Yamaha G1 Only Runs with full choke and full Throttle

[texastom1]

I just purchased a 1983 Yamaha G1 and it looks like it is pretty good shape. The problem is that it wouldn't start with out using starting fluid, so I took the carb off and cleaned it completely with carb cleaner including removing all the jets and adjustment screws and cleaned them making sure I could see daylight through each hole. Then I adjusted the float so it stops the flow when the float is just at level. Then I took the fuel pump off and took it apart and cleaned it out. Everything seems to work as it should. Then I put it all back together and set the mixture to 1 1/2 turns out. Then it started with the choke pulled out fully. I took it for a short ride and it has all kinds of power, but it only runs at full throttle and with the choke out all the way. I took the fuel line off and turned it over with the starter and only a little fuel came out. When it started and revved up a lot of fuel came out, so I assume the pump is working OK. I then ran a new fuel line from the fuel input of the carb to a extra gas can so the gas would flow by gravity into the carb. I wanted to see if it made any difference in the way it ran and it didn't. I had plugged the fuel line coming from the pump with a bolt and I did notice that gas was pushing out of the fuel line past the bolt so I think the fuel pump is working good since it seems to have enough pressure to push it's way out. I am at a loss as to why it won't run unless the choke is on and it only runs full out. If I let off of the gas to say half peddle it starts spitting and sputtering and then dies. By the way I did disconnect the black and white wire so it will idle. I did notice that if I hold the choke out I can let off of the gas pedal and it will stay running at it's fastest rpm's or at least as fast as the governor will let it. I have adjusted the mixture screw in and out to as little as a 1/2 a turn out to as much as 4 turns out without much change in the way it runs. Any help would very much be appreciated.
Thanks for looking,
Tom

[85.G3]

One possibility is you may have lean condition. Is the air box stock? Check for air leaks from the filter box to the head and test the compression.

[bigstik40]

I know you said you gave the carb. a good cleaning, but I would double check the inlet needle and seat to make sure it is clear and free flowing. Also check for cracked carb. spacer and good gaskets on both sides. If you need full choke to run, as you suspect, it's probably not getting gas. Good luck - RAY

[texastom1]

Thanks guys for the feedback. I looked real close at the rubber adapter plate that the carb attaches to and it has some hairline cracks between the 4 bolts at the corners and the center opening where the carb basicly plugs in. Could these cracks be leaking air so without the choke closed it's getting to much air? I will take the carb off again in the morning and check for cracks in the housing.

[750brett]

I would check the reeds and crank seals.

[OgreTX]

Originally Posted by texastom1

Thanks guys for the feedback. I looked real close at the rubber adapter plate that the carb attaches to and it has some hairline cracks between the 4 bolts at the corners and the center opening where the carb basicly plugs in. Could these cracks be leaking air so without the choke closed it's getting to much air? I will take the carb off again in the morning and check for cracks in the housing.

Tom, let me give you my thought process, with the similar issue.

I did enjoy reading in one of the manuals (forget which one) that the choke enriched the fuel, and allowed better ignition when the engine is cold ... Bwaa haa haa. The choke does exactly what is says ... it chokes off the air so that there is less air for the same amount of fuel ... period.

Based on that, most suggestions will be that you have a leak somewhere allowing extra air, and the choke only stops some of it. It could be from a weak fuel supply requiring less air to get a combustible mix, but most likely too much air, and there are a lot places it could happen.

I started with the simple first ... air box. There is a plug in the bottom. If missing, you will get too much air. Mine was missing, so I plugged it, now I don't need as much choke. I'm fairly new at this so I have a lot more to do, but that helped until I get some other work done on my G1.

Start simple and look further after you correct the simple. As many (much smarter than me) have stated it could be several different air leaks combined, insufficient fuel, or one large air leak.

From one Newbie to another best o' luck,
Ogre

[texastom1]

Originally Posted by 750brett

I would check the reeds and crank seals.

Being a newby to the Golf cart world I don't know what the reeds are, cam you please explain. I did order the service repair manuel from ebay for $11 it's a digital copy but all I need is the information.

[texastom1]

Thank ya'll so much for you help and suggestions.
I checked the carb for cracks and didn't see any. When I used a gravity feed fuel source to see if it ran better than with the fuel pump. I used a bolt to plug the fuel line coming from the fuel pump that went to the carb. It didn't change the way it ran at all but I did notice that when it was running that fuel was pushing past the bolt to come out of the line. The bolt was a tight fit and I had to screw it into the hose. So I assume that the fuel pump is working well to build that much pressure. Am I right?
So I think I am leaning towards an air leak. As I said earlier the rubber adapter plate (I think that’s what it is called) where the carb connects to the motor has a few hairline cracks around the connection point. I wouldn't think they could cause this much trouble but I don't know. I am going to try and seal them to see if it makes a difference. If it does I will buy a new one. At this point I am just grasping at straws. So if anyone has any other ideas Please don't hesitate to post them.
I know this thing is going to be a lot of fun when I get her going.

Thanks,
Tom

[85.G3]

Tex .... Since you are running at full throttle I say your fuel delivery is good. Remove the rubber carb boot and inspect, if any cracks go all the way thru replace it. You will find your Reed Cage behind the boot. If everything looks good put it back together with a thin coat of grease on the rubber boot seal and the gaskets to get a good seal. Also check for leaks between the carb and filter. If thats all good and the cart was not running when you got it there could be some bad jetting. My jets had no size markings to ID. I would do a compression check and call Don at Plowmans with the info. Replacing the jets with new stock would eliminate an unknown. Plowmans info is on the Site Sponsor page, he will take the time to talk and has everything you need.

[texastom1]

I took the rubber carb boot off and inspected it, but none of the cracks went all the way thru it. The Reed Cage looks good I think. Are the metal reed plates supposed to seal flat or is it OK for them to have a very slight opening at the tips (about 1/64" opening)? They just kind of stand off just a touch. Someone had used a silicone based gasket paste on the gasket and the reed plate. Shouldn't these gasket be applied dry? So I think they may have been trying to fix this problem as well. I am going to order a new gasket and see if this helps. Thanks again for your help.
Tom