HD-25 carb settings

[jimbrizzolara]

I just put my HD-25 back together, I had an earlier post about the float, which I made and works as it should. Good spark and 80 psi on both cylinders, and I cleaned the carb as well as I could without removing it. Plenty of fuel going to the carb. When adjusting both needles on the carb the best it will run is a surging fast idle. The main needle is 3/4 of a turn out, the smaller needle on the right side of the intake is 1/2 a turn out. I also noticed in the sunlight as it was running that a fine spray of fuel is coming out of that intake. It’s like the motor wants to run faster and is almost there. It’s been a while since I worked on a TD or HD, I forgot how “fun” it is to work on those carbs. What do ya think, a blockage in the carb?

[Buccaneer]

Prepare to be boarded!

[jimbrizzolara]

Thanks for that information. It looks like my needle settings are in the ballpark. That’s why I think there’s a fly in the oinment somewhere.

[aquasonic]

The large stainless screw on the bottom of the carburetor is the check valve. The check valve screw has a screen around the outside, and a tiny cylinder on the inside that prevents backflow. If this check valve is not free, there will be no idle. See this website for lots of good information. http://pochefamily.org/outboard/CarbService.html

If the check valve is stuck, soak the screw in a solvent like isopropyl alcohol or acetone. Take it out of the solvent and tap on the benchtop until it comes free, repeat as necessary. Once free, you can feel the cylinder moving back and forth when shaken.

Improvise-Adapt-Overcome

• This reply was modified 4 years, 1 month ago by aquasonic.

[jimbrizzolara]

Thanks for the tip. I did clean and inspect the screen and check valve. The valve was working.

[lloyd]

80 Psi is great for that model and it’s firing, so those two factors are covered. Surging (and or backfiring/popping) at any speed is usually a sign of lean mixture, and you say the low speed needle is 1/2 turn open which too lean. Have you tried opening the low speed needle to 3/4 turn where it should be?
And try cleaning out the check valve and screen as aquasonic suggested. And the line from the check valve to the low speed orifice may also be blocked with dirt or old varnish so it should also be cleaned out. And are you sure that fuel is getting to the high speed needle?
My wife was raised in Grand Rapids and we are in Traverse City. Give me a call by phone and maybe we can figure it out. I am a very slow typist. 231-929-7479

[aquasonic]

lloyd wrote:

80 Psi is great for that model and it’s firing, so those two factors are covered. Surging (and or backfiring/popping) at any speed is usually a sign of lean mixture, and you say the low speed needle is 1/2 turn open which too lean. Have you tried opening the low speed needle to 3/4 turn where it should be?
And try cleaning out the check valve and screen as aquasonic suggested. And the line from the check valve to the low speed orifice may also be blocked with dirt or old varnish so it should also be cleaned out. And are you sure that fuel is getting to the high speed needle?
My wife was raised in Grand Rapids and we are in Traverse City. Give me a call by phone and maybe we can figure it out. I am a very slow typist. 231-929-7479

Jim, I strongly advise you to take up Lloyd on his offer. There is no one more knowledgeable about these motors.

Improvise-Adapt-Overcome

• This reply was modified 4 years, 1 month ago by aquasonic.

[jimbrizzolara]

Oh yeah, I’m in my workshop right now checking things out before I call him. Lloyd is the guru of these motors.

[jimbrizzolara]

Problem solved. I took some good advice and contacted Lloyd. I was convinced it was a fuel problem and had a couple of conversations with him during which he suggested I check certain things out. Nothing did the trick, so we decided to look at the ignition. I removed the flywheel, planning on swapping out the condensers. While giving the mag plate a quick look I noticed one of the condensers was not connected to the post where the points wire is attached. The condenser wire terminal was just contacting the post. When the motor was serviced who knows when the condenser wire wasn’t attached. Fifteen minutes later the HD was running great, and at 80 lbs. compression on both cylinders (I know, surprising) it idles down to about 50 rpm. Well, I could be exaggerating a little bit. It’s always a relief to solve these tough ones. Thank you for all of your assistance, Lloyd.

[dave-bernard]

you will never forget it for the rest of your life.

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