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2018/05/24 10:53:18
frenchman

Kawasaki FC420V: 1 psi compression in cylinder?

Hi all,
Can someone lead me to the first things to check when you face almost no compression in sparkplug mounting hole?
Obviously, as a result, I have a "no-start" condition.  Yes I have spark and fuel seems to flow correctly.
Compression is supposed to be 71 psi minimum. I get maybe 1 psi.
I have found a shop manual on the FC420V but I am looking for advices on, maybe, basic things to check before I start heart surgery on the engine piston.
Thanks
Richard
14 comments Leave a comment
Roy
Remove the valve cover to see if the valves are working properly.
2018/05/24 11:59:53
Mikel1
You sure piston is moving?
2018/05/24 12:10:53
frenchman
Hi Roy, Mikel1,
I will open the valve cover. I will have to read what to look for as far as how the valves are supposed to be adjusted to and if they are in good working condition.
Mikel1,
I am not sure best way to check for piston movement.  Can you offer some guidance there?
Thanks
Richard
2018/05/24 12:19:00
Mikel1
Take out spark plug, put a long screwdriver or similar into hole.
Manually rotate engine by hand, does screwdriver move in/out while turning?
2018/05/24 12:48:53
frenchman
I finally checked the piston travel. It seems to move ok just by sticking a wooden rod through the sparkplug hole. I also sprayed some oil into the cylinder to see if it makes any difference in the reading:  No difference.
But see picture attached: The bottom valve stem was found totally detached on both ends.
Looks like I am going to replace the valve there.  Are there any special tools needed?  I can do it if I have some instructions to follow. Not sure that the shop manual I found online is self explanatory. It assummes I am very used to this type of repair. I can do mechanical repairs but I have never opened up an engine before to that extent.
Thanks for your input.
Richard
 
2018/05/24 22:57:17
frenchman
Hi all,
I wanted to correct my previous message. I used the wrong terms in describing the problem seen under the valve cover.  It appears the valves may be just fine but the bottom (exhaust) valve is not getting any movement because the rocker arm is no longer linked up with the push rod and tappet.  All those parts are described in the Jacks Small Engine website in the assembly diagrams.
Hopefully, I can reconnect the tappet + pushrod to the rocker arm.
Question:  How can the pushrod "fall off" its rocker arm seat location?
Thanks
2018/05/25 09:47:46
Mikel1
Looks like valve is stuck open which is why compression tester was so low. I would pull the head off
2018/05/25 10:31:09
frenchman
 
Oh yes. That's right. The valves should be closed if the rocker arms are not pushing.
The exhaust valve did not return to its closed position. Hence the loose rod.
I will investigate and let you know what is going on with that valve.
Thanks for your input.
Richard
 
2018/05/25 13:01:05
frenchman
Memorial day weekend:  I have removed the cylinder head and found the exhaust valve not able to slide back and forth. I have removed the valve from the head and saw that the valve stem was quite rough near the sealing portion. The stem rubber seal was broken too. I think it may cause the oil to get on the stem surface, burn and attack the stem surface?
After I polished the stem surface with fine sand paper (320 and up) I got the valve to slide easily and  to close on the head opening.  But is it normaly feasible to restore the valve this way? It may not be perfect like a new part but I thought it would be sufficient if it slides without effort.
Someone told me I needed to "lap" the valve with the head opening if I want to make sure it seals correctly so I will do that.
There are other things I wanted to verify with you all:
I will buy two oil seals ( I will replace the intake valve oil seal as well). Is this correct that I should not have to lubricate the stem before assembly? I mean that it is designed NOT to receive crankcase oil?
The cylinder head gasket did not look damaged. Sort of metallic in nature. Looked in good shape but the manual talks about the new gasket having a special sealant on the surface. So, would I need to replace it anyway to get the gasket with that special sealant?
Thanks for all your help.
Richard
2018/05/29 13:00:27
Mikel1
How is the valve guide on that valve, hasn't moved has it?
Not a bad idea to lap the valves while head is off, doesn't take long.
Personally I like to use a new head gasket on ohv
2018/05/29 21:38:05
frenchman
Hi Mikel1,
Thanks for the reply. 
I am waiting on parts to arrive so the engine is still open. Glad you mentionned the guide location.
I noticed the guide on the stuck valve side (exhaust valve) was protruding much less than on the intake valve side. Do you think it has shifted? Wonder how it could move down away from the engine side. Maybe I did it when I used a mallet to get the valve to move into the closed position? I was very careful when I did it but, maybe I accidentally caused the guide to move away. When I saw the difference in heights, I thought it was designed that way.
Is it something I can adjust/fix or does it mean I need to replace the head?
About the metallic head gasket:  I was wrong in saying the old one was like new. A new gasket is not a flat piece. It has lips around each openings. The old gasket is completely flattened.  When you place a brand new gasket in the assembly, you crush the lips to form a seal. So, it seems that whenever the head is removed you need to replace that gasket.
Thanks
Richard
2018/05/30 12:02:59
frenchman
Ok... wrong statement on my part.  Sorry about that...going too fast here. 
The valve guide that appeared to have moved is actually shifted towards the engine side. I mean that it is recessed on the valve cover end when compared to the top valve (intake). Now it makes sense that, when I applied C-clamp pressure to the spring end of the stuck valve, I most certainly caused the guide to move. Plus I probably cracked the oil seal body when the guide moved.
If the guide is press-fitted into the casting, I should be able to move it back into position. I have a vertical press I can use.
Let me know what you think.
Thanks
Richard
2018/05/30 12:37:23
Mikel1
Obviously your not the only one going to fast, I meant a new head gasket not head, have to edit it now.
You could give it a try, worst case scenario a new head
2018/05/30 19:08:28
frenchman
Hi Mikel1,
So, the two valve guides should be at equal heights, correct?
Do you see any issues with trying to push the exhaust valve guide back to the proper location?
Did you have to reset a guide before?
Thanks
2018/05/30 23:51:21

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