone knows what it's supposed to flow but I would think if it flows at a steady rate of at least a pint every few minutes you're probably good.

Any hose that might have swelled or deteriorated in your fuel flow?

I'm sure some of the smart guys will jump in soon...

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Re: 52 pan coughs while crusing

#3

Post by james » Fri Jun 12, 2009 6:25 pm

It's a new cotten float. It act's like it does when you run low on fuel and you have to pull the reserve. Pulling the reserve makes no change. There are no rubber fuel lines, everything is stock / stock, except for the ignition.
jim

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Re: 52 pan coughs while crusing

#4

Post by LittleAl » Fri Jun 12, 2009 8:57 pm

then I'd say it's probably a cap not venting (try with the left tank cap loose) or my original suggestion, improper float adjustment, or maybe something lodged in the needle & seat

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Re: 52 pan coughs while crusing

#5

Post by NightShift » Fri Jun 12, 2009 9:36 pm

LittleAl wrote:"older" Cotton float? I remeber reading recently about the very newest gas not necessarily being compatible and swelling causing the float to rub inside the bowl
...
Old or new, Cottons floats floats the same, unless maybe the old ones start to rub the bowl.

Then he sends you a new one for free.
And kicks me around the barn.

NightShift.

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Re: 52 pan coughs while crusing

#6

Post by awander » Fri Jun 12, 2009 10:13 pm

This sounds like the problem I am having with my '52-also with a Linkert 74B, but no special float.

Mine coughs once, when I am cruising at about 1/8-1/4 throttle, if I roll on slowly. If I then open it up, the cough goes away, and the bike surges forward.

It got better with a fully-charged battery(love that 32E generator) but it is still there sometimes.

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Re: 52 pan coughs while crusing

#7

Post by NightShift » Fri Jun 12, 2009 11:02 pm

Y'know,
Sucking air at the wrong places occurs to me.

Just thinking,

NightShift

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Re: 52 pan coughs while crusing

#8

Post by james » Sat Jun 13, 2009 1:44 am

NightShift wrote:Y'know,
Sucking air at the wrong places occurs to me.

Just thinking,

NightShift
I think I'll pull the carb off again and look inside
Does anyone use any type of sealer on the intake to head fittings before cranking them down?
I did not.

Thanks for the ideas so far
I have had a perfectly wonderful evening, but this wasn't it.

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Re: 52 pan coughs while crusing

#9

Post by doug_heisel » Sat Jun 13, 2009 3:00 am

Just a shot in the dark but maybe sediment clogging shut off valve? or fuel filter?

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Re: 52 pan coughs while crusing

#10

Post by panfreak » Mon Jun 15, 2009 4:32 pm

Are you using stock tanks, or aftermarket, and is the fuel draining from both? I may be off base, but it will be helpful info anyways to know that I used a stock rod in an aftermarket tank and had similar stalling issues. I noticed my right tank was always empty when this occured, but was stimied because the left had lots of fuel in it. After some measurements, it turned out that the aftermarket tank was a bit shallower than the split pin on the rod allowed. Once I relocated the split pin slightly higher on the rod it allowed me to access the gas in the left tank and no more problem. This may not help you, but take it for what it's worth...
Chewy.

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Re: 52 pan coughs while crusing

#11

Post by james » Mon Jun 15, 2009 6:03 pm

panfreak wrote:Are you using stock tanks, or aftermarket, and is the fuel draining from both? I may be off base, but it will be helpful info anyways to know that I used a stock rod in an aftermarket tank and had similar stalling issues. I noticed my right tank was always empty when this occured, but was stimied because the left had lots of fuel in it. After some measurements, it turned out that the aftermarket tank was a bit shallower than the split pin on the rod allowed. Once I relocated the split pin slightly higher on the rod it allowed me to access the gas in the left tank and no more problem. This may not help you, but take it for what it's worth...
Chewy.
Hi Chewy
Everything is stock and it all worked fine last year before I tore everything down to restore. I know if it aint broke don't fix it.
The fuel delivery is fine, I'm leaning towards the intake manifold nuts and the float adjustment. By now I'm good at doing everything twice or 3 times till I get it right.

thanks, Jim

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Re: 52 pan coughs while crusing

#12

Post by FlatHeadSix » Mon Jun 15, 2009 6:24 pm

LittleAl wrote:then I'd say it's probably a cap not venting (try with the left tank cap loose)
I'm with Al, I would double check the caps to make sure they are venting. After that I would set up for a manifold leak test, put the air to it, soap everything up, and look for bubbles.

mike

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Re: 52 pan coughs while crusing

#13

Post by NightShift » Mon Jun 15, 2009 7:51 pm

james wrote:Does anyone use any type of sealer on the intake to head fittings before cranking them down?
I did not.
Dear James,

Just use anti-seize or grease on the nuts and the seal cones. The crappy gas eats sealers.

And its a good thing it eats loctite.
Just hope your bubbles dont come from between a insert and the head.

The NightShift

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Re: 52 pan coughs while crusing

#14

Post by Kuda » Tue Jun 16, 2009 7:52 pm

james wrote: My problem is after about 2 miles the engine will cough as if it's starving for gas or like the gas level is low and you pull up on the gas reserve. It will stop coughing and move on but I fear it will leave me stranded. jim
I'd recommend you check your cap vents. The aftermarket caps vent through little holes in the outer rim of the caps, while the stockers vented through little embossed channels on the edge of the cap. The big diff is that a thick rubber gasket can compress enough to cover the vent holes on an aftermarket cap leaving you stranded, while the stockers can't be easily covered. Next time it does that, loosen up the caps and see if it goes away suddenly. Then pull over and tighten up your caps or end up chasing them down the shoulder. :roll: If that fixes it, just trim back the outter edge of the gaskets or switch to the leather gaskets and have a good ride...

-Kuda (it's the "after 2 miles" that makes me think caps...)
'49 panchop

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Re: 52 pan coughs while crusing

#15

Post by awander » Tue Jun 16, 2009 7:55 pm

I rode about 75 miles over the weekend, and toward the 45 mile mark, my '52 started coughing when I got on teh throttle hard.

Turning the lights off made the cough go away.

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