Engine valve lash adjustment

Discussion in 'Lawn Mowing' started by Boit4852, Jan 13, 2012.

  1. Boit4852

    Boit4852 LawnSite Member
    Posts: 2

    Maybe this subject has been covered in different ways, but I'm hitting it anyway. My '07 Exmark has a Kawasaki FH580V engine that began showing signs of needing a valve adjustment by making a 'clicking' noise and declining power. After acquiring the manual online, I read over the procedure and decided I know a better and more precise way of making this adjustment. I used a piston-stop bolt from Summit Racing, and a homemade degree wheel made out of a simple paper picnic plate, some duct tape, a fine tipped marker, dial caliper, and the right tools...plus a set of replacement valve cover gaskets. Took me about 4 hours to do the job, mainly because of meticuously cleaning the old gasket material off without damaging the mating surfaces for the new gaskets so that oil wouldn't leak. The actual adjustment time was only about 30 minutes per cylinder. The result; the engine has like-new power.....is now very quiet and smooth...starts easier with little choke and will idle smoothly even if I turn the choke off right after starting even if it's 30 degrees outside. It didn't run this good when brand new. The manual says to use a flat spot on the coil pick-up as the TDC reference but using the piston stop and degree wheel is much more precise....in my opinion. This is probably the most overlooked and/or avoided maintenace task on any engine, espeically mowers/tiller/generators/...etc. If you perform this task after about 70 to 80 hours of operation, you can probably then extend the hours to about 200 after that because of the break-in period. If you are not knowledgable about how a 4-stroke engine works, don't try this yourself or you could destroy your engine by not understanding about how to set your engine at TDC(Top Dead Center of compression)....not knowing how to have that 'feel' using a feeler gauge. We're talking ONE THOUSANDTH'S of an inch measurements here. If you set the lash too tight, you run the risk of a valve not closing completely thereby allowing either air/fuel not being contained in the combustion chamber, or..exhaust gases flowing backward into the intake. I'm saying that these are PRECISE measurements and you should have a good working knowledge of how a 4-stroke works. This engine was fairly simple to work on as I have experience with 4-stroke motocross engine tuning. The FH580V engine utilizes a simple 2-valve per cylinder/pushrod configuration with manual rocker style lifters. This is about as simple as it gets. Hope this helps someone. BTW...set valve lash at .004" intake and .006" exhaust. The exhaust lash is larger because it runs hotter and the metal expands more than the intake. The intake runs so much cooler because of not only the air/fuel mixture entering, but because of the intake vacumn.
  2. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    I think you went through a whole lot of tedium for nothing. The reason you make sure the cylinder is at top dead center is to assure that the camshaft lobes are on the base circle. This is not a precise operation because the base circle runs for 180° around the camshaft. The base circle is the flat part of the camshaft lobe where there is no lift. The lifter can be on any part of the base circle and you would have acheived the same result. The important part is that the lifter is on the base circle.

    One way to assure this is to make sure that you only adjust one valve at a time. If you're adjusting the valves on cylinder 1 then simply make sure that the exhaust valve is at full lift and then adjust the intake valve. You can put your finger on the rocker arm and feel when it gets to the top. Or watch it. It's not a precise operation. If the exhaust valve is at or anywhere near full lift then the intake valve must be on the base circle. Then to adjust the exhaust valve make sure the intake valve is at full lift. Then switch over and do cylinder number 2 the same way. The entire procedure shouldn't take any more than about 10 minutes.

    The reason you acheived such great results wasn't because you used a degree wheel. It was because you adjusted the valves after the break in period. A flat tappet has to settle into the lobe. It doesn't settle much and other parts need to settle into their permanent positions too. This can change the clearences. You just put the clearences back where they are supposed to be.
  3. orangemower

    orangemower LawnSite Silver Member
    from pa
    Posts: 2,773

    simple valve adjustment was all he did. A degree wheel isn't needed for such a easy task. He sure made it sound good though. :D
    Posted via Mobile Device
  4. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    I can think of ZERO reasons why a degree wheel would ever be needed on a small engine. I use a Comp wheel and a dial gauge to set cam timing on high performance engines but aside from that I don't have another use for it. At the shop I hang out at he has a 24" degree wheel. That thing is huge.
  5. SouthSide Cutter

    SouthSide Cutter LawnSite Bronze Member
    Posts: 1,333

    I think mine is bigger than that it looks real funny on the motor. And alot of guys adjust vv's both intake and exhaust at the same time. I always done one at a time. And when I went to Jesel rockers man did that make a difference.
  6. soloscaperman

    soloscaperman LawnSite Gold Member
    Posts: 3,045

    This is why I love my Kohler, I don't have to worry about this.
  7. Think Green

    Think Green LawnSite Silver Member
    Posts: 2,746

    Well, if a person adjusts the lash at or near close to TDC, then the lash is off?
    So, do you adjust the lash at full compression of each cycle?
  8. weeze

    weeze LawnSite Fanatic
    Posts: 8,903

  9. herler

    herler LawnSite Fanatic
    Posts: 5,144

    Yeah but it's always "just a simple valve adjustment" until the day it doesn't turn out the way it was supposed to, maybe to some folks it's nothing but to me it is critical engine work when one mistake could mean expensive trouble... And a valve lash adjustment needs to be done right or you could be looking at all sorts of headaches so I like what this guy did because he was meticulous to make sure it was done right and that is important because better done right to begin with than to have to do it over.

    'k I reckon I can step off the soapbox now
  10. dhardin53

    dhardin53 LawnSite Senior Member
    Posts: 711

    Of all the mower repair I have done over my life time adjustment valves runs low on the list of things that have really solved the problem. Having said that I have a Onan CCKB needing valves adjusted right now.

Share This Page