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Sizuki 2 cycle (Toro ProLine) problem

Discussion in 'Lawn Mowing' started by Roger, Jul 25, 2005.

  1. Roger

    Roger LawnSite Fanatic
    Messages: 5,943

    I don't know much yet, but will post what I have hoping for some answers. I just dropped by the house for lunch, and need to get back to work, but maybe somebody will understand the problem.

    I was using my Toro this morning, fired it up, finishing the first bag. It has a 5.5hp 2 cy Sizuki, four season old, but probably only about 1,500 service hours (shares hand mower work with a LawnBoy). The Sizuki has never provided one problem -- always has run well and very efficient.

    I stopped it to change the bag, and when I went to refire, it oversped. It started on first pull, but was clearly overspeeding. I moved the throttle back and forth a couple of times, but the action made no difference in engine speed. I stopped the engine after a few seconds.

    I took it to the truck, pulled out my tools -- took off the air cleaner cover and found the choke butterfly was not able to move. It would not move easily with either the throttle to "choke" position, or when I pushed on it manually.

    I took off the air filter housing to expose the end of the carb. I couldn't see clearly inside the throat, to got my flashlight. On the added light, I could see some obstruction in the throat. It was black, looked like a plastic object, and it was "loose" when I pushed on it with a screwdriver. Using small narrow-nosed pliers, I tired unsuccessfully to pull it out past the butterfly. In moving it a bit further in, the butterfly was able to move freely again, both manually, and with the throttle to "choke" position.

    At that point, I decided repair was not so simple, so buttoned it back up. I fired the engine again, and the response was the same -- overspeeding. I shut it off quickly and loaded it on the trailer.

    I had my LawnBoy to finish and to continue for the rest of the day, so I'm not down and out.

    Clearly, the loose object should not be there. But, without further inspection, I don't know what it might be, and how it got there.

    After I am done with my mowing rounds this evening, I plan to pull off the carb, but I get a bit edgy with all the connections, tiny springs, etc. Maybe somebody has some experience with something similar and can provide some guidance to help. I'm comfortable with tools, but have not done detailed carb work. Typically, I do all my repair work, but this matter makes me concerned about success.

    I apologize for the lack of more detailed info, but with the limited observations made while kneeling in somebody's front yard is the best I have now. Maybe I'll learn quickly after I start taking off parts.

    Thanks for any suggestions, experiences, and observations.
  2. Roger

    Roger LawnSite Fanatic
    Messages: 5,943

    ... having used all the suggestions .... just kidding!

    Obviously, by the lack of response, my situation was unusual. And, when I dug into the problem this afternoon after my Tuesday short-schedule (hot, dry here -- little grass to mow), I learned how unusual.

    After taking off the air cleaner body (the plastic part that houses the foam filter, and has several compartments), I started poking through the carb throat. I was able to pull it out from the posts an inch or so, and found a small piece of plastic protruding from the opening in the carb. More pulling on the debris with narrow-nosed pliers, and I was able to get a part of it out. Quickly, I understood what had happened.

    I looked closely at the body unit, and saw some plastic missing from around the mounting holes. The debris fit the arc. After some more poking and pulling, the final part came out from the carb throat and it too fit a missing part.

    Obviously, what happened was the plastic part of the body broke off and got ingested into the carb throat. I cannot recall the last time I had the body off the engine, but I don't recall taking it off during the off-season PM routine, so it was long ago.

    I remounted the body, tightened down all bolts, and fired the engine. Works fine!

    FYI, before I investigated closely, I checked on availability and cost of a new carb. MSRP on a new carb: $120. Ouch!

    I don't know if other missing small pieces where ingested and got melted and discarded through the exhaust port. So, those with these engines might wish to check the integrity of the air cleaner body around the mounting holes for the carb studs.

    While you are checking small parts, you may wish to check the links on the top ends of the ground drive cable (left side) and operator presence cable (right side). A few weeks ago, the OP eye that is over the hook on the movable part of the handle came apart. It had worn through. I looked closely at the ground drive cable on the other side, and found the eye to be badly worn too, not quite ready to pull through. Obvioulsy, these were two wear points I did not check in the offseason. Installing both cables took about 1 1/2 hours of casual time.
  3. S man

    S man LawnSite Gold Member
    Messages: 3,562

    A trip to your toro dealer would be good.
  4. iluvscag

    iluvscag LawnSite Senior Member
    Messages: 743

    Your improving. :)
  5. S man

    S man LawnSite Gold Member
    Messages: 3,562

    You don't know what I'm capable of. :D

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