86 G1 complete rebuild, frame off

[daveswaves]

Just acquired an 86 Yamaha G1 gas cart, planning a frame up build. Newbie with carts, old hand at 2 strokes. I rebuild Mercury inline 6 outboard motors from the 60,s 70,s and 80,s. The old Towers of Power. I have the cart completely disassembled and the frame cleaned. Since 2 strokes are my thing, I pulled the engine apart. J1000, 215 CC, standard bore. The engine had low compression due to a chunk out of the piston between the rings, directly in line with the exhaust port. I have never seen this on any of the marine stuff I work on. Is this usual with the Yammie? I will post a pic, in the mean time here is a pic of the cart. Bought it for $50. These things aren,t addictive like merc outboards are they???

[TheNewGuy]

Welcome to BGW!

Golf carts addictive.....nooo.

[slonomo]

I think the G1 is prone to the pistons breaking only because of the amount of cheap Chinese pistons available. I have an 84 model with the original jug and piston and it looked better than the brand new Chinese stuff I ordered off the internet. I am thinking of changing back to the orig parts. I think they wear better and real Jap Yamaha parts are hard to beat if you ask me.

These are great carts. They are limited in power, but for golf carts they go pretty good when tuned right. Stock with some mods could get 25-30 mph, but will cruise well at 19-22 mph.

Are you going to lift it?

[daveswaves]

Originally Posted by slonomo

I think the G1 is prone to the pistons breaking only because of the amount of cheap Chinese pistons available. I have an 84 model with the original jug and piston and it looked better than the brand new Chinese stuff I ordered off the internet. I am thinking of changing back to the orig parts. I think they wear better and real Jap Yamaha parts are hard to beat if you ask me.

These are great carts. They are limited in power, but for golf carts they go pretty good when tuned right. Stock with some mods could get 25-30 mph, but will cruise well at 19-22 mph.

Are you going to lift it?

Interesting you mentioned that. There was half of a broken ring underneath the engine, lodged in the frame. Perhaps the previous owner put a cheap piston in it. The jug is original. I would like to lift it but I have to decide its final fate first. Here in Ontario the laws are punitive for golf carts. Only your own property or a golf course, that's it. One of the reasons I play with boats, I can go anywhere on the water, as fast or as slow as I want, with whatever modifications to the engine I want to do. We have an excellent trail system where we live.....no golf carts.
If I do lift it seems like 6 inch jakes are the way to go. If I do lift it I can use it for ice fishing (I think).
Likely I will rebuild it stock, no lift. I can always lift it later if I go that route.

[sho305]

They have not made G1s in a long time as well, maybe not in CAN but here they get a lot of hours put on them and seem to run forever until one day they don't lol. One of the best carts ever built, but louder and stinky compared to newer ones. It should go faster than any other stock cart unless they have gears in them, this 2 stroke will rev out pretty high since it is based on an old yami sled motor.

I have an old tower that should be rebuilt, but don't want to afford fuel for it so there it sits. It would spin a 20 laser 6K on a checkmate BR, about 50mph. Kinda big boat for it I need a viper or something lol. I'd be happy with a vector.

Anyway when you do it cut the head down for some more compression, advance the timing plate for forward, and make sure the muffler is not plugged up. With a clean bore it should run well, should be able to spin the tires a lot on gravel or grass.

[daveswaves]

Thanks Sho, I hear you on the fuel for the inline, they are thirsty!
I will bring the compression up a bit on the Yammie.

[Mike Mac]

Originally Posted by TheNewGuy

Welcome to BGW!

Golf carts addictive.....nooo.

Not in the least! Thats why Ron's only been here since 2006!!

[sho305]

Lol, I used to get 10gal and run around for a couple hours on the weekend. Then I got a 16' with a force 85 and would get 6gal and run around for an hour or whatever run time. Now I put that in the cart a few times a summer and ride on someone else's boat lol. Sad but too many other toys and projects its just not worth it, that lake is dead now compared to what boats it used to have. I think it is an untouched 1500 though, can't see where any of the bolts have been out of the block and it was not painted. Comp was just over 100 on all so it must be down on power. It has not been run much in the last 20yr lol I know the previous owner.

Anyway the G1 is like 6:1 compression to run junk fuel. IIRC you can just about deck the head to the squish ring. The piston is also lower than the cylinder...but check that, I'm thinking that way you can't really have too much comp unless you over cut the head. I could hardly get advance on the plate I worked on that for a while. I also worked on the exhaust port tried to make it 0.5mm higher approx. I sanded on it for around a week every time I walked by it lol. I doubt it cut much out but that cart ran really well. Lots of powerslides/donuts with it.

[daveswaves]

I hear ya SHO 305. I run mine in bass tournaments, I carry 20 gallons of fuel in the inboard tank and an extra 5 gallon in a portable tank (so I can get back for weigh in). Mine is a 1500 block bored out .030 oversize on all 6, high dome persan racing pistons, modified reed blocks, completely balanced and blueprinted reciprocal mass. Custom flywheel and distributor-less ignition. Compression on all six is 155. If you ever want yours freshened let me know, I will walk you through it.
Maybe I can cross contaminate my addictions, add a radiator to the cart and lay in an inline 6. May have to change the clutch springs Belts are cheap.

Back to reality, I will deck the head and work on the advance. Not a lot you can do with 215 cc but I'm sure the factory left a little on the bench, all that reliability stuff. Probably more available with a tuned pipe rather than the golf muffler.

[daveswaves]

Attached are two pics of the piston. I is difficult to show on the piston top but the exhaust side of the piston top has curled into a knife edge. I tried to back light it. You can see the chunk of piston missing on the side shot of the piston. Mentioned previously this was a std piston, I will go oversize with replacement. There is evidence of detonation on the piston top and there is evidence of overheating on the inside of the piston top.

ignore the date on the pic, batteries died, forgot to change the date.