94 G9 misses/won't rev higher

[avgjoe]

So I bought a used G9 that had more issues than I have ever seen. I should have known better than to buy it in the dark in a rush. But that is water under the bridge. I have fixed more things than I can count and now it runs at least, sort of. It seems to miss and lose power as I try to accelerate. In the middle of this, the CDI completely failed. So far, I have replaced the plug, CDI, coil, carb, carb spacer, and all associated gaskets with parts I found on Amazon. I also adjusted the vales which were way out. Compression is now 140. Now the worse news, the idiot who had it b4 me, removed the air box lower and just had the upper lid and filter attached. He also removed the factory exhaust and welded a crappy 1" $20 glass pack motorcycle muffler to what was left of the exhaust. He was an idiot of historic proportions based on some of his other "work". He was trying to make this a "hot rod" on the cheap. So I replaced his muffler with a real one on a 1.25" exhaust pipe but it is NOT factory. I replaced his improperly rebuilt (backwards butterfly) knockoff carb, with a new knockoff. The governor was already bypassed with a direct carb throttle cable. And this is where I am. I have read many posts about the air box, cheap carbs, and their effect on performance. As near as I can tell, I just might need to re-jet this carb if that is possible, but I would like other opinions. I have already sunk too much into this thing with parts from Amazon. The most similar post I found to my circumstance had good info but was never "finished" by the OP saying what their final solution was. If I had an original carb and exhaust, I would use them. But my problem could be the cheap CDI/Coil from Amazon according to other posts. Not sure where to go from here.

[nitro1]

How about u sell me your motor?? I’m looking for one to fully rebuild And u have funds to buy a predator 420 and u would not have to worry about the cdi or air box or the old wiring harness ? The cheap cdi is going to be waste of money because they don’t last or u can do a Chrysler mod but u will need to know how to wire everything up and wires everywhere lol

[avgjoe]

Originally Posted by nitro1

How about u sell me your motor?? I’m looking for one to fully rebuild And u have funds to buy a predator 420 and u would not have to worry about the cdi or air box or the old wiring harness ? The cheap cdi is going to be waste of money because they don’t last or u can do a Chrysler mod but u will need to know how to wire everything up and wires everywhere lol

Be happy to sell you the whole thing just to get my money back out of it. II am moving soon and can't take it. $2K...done. I was planing to sell it anyway. IF my problem is only the CDI, then I have no problem with wiring issues. This one had many that I fixed. What is a Chrysler mod?

[CP241]

Ok where to start…

140psi compression is low. Service manual specifies compression 140-175psi. Adjust the valves and see if it comes up. If not, Plan on a rebuild soon.

The stock exhaust is very restrictive. Putting anything else on is gonna make it lean

The stock airbox is restrictive. Taking it off is going to make it even leaner.

Aftermarket carbs suck. I feel your pain not having an oem one. I’m in the same boat. Buy a $10 jet kit from Amazon. Start with a 140 and drive it. Then 135. Then 130. Until it runs good. Then you’ll find one that’s slightly lean and it runs REALLY good but it will run hot if you keep on it. Then go back up to the next higher size jet. You can verify you’re good by taking it for about a 5 mile drive and read the spark plug. This is probably going to take a few hours of swapping jets and tinkering but it’s the only way to get an aftermarket carb to work half decent.

Aftermarket cdi is complete garbage. My first G9 I went through about 4 or 5 before I gave up and did a Chrysler conversion. If an oem ignitor is in the budget, that’s the best solution though. And your CDI/Ignitor probably failed because of a crappy engine ground. This is very common. Reinforce the grounds from your Meg battery terminal to the frame and engine block. These carts are notorious for bad grounds.

You’re going to want to be careful running no governor. There’s nothing to limit the throttle and the valves are gonna float as it’s much easier to overrev it. Get a tach

Unfortunately when you buy a basket case, you buy a basket case. Especially with golf carts and ATV’s. When backyard ninjas get ahold of them they REALLY butcher stuff up. You’ve got a lot of work ahead of you to make this thing right. And in all honesty nitro may have a point, at some point you may want to weigh the price difference between fixing it right and dropping in a clone 420 motor. To do this thing right it wouldn’t surprise me if you’re near the $1k mark between ignitor, muffler, airbox bottom, rebuild parts, etc. and we don’t know for sure if your clutches are working properly yet or if they’re best because it’s not running right.

Just my .02 but you’ve got quite a science project. These Yamahas are very picky about what they need to run and how.

[avgjoe]

Originally Posted by CP241

Ok where to start…

140psi compression is low. Service manual specifies compression 140-175psi. Adjust the valves and see if it comes up. If not, Plan on a rebuild soon.

The stock exhaust is very restrictive. Putting anything else on is gonna make it lean

The stock airbox is restrictive. Taking it off is going to make it even leaner.

Aftermarket carbs suck. I feel your pain not having an oem one. I’m in the same boat. Buy a $10 jet kit from Amazon. Start with a 140 and drive it. Then 135. Then 130. Until it runs good. Then you’ll find one that’s slightly lean and it runs REALLY good but it will run hot if you keep on it. Then go back up to the next higher size jet. You can verify you’re good by taking it for about a 5 mile drive and read the spark plug. This is probably going to take a few hours of swapping jets and tinkering but it’s the only way to get an aftermarket carb to work half decent.

Aftermarket cdi is complete garbage. My first G9 I went through about 4 or 5 before I gave up and did a Chrysler conversion. If an oem ignitor is in the budget, that’s the best solution though. And your CDI/Ignitor probably failed because of a crappy engine ground. This is very common. Reinforce the grounds from your Meg battery terminal to the frame and engine block. These carts are notorious for bad grounds.

You’re going to want to be careful running no governor. There’s nothing to limit the throttle and the valves are gonna float as it’s much easier to overrev it. Get a tach

Unfortunately when you buy a basket case, you buy a basket case. Especially with golf carts and ATV’s. When backyard ninjas get ahold of them they REALLY butcher stuff up. You’ve got a lot of work ahead of you to make this thing right. And in all honesty nitro may have a point, at some point you may want to weigh the price difference between fixing it right and dropping in a clone 420 motor. To do this thing right it wouldn’t surprise me if you’re near the $1k mark between ignitor, muffler, airbox bottom, rebuild parts, etc. and we don’t know for sure if your clutches are working properly yet or if they’re best because it’s not running right.

Just my .02 but you’ve got quite a science project. These Yamahas are very picky about what they need to run and how.

All very good info. You are right on the grounds. I had already fixed that. But the spark plug boot opened up and I think that caused the oem CDI to fail. That really threw me off. The boot originally worked but separated from the spark wire the first time I took it off. When I looked at it, it had a "screw" in the center that dug into the silicone center wire. While it worked for a while it eventually opened and had no continuity between the screw and the plug connector. Anyway, I replaced the whole lot with a new coil and ignitor kit from amazon. Now it runs again but not well at higher rpms (never has) and limited power. I want to try the jet, but I see many mukuni kits on amz and they look very different. There seems to be a "v" number that relates to which one is needed. I could not find your other post with the kit link you used. Is the V22 kit the right one? When yours ran poorly, would you describe it as occasional misses and surges? I want to work on the biggest issue first.

[nitro1]

I used the amazon carb with This jet kit

KIPA Carburetor Main jet kit Replace for Mikuni VM22 VM24 VM26 125cc 150cc 200cc 250cc Dirt Bike Pit Bike ATVs Pack-15 From 88# To 150#

And used a 120 jet ran fine with a little turn to give it more fuel that was it. Sounds like your problem might be your cdi box is weak but still somewhat working

[avgjoe]

Originally Posted by nitro1

I used the amazon carb with This jet kit

KIPA Carburetor Main jet kit Replace for Mikuni VM22 VM24 VM26 125cc 150cc 200cc 250cc Dirt Bike Pit Bike ATVs Pack-15 From 88# To 150#

And used a 120 jet ran fine with a little turn to give it more fuel that was it. Sounds like your problem might be your cdi box is weak but still somewhat working

My CDI is brand new. It has good reviews on amz. But many here say those are no good. It did not run better with the oem cdi before it failed. Do you think I am wasting my time on the jets? Did yours miss/sputter and surge with the wrong jets??? I wish I could describe this better.

[CP241]

Mine ran lean. Ran fine but very lean so it ran very hot. It did bog a little at higher rpm but I was also dealing with a cart I bought with no exhaust, no airbox, a gas tank half full of water (how it ran at all on what was in the tank still is somewhat baffling to me) and just generally “beat”. Valves were tight, clutch had enough rust on the sheaves it obviously hadn’t ran for a while. Had a different fuel pump on it, wrong spark plug, disheveled wiring, battery had a big hole in the side from where it fell into the clutch, broken roof supports, etc. just a general basket case.

When you get into science projects like this, no two are alike. If you’re gonna buy a basket case you really need to know the machine, it’s in-and-outs, how what is supposed to operate, etc. I’ve rebuilt several of these G2/G9’s now so I wasn’t fearful going into it. I pretty much knew what I was in for before I ever went to go get it.

These Yamahas can be extremely finicky if things aren’t perfect, especially with the air/fuel and ignition. they can be tricky to get tuned right even if everything is stock and 100% complete. If you’re missing the airbox AND have the wrong muffler on it, you’re in for an uphill battle to begin with.

[nitro1]

Well said CP241 ^^^

[avgjoe]

Originally Posted by CP241

Mine ran lean. Ran fine but very lean so it ran very hot. It did bog a little at higher rpm but I was also dealing with a cart I bought with no exhaust, no airbox, a gas tank half full of water (how it ran at all on what was in the tank still is somewhat baffling to me) and just generally “beat”. Valves were tight, clutch had enough rust on the sheaves it obviously hadn’t ran for a while. Had a different fuel pump on it, wrong spark plug, disheveled wiring, battery had a big hole in the side from where it fell into the clutch, broken roof supports, etc. just a general basket case.

When you get into science projects like this, no two are alike. If you’re gonna buy a basket case you really need to know the machine, it’s in-and-outs, how what is supposed to operate, etc. I’ve rebuilt several of these G2/G9’s now so I wasn’t fearful going into it. I pretty much knew what I was in for before I ever went to go get it.

These Yamahas can be extremely finicky if things aren’t perfect, especially with the air/fuel and ignition. they can be tricky to get tuned right even if everything is stock and 100% complete. If you’re missing the airbox AND have the wrong muffler on it, you’re in for an uphill battle to begin with.

That is very close to my situation. I had every issue you describe. But this is my first gas cart and I did not know what to look for. Now that I have done some research, I way overpaid for this project cart. Seems like every time I look at it, I find something else I need to fix. BUT, I am not afraid, just need and appreciate the input from those who have done this before. It seems like I am nearing the finish. At least from where I started! If I can figure out this higher rpm sputter/miss, I can call it a success.