Hi guys,
FINALLY got time to rebuild the engine.
Mate...talk about a saga...when you get something second hand, you never REALLY know what you have till you pull it apart.
The piston and bore had almost no wear making them well within service limits.
The new head is excellent and the engine have gone back together with all new seals, bearing and the new head. All gaskets surfaces were cafefully cleaned and polished, gaskets greased, new component assembled with assembly grease, new valves adjusted and all old components well cleaned, the carby was given a thorough clean and all bolts and nuts tightened to correct torque settings. Compression is now almost the same as new.
The output shaft was carefully linished and a good dose of copper anti-sieze applied to stopped the clutch housing corroding and locking on to it again. The same was done on the mower drive shaft.
The woodruff key on the drive shaft side of the clutch housing had snapped and the groove was well flogged out. We fabricated a new key and built the groove back up with the mig and ground it back...looks like new. The engine is mounted on a Scott Bonnar Model 45 that is a total bitza - some really dodgey home handyman fixes have been applied to it by the previous owner and it appears to have been poorly maintained...this was also evident with the engine. I am currently on the hunt for another Model 45 to move the engine to and use the current one for parts...not that there are too many good ones on it...but hey, it was free and it actually cuts really well.
The cylinder blade is almost shagged though, so that is a big motivation to find another frame with a good set of blades. Missed out on an awesome bargain on the weekend due to being stuck in the workshop.
An 8yr old Rover Mod 45 went for $122.
Anyway, I started the engine for the first time yesterday and ran the new rings in with a good quality 30 weight mineral oil. The engine fired on the first pull and sencond pull, but did not run. My new, recently purchased, Honda brushcutter does the same thing if the choke is used - it doesn't need the choke to be started. Turns out it was the same thing with the GX160. As soon as I turned the choke off, it started first pull, so I assume that the engine is essentially new now, it doesn't need the assistance of the choke anymore.
The engine run much smoother, there are no leaks and is significantly quieter than it was before - in terms of both mechanical noise and exhaust note. It is also much more ballsy in power delivery than it was before - I didn't realise how tired the engine actually was before till now and she idles beautifully. Oh...and no smoke anymore!
I'll change the oil out after a couple of hours operation for good quality multigrade oil, but so far, I am very happy with the improvement.
In terms of parts and consumables, the engine owes me ~$170 including the carton of Coronas for my mate whose expertise and workshop I used for the project.
Now that the clutch and engine can be easily separated, maintenance will be a whole lot easier. I'm kicking myself for not replacing the clutch cork while I had the clutch off - I had the new cork sitting there - but that is an easy job I can now do at home.
Sorry I don't have any photos - apart from the fact that I forgot the camera, I probably would have forgotten to take the photos anyway.
Time taken was a bit over 6hrs for mower and engine disassembly and ~7.5 hours for cleaning, fabrication, repair and reassembly...and that was with two experienced guys working on it. If you didn't have the skills, tools, etc and had to take it to a mower shop, it would not have been a financially viable project. If the mower and engine had been well maintained, I think the whole lot could have been done in half to 3/4 of a day.
Ben.
