1957 G with M-18 Linkert. Carb issues

[Lonewolfrevivals]

New to me bike. Correction. It's a '54.

Wouldn't start at all. Adjusted valves, timed bike (still using manual advance) went through carb and annealed the copper intake seals. I've sprayed carb cleaner and no noticeable intake leaks (well, not enough to affect it this badly)

Bike will start now and idle fine. As soon as I give it any gas, it bogs down. Let go of gas and it goes back to a nice idle.

Timing light shows flywheel mark dead center in the inspection hole with circuit breaker fully advanced.

My linkert has a #19 jet in it. I'm thinking the bike is running way too rich. I have 90 psi on both cylinders and bike soots up the plugs. And spits gas out of the carb opening when I try to rev. Runs worse when I turn on the choke so I don't think it's a lean issue.

What size jet should be in the m-18? Should it be three plugs in there? I have adjustable needles for high and low.

Been around linkerts and manual advance before (I also have a 49 Pan with a M-74B).

Any ideas? Thanks!

[T. Cotten]

Lonewolfrevivals!

The M-18 did not use a fixed jet. It should be plugged.

If the barnyard trick of spraying stuff around the manifold shows any leak at all, its a big one.

A tiny one will still give you trouble, sooner or later.

....Cotten
PS: You meant brass, not copper seals, right?

[Lonewolfrevivals]

Lonewolfrevivals!

The M-18 did not use a fixed jet. It should be plugged.

If the barnyard trick of spraying stuff around the manifold shows any leak at all, its a big one.

A tiny one will still give you trouble, sooner or later.

....Cotten
PS: You meant brass, not copper seals, right?

Thanks Tom for confirming. My next step was to silver solder it shut. Yes, I meant brass seals and I will do a proper leak test, but it's running so bad I wanted to sort that too.

Thanks again. I'll report back with my findings.

[T. Cotten]

Lonewolfrevivals!

Don't forget that jet fits your M-74B.

A proper plug is only like four bucks.

But soft solder is easier if you must. You did mean the jet, right?

....Cotten

[Lonewolfrevivals]

Yes, the jet!

I'll get a proper plug after my testing and then clean the jet for the m-75.

That m-75 carb is all setup and running great, thanks to reading a lot of your posts over
the last year.

[T. Cotten]

Lonewolfrevivals!

The M-75 did not use a fixed jet either.
I think that's better than the M74B!

....Cotten

[Lonewolfrevivals]

Lonewolfrevivals!

The M-75 did not use a fixed jet either.
I think that's better than the M74B!

....Cotten

So I soldered the jet shut and bike wouldn't start at all. I even unscrewed the idle needle almost all the way out. So I drilled a small hole in the jet (maybe 1/3rd of the #19 size) and the bike fired up but wouldn't rev again. So I started backing off the power needle and the bike came to life.

Then I found a good balance between the idle jet and the power jet and set the idle plate screw to a good idle. Bike now starts first kick, and revs like it should.

I have no idea what size the jet is now, but I'm assuming that the #19 jet was too big and the needles weren't able to make a difference and whatever size I made the jet, I was able to meter the fuel to where it needed to be. In this case, the power and idle needles definitely affected each other. I still will need to see how the bike operates under load, but I know it's all in the jetting.

Eventually, I'll probably get a small proper jet, but it seems to be resolved.

Thanks Tom for your help.

[Rubone]

A stock M-18 has ALL high speed adjustment in the power needle, it is not a trimmer like an M74b uses. They never used a jet, just the needle. So if you have a jet you are still not quite there.

[Lonewolfrevivals]

A stock M-18 has ALL high speed adjustment in the power needle, it is not a trimmer like an M74b uses. They never used a jet, just the needle. So if you have a jet you are still not quite there.

When I had the jet soldered, I couldn't get anything. When I put a small opening in it, the high speed needle helped off idle response as well.

Learning a lot as this is only my second linkert ever. Thanks for all the input.

[Lonewolfrevivals]

A stock M-18 has ALL high speed adjustment in the power needle, it is not a trimmer like an M74b uses. They never used a jet, just the needle. So if you have a jet you are still not quite there.

Robbie, I reread your post and I think I misunderstood you. Now I think you are saying that the high speed needle controls ALL metering off of idle. Maybe I didn't have the needle out enough when I had the jet fully blocked. What is the # of turns out on initial setup? I had it at 1.5 turns out and it did nothing.

[T. Cotten]

Robbie, I reread your post and I think I misunderstood you. Now I think you are saying that the high speed needle controls ALL metering off of idle. Maybe I didn't have the needle out enough when I had the jet fully blocked. What is the # of turns out on initial setup? I had it at 1.5 turns out and it did nothing.

Lonewolfrevivals!

One and a half with no jet is just about right.

Perhaps your manifold is sucking so much air that it needs huge amounts of fuel to run at all.

....Cotten

[Lonewolfrevivals]

Lonewolfrevivals!

One and a half with no jet is just about right.

Perhaps your manifold is sucking so much air that it needs huge amounts of fuel to run at all.

....Cotten

You may be spot on. I'll have to do a leak test for sure. Since I annealed the seals, and all my threads are in good shape, what's the next best step to sealing the intake?

[T. Cotten]

Lonewolfrevivals!

First you have to find out exactly where the leaks are.
Bubbles make it easy: http://virtualindian.org/11techleaktest.html

If the assembly fails the test, then you must remove the manifold and test the inlet nipples separately.

If the inlet nipples are sound (Gs usually are), the rest is easy.

.....Cotten