Ring tolerance on 14 HP Kawasaki FC420V - pre-purchase info

Discussion in 'Mechanic and Repair' started by ninensei, Jun 9, 2007.

  1. ninensei

    ninensei LawnSite Member
    Messages: 10

    I bought a used JD with a FC420V that was dumping oil at a rate of gallons per minute when the engine started up. Found that the crankcase was full of gas and was popping the oil-filler tube off. After cleaning up the gas/oil as best I could, found that engine was burning oil big time so I figured the rings were shot. I have never torn an engine apart before, so this is all new to me. I opened her up expecting to find a mess inside, but the thing looks brand new (meter reads about 415 hours run time). Piston has no scorching or gouging, rings looked in great shape and there was hardly any carbon on the piston head. Intake valve looks great. Exhaust value doesn't look so great but maybe that is normal (I figured they would look the same but they look like they came out of different engines). Did a leak-down test before disassembly and there was no leakage past the intake or exhaust value. Now on to my main questions.

    I removed the rings from the piston and placed them one at a time in the cylinder (per the JD tech manual instructions) to measure the ring's end gap. One was 0.9mm and the other was 1.5mm. This is out of spec per the manual. Manual says they should be 0.2mm to 0.9mm. Those with rebuild experience, would you expect a motor with 415 hours to have worn the piston rings this far out of tolerance? Should a gap of 0.9mm produce a cloud of white smoke so thick (in under a half a minute) that you can't breathe or see 5 feet in front of you? Or did the gas in the oil produce pressure in the crankcase that forced oil into the cylinder? I've pretty much decided to swap out the rings, but I hate to spend $50 for 5 ounces of metal if it is just going to get me from 0.9mm to 0.7mm, especially if the oil burning is due to a different problem. Is $50 for a ring set (from JD parts website) a normal price or I should be shopping elsewhere?

    Side topic...

    I notice a lot of people on here with blown FC420V engines that are destined for the junkyard. Before you do that, I need a FC420V air filter housing (plus screws and gasket) and a flywheel blower screen, circular shroud, mounting plate and screws. I guess the guy I bought it from figured these parts weren't important. Contact me if you are interested in parting with these things.

  2. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 965

    Sounds more like a head gasket problem to me.
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Steve, Since your in there I would go ahead and de-glaze the cylinder and replace the rings. But the kicker is the rings was not your smoking problem.

    When the carb. flooded into the cylinder and filled the crankcase with fuel it raised the oil level and the oil/fuel mix seeped/got pushed past the rings thus filling the muffler with fuel/oil mix. It can take up to 30 mins. or more to burn all the mix out of the muffler to where it wont smoke.

    The big question is; Did you repair the flooding carb. problem ? Clean/replace the float needle valve ?

    Deere bought the rights to this engine so they are the only ones you can get parts from using the spec. number off your engine. If you post the spec. number off this engine I will see about another spec. number where you can get parts from any Kawasaki dealer and leave Deere's high pricing alone.

    The below place has the rings for $33 and change which is a couple bux cheaper than Kawasaki's suggested list price, But there is no parts look-up on this site. You must already have part numbers and enter them in the "FIND" box then add them to your shopping cart.

  4. ninensei

    ninensei LawnSite Member
    Messages: 10


    Well, I didn't provide all the information in the original message, but your explanation sounds perfect.

    Here is the missing information...

    When I would start the engine (cold), it would run perfect for about 10 to 15 seconds (no smoke and sounding like a great engine). After 10 - 15 seconds, the smoke would start to show up in the exhaust; just a trickle at first, but after 1 minute it would look like an old coal-fired locomotive. The engine sounded great the whole time. In my limited experience, I didn't feel that the rings were the cause because I figured that the smoke would have started a lot sooner and would have been more consistent in the amount produced. It seemed to me to be somewhat related to heat, but I couldn't think of any other way that oil could be burning besides in the cylinder. I never even considered the possibility that there might be oil in the muffler burning off from superheated exhaust gases. So, I am happy to have a better understanding of the problem, but sad that I wasted all the time and money repairing something that didn't need repair.

    That brings me back to the "fuel in crankcase" issue. There are only three ways for gas to get in the crankcase that I can think of. First is via the fuel pump. I verified that there is no breach in the pump diaphragm, so that is not it. Next is the carb. My experience is once again lacking, but here is what I know. When I ran the engine, it sounded fine. No sputtering or excessive gas smell, and throttle up/down/full throttle/idle were no problem. I could not detect any air leaking past the intake value. Since I could not detect any erratic engine operation with respect to fuel, I assumed that the carb was not the issue as I would expect if excessive gas was flowing from the carb into the engine, I would get a "flooded" type of operation. So I came to the conclusion that the only way the huge amount of gas got into the crankcase was that the previous owner had mistaken the oil fill tube for the gas tank and filled it to the top.

    There is one last thing that I found during disassembly that I had missed during general troubleshooting/inspection. Apparently, a mud wasp had decided that the breather orifice would be a good place to build a nest. It had crawled up all the way to the valve cover, but not far enough in to be visible with the valve cover removed. I am thinking that this would have had an affect on the pressure in the crankcase relative to the air pressure outside the crankcase. Maybe this is the cause of the gas problem. However, I just don't see how that much gas would get in the crankcase via this route. I have not disassembled the carb yet, but I will take your advice and check out the float needle valve.

    Thanks for the link to the parts. That is definitely an easier pill to swallow. I don't have the engine number available at this moment, but I do remember it was a very early engine (revision -AS00). I looked on the Kawasaki web site and could only find stuff as early as BS01. But, parts is parts, right? ;)

  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    In most cases basic block parts are the same (Rings,Pistons,Rods,Gaskets).

    It is my belief that possibly the previous owner had the bad run problem so parked the unit and never had it repaired. He most likely got a piece of trash under the float needle valve that caused a bad run situation so when it was turned off the engine stopped with the intake valve in the open position. This let the fuel gravity feed right into the cylinder and seep past the rings over time (doesn't take but a hour or so) to fill the crankcase.

    It's possible while moving/transporting the unit to your place dislodged the trash so you are now getting a non-flooding smooth run. It would be worth your time to check/flush the fuel tank, Flush the fuel lines (hold the line off carb. over a container and crank the engine over). Then clean the carb out with carb & choke cleaner checking the float valve for any wear rings around the tip then install a new fuel filter.

    Also, Keep a eye on the oil level for a while. I never start a unit up without checking the oil first.
  6. ninensei

    ninensei LawnSite Member
    Messages: 10

    I'll go tear the carb apart right now. I already cleaned up the tank (it had quite a bit of varnish in it) and replace the fuel filter. The fuel pump was clean. I think this was definately sitting for a while.

    Thanks for your input! I'll be back with more...
  7. rob7233

    rob7233 LawnSite Senior Member
    Messages: 876

    notice a lot of people on here with blown FC420V engines that are destined for the junkyard. Before you do that, I need a FC420V air filter housing (plus screws and gasket) and a flywheel blower screen, circular shroud, mounting plate and screws

    I believe that I just saw most of what you want listed on Ebay! :clapping:
  8. ninensei

    ninensei LawnSite Member
    Messages: 10

    Carb status.. Looked brand new inside. No varnish or anything. No wear detected. All holes appear unclogged. There is a bit of orange discoloration on the walls in the fuel/air mixing chamber just past the choke plate, and the plate itself is very rusty.

    Missing parts status... Haven't seen anything on ebay yet. That's ok though. I just ordered new OEM replacment parts this morning that were crucial to engine operation (air filter assembly). Thanks for letting me know.

    Engine status... Okay, everything has been disassembled and checked. Now I just have to wait for the new parts to arrive, put the thing back together, cross my fingers and turn the key.

    Thank's for all the support and suggestions. I'll let you know in a week how it went.

  9. bobby perez

    bobby perez LawnSite Member
    Messages: 86

    I might be able to help you with some of them parts
  10. ninensei

    ninensei LawnSite Member
    Messages: 10

    Aaarrrgggghhh!!! Parts came today, but I order the wrong gasket!!! I did try out the new rings and the gap is down to 0.018(0.45mm) which is half of max tolerance. This is much better than the 0.96mm and 1.54mm I had, so I am happy.

    I don't know who worked on this tractor before I got it, but they put stuff in it that did a number on the hydro. I spent all day today cleaning it out and I've still got another day to go. No hurry since I've got to place another parts order.:cry:

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