Linkert DC discharge port

Classic short-frame models

Re: Linkert DC discharge port

Postby wz507 » Tue Nov 23, 2021 5:01 pm

If you suspect something is wrong and it is not firing I would remove the air cleaner, introduce 2 cc of fuel directly into the throat of the carb, retard spark, give ¼ throttle and start kicking. It should fire readily and rev once before the fuel is consumed. If it does not fire and rev you have some issue other than fuel supply to deal with. Alternatively, the fuel could be introduced via the sparkplug holes (1 cc/cylinder) or starting fluid could be sprayed in the carb to assure the cylinder is wetted down appropriately. If the engine is well wetted down with fuel and the spark is fully advanced it should kick back constantly while you kick it. If it does not kick back at full advance with fuel in the engine, this suggests you have an ignition related issue to deal with.

If it starts and revs well using any of the above suggestions then you are assured the ignition is OK and you are dealing solely with a fuel supply issue that should be relatively straight forward to remedy.

A setting of 1.5 turns open on high and low speed circuits should be more than adequate to get it started and running reasonably. When you are priming it I’d close the choke totally, hold the throttle wide open and kick it through 2 compression strokes with no ignition. Thereafter I’d open the choke fully, retard spark, apply a small amount of throttle, turn on the ignition, start kicking and it should go.

Eager to hear how you make out.
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Re: Linkert DC discharge port

Postby Ferrous_Head » Tue Nov 23, 2021 6:33 pm

I have a similar engine sitting on my bench that is nearly finished and will be going into the bike shortly. I have KH flywheels and Dytch 3 3/8ths with minus minus cams. It's a 58.

I have an MGAL to go on it.

I am now using "Fake" S&S Super E's to do first starts. You can get them jetted for 1200 engines as a start. $49 on ePray with spare jets.

I'm not sure a DC, even a bored one will feed an engine this big. That's why George made the bigger carbs. Wouldn't hurt it at lower revs, it would actually help.

But yes, a quick spray of Aerostart will tell you if you have a fuel/carb problem. Throttle wide open, 2 second spray.

As a sanity check you might also do a compression check. New build, you never know.
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Re: Linkert DC discharge port

Postby panic » Tue Nov 23, 2021 10:35 pm

Have a nice day
Last edited by panic on Thu Nov 25, 2021 11:05 am, edited 1 time in total.
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Re: Linkert DC discharge port

Postby xlh59 » Thu Nov 25, 2021 6:34 am

Hi to all,

thanks for your replies -- I had thoroughly checked my engine and I am pretty sure, that the ignition and basic settings are fine. But from your answers I could read that most likely I should have a very general problem, so I went on thinking and reading, thinking and reading again, talking, thinking ... :D

Although I have not tested my "solution", I think I found my problem:
As written before, my main suspect was the fuel supply, specifically the float level. From my experience and the thougth of a friend (with a 57XL) the plugs were just not "wet" enough. Kudos to our Dr., the answer existed already somewhere in the ether (here the xlforum), I just needed to find it.

According to different inputs, I thought it to be a good idea to raise the float level a bit. Dr.s Quote: "Though I find raising fuel level a bit, about 1/32" generally gives me better overall metering." -- but a little knowledge is a dangerous thing! And picking single aspects from a complex system even more. This is how the sentence continous: "You definitely need to bring it to the fsm specs if fuel level is low. Remember: a shorter measurement is a higher fuel level." -- Oh man! :oops:

IMG_20211125_105230_923.jpg
IMG_20211125_105230_923.jpg (461.64 KiB) Viewed 1854 times


I will keep you updated -- next starting phase will be tomorrow
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Re: Linkert DC discharge port

Postby xlh59 » Thu Nov 25, 2021 6:53 am

@Ferrous -- our setup seems to be quite identical. My cylinders are 3,25" with 0.05" oversize custom pistons and made of aluminum. I also use the minus-minus cams and I also have a GAL on my shelf -- but I also had the DC-11 and I would like to use it if possible. From my understanding a 1,5" carburetor would be not completely "of" for a 77cui stroker engine. Eventually we should meet halfway (maybe Sri Lanka?) to have a 1/4mile race :D :D
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Re: Linkert DC discharge port

Postby Ferrous_Head » Thu Nov 25, 2021 9:08 am

Yeah, I have no idea what the flow numbers on a DC are. And a bored DC is going to be even rarer.

If Harley sized them correctly to begin with (picked the size they needed) then they would be adequate for a stock 900 engine. But at 77" tour a long way above that. Add in improvements to cams and exhaust not to mention porting (which I assume you have) and I think you'll find it strangled on the top end.

I've never been that concerned about float height. I used to be meticulous about it.

But then I thought about what happens when I turn off the fuel supply. My engines keep running until the bowl is drained. And I know that the height varies while I riding the bike. Gravity and centrifugal force combines with inertia and vibrations mean the fuel height isn't static to within 50%.

But that's just my opinion, others may disagree.

When troubleshooting I always use a systematic approach.

I know what an engine needs to run.
Enough compression
Fuel and air
a spark at the right time.

I check in that order. A comp check is quick and easy and rules out so many problems.
The fuel air/thing can be done with a can of Aerostart to begin with.
I leave the ignition stuff until last as it's the most time consuming.

Oh. Also, I start these things on rollers. I'm too old for a lot of kicking.

Also, they are already on the rollers as I use them to pump the oil through the engine before I start it. It takes 60+ kicks to get the oil to return the first time. I'm too old for that now.

I don't think we can go to Sri Lamka. Covoid restrictions.
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Re: Linkert DC discharge port

Postby panic » Sun Nov 28, 2021 6:31 pm

[crickets]
Last edited by panic on Tue Nov 30, 2021 9:20 am, edited 1 time in total.
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Re: Linkert DC discharge port

Postby panic » Sun Nov 28, 2021 10:03 pm

[crickets]
Last edited by panic on Tue Nov 30, 2021 9:20 am, edited 1 time in total.
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Re: Linkert DC discharge port

Postby panic » Mon Nov 29, 2021 5:00 pm

[crickets]
Last edited by panic on Tue Nov 30, 2021 9:21 am, edited 1 time in total.
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Re: Linkert DC discharge port

Postby panic » Mon Nov 29, 2021 5:12 pm

[crickets]
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