Won't prime

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Buddhahoodvatoloco
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Re: Won't prime

#16

Post by Buddhahoodvatoloco »

Sometimes the venturi is lose not allowing a complete suck. hehehehehe.
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Re: Won't prime

#17

Post by Excalibur »

The guys have put forward a lotta good ideas for you to pick over, isolate and eliminate. Hope something is working..

If nothing else is working, you may be giving it more fuel than you realize. The engine may not be able to light off because it's over rich but not showing on plugs as "wet". Cold start does dictate enrichment but there's a limit. Too much and it will give you the silent treatment. I suggest as a trial, use somewhat less choke. If you get a response but it doesn't run, give another little prime sniff and another and another until it lights off. There's an ideal mixture which is better to approach from the lean side rather than trying to recover from excess richness. Put another way, gradually adding fuel to the cylinders they will eventually cross over the threshold of ideal air/fuel ratio.
Kinda like bribing it to run. I hope that makes sense.
Good luck.
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Re: Won't prime

#18

Post by Excalibur »

It would pay to check tappet clearance. Too tight and it would explain these 3 things:
1/. low compression,
2/. hard to cold start,
3/. starting improves when it's warm/hot.

Hope this helps.
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Re: Won't prime

#19

Post by kfelt »

Andygears wrote: Sat Aug 18, 2018 12:27 am When the Linkert was rebuilt, you didn't use a float needle with a rubber (neoprene?) tip that can stick in the hole until the bike starts and shakes it loose? Just a thought.

Andygears
Happened to me. Rubber tip separated from needle and kept getting stuck. Bike would start and run for a minute and die. Start and die, start and die.
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Re: Won't prime

#20

Post by white1j0 »

Away for a few days, back at it this afternoon, put a squirt of oil down cyl. got the compression up to 50 psi, needle valve is steel, had the same problem on my other Knuckle w/ the plastic tip sticking (junk), venturi had a very small gap, 1/3 around bought a new one from Colony, had a large gap all the way around, sent it back, wrapped a piece of .001 shim stock all the way around old venturi, no light at all shinning through now, valves are set perfect, opened up the low speed a couple clicks, tried one prime, up to 15 prime kicks, still nothing
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Re: Won't prime

#21

Post by Andygears »

Excalibur wrote: Sat Aug 18, 2018 11:27 am The guys have put forward a lotta good ideas for you to pick over, isolate and eliminate. Hope something is working..

If nothing else is working, you may be giving it more fuel than you realize. The engine may not be able to light off because it's over rich but not showing on plugs as "wet". Cold start does dictate enrichment but there's a limit. Too much and it will give you the silent treatment. I suggest as a trial, use somewhat less choke. If you get a response but it doesn't run, give another little prime sniff and another and another until it lights off. There's an ideal mixture which is better to approach from the lean side rather than trying to recover from excess richness. Put another way, gradually adding fuel to the cylinders they will eventually cross over the threshold of ideal air/fuel ratio.
Kinda like bribing it to run. I hope that makes sense.
Good luck.
I kinda agree but would take it a step further, yank the air cleaner off, leave the choke open and "Hand Choke" it by holding your hand over the carb mouth! Do you feel the suction? No suction, no draw of gas. Now that it's open, if it won't start, dribble the smallest amount of gas in, no start, little more gas, when it starts, let it clear and shut it off, give it ten min. and try again, no choke, hand choke, dribble, and so on. You should be able to get a feel for what is happening from cold to warm.

And double check timing that it's not too far retarded.

Andygears
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Re: Won't prime

#22

Post by RooDog »

Your compression is ridiculously low. Really! Are you holding the throttle wide open while cranking that engine. 45 Lb is like 3:1....
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Re: Won't prime

#23

Post by white1j0 »

RooDog wrote: Tue Aug 21, 2018 12:36 am Your compression is ridiculously low. Really! Are you holding the throttle wide open while cranking that engine. 45 Lb is like 3:1....
RooDog
I think I found the problem, the bike seems to start well with the timing retarded about 1/3, as far as the compression, I don't think my HF tester is functioning properly, I'll find out later today when I borrow my brothers Snap-On tester, I want to thank everyone for there help, Whitey
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Re: Won't prime

#24

Post by PanPal »

Just for shits and grins, make sure your clutch isn't slipping and adding to your starting issue.
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Re: Won't prime

#25

Post by Andygears »

white1j0 wrote: Wed Aug 22, 2018 4:28 pm
I think I found the problem, the bike seems to start well with the timing retarded about 1/3, as far as the compression, I don't think my HF tester is functioning properly, I'll find out later today when I borrow my brothers Snap-On tester, I want to thank everyone for there help, Whitey
So it starts well with timing 1/3 retarded? Other pans start well with timing fully retarded, correct? Does it bite when you try with it fully advanced? It should!

It would seem that you are 2/3 too retarded. Do a good static timing per the knowledge base, let me know if you find my old comment on how a Harley will "Run" well with the timing 20 degrees either way, the only time you notice it is starting. Perhaps someone has a conversion from "thirds" to degrees.

Seriously, I'm glad you're making progress.

My two cents
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Re: Won't prime

#26

Post by RooDog »

Greetings Fellas. Just for comparison: I have my 74" Panny, 8:1 FLH Pistons, Andrews #1 cam, Bendix carby. Static timed at the rear of the hole. I retard the timing about 1/2 way to start, and then to full advance as soon as it fires. It will lopey idle if fully retard once started. RooDog
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Re: Won't prime

#27

Post by Excalibur »

At the risk of saying something you already know, time it using the diagram below.
lzeGg6MO_b.jpg
lzeGg6MO_b.jpg (10.37 KiB) Viewed 2199 times
I'd put a (retard starting) mark on my timer control twistgrip. I roll the twistgrip exactly 5/8" for starting. This is right on the threshold of being out of range of kickback. The proviso is that full advance is set accurately in the first instance.
Hope this helps.
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