G2 engine issue.....

OYSIFLY

I have a 1986 yamaha G2 that I just bought.

The engine smokes at first but after about 10 minutes of running it stops smoking.

The compression test was at 190psi so I think that the piston and rings are fine?

I'd like to take the head off and put in new valves and valve seal. Will I need to pull the whole engine out or can I do the head job without having to remove the engine?

Any other ideals on why it's smoking would be appreciated. Thank You

BGW

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Mike Mac

I'm a broken record here, but the first thing to do is start a through maintenance program on the car, (only 1 qt. of oil, make sure the air filter is not oil soaked, vacuum lines are not split or leaking, fuel pump, adjust valves etc.) Alot of cheap stuff to be done before you spend money and time on the head.

Read this site from the last page to the first, you will learn tons, and meet a lot of sick people in the process.

The head may still need to be done, but the maint. will only make it run better. By the way, 190 seems high for compression. Compression at this point, seems good. So I wouldn't be questioning internal problem yet.

OYSIFLY

Replaced plug, air filter, oil and no leak in air box. Thinking it must be the valves?

GMB74

Drain the oil, refill with 3/4 qt of 10w30 plus 1/4 qt of Marvel Mystery Oil or automatic transmission fluid. Run it with this mix for awhile, no extended high speeds or heavy loads and check your level frequently. You may get lucky and free up a stuck oil ring.

If that doesn't help I would consider replacing the valve seals. They can be replaced without pulling the engine or even removing the head.

If that doesn't improve things, it's teardown time.

sho305

The G2 has more compression than the G9, and newer carts are less yet they kept making it lower and lower. It is common for the oil ring to go bad and comp rings are still good, so I'd do the valves just in case but odds are the oil ring is bad. When oil level gets low it will stop smoking, but then you have no oil. Usually bad valves will smoke more on startup as the oil runs into the valves while it sits and cools off. I run my G9 mostly on weekends, bought it in 99 from a golf course trade, its a 91. I have run only synthetic in it until this year and it started to smoke a little I changed to 10-40 and it barely smokes (visibly). For the last three years it has lost power when hot in warm weather and smelled funny, I knew it was going. I used to run trails for up to 6 hours at a time with it. I took the cowling off and cleaned the fins when it started but there was not that much in them. But I'm putting a clone in it, did another G9 and its working well lots more power too.

OYSIFLY

sho305,

where are you getting the clone? I'd like to look into that. Thanks.

OYSIFLY

Pulled the head and have redone it. New stem seal and valve lap.

Still smoking at start up and then clears out after running. but right when i stop and go again, smokes again.

I have added Marvel to the oil to try and loosen up a stuck oil ring but no luck yet. How long should I run it like this to see if it will free up? I have about 20 minutes on it.

Mike Mac

I'd do 20 hrs. no hurry. Then put regular oil back in it.

When you pulled the head, did you look to see if the cylinder was scored? (scratched along the side)

sho305

Right now home depot has them online for a good deal but I might as well wait until spring now, but early enough I can mod the engine before the weather turns....if I don't run into other problems like I did this year.

I found if I go up a steep hill mine smokes the most, assuming the oil splashes more that way and causes it. On flat ground it barely does when I floor it. It does more when hot, I was pulling a big sled of leaves around and could see it going up a hill. Stinky.

OYSIFLY

No, other then carbon build up on the top of the piston- the walls of the sleeve was perfectly smooth. I'm really hoping it's just a stuck oil ring.