O & R Carb Repair Tutorial

[Freak 0]

Cool!!! Thanks, David. What's the accepted method of making this work?

 

[factory 487]

Send a PM (private message) to either Webhead or Wallfish to ask about parts, if you need help with anything else other than carb problems with your chainsaw it would be best to start a new thread about it.

 

David

[Freak 0]

Thanks for the heads up about the forum. I appreciate it.

Freak (aka Rudy)

 

[factory 487]

Here is an exploded parts diagram for the O&R carb (slotted needle version).

 

David

 

[Zak 0]

Hey guys, i'm attempting to do this on my own ohlsson & rice engine i got around 10 years ago ago from a relative back when i when studying automotive in highschool haha, sparks great, compression's good, took off the air intake and had the same disintegrated foam air filter issue - cleaned it the best i could, but its the type that doesn't come apart

anyway i'm a bit 50/50 on this - even if the foam is disintegrating, how would it get back into this part of the carburetor?? is it worth taking apart and having a look?? more importantly, if i undo the 3 top screws, will all the springs pop out and the mechanism come apart???

 

All that being said, i finally was able to start it for the first time ever after spraying some fuel down the air intake - though didn't run long since i'm sure its not getting any fuel which is due to either the carburetor, and/or blocked fuel lines (got new ones so hopefully all good) - anyway would you recommend this to a dude who's been out of the automotive game for almost 8 years??? 

 

Also - on the left hand side of the re assembled carburetor/air intake system - what is the purpose of the screw with the spring on it?? - and the 2 holes underneath - for a throttle cable i'm guessing?? - after your engines started in the choke open position, would you only use the small choke to run faster/slower???

 

Many thanks, Zak

[factory 487]

Hi Zak,

 

Both the single and double air filter have one housing that doesn't come apart.

I usually use the little pick tool (shown in the linked post) or a small screwdriver to poke as much of the old filter foam out using all the holes in the housing. Compressed air can help with the remaining bits, I usually give it a wash with petrol/gas after.

The new foam is then squeezed in through the opening at the back and again poked through the holes at the front to spread it out to fill the housing.

 

 

Your carb will probably need to be stripped and cleaned following the procedure at the start of this thread, Old fuel/oil mix tends to gum up all the parts. Take your time, nothing should fly out, but have a tray underneath to catch any small parts if you want.

A new primer diaphragm gasket is usually required for the engine to run at it's best, the old ones usually dry out & crack (Wallfish or Webhead on here have new diaphragms, as well as the check valve gasket if you need them).

 

The screw with the spring of the left of the carb is the idle stop adjustment screw, the holes underneath are used on some tools for the throttle cable.

The small quadrant control on the other side of the carb is used to adjust the governed speed. There are two types of this control, one can be set to any position and the other is moved by lifting the spring loaded washer & has five positions. Early production carbs don't have this control.

 

 

 

David

Edited March 10, 2019 by factory
Corrected dead link

[Zak 0]

Ahhhh sweeet! will give that a try for sure with the air filter

 

And ahhh damn....now that i think about it, yeah....should probably do it.... fuel line from fuel tank to carburettor was in pretty bad shape, seemed to be blocked at both ends, also iv'e got  another fuel line that just runs across the fuel tank? (with the one i have the fuel tank is sort of built into the engine you could say - its under the engine/crankcase so gravity will do me no favors it seems.....though as long as iv'e got a clean carb, clean fuel lines,and cylinder compression, that *Should* suck the fuel from the tank into the carb right???

Could i test to see if the carb fuel line hole is clear by poking a small needle through it? or would that penetrate some sort of filter in there....would opening it up and pouring some petrol to see if it leaks out out the port work?? or is it a one way valve? Thanks for the advice on the diaphragms as well!!! will see how they are, rubber air intake gaskets were in surprisingly good shape so hopefully all good

 

and ahhhh nope no governor/quadrant control for me, though i have some sort of metal strip/ air vane connected to the cylinder that apparently acts as a governor....think i put it back on the wrong way though after reinstalling the air intake/carb....if i'm right it should be placed on the bottom left of the butterfly valve/throttle- making it closed partially??? 

 

Thanks heaps for the advice - this forum is a godsend!!! Haven't worked on Engines for about 8 years now, so a lot to lean/re-learn, but its coming along well....last ones i worked on back in highschool were the small single cylinder 4 stroke's, and then the big 4 cylinder holden engines (though we had A LOT of instructor guidance for them haha!)

anyway hopefully i can work on the carb one of these mornings before doing afternoon shift, would love to give it an entire weekend to work on, but never easy when have the girlfriend to deal with!!! haha 

 

 

btw not carb related, but could i theoretically clean/flush out the crankcase/ cylinder by overloading it with the gas/oil mix while the air intake and cylinder are removed, and then turning the crank?? good or bad idea??? need to see more vids/pics, but cylinder/exhaust assembly seems to just be able to be unscrewed after taking off the starter??? just a bit cautious of having to disassemble/reassemble the entire crankcase/piston assembly....plus theres the coil and electrical system which i don't even want to mess with since it still works haha 

 

 

Many thanks again!!!   

[factory 487]

See the linked post for checking the carb inlet, there is a one-way ball valve inside the diaphragm chamber.

It's best to disassemble and clean all the parts of the carb using either clean fuel or carb cleaner.

 

The air vane fits inside the shaft of the butterfly valve (left side of carb), here is a picture I took earlier. The butterfly valve will be open normally, it closes when the blade part above the flywheel moves up with increasing air flow.

 

 

There shouldn't be any need to clean the crankcase with the cylinder removed unless there are bits of the old air filter inside (these would be visible inside the carb & induction housing), I would follow the engine rebuild thread if you have this problem, which is caused by running the engine without removing the old disintegrating foam.

There is a special tool that fits the slot in the top of the cylinder for unscrewing it, you will need to replace the exhaust collector gaskets if you need to remove the cylinder for de-carbonising, they tend to leak if you don't replace them.

See the last post in the engine rebuild thread for a details of the cylinder removal tool.

 

Taking pictures as you dissemble things will help when you put it back together, I always take more than I need to and not just with engines (vintage electronics is my other hobby).

 

David

[Zak 0]

Ahhh i see.....carb cleaner and fuel it will be then - safe for all the metals in the carb/engine right??? heard that stuff can damage/eat away at plastics or gaskets???

 

and hmmmm yeah i think i saw a few small pieces of the old foam air filter inside past the air intake when took the carburetor off, so probably best to just give it a check out,  might be a pain with my limited knowledge lol, but better than running with it and possibly causing damage   only other thing i'm worried about for disassembling/reassembling (cause i have no idea) is the electrical/spark system - will that need to be timed to the piston cycle? or nothing to worry about???

 

Thanks again for all the help!!!

 

 

[factory 487]

You may be best using clean fuel then, as I've never tried carb cleaner I don't know what it can damage (certainly some electronic & switch cleaner sprays can damage plastics or cause other problems with vintage electronics).

 

Be careful the power output shaft doesn't slide out & let the tiny bearing rollers fall out, if you take the induction housing apart and nothing is attached to it.

 

The only adjustment for the timing is the contact breaker gap (should be listed on the starter decal along with the spark plug gap). The flywheel position is fixed with a key.

 

David

[Zak 0]

Ahhhhh i see i see....hmmmm maybe just carb cleaner for some definitely metal parts lol, and the air intake + exhaust since theyr'e especially rusted out with my one....

 

and ahhhh alright then sounds awesome!!! if the flywheel is fixed with a key and then contact breaker gap is the only timing adjustment then should be a lot easier  seen it opened up/how it works in one of the youtube vids so makes it a lot easier for me haha

 

Very much appreciated for helping me out here!!  i know iv'e said it a lot, but its been literally 10 years iv'e had this engine and in that time all i knew was that it was a model engine, had compression and spark, and thats it, lol,  never worked up the courage to disassemble it properly or do any serious trouble shooting on it   

 

I could ask like a million other unrelated to carb questions on here, but should i put them on another thread??

 

Thanks heaps David!!!  

[factory 487]

Hi Zak

 

You could start a new thread, or add to a relevant existing one and we can help with any other questions you may have.

The Compact engines were of course designed as a small industrial engine to be used for powering all sorts of portable tools, but were also used for powering (and still are) models.

 

David

[Zak 0]

Awesome as!  hmmmm i might as well start a new one not as to go too off topic from this carb repair thread  i'm sure il'l have tonns more carb questions when i actually get the time to take it apart haha

[SparkFireRun 1]

Hi guys, Thanks so much for this thread. An old gent asked me if I would get his tiny Tiger 300 running for him, and when I opened the carb, those little bits were rolling around in there. I'm lucky I didn't lose any of them. There's no way I could have figured this out on my own.

Best,

[Richard Carr 1]

Looking for carb diaphragm for Tiny Tiger.

 

[factory 487]

 

Webhead & Wallfish on here have new carb diaphragms for these engines.

 

David

[Richard Carr 1]

Thanks for that.I have arraigned to get one.

[WOWaLotOfBees 0]

I have one of the older models of drill that uses this carburetor. Could someone please tell me how to take the difficult to reach screw off? Is there a trick to it?

[factory 487]

 

Here is what the manual suggests for getting the lower Carb screw out;

 

 

This is what I have been using if I need to get the carb screw out without removing the adaptor plate or gearbox (but I usually do a complete engine rebuild instead and remove the adaptor plate or gearbox first).

The first two pictures below shows a small flat blade screwdriver (being misused) that fits between the adaptor plate or gearbox mountings, you may need to remove the cylinder plate to gain access.

And the last picture shows some other Phillips screwdrivers together with the flat blade one, to use these they would need grinding down to fit between the mountings, I don't want to do this to the orange Wera one but the cheapo one may get modified vandalised.

 

 

Hope this helps.

 

David

[Roger Murray 0]

On 11/29/2014 at 3:14 AM, Wallfish said:

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.

Where can I get a diephram for my O&R engine fuel pump I live in Scotland but prepaid to pay for one from any where 

[factory 487]

Webhead or Wallfish on here should be able to supply a new carb diaphragm for your O&R engine.

 

David

[CNew 404]

On 6/4/2016 at 4:34 PM, factory said:

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

 

 

The valve on one of my carburetors has a tiny groove machined into the needle section. Is this the needle referred to in this notice?  There is no other indication of a “X” anywhere on it that I can find.

[factory 487]

52 minutes ago, CNew said:

 

The valve on one of my carburetors has a tiny groove machined into the needle section. Is this the needle referred to in this notice?  There is no other indication of a “X” anywhere on it that I can find.

 

No that is one of the standard slotted needles mentioned in post #2.

The page mentioning the X was saved from an ePay listing (I added it in case anyone came across one of them), standard needles have either the T or a slot cut into the top of them (as yours does), early engines have a tiny needle on the side of the carb (this has a different setting too).

 

David

[CNew 404]

On 11/28/2014 at 7:59 PM, factory said:

Copied from the original thread from the old forum saved by the internet archive, tutorial courtesy of laserscottman.

 

(snip)

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!

Just did another carburetor rebuild and learned something that might be a helpful tip when getting to the step where you run the filament under the fingers of the retainer spring. If you loop some filament under the pivot roller before sliding the spring in it makes it easier to get the filament under the fingers. You simply put the spring in between the loop and then slide the loop forward as the spring goes under the roller.

Edited April 4, 2019 by factory
Edited the quoted post to show relevant parts only.

[factory 487]

On 2/24/2019 at 8:42 PM, CNew said:

Just did another carburetor rebuild and learned something that might be a helpful tip

 

Sounds good, I've also successfully tried the O&R service procedure and I can say that the method in this thread is far easier.

By the way I usually create a link to another post, or edit the quote to the relevant part (if the quoted post is a long one or has many pictures).

 

I now have a stock of laser cut carb diaphragms, diaphragm bowl gaskets & the mylar check valve (courtesy of Wallfish ) so can now help anyone in the UK or Europe that needs a set for a carb rebuild.

PM's have been sent to the two members that recently requested them.

 

David