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Old 10-03-2017, 05:27 AM
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Default Johnson 2001 15HP - Run Float Chamber Dry or Not?

Hi again.

My mini-overhaul project has come to an end and generally I'm happy with the result.

The only thing that bugs me a little is I have a slight weep from the float chamber mating surface (Item 16 in the attached image). The float chamber is plastic and the housing itself has embossed numbers to identify the screw tightening order. But in my reluctance to overtighten to avoid cracking the housing, it seems I've undertightened the screws. The fuel weep is coming from the chamber-gasket-carb body joint.

I guess I have the option to remove the carb and tighten the screws. Or just live with it.

If I run the engine out of fuel at the end of the day and wipe away any weeping fuel, then problem is probably just a niggle.

But is running the engine completely out of fuel a good idea?

Thanks.
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Old 10-03-2017, 02:07 PM
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Unfortunately you would need to remove the carburetor anyway to double check the float level.

Those screws do need to be pretty well snug though.

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.
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Old 10-06-2017, 08:26 AM
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Thanks Joe.

I hope to get the chance this weekend to get the carby off, check the float height and button the assembly back up.

I hope the rubber gasket has not been damaged beyond re-use. I don't have a spare.

Is there a Permatex gasket product that could be used to help the gasket seal as a belt and braces solution? I had been thinking of using aviation gasket maker but it may not be a good idea.

And would you recommend running the engine dry (i.e. using all the fuel in the float bowl) at the end of the day? I've never been sure if that is a good idea or not.
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Old 10-06-2017, 11:50 AM
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DO NOT use any kind of sealer anywhere on the carburetor or intake manifold assembly... it will find its way into the fuel passageways and raise havoc!

If the engine is going to remain vertical and be used often... no need to run the fuel out.

If the engine is going to be laid down horizontally, be put in storage, not used for quite some time.... since it has but one carburetor, it won't hurt to run it out of fuel. See the following..................
********************
(Running Engine Out Of Gas)
(J. Reeves)

If the engine has but one carburetor, it's unlikely that running the engine out of gas would do any harm. When the carburetor runs out of the fuel/oil mixture, the engine stops running.

However, a engine that has more than one carburetor should simply be shut off. The reasoning is that the top carburetor will run out of fuel first due to gravity and the engine will continue to run on because of the still existing fuel in the other lower carburetors.

This results in having at least one aluminum piston running up and down a steel cylinder wall with improper or no lubrication. Not a good idea!
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Old 10-08-2017, 05:55 AM
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Thanks for the reply Joe. Much appreciated.

I idled the engine, in 5 minute intervals, for around half an hour today. Gave the fuel line bulb a typical squeeze until firm or the first start. Unexpectedly, there is was no fuel weep at the end of the day. Maybe the rubber gaskets swell in the first few days after exposure to fuel to help sealing?

I didn't change the existing float for the new one in the carby overhaul kit. From memory it was 6mm higher than the carb body when the carby was held upside down.

What are the symptoms in idling behaviour when the float height is not set correctly?

My engine isn't really the easiest to start from dead cold even in our moderate 25 deg C days recently. The manual says part open the throttle (twist grip) and pull the choke all the wayout. It might fire once or not at all in 6 pulls but it won't start this way. I need to put the choke at 1/2 closed for the engine to start before it whimpers out and dies. With the choke all the way in and some throttle opening via the twist grip, it will then spring to life. If I let it run for 30 seconds or so at around 1800rpm via twist grip position, it will then settle to idle at around 1020rpm.

I'm using 95 RON fuel with Valvoline 2-stroke mineral oil at 50:1.

It's idling is rather rough with a fair degree of head shaking. It's a bit more agricultural than hoped for but perhaps I'm asking too much?

Last edited by brw0513; 10-08-2017 at 07:15 AM. Reason: More info.
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Old 10-08-2017, 11:11 AM
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Having retired in 1991, I'm not too familiar with the 2001 models... BUT... the carburetor looks similar, small changes. In the carburetor graphic.......

I a$$ume that #23 is the fixed High Speed Jet... just make sure it's clean.

I also a$$ume that #15 is the adjustable Slow Speed Needle Valve. Adjust it as follows:

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
********************
A float set wrong will result in either starving or flooding depending on which way it's set excessively. Sounds like you've got it about right... but only you will know for sure.
********************
Gaskets do have a habit of swelling slightly.
I have no idea what a "RON" is pertaining to fuel. In the US, 87 Octane would be fine.
********************
If everything is as it should be, the starting sequence would be:

Pump the fuel primer bulb up hard.
Apply a slight bit of throttle.
Pull the choke full out.
The engine should start and run within 3 or 4 pulls tops!
With the choke still out, the engine will load up fast (flood out)... regulate the choke if need be until the engine warms up.

Let us know how it goes for you.
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Old 10-09-2017, 05:36 AM
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Quote:
Originally Posted by Joe Reeves View Post
...
.
.
.
Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.
.
.
.
...
Good info as always Joe.

When you say "set the rpms" do you mean adjust the position of the threaded throttle cable anchor (#25) on the throttle cable (#8). This is the only real adjustment I can find.
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Old 10-09-2017, 09:50 AM
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Quote:
Originally Posted by brw0513 View Post
When you say "set the rpms" do you mean adjust the position of the threaded throttle cable anchor (#25) on the throttle cable (#8). This is the only real adjustment I can find.
No... What I mean is to simply turn the throttle handle (#9).

When you have the engine running properly, you can set the idle stop (#6) at whatever rpm you wish.

Last edited by Joe Reeves; 10-09-2017 at 09:53 AM.
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