Honda GXV120 rebuild

[tom3]

Question, maybe kind of dumb. When you took apart the motor was there a lot of cut dried grass and dirt in the cooling fins? Might explain some of the wear and resulting oil use.

 

[Chris Parman]

Question, maybe kind of dumb. When you took apart the motor was there a lot of cut dried grass and dirt in the cooling fins? Might explain some of the wear and resulting oil use.

Tom, no the cooling fins were clear of debris.

 

[Chris Parman]

Here some pictures of the Cylinder head and Valves. I clean the cylinder head in a Ultrasonic cleaner and it came out pretty clean except for the exhaust runner and valve pocket, which I already started to grind out the carbon build up. I'm not entirely sure if this engine ever had valve steam seals and I did see evidence of any seal debris in the oil sump. Also, there is quite a lot of carbon build up on the exhaust valve (see pictures) not sure if its due to worn piston rings or valve guide. However, initially when I took off the cylinder head I noticed a small pool of oil at the bottom of the cylinder when the piston was at top dead center. I know I need to oder the GXV120 Service manual (and I ordered the manual today from Honda), I was just wanted your thoughts thus far in the rebuild cycle. As always I appreciate everyones input.

 

[jp1961]

Hi Chris,

The exhaust valve on my GXV140 looked similar. I used a Dremel hand grinder with wire wheel to remove most of the carbon and did resurface the valve seat face with the compound on my lathe set to 45 degrees. If you had a pool of oil in the cylinder, I would suspect it's leaking past the valves. Is there a lot of play in the valve stems when inserted into the head?

Regards

Jeff

 

[Chris Parman]

There is slight play for both the Intake and Exhaust valve to valve stem guide, more so with respect to the Exhaust valve. I can feel it at the spring end, as opposed to the combustion chamber end of the valve. If it's the valve stem guide it's going to be tough because I don't have special tools.

 

[jp1961]

Hi Chris,

Assuming you have a 0-1.00" micrometer, i'd try to find the largest diameter rod that will fit into the valve guides and then mic your valve stems where they come into contact with the valve guides, if > .001" I'd replace the valve guides. Mine were within 1/2 thou or so (i.e. .0005"). I understand about not having special tools, my Intertec manual says a special tool is needed to install the guide(although a right sized deep well socket would probably work) and they must be reamed after installation, again using a special reamer, however reamers can be purchased at like .0005 increments.

Correction on the cylinder bore diameter,,,the Intertec manual says 2.262-2.363, I believe is a typo (by Intertec, not me) I think they mean 2.362"-2.363. Makes sense as the piston is 2.360"-2.361". Sorry,,,I try to triple check what I type for accuracy.

Jeff

 

[logert gogert]

hey guys, i know this is off topic, buuut lets say i wanted to rebuild a engine, ( which i don't )
HOW do you get those precise measurements, i mean you can't just whip out a ruler and go, alright the cylinder is 3.0001276
like wut?

 

[jp1961]

Hello,

You need a 0-1.00" micrometer and 0-6" set of calipers. a set of bore micrometers is useful too.

Regards

Jeff

 

[jp1961]

Hello,

You need a 0-1.00" micrometer and 0-6" set of calipers. a set of bore micrometers is useful too. A machinist rule usually goes down to 1/64" increments, which is REALLY hard to read unless you're eyesight is very good. For this old fart i use the 1/32" scale.

Regards

Jeff

 

[logert gogert]

?
whats post #19 supposed to mean
you already said it in post 18 so, was it an accident