Robin 350 Engine Rebuild

[tsutrailblazer]

I bought a 2002 ezgo workhorse gas and it smoked when I bought it. Therefore, not knowing much about the history of the cart, I pulled the engine and tore it apart for a rebuild. Once apart, I measured all the dimensions per specifications and wound up just being the worn valves. Being new to 4-stroke golf cart engines with valves, I wanted to get thoughts. Per the Robin 350 assembly guide, I should lap my new valves until there is a 0.040-0.050" wide grind mark on both the valve and seat. I did this, but before I put engine back together, wanted to make sure it was correct. I have read about a liquid test, therefore, used starting fluid. This leaks out. If this is leaking out, is this fluid too thin, and should I test with something else? Please let me know your thoughts on how best to check the valve seats.

[Cartmaster]

If you have lapped as you say, it should be fine to put back together. Starting fluid is really thin, the valves will bed in nicely on their own anyway on these engines as they are quite soft.

If you want to double check, then use a thin oil. I assume you have the springs assembled when testing the seal?

Smoking is not caused by worn valves but could be rings, valve guides or valve seals. If the engine has sat for a while, then it is quite likely to be the valve seals. If the air filter was clogged, you may find the smoke was caused by high crankcase pressure and oil being drawn up via the PCV valve. The air filter and valves are the two things to watch on these engines.

[Spicyunicorn]

I agree with cartmaster since you had it apart I hope at the very least you put new rings in

[tsutrailblazer]

Thanks for the help. Yes, since I had the engine apart I am replacing pistons, rings, valves and all the gaskets and seals.

My rocker arms have a few small flat spots on them. Is this concerning, should I sand smooth, or is it ok?

[Cartmaster]

I cannot remember if the rockers are hardened on these or not but I think they may be. If so do NOT sand or grind them. You will break through the case hardened skin and they will wear super quick. If only very light notching re use them as is or replace if you feel the need. I hope you have a honing tool to give the bores a light De glazing before rebuild or new rings will be pointless. If you don't have a honing tool then make one with a piece of wooden rod that fits your drill chuck, cut a two inch slot in one end, fold a piece of Emery cloth (or whatever you call it over there lol) rough side out and slide it into the slot you cut. It needs to be longer than the diameter of the bore. You can then spin this in the bore with a squirt of thin oil on it to take off the glaze. Hope this helps. I assume you have the rebuild manual as I believe it explains how to de glaze.

[tsutrailblazer]

Yes, I bought a flex hone and made the cylinders look great.

[Cartmaster]

Ok
I will shut up now then lol

[tsutrailblazer]

No Problem. Appreciate the help and will let you know how everything else goes.

One other question: I was trying to install new pistons and rings after I honed the cylinders. I tried using a piston ring compressor, but the adjustable compressor would not allow the rings to be compressed 100%. It created more of an oblong cylinder that did not compress well. I am thinking to add a hose clamp near bottom to make more cylindrical. Any other guidance?

[Cartmaster]

If you are using an ordinary auto compressor it may be too big and therefore distorting by reducing the size down the your piston size. I use a homemade one of spring steel and two hose clamps or maybe you can find a smaller motorcycle one for the job. I have even worked the rings in with my fingernails occasionally too. Lol. I know there are several tricks with tin can and hose clips, just Google diy ring compressor and see what you find.

I just recalled using zip ties and doing one ring at a time and also a piece of plastic pipe around an inch long and a split in the side. You don't even need to clamp it if tight enough, just grip it round the rings with fingers and push piston with other hand!

[Spicyunicorn]

When in a pinch I have used very slight down pressure and work your way around the ring with a small screw driver