OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines Suzuki 2 stroke carburettor assembly

A friend brought me this Suzuki mower that would not start. It had good spark so, thinking of a fuel problem, I took off the carburettor and found the main jet screw lying loose in the float bowl and the brass circular washer (in red) also loose in the bowl. I'm not sure where that washer goes. I've had a look at what I think is the manual (http://golftechs.us/Manuals/Suzuki.pdf) but I can't see it on the carburettor diagram.
Grateful for any help.

Hi sparker, your carburetor does not seem to be the one normally found on a Suzuki M120X - they usually have an emulsifier, and yours does not. No doubt there are other differences too.

Let's see if Mark Electric, a notable Suzuki mower engine enthusiast, can place it. Meanwhile you might look at this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=49918&page=1

Hello Grumpy, there is an emulsifier tube but I didn't show it in the photo, sorry for the confusion. Here it is. the washer fits loosely over the tube at the non threaded end but also fits neatly into the end of the emusifier aluminium pipe at the bottom of the emulsifier.
I had have a look at that post but couldn't see the washer.

The washer isn't shown in the assembly diagrams as well as not being in the carburetor shown on that other thread, sparker. It has to be a seal, and its purpose may be to stop air from reaching the carburetor venturi without having passed through the emulsifier. If so it would go on the top of the rib around the emulsifier, near its top. However if it goes there it will have been compressed when it was previusly installed, and you can probably find crush marks on it, which should match both the emulsifier rib and the step in the carburetor body that it clamps against.

I'll have a look for crush marks but if that is the correct location then it couldn't have been installed correctly when I took the carburettor apart as it wouldn't be able to fall out of that position. I found it in the bowl with the main jet screw. The emulsifier was still insitu. I've had these mowers before and worked on the carburettors but I don't remember seeing this part. Alzheimers I guess.

I just tried it there. The emulsifier can't go up the tube with that washer on. It's too wide. The other places that it would fit are at the bottom of the emulsifier (but there it is not secure) or as a second washer on the main jet. There is already a washer on the main jet but there does look to be a "shiny" and non threaded portion that would take a second washer. I'll give it a go there and see what happens.

Since the part is not shown in the manual, there's a good chance it isn't supposed to be in the carburetor at all.

There is no functional purpose in putting two sealing washers one on top of the other, unless someone thought the main jet needed to be spaced down further, for example if the tip of the jet was fouling on the screwdriver slot of the emulsifier. Have you checked for graunch marks on the tip of the main jet and the slot of the emulsifier, due to them fouling each other before the extra washer was fitted?

Here is a rather unsupported theory for you. The previous tenant had carburetor problems with his Suzuki M120X (what a surprise). Somehow he decided that he could save the day by putting an extra washer on the main jet. However not only did it not work, it also caused the main jet to fall out in service.

I found a photo with the washer. damn washer . It's page 3 of the thread you referred to.

Success!! Smoky as all hell but I didn't mix the fuel. Thanks grumpy. It's good to have someone to bounce ideas off and get advice.

Do you mean that second washer under the head of the main jet? That seems to be a thick brass washer, while yours looks like a thin plastic one. I didn't connect the two at all.

Please let us know whether it runs well throughout the speed and load range, or you have Jaffa J's problems in getting to into shape.

Yes, that's the one - a thick brass washer. Mower seems to run and stop OK but I haven't tried it actually mowing anything. It doesn't surge or hunt so far. I'll mow some grass tomorrow.

I think I've worked out why Mikuni used that thick brass washer. They decided - for fairly good reasons having to do with not picking up too much garbage from the bottom of the float bowl into the main jet - to use a horizontal main jet rather than the traditional vertical one on that carburetor. However they wanted to use as small a diameter as possible for the vertical fuel-pickup tube (on which both the main jet and emulsifier are mounted), in order to save cost and weight. They also wanted to use a standard main jet, rather than invent a new non-standard one for that carburetor (which would have caused inconvenience to their spare parts department). Since the standard main jet was too long to suit their small-diameter fuel-pickup tube, the simple solution was to put a spacer under the head of the jet. All sensible decisions, but the result was an odd-looking design.

Yes, Grumpy that sounds likely to me. The idea was good-keeping the jet away from debris and it seems to work OK. I was told Suzuki was going to continue making these mowers, as they were popular, but found it too expensive to comply with new environmental restrictions.

Well, whoever assembled it last time did not do that screw up properly. The vibration must have shaken it loose as I found both the pilot screw and washer in the float bowl. No wonder it wouldn't start. I was confused because it already looked like that jet had a washer on it and that's why I couldn't work out where the thick washer went.

Isn't the washer that stayed on the jet, a split spring-washer that is non-detachable, and comes as part of that standard jet? Mikuni's design, by adding the spacer, eliminated contact between the split in that washer and the carburetor body, and hence meant keeping the jet from falling out was achieved only by the friction between the spacer and the carburetor body. That made it important to tighten the jet firmly, which would not be the case if it didn't have the spacer.