GX160 valve guide replacement procedure?

K

knighty

Member
I'm now seeing a few engines with black soot inside the rocker area around the exhaust valve, whereby the exhaust valve now also has big radial play. It seems the exhaust valve guides are quite worn. I have never replaced any before, but having a google around the procedure seems to be:

1) Heat the head with an electric paint-stripper gun.
2) Hammer / press out the old guide with a good fitting mandrel.
3) Heat the head again for re-assembly.
4) Apply some green Loctite to the OD of the new guide.
5) Hammer the new guide back into place with a well fitting mandrel.

Have I perhaps missed something?.......is the green Loctite really required?

I'm guessing this may have been first caused by a worn or faulty valve stem seal?......or just a build up of soot?
 
A press is the preferred method, we never used loctite, you can make or have made the mandrel. You must recut the valve seat after new guides are installed.
 
Many thanks for that, most appreciated......yes, admittedly I'm not into hammers for anything precision related, I have access to a fly-press so will give that a go. OK I will get a T-bar style valve seat-cutter as anything more exotic is just not worth the investment.......do you perhaps know the angle of the valve seat, or should I just measure up the angle of the valve and determine it that way?
 
Kart43 said:
A press is the preferred method, we never used loctite, you can make or have made the mandrel. You must recut the valve seat after new guides are installed.
Click to expand...

Good advice. They are not hard to press in. I have used a drill press(not on of course) to press them in before. If this is a true high performance race engine, you may want to recut the seats after installation. A good 3 (or more) angle is important anyways. However, if its a yard or fun kart application, simply lapping them in may be enough.
 
jsstump#70 said:
Good advice. They are not hard to press in. I have used a drill press(not on of course) to press them in before. If this is a true high performance race engine, you may want to recut the seats after installation. A good 3 (or more) angle is important anyways. However, if its a yard or fun kart application, simply lapping them in may be enough.
Click to expand...

Its an 8hp selected parts engine, for circuit racing in the uk, revs to 6600rpm, all standard honda, but everything has been built to a blueprint spec as per the regs. From what you say i think just a valve lap will do the job. We have a shadow-graph at work so measuring the valve seat angle can be done on the valve. Then i can get the right angle cutters should i need to, if a lap is not enough, many thanks folks.
 
The seat is 45* cutting the seat guarantees concentricity, you can lap away if you don't get it to seal you will have to cut the seat and then buy a new valve, as you have just ground the face out of shape. Proper procedure is cut the seat lapping is a finishing process.
 
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