O & R Carb Repair Tutorial

[factory 487]

Sources for new reproduction Carb Diaphragms

 

USA, contact either @Wallfish or @CNew by personal message (PM).

UK & Europe, contact me @factory by personal message (PM).

 

O&R Carb Repair Tutorial

 

The tutorial below was copied from the original thread from the old forum saved by the internet archive, tutorial courtesy of laserscottman.

 

Here we go! The first pic in this thread shows how it all began. Following are the things I encountered along the way, during cleaning. After receiving the new diaphragm in the mail, I fully used Webhead's excellent instructions to reassemble the Primer/Diaphragm Valve Assembly successfully, with the following pictures detailing how I understood it. Got a block of soft wood and gently screwed the valve body down to hold it still to work on it. Fashioning a suitable 'filament' to thread through as shown, the filament is then used to lift the Diaphragm Arm Spring ends to allow the Diaphragm Roller to be laid in it's place at the right time in the assembly sequence. Then the Disc, Diaphragm and Cover are assembled.

The gum package is just a dark background to show the loop on the filament end to better grasp it. A non-magnetic pair of tweezers helped lay the roller in when it was time. The dental tool made it easy to pull/lift/move the Diaphragm Arm Spring to the various positions during assembly.

This is a detail view of how the spring will end-up over the roller in the end. Good practice to 'feel' how those spring ends will react to the filament tugging them.

Now the Spring is lifted and stays at this position, to allow for installing the Diaphragm Arm. Note that the Roller and the Diaphragm Valve Ball are in place before the Arm is laid in place.

The next part is tricky. Using the dental tool to push the Spring over the Lever toward the Roller, you must help the Spring tips over the Roller by using the filament, and helping the Lever to stay draped over the cross pin, until the big end of the Spring is seated well in the Lever short end, and the Spring ends are capturing the Roller. All this is done kind of simultaneously, according to the position of the parts. You will be glad you only need 1 hand to hold the filament, and that you have a fine tool like the dental tool!

Perfectly aligned, and will stay if the Lever Arm is not lifted all the way up--which is what got me in this jam in the first place! Now, you must carefully remove the filament. I cut the long end near the Lever Arm, and gently removed the filament.

There it is!

Then you can sequentially assemble the remaining parts. Be sure to install the screws with fingers, loosely, to avoid bunching up the Diaphragm in the threads. Don't overtighten the screws; the cover can be warped a bit, and may "bite" through the rubber Diaphragm.

This assembly then gets the thick Gasket and Diaphragm Valve installed with the clear plastic valve against the body, covering the hole. This is a one-way valve that opens and closes rapidly during operation.

The Needle Valve Assembly and the long screw mount the Primer Diaphragm Valve Assembly to the "Quadrant" Carburetor Assembly (carb body). Remember you are tightening a hollow brass part to an aluminum part! Snug, but not overly so. Kinda looks like the Starship Enterprise, don't it? Now this Dinosaur fits in among his smiling friends!

Little, but MIGHTY!

Many thanks to Webhead for his patient guidance and sharing of parts and resources! And thanks for this forum! Cheers!

 

Extra Information

 

Another important post courtesy of Webhead who you can contact on here to buy replacement carb diaphragms.

 

"One thing that Scott mentioned that is VERY important- do not over tighten the brass needle valve assembly! I use a nut driver and give it a slight snug. In my earlier days, I snapped off two or three by using a 5/16" wrench. With a wrench, it seems like you always want to give it a little more and then snap!"

 

David

 

Edited;

Nov 28 2014 to add the pictures to the forum.

Dec 07 2020 to update diaphragm sourcing info.

[factory 487]

Carb Setting

 

These posts are from the old forum thread for setting the carb needle.

 

Original post by Webhead.

 

"1 and 1/4 out for starting. I have had units run good between 3/4 and a full 2 turn
out."

 

Original post by usedtoolman.

 
"If I recall there is one more factor on the needle setting. If you have a slotted needle
the setting is 1/2 turn as opposed to 1-1/4 for the non grooved needle."

 

Original post by Webhead.

 

"I have a service bulletin in my dealer's manual that notifies all techs to remove the
screen from the carb, on any engines that they worked on. Apparently the screen
getting clogged caused more problems than if there was no screen at all. The later
carbs were completely void of the screen."

 

Filter Foam

 

Don't forget to remove and clean out all traces of the old air filter foam while you have the carb apart.

The early engines only have one section which doesn't come apart, the later ones have an extra section as shown in the pictures.

 

If the filter foam has already disintegrated and got sucked into the engine it can cause damage to the cylinder & piston.

 

 

New filters can be easily made by cutting them out from a larger piece of new filter foam (such as the pre-filter below, that I got from my local lawnmower repair shop).

 

 

Fuel Mix

 

We recommend a fuel mix ratio of 32:1, using non-ethanol gas/petrol (aka non-oxy) and mixing it with a good quality mineral based 2-stroke oil (such as the red color Stihl HP mineral oil, other brands are available).

 

David

[Wallfish 698]

Thanks David!

I was trying to post the ENTIRE thread but it would not allow me to do it with ALL the pics and gifs copied into it. At least we have the vitals posted!

And Thanks Again to Laserscottman for doing this in the first place. It was by far, the most viewed thread on our old forum.

 

Testing check valve

Once it's all back together use a piece of fuel line connected to the inlet and try to blow in it. It should only allow air to pass when the primer button is pushed. If it's allowing air to pass otherwise it's not sealing and therefore not check valving.

Some carbs allow the cover to push down on the little arm ever so slightly too. I typically don't use a paper gasket along with the diaphragm but I do add one when this condition occurs. It's an easy solve compared to trying to bend that little arm.

[majorxlr8n 2]

Thanks David! And thanks again to Laserscottman for doing this in the first place. It was by far, the most viewed thread on our old forum.

 

Indeed!! just in time for my carb surgery. MUCH THANKS!!!!

Marty

[factory 487]

Don't forget to remove and clean out all traces of the old air filter foam while you have the carb apart.

The early engines only have one section which doesn't come apart, the later ones have an extra section as shown in the pictures.

 

If the filter foam has already disintegrated and got sucked into the engine it can cause damage to the cylinder & piston.

 

New filters can be easily made by cutting them out from a larger piece of new filter foam.

 

This information was intended to go at the end of the first post but the editor timed out, the four pictures somehow appeared though.

 

David

[tackdriver56 2]

That Filter Foam is a scary thing! My air cleaner housing on the Polaris Power Pole snow-thrower is EMPTY. Hopefully, as a snow appliance, it was ALWAYS empty.
So far I've only inspected the carb diaphragm, which is stiff but intact. It has run, but not very well. Since I attempted to use gear oil in the gearbox, and the engine sucked it all out and burned it, I suspect the shaft seals. At least everything is well lubricated ;-)
 

[factory 487]

Its usually obvious if they have been run without removing the foam, bits of it are usually stuck to the inside of the carb intake & can be seen in the reed assembly in you remove the carb.

The carb diaphragm should be flexible, they are usually stiff & need replacing, although engines that were never run from new may still have a flexible diaphragm.

 

David

[tackdriver56 2]

Thanks David

[old allis 0]

HI to everybody i have just joined this forum and trying to find my way around , my interests are vintage tractors ,3 Allis Chalmers , 1 Normag C10 , 1Bolens garden tractor . Also i like to biuld old motor cycles to my own specification . A third hobby is collecting vintage model engines , this leads to recently buying an Ohlsson and Rice 3/4 HP boat engine , unfortunately the diafram pump assemble is missing from the carburettor . Can any one out there sell me any of the parts or carb complete ,or point me in the right direction .

 

Regards to all

 

Mike G .

[Webhead 95]

^{I have what you are looking for.}

[old allis 0]

Hello good morning Webhead , thanks for replying so promptly to my request  , Please give me your price and i will figure a way of getting the money to you  . If you have Paypal it would be very easy i think .   Another problem i have since encounterd is the recoil spring is weak and one of the ratchet pawls is missing the little spring . SO can you also supply a new recoil spring and two ratchet pawls . Your help with this project will make me a very happy man .

 

Good luck with all you do .

 

Regards from Hampshire England

 

Mike Guilford

Edited July 14, 2019 by factory
Email address removed to help prevent unwanted or spam mail.

[tackdriver56 2]

Webhead: diaphragm received and metal disc transplanted with Seal-All adhesive. Curing overnight. Tomorrow will be the moment of truth...

[tackdriver56 2]

Still not running. I've replaced the diaphragm, ensured good fuel flow through the check-ball to the priming chamber, but the motor will only run as long as I manually pump the priming button, even in full choke to half-choke. (It won't run at all without choke).

 

I pulled the needle and cleaned it (set to 2 turns).

 

What am I missing?

[tackdriver56 2]

I guess my next step is to dismount the carb, and see if I missed a passage that needed cleaning?

[Wallfish 698]

Try connecting a clean piece of fuel line to the carb and blow into it. It should only pass air when you push the primer button and the little ball should check valve the air when you suck air out. If air is passing without pushing the button you will need to inspect inside and find out why. The arm may need adjusting, check valve ball is stuck or needs replacing, ect, ect.

[Webhead 95]

Sounds like a possible seal leakage issue that needs more fuel to compensate for air being sucked in. And, John is correct, the carb must be put together correctly for it to perform. Do you hear a slight squish sound when priming? Another sign that the primer is doing it's job. Don't forget, these things can be head bangers.

Edited February 16, 2015 by Webhead

[tackdriver56 2]

Thanks guys. The manual priming works well., and I did perform the flow/no-flow checkball test with clean fuel line. (also blew carb cleaner through it, without the diaphragm installed).

[Wallfish 698]

I've done it that way too with just blowing carb cleaner through but without a doubt, complete dis assembly and a thorough cleaning is better. I know it's a PITA but...

 

It's also recommended in the service manual to change the ball every time the carb is serviced. I've reused quite a few but also found replacements at an "old school" hardware store in a drawer for bearings. He didn't have too many and I bought them all, 12 or so. Cost was about $2 or $3 but I also have a bunch of engines and it's probably not worth the time and effort for just one.

[tackdriver56 2]

Just to be complete, the priming assembly did need to come off for proper cleaning.

It's not obvious in the photos, but the passage out of the diaphragm/priming chamber is funnel shaped, with a tiny hole at the bottom.

Mine had been partially blocked by some debris, which became obvious when I removed that assembly.

There was also debris in the filter screen, in the carb body, below that "funnel".

So it's well worth the effort to disassemble and clean thoroughly.

Thanks again for the advice.

[Dixson 0]

I have a carb that doesn't have a primer button and I can only get the engine to start but not run. Do I rebuld the carb the same? I didn't see any ball in chamber where the spring and lever and roller is. There is just a glob of rubber on the lever.

[Wallfish 698]

 

Your carb is probably from a Chicken Power bicycle engine. The primer wasn't needed because the fuel tank is mounted above the carb and the rubber stopper type carbs are the newest style. Hopefully the little rubber thingy isn't dried out and hard because we haven't found a way to replace just the little rubber, only change the whole arm if you can find one. Member Webhead may have some if you need one, he is also the same guy who sells the diaphragms on ebay. A good remote control fuel line check valve may substitute but I haven't had the need to try that yet. That's all that little ball or rubber does, check valve the fuel so it only flows in the direction of the carb. You can test that rubber valve by connecting a clean piece of fuel line and see if you can suck air past the valve. if you can, the arm will need to be replaced unless you can get it to seal properly.

 

A new diaphragm will help pump enough fuel and usually needed to get these engines running.

[renovator 0]

Excellent!  Thanks for a great article!  I have an AMP CHAMP in terrific condition.  It is a little generator run by the attached O&R engine.

 

Looking to sell to a collector who would appreciate it. Thanks!

Edited September 21, 2019 by factory
Email address removed to help prevent spam, it's best to send contact information by personal message (PM).

[factory 487]

Here is another bit of information on the needle valve setting for needles with an X on the valve head, this valve has a .015" orifice along the tapered seat of the valve. According to instructions the setting is to have the valve gently bottomed.

I'm sure I have some carbs with an X on valve head and but haven't tried this procedure yet.

 

David

 

[Freak 0]

A very helpful tutorial. I have  a chainsaw with an O&R engine, and the tutorial was exactly the issue. Forgive me in I cross a line here, Where do I go to find replacement parts?  

Thanks in advance.

[factory 487]

48 minutes ago, Freak said:

A very helpful tutorial. I have  a chainsaw with an O&R engine, and the tutorial was exactly the issue. Forgive me in I cross a line here, Where do I go to find replacement parts?  

Thanks in advance.

 

Webhead and Wallfish on here have spare parts for these engines as well as the new diaphragms for the carb.

 

David