G9 stock rebuild questions

sho305 · 10-06-2009, 12:07 PM

I've been told if a cart is stock and running still, a .25 over piston will work fine...yet I see all .50 over kits for sale? I mean odds are I'll never have to do it again anyway, but what gives here? Just people looking for the 0.1hp they might get from larger displacement? It covers everything? I usually don't bore more than I have to.

I have to do one that runs and another that runs but the oil ring is gone. Both lose power when hot.

How about replacing the valve springs or shimming them, given the high rpm they see? (lifted carts with 22s, run trails a lot)

Was planning on putting in advance crank keys, but how about cutting the head?

Still have to do something with the mufflers, but I don't want the carts loud.

They need to stay reliable and sort of quiet, do some yard work and run them near other houses often. Thanks for any tips.

smallblock450sl · 10-06-2009, 06:12 PM

You only have "std/.25 and then .50 over", so if you bore to .50 over and something goes wrong again...you'd have to by a new block.

TheNewGuy · 10-06-2009, 06:53 PM

Dave, is the .25 over kit still available from Yamaha? sho, I think you can still get the .25 over kit.

sho305 · 10-06-2009, 10:05 PM

I see the .25 piston listed, but most kits say .50....maybe you just ask for what size you want. Now have to pick the best place to get it from....

Right, like I said I usually bore only as I need to....you would have to get another block if it trashed the .50 bore. I'm sure it is original though we bought these in '99 from a GC, they sure last a lot of miles!!! I'd like to speed them up but I know there is not much to do with them, however they are so tired I bet they go a lot better. I used to spin the tires easily with mine over sand and I barely can anymore. It hates hills on trails now and it used to go right up them with a little huffing and puffing...now it wheezes.

crash12888 · 10-07-2009, 12:39 AM

When you have the motor out doing the rebuild, redrill the cradle and move the motor forward a 1/2".
That will give you a 1 inch shorter belt and it will pull like you got a granny gear in it.
I just did this to a G14 along with adding a .060 shim behind the driven clutch spring. Big improvement!

sho305 · 10-07-2009, 10:41 AM

I put new tension cable on mine, but not all carts have them. Anyway I messed with it for a while, if I tighten it up to pull the motor forward it will rev more from a dead stop. I was starting forward on a short but steep hill and it would zip right up it. If I let it out loser it didn't want to rev as much. But with it tight I lost top end, I was gps'ing it each test too. I set it tight as I could without speed loss and it would climb pretty nice, was getting 28mph on a sandy drive in 150yds or so. I also reground the ramps, so once it moves it really pulls up to 5mph or something then it shifts normal. I could pull my boat out of the lake and it would spin the tires. Problem is the motor got tired plus the belt wears, then it changes. I drilled the weights in the clutch too but that didn't do much. On another one I put a cut sheave on, it seems to work better but not been able to test it that much. Kept the stock spring in it, thinking about the yamahauler spring for the secondary as I don't want a kit.

10-06-2009, 12:07 PM	#1
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,443	G9 stock rebuild questions I've been told if a cart is stock and running still, a .25 over piston will work fine...yet I see all .50 over kits for sale? I mean odds are I'll never have to do it again anyway, but what gives here? Just people looking for the 0.1hp they might get from larger displacement? It covers everything? I usually don't bore more than I have to. I have to do one that runs and another that runs but the oil ring is gone. Both lose power when hot. How about replacing the valve springs or shimming them, given the high rpm they see? (lifted carts with 22s, run trails a lot) Was planning on putting in advance crank keys, but how about cutting the head? Still have to do something with the mufflers, but I don't want the carts loud. They need to stay reliable and sort of quiet, do some yard work and run them near other houses often. Thanks for any tips.

10-06-2009, 06:12 PM	#2
smallblock450sl Sometime's............ Join Date: Oct 2007 Location: Tacoma Washington Posts: 11,874	Re: G9 stock rebuild questions You only have "std/.25 and then .50 over", so if you bore to .50 over and something goes wrong again...you'd have to by a new block.

10-06-2009, 06:53 PM	#3
TheNewGuy Admin/Moderator Join Date: Dec 2006 Location: Ohio Posts: 18,046	Re: G9 stock rebuild questions Dave, is the .25 over kit still available from Yamaha? sho, I think you can still get the .25 over kit.
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10-06-2009, 10:05 PM	#4
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,443	Re: G9 stock rebuild questions I see the .25 piston listed, but most kits say .50....maybe you just ask for what size you want. Now have to pick the best place to get it from.... Right, like I said I usually bore only as I need to....you would have to get another block if it trashed the .50 bore. I'm sure it is original though we bought these in '99 from a GC, they sure last a lot of miles!!! I'd like to speed them up but I know there is not much to do with them, however they are so tired I bet they go a lot better. I used to spin the tires easily with mine over sand and I barely can anymore. It hates hills on trails now and it used to go right up them with a little huffing and puffing...now it wheezes.

10-07-2009, 12:39 AM	#5
crash12888 Gone Crazy Join Date: Jan 2007 Location: Chesterfield, Va Posts: 6,021	Re: G9 stock rebuild questions When you have the motor out doing the rebuild, redrill the cradle and move the motor forward a 1/2". That will give you a 1 inch shorter belt and it will pull like you got a granny gear in it. I just did this to a G14 along with adding a .060 shim behind the driven clutch spring. Big improvement!

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10-07-2009, 10:41 AM	#6
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,443	Re: G9 stock rebuild questions I put new tension cable on mine, but not all carts have them. Anyway I messed with it for a while, if I tighten it up to pull the motor forward it will rev more from a dead stop. I was starting forward on a short but steep hill and it would zip right up it. If I let it out loser it didn't want to rev as much. But with it tight I lost top end, I was gps'ing it each test too. I set it tight as I could without speed loss and it would climb pretty nice, was getting 28mph on a sandy drive in 150yds or so. I also reground the ramps, so once it moves it really pulls up to 5mph or something then it shifts normal. I could pull my boat out of the lake and it would spin the tires. Problem is the motor got tired plus the belt wears, then it changes. I drilled the weights in the clutch too but that didn't do much. On another one I put a cut sheave on, it seems to work better but not been able to test it that much. Kept the stock spring in it, thinking about the yamahauler spring for the secondary as I don't want a kit.

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