Honda 50 HO 4-stroke- NO COMPRESSION

Red5 · 27 February 2012, 19:22

So I bought this 14 foot Alliance RIB. It has a Honda 50 ont eh stern. The motor looks great, but it has like 4 pounds of pressure in each hole. Looked at teh Cyl walls and they looked fine. Any ideas on what could have happened or how to fix this?

captnjack · 27 February 2012, 19:28

The valves are stuck open.

Red5 · 27 February 2012, 19:47

Quote:

Originally Posted by captnjack

The valves are stuck open.

I just pulled the cover and it appears that everything is going in and out....

Do you know how I would check the timing on a Honda 50hp? How wold I check to see if the valves are stuck?

captnjack · 27 February 2012, 20:11

Quote:

Originally Posted by Red5

I just pulled the cover and it appears that everything is going in and out....

Do you know how I would check the timing on a Honda 50hp? How wold I check to see if the valves are stuck?

Does it start? She needs to be running to check the timing. Just because the lifters are going up and down doesn't mean the valves are sealing like they should. Zero compression in a 4 stroke suggests stuck valves to me. Or you have no functional rings in there which seems unlikely. Its possible the Honda actually has a decompression feature to help pull start her.

I don't know how to do a valve job on an outboard, that's beyond my pay grade. You'll need a shop manual to start at the very least. That should give you some idea of what you're taking on.

Red5 · 27 February 2012, 20:43

Quote:

Originally Posted by captnjack

Does it start? She needs to be running to check the timing. Just because the lifters are going up and down doesn't mean the valves are sealing like they should. Zero compression in a 4 stroke suggests stuck valves to me. Or you have no functional rings in there which seems unlikely. Its possible the Honda actually has a decompression feature to help pull start her.

I don't know how to do a valve job on an outboard, that's beyond my pay grade. You'll need a shop manual to start at the very least. That should give you some idea of what you're taking on.

It won't start, no compression..

I think I have it narrowed down to two possibilities..
1. The rings are stuck on the piston.
2. The valves are stuck open.

I'm guessing that I have to pull the head to find out? Or is there a way to check without pulling the head?

TomKat · 27 February 2012, 20:54

could there be holes in the pistons if the valves and pistons have met at some point?

I guess a flashlight would reveal this?

Could someone have adjusted the valves to such an extent that they never close?

Nos4r2 · 27 February 2012, 20:58

You should get more than 4psi compression with stuck rings and stuck rings on all cylinders is unlikely (though possible).

Spray some WD40 down the bores and turn it over a few times by hand then retest it. If the compression jacks up it's the rings.

m chappelow · 27 February 2012, 21:07

few drops of oil down the spark plug holes into the bores see if that makes any difference,may give enough compression to start it ,
any ideas when it was last run ,,if its been stood a long time compression should come up with running unless its badly worn.

Nos4r2 · 27 February 2012, 21:15

Quote:

Originally Posted by m chappelow

few drops of oil down the spark plug holes into the bores see if that makes any difference,may give enough compression to start it ,
any ideas when it was last run ,,if its been stood a long time compression should come up with running unless its badly worn.

Wouldn't want to try that without hand turning/rechecking the compression 1st.

If it's sticky valves you may end up with them contacting the pistons if it fires up on one pot.

Downhilldai · 27 February 2012, 22:12

As Nos says, whip the plugs out and turn the crank/flywheel by hand.
If you remove the valve cover, you can check the valve clearances when the valves appear to be fully closed. If there's excessive clearance, then the valves are likely to be stuck open.
If this is the case then you may be able to free them off by applying some releasing oil on the stems/guides and continue turning the flywheel by hand to work them free.

Red5 · 28 February 2012, 14:14

Quote:

Originally Posted by Downhilldai

As Nos says, whip the plugs out and turn the crank/flywheel by hand.
If you remove the valve cover, you can check the valve clearances when the valves appear to be fully closed. If there's excessive clearance, then the valves are likely to be stuck open.
If this is the case then you may be able to free them off by applying some releasing oil on the stems/guides and continue turning the flywheel by hand to work them free.

This sounds like a good idea. It appeared that the valves were opening and closing. At least it looked that way from. where I was standing.

Perhaps I should take a HD video of the valves and you could tell me. (?)

I'm thinking this thing may have jumped time in a big way. If I turn it by hand it will only turn so far before it stops me. But if/when I hit the key it rotates fine.

Red5 · 28 February 2012, 14:16

BTW: Here is me trying to raise hell in an old stock miata from two days ago. lol

http://www.youtube.com/watch?v=nPuHq...layer_embedded

Nos4r2 · 28 February 2012, 17:06

Quote:

Originally Posted by Red5

I'm thinking this thing may have jumped time in a big way. If I turn it by hand it will only turn so far before it stops me. But if/when I hit the key it rotates fine.

Hopefully no bent valves...

Red5 · 29 February 2012, 22:54

The motor had jumped time. Put it back in time and poof- i now have compression.

Thanks for all the help.

captnjack · 29 February 2012, 23:03

Quote:

Originally Posted by Red5

The motor had jumped time. Put it back in time and poof- i now have compression.

Thanks for all the help.

LOL How? Did you leave out that you had replaced the belt or something?

Downhilldai · 29 February 2012, 23:45