Yamaha G9 Gas - Tons of Smoke - Rebuild?

[Ktrilla]

I am working on a G9 that was given to me for free... I have very little money in the project ($120 or so). I am pretty handy but my skills with cars / motors is limited. I love a good project so I am up for the challenge, but my skills have a limit. Thanks in advance for the help!

The cart is running very good but the smoke is unbearable. The smoke is mostly white to me but I think you'd consider it blueish. Through my reading I am thinking I have a valve issue or oil ring problem. I've probably ran it for hour over the past few weeks to see if it would clear up, no luck.

Here is a the bullet point summary of where I am at thus far. The G9 sat for at least 5 years. Looks like it was "flipped" or in a wreck. This is what I have done so far on the cart
- New battery and key switch.
- Multiple oil changes... The initial oil change was like tar / gum / slime. It is now running clean. Added sea foam and Mystery Oil to the crank case to help clean things out.
- Flushed all old fuel multiple times. New fuel filter but the gas line was clean so I didn't change it. Ran Marvel Mystery and Sea Foam through the tank as well as some regular fuel.
- Changed fuel pump
- New carburetor
- New air filter... The air box may need to be replaced as it has a hole. But, I temporarily patched the air box and made sure it is well sealed.
- New spark plug
- Tried a few tricks of trade... Mystery Marvel in the spark plug hole to see if we can rule out sludge or free anything that is stuck.
- Compression was around 120 PSI
- I don't see any noticeable leaks, but there is definitely an issue with oil getting in the mix.
- I read on here that to much oil is a problem. I tried running it on 1/2 quart to be sure I haven't overfilled it. Still no difference.
- Blew air through some the oil delivery system that runs to the valve cover to rule out sludge or blocks.

When I first ran the cart it wasn't misfiring like crazy. Opened up the valve cover and one of the "rods" was off the valve. I don't know the terminology, but I fixed that back on and tuned up the spacing. The cart started running really well... But the smoke is the issue.

Recommendations for next steps? Is it time to throw in the towel and scrap the project? Time to have someone service the motor as it is beyond my armature skill set? Are there other quick fixes to try? Anything I can try to rule out other issues?

I appreciate you taking the time to read the whole description. I am trying to get this thing running for my kids...

[cgtech]

Yep, rebuild. The oil control rings are usually the first to go on those, with the compression rings still doing an ok job. That's why it runs ok, but blows smoke. Over the last 13 years I been doing this, I have seen your exact scenario several times (and owned one yamaha "smoke machine" myself).

[raydhd]

Same situation with my G 14

[Ktrilla]

Thank you for the guidance.

Now I will show my ignorance... I see people refer to "rebuilds" regularly on this site. But, some people seem to be doing a smaller projects that imply taking things apart and replacing rings. Others are talking about what sounds like honing and retooling the cylinders.

Is there a rebuild that a DIY kinda guy can pull off? It would be my first attempt at engine work.

Lastly, what type of expense am I looking at and it is regularly worth it?

[raydhd]

A lot of that depends on where the cylinder bore is size wise ie overbored or not, condition wise ovaled or not, and fit of the present piston.BUT if the engine is not on the final overbore really worth the work. That being said until you tear it down you won't know what you are dealing with and the condition of the internal parts in general. Pretty easy to tell one that has been run with no oil or oil in poor condition.

[meimk]

Before you get too deep into a rebuild, try valve stem seals. Sitting that long they could very well have dried out and shrunk back or split. Originally Yamaha only put a seal on the intake side, but I usually put seals on both intake & exhaust valves - exhaust won't dribble oil into the cylinder, but could put some into the muffler and burn it off there. You can do those without pulling the engine and they only cost a couple bucks each. That's fixed a couple Yamahas that smoked like a mosquito fogger.

[raydhd]

With all the sludge you found and a compression # of 120 I would tear it down and see what is what

[slonomo]

To the OP:

You said this would be your first attempt at engine work? I would highly recommend getting yourself a copy of the Yamaha Factory Service Manual. It will outline all the steps necessary to the disassembly and reassembly, as well as all the tools needed to do the job. If you are mechanically inclined you can read everything you need to know. And, you always have rayhd to tell you what you should do lol But seriously, think long and hard about what your abilities are, getting knee deep in a rebuild and taking a box of parts to a mechanic are usually not the direction you want to go.

Might I suggest contacting Don Plowman. He's a Yamaha specialist. Maybe he can price out the rebuild for you? He can also price out the parts for you, but you're probably looking at the $300-$400 range by the time you buy parts and have some machine shop work. Might be more depending upon what parts you buy.

https://www.plowmanscarts.com/

[raydhd]

Redoing my smoking G 14 was my first golf cart engine redo. Rings, bearings and gaskets were less than $200. Invest in a decent primary clutch puller and one inside the engine you will see it is a very simple 1 cylinder splash oiled engine and worn or damaged parts are usually obvious. Plenty of help here if you need some aid. And yes Slo I am one that actually Did one rather just talking

[slonomo]

Originally Posted by raydhd

Redoing my smoking G 14 was my first golf cart engine redo. Rings, bearings and gaskets were less than $200. Invest in a decent primary clutch puller and one inside the engine you will see it is a very simple 1 cylinder splash oiled engine and worn or damaged parts are usually obvious. Plenty of help here if you need some aid. And yes Slo I am one that actually Did one rather just talking

I suppose you can rebuild a Yamaha engine with ebay parts for cheap, but not sure that's the route I would go. When I rebuild engines I always buy factory parts and gaskets, unless it's a Plowman's certified part then I'd be ok with that. And yes Ray, I said "when I rebuild engines". I turned wrenches for a living, I'm thinking I've have my hands on a few. To the OP, there are lots of guys on the forum who have done what you are about to do, so if you decide to take the project on, with good documentation and photos you can get tons of "good" help.