I picked up a non running Honda mower with the GXV140 engine some time ago. The seller had taken it upon himself to try and diagnose the non-disclosed issues by removing the pushrods, rockers and fixing nuts and for some reason the governor spring.
After assuring me he would get the parts and let me know when I could come and get them, he can't find them so i was left in an unfortunate situation having shelled out $50 for a mower that I couldn't even try to start.
Fortunately, I had a Chonda for spares and was able to swap the parts over and get it to a functioning state.
I cleaned the carb, set valve lash and the mower starts and runs fine. The issue I am now facing is that after 1-2 minutes, after the engine has warmed up, I start getting blue/white smoke from the exhaust.
I performed a compression test and got 75 psi. I then added some oil to the cylinder and ran the test again, this time the compression upped to 115 psi, much better.
At this point I was ready to disassemble the engine and inspect the piston/cylinder and replace the rings. I removed the head and checked the cylinder bore and found some odd damage marks, right at the top of the piston stroke. I have attached photos of this damage. I can feel a distinct roughness and lip where this damage is.
I disassembled and removed the piston and checked ring gap. The top ring has 0.65mm and the bottom ring has 0.35mm, this seems to be well within the service limit from what I have read. The piston itself looks fine.
The point I am at now is assuming that the damage to the cylinder wall is where I'm losing compression. I've not ever really seen damage like this before and don't know how I could go about repairing it, or if it's even worth repairing at all.
I can either try honing the cylinder but it may not do enough to remove the damage. The only other option would be to bore out the cylinder, but that may not be a viable option.
Has anyone seen damage like this before or could offer the best way forward?
Hi sk8erade, and welcome to the forum, I personally have not come across damage like this before, so it's either an imperfection in the casting process or water has been sitting in the bottom of the bore and caused it to corrode. Cheers, Ted
I agree with Bigted that is is probably water damage. Rain water nowadays is more acidic then it once was and can do more damage as it concentrates the carbonic acid as the water dries out.
Here I would use my rigid hone to oversize the cylinder and would do it before ordering any parts as there could an inculsion air pocket that makes the bore unusable. I have seen this a couple times on Briggs engines.
Thanks for the replies. I don't know how long the mower had been out of service before I got it but I suspect the spark plug was left out and that's how water got in.
There's no rust damage to any other internal part so I might have been lucky in that regard.
I don't have a cylinder honing tool but I was planning to buy one, they're reasonably cheap at around $20. To oversize the cylinder, that would probably be something a shop would have to do for me I suppose, I don't have the tools to verify that I've done the job properly.
I can buy an oversize piston and ring set for $40 from Thailand, it is 0.020" (0.50mm) oversize. It seems to be the only oversize piston available for this engine so it would have to do I suppose.
