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Linkert transition slot

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Tunglegubbin
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Linkert transition slot

#1

Post by Tunglegubbin » Sun Jun 17, 2018 7:37 pm

This is my first bike with a Linkert, and I have a really hard time starting it.
I have actually only got it started twice and it’s a new rebuild.
I have pressure tested the intake, taken out the fancy electronic ignition and put the points back to be dead sure I know when it fires. Checked against flywheel timing for both cylinders.
I have changed out the twin lead coil for two single lead coil. Nothing makes a difference.

And my thigh confirms there is plenty of compression.

I think I’m down to a fueling issue.
When priming the engine, are you supposed to do that with open or closed throttle?
I have been doing it with full open. Where does the choke enrichment draw its fuel?
The main well or the transition circuit?
No matter how much I prime I only get a small backfire through the carb. I cannot get my plugs wet.

With the carb off I checked the float height. It was 1/4” from the bowl flange to the top of the float.
On cars you always set float height measured from the top of the actual fuel level.
It seems weird to set it dry.
Or have I misunderstood the procedure?

The only strange thing I have found is the position of the throttle blade vs the transition slot.
The blade has the slot fully uncovered at fully closed position.
On cars you aim for a square uncovered area of the slot with the blade at idle speed position.
Could this be my problem?
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panheadrider1961
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Re: Linkert transition slot

#2

Post by panheadrider1961 » Sun Jun 17, 2018 8:57 pm

ok , good looking scooter make sure that plate is fully closed when throttle is closed if not loosen screw on shaft and take a pencil or wooden dail and hold it closed careful not to bend tighten shaft screw ,watch plate open throttle wide open should be in center with no plate showing buy this i mean take a coin in your hand hold it to where all you see is thin edge this is what the plate should look like in carb thin edge , close throttle, plate should be fully closed if not work with it till you have it perfect , by the book screw on right side of carb low speed needle turn it down to close do not jam just feel it touch ,now turn it back out 5 turns this is rich when it starts running adjust 5 to 10 clicks back down this should be a little rich new motor you wont it a litte rich needle on left close careful do not jam open 1and 1/4 turns no more than 1 and 3/4 this you adjust riding click at a time but 1 and 1/4 should be it, you said float was good at 1/4 and it cannot rub bowl it has a small offset to the left 1/16 looking at bowl in your hand , you have fire? put breather back on it will not draft as good with it off to much air flow ,make sure key is off open throttle wide open close choke completely shut kick over motor 2 to 3 kicks on my pan does it look at back jug you should see mist of gas on it this is called hot you have primed the cylinders ,if you dont see this intake or carb not sealing and you do not have good vacum to draw gas into cylinder , next close throttle pull choke up 2 clicks turn on key, advance is in retard kick motor and if everything is right she should fire off and run turn breaker to full advance and its ready to go ,good luck and break it in buy the book slowly and cool down, start and ride some more

1950Panhead
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Re: Linkert transition slot

#3

Post by 1950Panhead » Sun Jun 17, 2018 9:41 pm

I think I’m down to a fueling issue.
Good chance you are correct.
If you want to test that theory use a spray oil can filled with gas, remove air cleaner, spray left and right inside carb for both cylinders, replace air cleaner.
If engine starts briefly or continues to run you have a carb problem.
When priming the engine, are you supposed to do that with open or closed throttle?
Closed throttle works best.
I have been doing it with full open. Where does the choke enrichment draw its fuel?
The main well or the transition circuit?
When you close choke vacumn increases in carb body drawing more gas from bowel through nozzle.
Or have I misunderstood the procedure?
The idea is to fill the bowl with gas without over flowing bowl.
The only strange thing I have found is the position of the throttle blade vs the transition slot.
With the throlltle closed the slot should be on the manifold side, the manifold vacumn draws gas for idle.

awander
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Re: Linkert transition slot

#4

Post by awander » Mon Jun 18, 2018 3:38 am

panheadrider1961 wrote:
Sun Jun 17, 2018 8:57 pm
...look at back jug you should see mist of gas on it this is called hot...
Really? You get a mist of gas on the rear cylinder when you prime it?

Tunglegubbin
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Re: Linkert transition slot

#5

Post by Tunglegubbin » Mon Jun 18, 2018 6:51 am

awander wrote:
Mon Jun 18, 2018 3:38 am
[quote=panheadrider1961 post_id=121280 time=<a href="tel:1529265427">1529265427</a> user_id=8647]...look at back jug you should see mist of gas on it this is called hot...
Really? You get a mist of gas on the rear cylinder when you prime it?
[/quote]

I’m also not sure what that means ? Where should this mist comes from?

Can anyone verify whether this much of the transition slot is OK?
On a Holley/Rochester type of carb this will result in a non responsive idle circuit since the carb will draw fuel from the idle feed restriction instead of the idle mixture screw orifice. And you have no working transition circuit to get you out of idle circuit to the main circuit.

awander
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Re: Linkert transition slot

#6

Post by awander » Mon Jun 18, 2018 7:17 am

From memory of the slot on my '52, that looks fine to me.

Are you sure you are getting gas flow to the carburetor, and that the filter is not clogged up?

Are you sure the carb bowl is filling?

If you put the choke on full, and give it 3 kicks with the throttle wide open, you should smell fuel.

Tunglegubbin
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Re: Linkert transition slot

#7

Post by Tunglegubbin » Mon Jun 18, 2018 8:33 am

I get fuel, but not enough it seems.
After 3 start attempts (9 primer kicks) ,with just a cough at each attempt, I pull the plugs and they are not wet.
This is the reason for my question regarding closed or open throttle during priming.
My thinking was that the vacuum created by the closed choke butterfly would make it draw fuel from the main nozzle.
And an open throttle would give less stuff in the way for the fuel into the cylinders.
But if, as 1950Panhead suggest, that closed throttle is more effective, the fuel needs to come from the transition slot?

I took the carb off last night, even if I had dinner between the last start attempt and draining the fuel bowl, it seem like the drained volume does not correspond to the bowl size.
I have fuel flow from the tank.
The filter is not clogged.
Needle and seat seems OK.

Is there a way to verify actual bowl fuel level?

panheadrider1961
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Location: macon georgia

Re: Linkert transition slot

#8

Post by panheadrider1961 » Mon Jun 18, 2018 9:39 am

awander yes it has the stock m-74b on it had it know for 35 years it comes out vent hole behind high speed needle, float is to spec everything good on carb 2 kicks cold 1 hot my friends 65 same thing and its original 2, nobody never said it should not if it does not mist it wont fire off .............advice if it is something wrong just done it all these years

panheadrider1961
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Bikes: 1961 fl 1976 fxe
Location: macon georgia

Re: Linkert transition slot

#9

Post by panheadrider1961 » Mon Jun 18, 2018 9:59 am

my friend you are dealing with a draft and draw carb not a................. newer carb or car carb that has accelerator pump if it does not draft it does not pull enough gas into venturi to shoot it into cylinder no air filter on will loose closed drafting it needs, look at the carb choke plate at very end and has a little flipper in it with it closed it only allows enough air to come in when kicking this is the enricher so to speak and it draws the gas out of bowl when put choke on watch low speed needle it raises up to open the circuit wide open this is where it draws through and as the manuel says full choke wide open throttle for cold starting 2-3 kicks lot of linkert advice and how to here in knowledge info

blewcrab
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Re: Linkert transition slot

#10

Post by blewcrab » Mon Jun 18, 2018 1:07 pm

close choke....throttle 1/2 open ....kick 3 times ...you should smell fuel .....open choke ....turn on ignition .....giva good kick while opening throttle.....if no start , kick again , and again ......if still no start , turn off ignition open throttle all the way and kick 3 times to clear flooding ,,,,,then turn on ignition and kick to start . this is my procedure , most guys develop slightly different starting methods .....good luck !

ozwick86
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Re: Linkert transition slot

#11

Post by ozwick86 » Mon Jun 18, 2018 1:13 pm

To check to see if gas is getting to the carb. Take the linkert strainer off the bottom of the carb and turn on the gas. You should see gas streaming the bottom if the lines leading to the carb are not plugged.

pan620
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Re: Linkert transition slot

#12

Post by pan620 » Mon Jun 18, 2018 1:21 pm

I do not think you want the plugs "wet", prime like everyone suggested take off air cleaner and see if you can see fuel in the back of the manifold. Hold throttle open slightly in case your idle is to low for it to start, or stay started have seen the happen before.

Tunglegubbin
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Re: Linkert transition slot

#13

Post by Tunglegubbin » Mon Jun 18, 2018 2:42 pm

Gentlemen,

Thank you for your replies, and panheadrider1961, in all friendliness, punctuation makes your reply so much easier to read.

I never talked about accelerator pumps or .....newer carbs.
We are talking about a carburator with butterfly throttle valve and venturi orifices that create pressure differences that moves fuel.
Same physics applies regardless if says Schebler, Linkert, Holley or Rochester on it.
I'm not trying to be an asshole. When I get conflicting information I try to understand the reasoning behind the advice.
If all I get is "-Because I say so!" or "-That is how we have always done it!" , that information doesn't help me understand the world.
Again, I'm not after pissing anyone off, just logical reasoning.

I get your reply that the cam on the choke shaft lifts the low speed needle higher (highest on full choke), meaning that the primimg fuel comes the low speed circuit. Since the low speed circuit exits on the engine side of the throttle blade, wouldn't the highest vacuum signal to the priming circuit be achieved with the throttle closed?

Right now I have three priming recommendations:
1) Fully open
2) Fully closed
3) ½ way

I know that each engine has it's own quirks, but I dont think Linkert's instructions was, -See what works best!
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Tunglegubbin
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Re: Linkert transition slot

#14

Post by Tunglegubbin » Mon Jun 18, 2018 2:45 pm

Pan 20,

I'm not looking for wet plugs.
Just that after 3 start attempts with no more that a cough, i would have expected to find that.

Making me supect that I cannot get it to prime properly.

awander
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Re: Linkert transition slot

#15

Post by awander » Mon Jun 18, 2018 3:41 pm

panheadrider1961 wrote:
Mon Jun 18, 2018 9:39 am
awander yes it has the stock m-74b on it had it know for 35 years it comes out vent hole behind high speed needle, float is to spec everything good on carb 2 kicks cold 1 hot my friends 65 same thing and its original 2, nobody never said it should not if it does not mist it wont fire off .............advice if it is something wrong just done it all these years
I've never noticed it, if it does happen on my bike.

I'm gonna' check next time I start her, though.....

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