I am replacing the connecting rod in a GXV140. When I snug up the rod big-end bolts, it turns ok. However, when I tighten the bolts to the 9 ft-lb spec it freezes up. I have polished the crank with 600 grit emery to no avail. My question: Should I keep polishing the crank or hone the big end of the rod?
Make sure of the fit, when final torque is applied you should be able to bump it and feel it move with a little slack if you can't feel it give , something is not right , be certain of the con rod / rod cap orientation there should be match marks to be right if not you may have it reversed.
The orientation of the rod to the piston triangle is correct. However, it appears the folks in Thailand sent me a .25 mm undersized (large end) connecting rod. The ID is 1.016 in. which is the spec for the undersized rod end. My crank pin is 1.026 which is in the ballpark of a standard crank pin since my $50 calipers only go to 3 digits. Back to Thailand! Things used to be much simpler before Honda obsoleted the GXV140.
Thanks to all for your comments; they helped me pinpoint the real problem; I could have been polishing and honing until next year.
P.S. If anyone knows where I can get a regular rod in the U.S., I would appreciate knowing.
#5
sgkent
if you know what the ID of the rod big end should be, you can ask an automotive machine shop to hone it to the proper clearance. Don't guess.
Ok, received the new connecting rod from Thailand, tightened the yoke to 9 ft-lb spec and it turns freely on the crank (out of engine to check tolerances with very little play). I thought I had won the war but no such luck. When I tried to turn the crank with the timing gear installed it turned almost one revolution and then stopped. I could force it to go past whatever is handing it up but that didn't seem like a solution. When I held the compression release mechanism on the timing gear out of the way by blocking the centrifugal mechanism it did the same thing. I am going to disassemble the crankcase again and add one component at a time to see if I can isolate what is binding. It could be that when the connection rod broke it did more damage than I saw.The good news is that I am a retired EE (geek) and this is satisfying my OCD issues.
Ok I replaced the connecting rod, piston (since I noticed one of the "ears" on the latter was broken), and rings. When I bolted the rod onto the crank, before attaching/installing the piston, and tightened it to spec is spun freely using a light finger flick. The piston appears to slide freely in the bore with a normal amount of pressure due to the rings. The bare crank turns freely in the bearing without wobbling or binding. However when I installed the piston and crank (but not the timing gear), it takes a wrench to get the assembly to turn.
When I first opened the engine before attempting to repair it, the yoke bolts had come out, the connecting rod was broken, and the piston was broken. Since the bearing appears to be ok, could it be that the crankshaft was damaged when the engine froze up? I seem to be getting in over my head and pay grade. Any help would be appreciated!
Unfortunately for me, I think I found the problems. When I put the engine back together and torqued all screws to spec, what I though were gouges in the interior of the engine due to the connecting rod breaking turned out to be cracks in the engine casting. I can only assume that this small amount of distortion was causing the binding of the crankshaft/piston assembly.
If anyone out there needs some free (excluding shipping) parts for a GXV140 let me know. I am not an Ebayer.
Ok, forget the used parts comment; it is running like a top. After replacing the crankcase on Ebay, installing the new piston/rings, and connecting rod it runs like a top. The only gotcha, solved by a local Honda mechanic, involved a sheared flywheel key, that screwed up the timing, when I didn't tighten the ignition coil tight enough and it hit the flywheel while running - rookie mistake.
Another bucket list item out of the way.
P.S. If you install a new connecting rod be sure to mark the end cap/connecting rod to ensure the rod is installed exactly as originally milled onto the crank shaft. Reverse it and it probably won't let the crank shaft turn.
