'91 Yamaha G9 sputter and dies, low power, intermittent, leaving me stranded! Help!

[HanSolo]

Hey guys. At my wits end with a 1991 G9 Gas Yamaha cart.

Fresh rebuilt motor (bearings, rings, etc)- rear torque spring, heavy duty drive belt, etc. It’s got great compression, but the thing has never run fast or strong. Been dealing with it’s low performance for the last year but it’s been getting worse and worse. Sometimes it’ll just die and won’t move until a few hours pass. Lately that’s been happening more and more. I need this thing to work! Critical tool for use on my property.

I figure with the rebuilt motor a solid, the problem has to be either fuel (pump or carburetion) and/ or ignition. I kinda want to throw the kitchen sink at it and just be done with f’in around with it and have it work reliably. Here’s my questions:

1) Carburetor- I’ve gone through a few (Chinese-Amazon, etc.) I’d like to get a factory carb and start with a known good. Where can I source the factory carb (Brand and model?) and what should I pay?

2) Carburetor Adjustment- where can I find information about how to adjust the carb once I get it? Also, I’d like to have some different jets available and on hand so I can change them out if need be. Where can I get them? (specs/ vendor?)

3) Fuel Pump- going to go through my pump as per the ‘sticky’ at the beginning of this Yamaha Gas forum… BUT… is it worth converting it to an electric fuel pump and be done with the problems/ questioning? How can I test flow/ pressure on my current pump to ensure I’m getting good flow always?

4) Ignition- I’ve seen a thread from CP241 talking about converting to a Chrysler ignition for $30 bucks. Sounds pretty good. I’ve got spark, but I’m not sure I’m getting what I should. I’d hate to spend a bunch of money on a factory ignition module and still have the same problem. I don’t mind tweaking the wiring to add the Chrysler stuff if it’s better. Chopping the factory harness is not against my morals… especially to get this thing rock solid.

Yes- factory airbox and airfilter and sealed. Yes- fouling plugs with current carbs.

Anything else you think I might have missed?? Thank you in advance for any and all help you may be able to render. Help me Obi Wan Kenobi... You're my only hope... - Thx- HanSolo

[CP241]

First thing is first. If you’re using an Amazon carb it’s probably insanely rich. You’ve got 2 options… pick up a mikuni jet kit (I’ve gotten them before and can find a link later to the one I used) or buy an oem carb. I wouldn’t diagnose ANYTHING any further until you know your carb is working the way it should. And if it’s a carb made by a 7 year old in mama Woo’s garage, I can almost guarantee it isn’t working right.

These carts are VERY picky about their air fuel ratio.

If you need an OEM carb give Don plowman a call. Www.plowmanscarts.com he usually has stuff like this in stock.

Jet kit will be cheaper but you’ll have to spend a lot of time tweaking it, and no guarantees it will be perfect. Should be able to get it pretty close, though. If you get an oem carb there should be little to no adjustment needed. They generally just “work”.

If you question your fuel pump, just replace it. You can get a genuine Mikuni for a Briggs and Stratton for about 22 bucks on Amazon. Excellent quality pump. On the Yamaha it will only mount with one of the two bolts but that’s okay. It isn’t going anywhere.

Also make sure you are using NGK plugs. Champion, duracrap or any of those other plugs just don’t work the same.

Start there and see what you’ve got left before chasing ignition stuff. You may very well still have an ignition issue but “garbage in, garbage out” applies here.

[CP241]

This is the jet kit I used on my last cart. I had to go way richer on mine because it had no airbox and you can’t buy the whole thing anymore, but it worked out pretty well. Not perfect but ballpark close

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# https://a.co/d/5h5TLHm

[HanSolo]

CP241- Thank you!!!

Sounds like great advice. I'll chase up the factory carb and the fuel pump you recommended and a new spark plug. Once installed I'll run it and give an assessment. Probably take me about a week or so and I'll let you know where I get.

Like to get what you recommend on the fuel pump. Sounds like a solid idea- If it's OEM and quality- I'll just get it for $22.

Any chance of a sending me a link on the fuel pump so I don't f!@#* it up?? ;)

Also, is there a spec/ test for the fuel pump output? Once the new one is installed, I'd like to verify I'm getting the proper fuel flow output and pressure required.

-HanSolo

[CP241]

This is the last one in my purchase history, I’ve gotten several of these for carts. Work great. I was wrong about the price. It’s $20

Briggs & Stratton 808656 Fuel Pump https://a.co/d/8reeJAJ

[CP241]

And to test pump flow, I believe these pumps are rated at 0.23 liters per minute, or about 8 ounces per minute. Take the fuel line off the carb, put it in a big mason jar, and spin the engine. See how much it pumps in. Do note that it will “spurt” fuel with every rotation of the engine, it’s not a constant “flow” like an electric fuel pump.

[HanSolo]

OK cool!! Thank you again. I'll post up some results when I get them!

-HanSolo

[HanSolo]

Hey CP241-
I called Plowman's and Don won't be back until Monday.

That said the woman on the phone said they don't sell the OEM carburetors. She said because they're not made anymore. She said Don 'goes through' an aftermarket one and sells that. What do you think?

Was gonna call him on Monday to hear it from him but do you think I should get one from him if that's the case? Any other ideas?

I ordered the fuel pump and it'll be here in a week

Thanks in advance!

-HanSolo

[CP241]

Don doesn’t sell junk. I’d trust anything that comes from him

[HanSolo]

Hey! So I finally had time to get to the cart! Thank you again for the advice!!

Put in a new plug, new carb from Don @ Plowmans, cleaned the air filter, changed the fuel pump to the one you reccomended, drained all the old gas and put in new gas, checked the fuel filter, and replaced any vacuum or fuel hoses that looked questionable!

The good news: It runs now- and reliably! Haven't had an issue in about a week since doing the work and it hasn't left me stranded! Which is about a 1000% improvement. Thank you.

The bad news: It doesn't seem to be making as much power as it should be. I still need to get it out next to my truck on flat ground and clock it but it's top speed on flat ground leaves much to be desired. And it's pretty **** slow on a hill (which my property is mostly!)

We can live with the cart as it is, but would love to make sure it's putting out it's peak power and we're getting all we can from it.

Any other advice? Thank you in advance,

-Dominic