FH770D Bent push rods I need a solution.

Discussion in 'Mechanic and Repair' started by captken, Oct 5, 2012.

  1. captken

    captken LawnSite Bronze Member
    Posts: 1,707

    camshaft pictures.

    problem kawasaki 010.jpg

    problem kawasaki 011.jpg

    problem kawasaki 012.jpg
     
  2. captken

    captken LawnSite Bronze Member
    Posts: 1,707

    Well, it's time to close this chapter on this old mower.
    So to Piston Slapper, Big Fish, Restrorob, Mowermankevin and sharpcut1, thank you for your help and insight it trouble shooting this problem.

    With a little help from friends, got through this without spending a lot of money and learned a lot. thanks.

    After getting the specs on the cam and looking at it to measuring it.....I noticed the obvious. There are no exhaust cam lobes left on the camshaft!
    For grins and giggles I measured and found the specs [exhaust] were 26.34mm and 25.63mm......they should spec out at 30mm...

    The [intake] cam lobes spec was 28.90 and 28.7mm they should spec out at 30mm as well.

    The exhaust lobes are all but gone, the intake, some wear.

    My new friend at Kawasaki told me the early engines had cams designs that probably were changed out for one reason or another...most possibly inadequate heat treatment....
    I ran the engine for about 10hrs. before I had problems, he said about 10hrs was all you could get on a non heat treated cam before the lobes were gone.
    So here are some pictures of that cam and of the old cam from my blown engine.

    The solution {I hope}

    Feel free to comment further, I'd never guessed it to be total cam failure in a almost new engine.

    kenny

    problem kawasaki 020.jpg

    problem kawasaki 021.jpg
     
  3. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,157

    I'm glad you got it figured out! If you would of only had the cam turned to give us a shot of all the lobes, it would have been obvious right then!
    See, it's all your fault!!!
    On closer inspection of the original pic #2 I can just barely make out whats left of an exh. lobe. You can tell it's definitely out to lunch!

    Going back to your first post, you never did say which pushrod was being bent.
    In my head I kept thinking intake.
    Oh well, at least now ya know.
     
  4. captken

    captken LawnSite Bronze Member
    Posts: 1,707

    big fish,

    hmmm, I thought I said intake, my mistake.

    I did not think problems with the exhaust valves could be the cause of an intake valve bent push rod problem....after thinking about it for a while....

    My thinking, and I am the first to admit that I am no mechanic by any stretch of the imagination, I just have common sense is this:

    The exhaust valve was incapable of opening up enough and with such a short duration, due to the cam lobe wear, open for a extremely short time, caused the exhaust gas pressures to build up in the cylinder with no where to go. At high rpms something had to give.

    Comes along the intake valve, trying to open. Due to extreme cylinder pressure, trying to overcome, taxes the weak link, the push rod.


    That is my thinking on what happened, what do you think?

    kenny
     
  5. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,157

    Sounds like it to me. Prolly would explain the backfire thru the carb also: pent up exh. gasses, int. valve opens, bang, out comes the exhaust!

    While your into it, you might wanna check the oil pump for any scoring, and take a close look at the lifters also. I'd also check the rocker arms for any pad wear and cracking and the mounts.
     
    Last edited: Oct 11, 2012
  6. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Ditto BigFish....Id do a complete teardown...wash everything..and check for wear and dulling of the bearing surfaces... About 10 years ago Kohler had a bunch of bad camlobes....looked like they melted like lead...all that metal in the oil destroyed a lot of engine blocks...
    The cams are only surface hardened...that's why you really need to use cam lube when replacing a camshaft or lifters (tappets)...one scratch on the hardened surface and it will wear out pretty fast...
    Posted via Mobile Device
     
  7. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,157

    So how did ya make out??
     
  8. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    The chicken came out perfect...as usual..
    Applejack ribs were amazing....
    Got in 6 hrs of welding and fabricating on the big dog...
    Might can fire it up next weekend...

    Pretty sure the FH770 is probably done...
    Posted via Mobile Device
     
  9. captken

    captken LawnSite Bronze Member
    Posts: 1,707

    Sorry I have been running the mower every day to get caught up!

    I gained a new appreciation for the guys who work on equipment to keep us up and running. I have never felt confident enough with my ability to work on the inside of a mower's engine. I would not have done so in this case, but to take the engine to a professional might have ran the cost on this bargain engine to near what I would have had to pay of a new one with a factory warranty.
    I had no economic choice but to try to learn what I could and to find out was was wrong and to fix it.
    This forum is valuable to those wanting to learn this trade and to others like myself who want to be able to fix their own equipment.
    Thank you guys who helped me.
    I am sorry but there no time for pictures, I had to concentrate on what I was doing!
    What I did was remove the camshaft and tappets, [the oil pump to check for damage] and the oil cooler and its lines.
    I left the crank and connecting rods alone.
    I got 3 large cans of carb/choke cleaner to spray every thing on the inside of the crankcase from where the push rods go through the cylinder head and engine block to every surface I could with the can straw to remove all traces of contaminate. I stayed clear of the connecting rods and crankshaft with the spray but rotated the assembly and cleaned what I could.
    I wiped every thing down with a lint free cloth.
    I then used PB Blaster behind that, spraying the connecting rods, crankshaft and cylinder bores, behind the piston and everywhere that I cleaned with the carb/choke cleaner. I wiped that all down the best I could and resprayed everything all over again with the PB Blaster until I felt confident that I did the best I could.
    The oil cooler and lines were cleaned out with gasoline and allowed to dry.

    The governor assembly, with the steel balls and plastic cover had to be removed from the bad camshaft and installed on the new camshaft and was sprayed with PB Blaster.
    I used Permatex Ultra Slick assembly lube, I don't know if this was a moly grease but the hot rod guys use it a lot, so it should be good enough here. The assembly lube was applied heavy on the cam lobes and the bottom of the new tappets.
    [The new tappet stems were dipped in engine oil and then inserted into the engine block]

    I assembled the oil pump and filled the rotor housing with engine oil.

    I used a lot of Ultra Slick for the cam bearings then poured engine oil in on top of that, both the engine case and the back case.

    I lined up the dots for the crank and installed the cam which was well lubed. I even used the Ultra Slick on all the gears of the cam, crank, and oil pump and went behind the assembly lube with engine oil to be damn sure I got every thing well slicked up.

    The oil pump gear I had to spin a little to get the gear to mesh with the other gears to get back cover to fit up, but the engine went back together with no problems.

    I got new push rods that was a no brainer but I got new rockers too, just in case!
    After the valves were adjusted, and the crank spun 360 degrees to be damn sure I got the adjustment right. .0004 in on tdc compression stroke. [If you rotate it 360 degrees after valve adjust and the rockers are loose you done it wrong.]
    I filled the oil cooler up with engine oil. [I left the oil lines dry] mounted it and poured engine oil into the engine through open valve covers and topped off the crankcase.
    I installed the engine into my Exmark LAS28KA604 Lazer Z and spun the engine over with the starter with no spark plugs to get the oil circulating and the fuel pump to fill.
    I put the plugs in and the engine fired right up with no problem. I let it run at low speed idle of 1500 rpm and held my breath. When it was all good and warmed up, I moved the control panel, with throttle maxed out get an indicated rpm of 3650 no load, then tightened down the two bolts on the control panel.

    I ran the engine under load for about an hour [mowed my yard] then changed the oil and filter.
    I have since ran the engine for 25 hrs or so with no oil consumption or discoloration. The exhaust on a cool morning has no smell,
    I might have dodged a bullet this time. I probably should have pulled the crank, but didn't.

    I do have a problem with an intermittent miss at mid throttle, it disappears under load at full throttle.
    Any idea where to check?
    Thanks, kenny.
     
    Last edited: Oct 20, 2012
  10. captken

    captken LawnSite Bronze Member
    Posts: 1,707

    Just re read my post....there are over 30 "I's" there.

    "I" could not have done it with out help from "U" lol...
     

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