Mcculloch 4hp no start

[amuller]

I’m sorta confused here. Are the rusty reeds from the one you are trying to run? If so, and given the poor appearance of the rest of the motor, I’d suspect rusted bearings also and a need for a complete teardown. Also, rusty reeds will break….

[joesnuffy]

I agree a total tear down may be next.

I think the original reeds were the very dirty ones. I think the better looking set came off the donor motor.

I don’t see rust on the crankshaft so I hope the bearings are good also but I do suspect worn rings on this motor. I think what were trying to do right now is get it to hit a lick which it has not. I think we have narrowed it down to the rings now if it does not hit a lick that is why I would like to know how much compression it has after a tad of oil is put into cylinder that and I read that particular motor needed a minimal of 90 lbs compression to run. A person would think 80lbs would do it but maybe not on this motor especially since its air cooled the rings could be just flat worn out.

Hope that helps,
Joe

[john8504]

That makes a good point. If it requires new rings then I can do it as long as I can get the parts. I’ll be bolting it back together tonight and see what happens afterwards.

The reeds did have surface rust surrounding the contact points where it seats. The newer reeds are from the donor motor and where near perfect. A little steel wool made it just right.

I took a peak at the needle bearings for the crank and they look fine from what I can see.

Before I tore the motor down, I did have the psi at 85-86 from 80ish after putting a little oil in cylinder. It kept acting like it wanted to fire off but never did. After replacing reeds, maybe I’ll get what I need to have it fire. We shall see.

[joesnuffy]

If you get it to fire up and run the compression may come up on the motor after some run time. You might try putting like a couple tablespoons of kerosene in the spark plug hole and turn the piston up like its facing the sky and let it sit a few days to free up the rings if they might be sticking then re-check compression before tearing it down.

Joe

[amuller]

My opinion here would be to take them both apart and try to make one good one. But I suppose it depends on where you are trying to go with this.

[john8504]

If I can get it running, then I know that what I have works. Ag that point I’m going to take the lower plate off, that goes under points, and put it on mine since it is warped. One issue might be that I know that not all of the gaskets are available anymore. Overall yes I want to have one, good running, decent engine that I can say that I brought back from the grave. I have a few mcculloch chainsaws that I’ve done the same things with and had to do a complete tear down. They run like champs now. This motor is just being a little bit of a pain.

Two questions. My tank has a dent on the side towards the opposite end of where the bung hole is. What is the easiest way to get this out. I’ve been thinking of using a air bladder and stuffing it in the tank, pump it up and try to push dent out. I’m also thinking this could break the seams. Secondly, what is correct lower unit oil to use? Will 80w90 be ok?

[john8504]

Well the new reeds definitely brought compression up over 90. The lowest picture is after reeds and the highest is after a couple drops on gear oil. I still have no fire. No burn. No pop. Nada. However I still have a flooding issue? I open fuel up about 1 full turn and I have fuel/carbon mixture dripping from lower shaft after cranking.

What should my adjustment be on these two screws? Screw 1? Screw 2?

Going to get someone to assist me in testing the distance the spark will jump and see what happens there.

---

Attachments:

[retiredoz]

Set the high-speed (#1) 1 1/4 turn open from closed, # 2 at 1/2 – 3/4 turns open from closed. If you’re still using starting fluid into the carb, you need to open the choke – that flap across the front of the carb. But I’d go back to putting fuel (or starting fluid) directly into the cylinder and crank. If that doesn’t produce a pop, your timing is off or your spark went somewhere..
The lower unit takes grease, not gear oil. Use whatever is commonly used in non-shift gear cases.

[john8504]

Hmm ok. I guest I have screw 2 open too far. I’ve got it 1.5 turns open and screw one I have at 1-1.5

[billw]

Have we been using the same spark plug the whole time? Sorry but I just don’t want to go back and read through the ten pages for that one.

I would pull the plug, clean it, if it is new and ding it, if it is old. Make sure it is not FOULED by putting too much oil in the cylinder. Then I would DRAIN the gas from the carb and try to make it at least pop with starting fluid, or better, a small squirt of gas/oil mix in the carb. If no fire, do like retiredoz says and put a small amount in the cylinder; then see if THAT will fire. If not, recheck your spark. It must jump MINIMUM 3/16", not just across a normal plug gap.

When you put it over slowly, with the spark plug OUT, does it make a noticeable, weasing sound, indicating that you have a little crank case compression? If not, you may have a massive lower crank seal leak, which could explain all the fuel/oil coming out of the leg, if it’s not flooding. When you get back to trying to start with a carb full of gas, pull the plug after cranking and smell it. Is it dry or does it smell like gas?

Long live American manufacturing!

[Author]

Posts