OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Rover Suzuki 2 Stroke

Well I took the mower out last night and gave it a good run for about 30 minutes in the long grass. I personally would rate it as one of the best performing mowers I have used in quite some time. The mower was taking care of thick above knee high grass with relative ease.
The engine was a little smokey however I am sure this was related to the lower than standard petrol to oil ratio. I then adjusted the ratio to what I like to call a rich 50:1 mix that was pretty close to a 40:1 mix simply because I was trying to be cautious in accordance with your recommendation.
The mower performed really well and emitted what I think was just a standard level of 2 stroke emissions.
I did have one minor query about the engine stop setup. When you move the throttle to the stop position is takes quite a few seconds for the engine to cut-out? Is there an easy fix to make the engine stop quicker or perhaps an adjustment to be made?
Otherwise I was very happy.

The kill switch (7) is operated by the end of the governor spring lever (3) - see Page 28 of the workshop manual.



I suggest that you take a look at that mechanism, while operating the speed control from full to stop. I don't have one in front of me, but your engine should stop firing the instant the lever (3) pushes the switch (7). You may need to apply a resistance meter to the switch to establish how far it has to move to kill the ignition, so you can adjust it correctly without over-travelling and breaking the switch.

You might post a picture of two so we can all understand the adjustments.

Thanks for the concise explanation. I managed to adjust the throttle cable to ensure items 3 & 7 meet. The mower now stops as it should...... However after the minor adjustment of the throttle cable the damm thing is hunting again and I have little idea why? It's hunting at idle and full speed.
The choke is opening and closing as it should.

Would resetting the govener arm again by turning clockwise as we discussed earlier be needed or do you think I have upset a setting by moving the cable ever so slightly.

I'd begin by re-checking the fuel flow rate from the float chamber, in case that problem has returned. If the flow is good, step two is gently moving the governor arm back and forth through its movement range, while looking closely at the linkage and feeling for any rubbing or stickiness. You should also check what the spark plug looks like, in case it is actually running just a bit lean.

Since the hunting seemed to clear up with proper governor adjustment, it sounds as if it is either a marginal problem or an intermittent one. These are the hardest to find. My history is that they are commonly caused by a mild air leak in the intake system, or a stiff diaphragm (fuel pump or metering) that makes fuel control marginal. Remember, you never did establish with any certainty that you don't have a crankcase air leak. You might look for oil around the crankcase and cylinder joints.

1) Fuel flow from the float chamber is ok. No obvious fuel flow restrictions.
2) The linkages all appear to move as they should. They do not appear to be sticking in my opinion.
3) I have checked the crankcase and I can see no obvious signs of leaks (It is very clean with no oil marks even after the last good run in the long grass
4)I re-checked the spark plug and its a light brown all over. I checked a few other 2 stroke engines I have and the plugs are all clean. I might be mistaken but could the slightly richer that 50:1 mix I am using be contributing to minor hunting issue, being that the engine is running to lean.

My test this morning revealed:
1) Idle is back to being ok (a little temperamental but pretty good for a two stroke)
2) Full speed is great as long as you get the throttle adjustment right, that is right on the full speed marker
3) Things get bad when you try any other throttle position as it starts to hunt quite a bit, so much it annoys me. I thought maybe these engines are only designed for idle and full speed.
I think we are getting closer to done. I am thinking about mixing a spot on batch of 50:1 unless you think otherwise.

I see no harm in trying 50:1 and seeing if it produces an improvement. However IIRC you had it running perfectly at 25:1 for a while, so it sounds as if the fault is either marginal or intermittent.

The carburetor has different systems in operation at idle and at high load/speed. It apparently gets slightly lean in the transition between the two. If there is no air leak into the crankcase or intake port, the most likely source of the problem is the carburetor. Does it have progression holes, or just a single idle discharge port? This is the one or more tiny holes right at the throttle butterfly. If there are several holes, it may be that the ones furthest upstream toward the venturi, are damaged very slightly or obstructed. If there is only one, my guess is that you are asking too much of the carburetor. It is very common with the diaphragm carburetors on chainsaws and brushcutters to have to set the idle mixture a bit rich, to get the engine to respond smoothly at part throttle. You might try noting exactly where the idle mixture adjusting screw slot is pointed at present, then turning it anticlockwise a bit (toward richer) and seeing whether the mid-range running improves.

When I said running really well I failed to mention the mid-range running was still questionable. I should have been clearer when describing my findings. Full speed and idle were both pretty good.
Would you be able to post an example of progression holes and a single idle discharge port as I am not familiar with these terms? I will however check this out tonight and try to get a photo for the forum.
The idle mixture screw is currently sitting about half way. I.e. half way between being fully screwed out or fully screwed in. I hope that makes sense. Turning the adjustment screw anti clockwise didn�t make much of a difference to the mid-range running when I gave it a try.
I am quite confident that I have covered all bases in regard to an air leak without splitting the crankcase and resealing it which I image would be a similar process to splitting the crankcase on a full crank Victa 2 stroke engine.

This is a picture from the Walbro WA Technical Manual. You can see that at idle, it emits fuel from a single idle port near the throttle butterfly. As you open the throttle, first two more idle ports chime in progressively, then the main jet joins in, and eventually the idle ports stop emitting. This multi-port system is used to get a smooth transition from idle, using just the first idle port, to fairly substantial throttle openings, when the main jet is in full song.

Not all carburetors have an idle progression system like that. Also, even if they do have that kind of system, there can still be lean spots in the progression if air is sucked in through the main discharge nozzle before petrol begins to flow out of it. Some of the Walbro carburetors have a one-way valve under the main nozzle to prevent this.

The carburetor is not the only possible cause of a mid-range flat spot like yours. It can be due to a small air leak, or retarded ignition timing, or leaky ports in a 2 stroke. However knowing that you have been having mixture problems, I'd start off with that as the most likely cause. It is interesting to note that we have had another thread about an M120X with lean mixture problems, but I don't think that one was ever solved.

It may be that your engine is particularly sensitive, or something may have been missed. I'm pretty confident that Suzuki designed an engine that was capable of running properly. I'd be continuing to focus on the idle system for the present. Are you sure that all of the jets are not only clean, but are still the sizes shown in this page from the workshop manual?



Edit: You might try reading this very long report on that Suzuki engine in a Toro mower:
http://forums2.gardenweb.com/forums/load/lmower/msg0423075515023.html
As you can see, the consensus is the same as I've said previously: aside from a problem with the fuel tank cap, the only problem causing surging in that engine is gunky jets, fuel passages, and air passages in the carburetor, presumably due to old oil going hard and staying put. I see one guy says you have to "boil it in carb cleaner". Not sure how you do that safely, but lots of people soak carburetors in carb cleaner, with good results. We are all headed in the same direction.

Here is an extract from the Toro workshop manual for the Suzuki M120X:


I suggest you just do exactly what Toro recommends, including remembering not to expose the plastic parts to carb cleaner.

I admit I got frustrated with this mower however I did not give up on it. I have been following the most recent Suzuki mx120 post and executed all instructions to the best of my ability.
So over the past couple of days I have been soaking the carburettor in carby cleaner with every possible part removed and soaked separately. I was careful to remove all plastic components and not expose them to carby cleaner.
The more I continued to soak the more gunk kept coming out. I also used a very fine drill bit clean the ports throughout the carby including the jets. A substantial amount of black gunk came out during this process.
I carefully put everything back together which isn�t really easy with this engine, being careful to set the governor arm correctly as per our previous discussion.
The result �
1) A first pull start
2) Kept the choke on few a couple of seconds and then slowly eased it off back to the full speed setting. No hunting at all.
3) Moved it down to idle after adjusting the mixture screw and it was pretty good for a 2 stroke I thought!
4) The biggest test was mid range running and it was pretty good. The engine barely hunted at all.
Note: I haven�t put the engine under load after this carby soaking exercise however I suspect it might be ok!
Nothing else I should double check?

Just be sure there is no air leakage across the carburetor insulator gaskets, and you should have it right. At the end of the soaking exercise you should blow out all of the passages with compressed air, because if you don't some of the gunk will still be there and will re-solidify, especially in tiny or blind-alley passages.

It sounds as if you have it pretty right. The final check I like to do on carburetors is to slide a jet drill of the size given in the specifications, through each jet, outlet and seat that has a specification. Don't twist the drill bit, just ensure that it will slide through with that slight drag that signifies a size-on-size fit. The purpose here is not just to verify that you have the jets etc clear - it is to see if there is any residue still in the carburetor. If you have residue in those specified places, you have it everywhere.

Life isn't normally this hard with carburetors, it just seems that the Mikuni used by Suzuki is something of a lady-dog when it comes to cleaning. However by all reports it is a very pleasant engine once you've got its carburetor cleaned out.

Thanks Grumpy. I most definitely used compressed air after each go of soaking and removing the oil build up. It appears the engine is running better after following this process.

It is a pleasant engine to start, it is idling very well. Full speed is great as long as you get the throttle adjusted at the right full speed setting.

I use the following process when using the engine and wouldn�t mind your thoughts as it is still a little touchy when adjusting the engine to full speed which makes me think the choke mechanism might be a little sticky. I could be wrong through.

1) Start on choke, wait a few seconds and then move the throttle to full speed, this hardly ever provides any issues. Full song sounds great.
2) Move the throttle down to idle , it then ides really well
3) Move the throttle back to full speed and I actually have to push the lever onto the choke for a second and then adjust it back to full speed. Following this process gives no problem������however if I push the lever from idle to full throttle it hunts. Follow the process of moving from idle to full speed by giving it a little choke then back to full speed and ����.no hunting.

Maybe I am on the wrong track but could the choke be a little sticky?

All the intake gaskets and brand new BTW.

I haven�t got a Jet drill kit so that might be a good idea to give the mrs for a Christmas present.

Getting very close now.

Hello Jaffa J,
I have been frustrated with setting these up in the past.
I must admit I just haven't been able to get some of them right.
After reading this post, can add a little bit.

1. fuel cap - the piece that is falling into the tank, the plastic they are made from shrinks to the point where it drops into the fuel.
2. there is a small hole that needs to be cleared in the exhaust port, it gets hidden because it is normally blocked with carbon, this seems to make them run better when it is cleared.(you may have done it already?)
3. I have noticed in the past with a lot of them that the governor spring gets stretched, this plays mary hell with getting them set right.
4.I have found that after a really good run the smoke clears and the power increases.

It is a fine balancing act between where the governor arm is on the shaft, the tension in the governor spring and where the mixture screw is set, also how your throttle cable is set.(I know what the manual states about the governor arm, but I have adjusted where it sits on the shaft slightly)

The only down side to these engines is how much you have to take apart each time to make minor adjustment's.
Sorry to cut in on this thread, but just trying help.
From Mark

Thanks for that, Mark. Your experience is likely to be useful here. With regard to Item 2, the function of the small hole in the exhaust port is to act as a decompressor. If it is blocked it becomes difficult to pull the starter cord, but there should be no other effect. On the other hand if the exhaust port, spark arrestor, or muffler is obstructed, any point of performance could be adversely affected: those areas should be kept reasonably clean. Jaffa, to verify that the engine has a fair chance of operating perfectly, please check that the exhaust port and muffler are clear, and that the engine shows compression pressure of at least 90 psi (that is the minimum service figure: it should be 120 psi).

Jaffa, one point to verify here is whether your engine has electronic or breaker-point ignition. The earlier units had breaker points, and they have to be set up carefully (the manual specifies use of a dial indicator, like on the old Kirby Lauson 4 strokes) to get the right ignition timing. Your slight instability problem sounds as if it could be due to an ignition timing error, so we need to know which system your engine has.

It sounds as if your engine is very sensitive to the precise adjustment of the speed control cable, and the setting of the choke linkage. You should lubricate the cable, and ensure that it slides smoothly, with no hysteresis between opening and closing. (In other words, there is no wind-up in the mechansism, resulting in the linkage being in a slightly different position depending on which direction the control is moving in.) You will recall adjusting the mechanism slightly to get the kill switch to work properly. You may now have it out of adjustment at other points in its travel. Please check the assembly against this diagram and instructions:

I have often thought about that hole in the exhaust port and the slot in some of the Victa powertorque ports aswell.
I clean them out and didn't really know why, thanks.
Here is an image of the Suzuki port, anyway.

Thanks for posting the picture, Mark. I wanted to ask for one but didn't think it would be a reasonable request when it wasn't relevant to the case.

The principle of operation is very similar to the normal 4 stroke decompressor which momentarily bumps the exhaust valve open about halfway through the compression stroke. Of course the 4 stroke ones disable themselves when the engine is running more than about 1,000 rpm, while that Suzuki one operates all the time - but is so tiny that its effect at high engine speeds would be negligible. Briggs has its Easy Spin feature on the side valve engines, which holds the inlet valve open by a few thousandths of an inch during the compression stroke. They say their experimental work showed that it had a negligible effect when the engine was running.

Grumpy & Mark
Thanks for your comments, I really appreciate it. I have tried to the best of my ability to address your questions.
1) The fuel cap and breather cap underneath the cap have been replaced with a brand new unit. Mark I had no idea how the original piece fell into the tank but now I know.
2) The small decompressor hole in the exhaust port is free from carbon. I gave it another clean to be sure about its condition.
3) I am fairly confident the governor spring has not been stretched it has good shape without any strange bends. I am also confident the governor arm is positioned correctly on the shaft as grumpy and I discussed this process earlier.
I do agree with your comments about how difficult the engines are to work on. Any fine adjustment requires time to dismantle everything. Its bl**dy frustrating.
I checked the compression and it is 110 psi so that is within the high end. I don�t think that is the problem.
I re-checked the exhaust post and it is free from carbon. I also check the exhaust and ran compressed air through it. It doesn�t appear to be blocked however if you have a better method of testing it I am open to suggestions. The exhaust did appear to be heavier than I expected but not blocked.
Grumpy unless I am mistaken the engine has electronic ignition. There was no breaker points under the flywheel unless the points for the engine are set up differently?
I did some investigating with the cable and you were exactly right with regard to the linkage being in a slightly different position depending on how the cable is adjusted. Can you please advise how I should lubricate the cable and the linkages if you think necessary?
I have also rechecked the linkages and they are as per the manual. Well they looked to be good with me checking!
I think I have addressed all the questions. We are getting close I think����..

Hello Jaffa J,
Have you noticed on the governor arm there are 3 holes, your governor spring can be placed in the top hole or the bottom hole, it is normally in the middle. You can raise and lower the rpm by plus or minus 150rpm.
It might be something to try, I have done it in the past and the machine ran better at a lower or higher rpm. The manual tells you.

With the muffler you can tap it all around with a rubber mallet, it may free some carbon up.
There are other methods people use, like heat the muffler, I have never done it.

I have never seen one with points.

With setting up the cable, I normally have the clap loose then I set the throttle to neally full choke. Then I push the cable at the clamp and watch the choke plate close, then tighten the clamp. This ensures the choke is closed when starting.

When starting I always look through the gap between the cowl and the air cleaner and watch the carby for the choke lever to move across.
They wont start without the choke closed.

My method for lubricating Bowden cables is to move the mechanism so all the cable inner is sticking out at one end - that is, either full choke, or switched off. Then hold the engine so the cable runs vertically down from the end with the exposed cable inner. Put a drop of oil on the inner cable where it sticks out, and operate the cable full stroke a few times. Then put on another drop and do it gain. Proceed that way until the cable inner is wet at the far end as well, due to oil running the whole length of the cable.

Well I investigated the throttle linkage problem a little more closely and I didn�t like what I found.
1) When you move the throttle from idle to full speed the engine hunts badly and doesn�t run well at all. I checked the position of the butterfly and when adjusted using this method it is fully open with no choke.
2) When you start the engine and move it from the choke position to full throttle (The position I thought it was running correctly at) the throttle butterfly is slightly closed and running proportionally on choke. I should have noticed this problem earlier as the full throttle running sound was slightly strange but not bad.



These findings again led me back to the carburettor to retrace my cleaning steps as there is obviously still some sort of restriction. I stand to be correctly if you think otherwise.
I did some more reading and went back to this carburettor picture where item 15 (nozzle) removable however I couldn�t get it out. Could that be the problem?
So it appears when it was running ok it was running proportionally on choke. I should have noticed this earlier.

Item 15 appears to be the emulsifier. If it won't come out that is usually because of hard-set gum holding it in. It happens quite often. I suspect that your soaking softened the gum temporarily but did not remove it, and it just set again afterwards. It seems to me that your cleaning work has not been fully effective.

Best next step is to go back to the cleaning, get all the removable parts out, and blast them with carb cleaner under pressure, then blow them dry with compressed air. From your symptoms it is probably getting lean mixture from the main discharge system all the time, but sometimes this is being overcome by the choke not opening properly. The primary culprits are probably the main jet (Item 8) and the emulsifier (Item 15), since the problem is associated with the main system, not the idle system.