OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Tecumseh / Kirby Engines carby adjustment

hi i have a cox Orion ride on with a 12.5hp B&s motor model 2030400 dom 9340(R)
and my question is it has a adjustment screw under the carby bowl can anyone tell me how many turns out it needs to be to start tuning. as when i got it it was screwed in and he said it wouldn't run properly and he didn't know why.now i own it.

Hi blackriverfish, welcome to Outdoorking.

Please post the full Model, Type and Code numbers for your engine so we can check its Illustrated Parts List and see what kind of carburetor it has. The numbers you have quoted are not correct - the Model has too many digits, the Code is just plain wrong, and you didn't give us the Type at all.

hi thanks
the motor is a Tecumseh 12.5hp and on the ID plate it has model OHV125 203040D (E)
then underneath it has D.O.M.9340 (R)
i assume this is a replacement engine???
thanks in advance for all the help just found this site and it is very helpful.

I can't find any reference to a model called Orion in the manuals section, if you have a model number I might be more successful.

The screw projecting vertically downward from the center of the float bowl is the main mixture adjustment. According to the Tecumseh 4 Cycle Overhead Valve Engines Manual, the preset adjustment for all models having that type of carburetor, is 1.5 turns from fully screwed in. Incidentally, with the screw fully in there should have been no fuel flow through the main jet.

This is the carby tp left is the id plate

The screw projecting downward from the center of the float bowl (circled in red) is the main mixture adjustment. The horizontal screw just above the top edge of the float bowl (circled in green) is the idle mixture. Preset adjustments (that is, the starting point for tuning the carburetor) are 1.5 turns from fully screwed in for the main mixture, and 1 turn for the idle mixture:

thanks for the quick reply
now all i have to do is replace start solenoid clicks but doesn't make contact

That is seldom a defective solenoid, about 8 times out of 10 it is a flat battery or poor high current terminal connection at battery or solenoid. Second most common is a poor low current connection at solenoid or key switch. Defective solenoid is (in general) a distant third most common. On used ride-on mowers, messed up wiring is a very common problem, so if the battery is OK and so are the connections, check the voltage at the low current terminal (from the key switch) of the solenoid when you turn the key to start. If voltage is low there but high at the high current solenoid terminal, trace the wiring, and find out how much damage the previous tenant did.

did all that put a multimeter across low side and it was open circuit put on a new one and away she want woohoo all is good next tune up as it is hunting.

You probably know that hunting is usually caused by lean mixture, but occasionally it is due to a misaligned/bent linkage causing friction in the mechanism. Sounds like the first step might be to increase the main mixture adjustment setting to a bit more than the starting pre-set of 1.5 turns.

yes i tried to adjust and it maid no difference so pulled out and it looks like someone has filed of the tip as it is short with a flat tip so will get a new one.

That sounds odd. It is obviously possible that someone mangled the needle, but the result should be that you can make it either rich or lean, with no transition in between. If the needle was simply cut off very short to make the mixture non-adjustable, it should be extremely rich. Since it was hunting, it is most likely lean, and it sounds as if something else sinister has been done, such as soldering up the bore of the main jet then drilling a smaller hole than it had originally, so it acts as a fixed jet instead of an adjustable one. I think you are going to need to remove and strip that carburetor, cleaning and inspecting the parts as you go.

i think so to.i just ordered a carby kit so will replace all when it arrives (632347). will take photo so u can see,when i cleaned the carby it was full of gunk and varnish so a good strip and soak with new parts will do it the world of good.

blackriverfish, I suggest you take advantage of a free download of the full service manual for your engine, which includes detailed carburetor overhaul information:

http://th.manualwebsite.com/pdf/4-cycle_ohv.pdf

Your carburetor is described as Series 3 or 4, so do not be distracted by instructions for the other types, up through Series 10 and the Walbro LMK used on the last of the OHV Tecumsehs.

Tecumseh carburetors have a fairly evil reputation, but most of them can be serviced very successfully by following the instructions and having a kit of service parts close to hand. Note the warning not to remove any "cup or ball plugs", but this does not apply to ordinary Welch plugs provided replacements are included in the overhaul kit. (However, I personally don't remove Welch plugs unless every other approach fails, which it seldom does.) I think you will need to use a spray can of proper carburetor cleaner to actually get the gum out, but do not put it on plastic or elastomer parts, and blow it out immediately after spraying it on or squirting it into passages. In my experience, lesser solvents do not remove hardened gum (and emulsifiers, in particular, often require multiple blasts to get the small radial holes clear. On Honda carburetors I often have to use jet drills on the radial holes of less than 0.5 mm).

Here is a diagram showing the working parts of your carburetor:


As I said previously, I currently suspect that there has been foul play in that carburetor, and you need to be on the lookout for "tenant's improvements" made before you got this machine. Look especially for signs that the "main nozzle" (a combined main jet and emulsion tube) is either fouled or modified. If you are lucky, it is badly fouled and the previous tenant amputated the working part of the main adjustment screw to compensate for this, rather than clean it out, then when the fouling progressed even further and it became lean despite the amputated adjuster, he/she disposed of the machine.

We are here to help at any time. Please don't become one of the people who conclude that Tecumseh carburetors are unfixable garbage: they are not unfixable unless made so by previous attempts to repair them.

wow thanks for all that information this a photo of the mixture screw and float after first clean it was ugly

You have to get the emulsifier/main jet out of the carburetor body before you will get anywhere. If it doesn't come out easily, it is probably stuck in by hard gum. That happens a lot to Honda emulsifiers, and is something of a hassle with them, because they are only held in by the main jet screwing up from below and pressing hard against the bottom of the emulsifier. With those, you mustn't push down hard from the top or you'll damage the top of the brass emulsifier, which is the discharge area. In the case of your Tecumseh though, I suggest that the emulsifier probably screws in with a thread near the bottom, and there is currently lots of hard gum gluing it in place along the length of that thread. Just check whether there is a screwdriver slot in the bottom of it, right above where the mixture screw goes in. (Most likely the slot will have been completely trashed by the yahoo who had it before you.) You have to remove the gum so you can unscrew it, and this whole exercise will be quite a trial if there is no slot left. Regardless of that, removing all of the gum is the first step. I rather suspect that in the end the emulsifier will be a total loss by the time you get it out, and you'll have to source another one somehow. I don't think it will be possible to clean out the lateral/radial holes in the emulsifier without removing it from the carburetor. Please keep us posted as you go with this, before you trash it the rest of the way, just in case we can find a non-destructive solution.

thanks well there no adjustment at all it ether surges or dies. and it looks like there is no slot to screw out emulsifier so i would say its a press fit hopefully the repair kit has one if not it will be softly softly till i get it out.in the old days we used to soak rusty tools in malases i wonder if that would work with this wont hurt but may help.

o no there is none in the carby kit.

I don't think molasses will help with hardened petrol gum, and I don't think it will penetrate a tight thread. The stuff that works is a spray can of carburetor cleaner, and it is almost miraculous if you haven't used it before. However it can't dissolve what it can't reach, and that may be a problem in this case.

Can you post a picture of the carburetor from underneath, as close as possible, so we can have a look at the "main nozzle" (that is, the emulsifier) and try to work out how it is retained in the body casting? I'm used to them being screwed in. I just can't see it being pressed in because you then wouldn't be able to get it out for cleaning.