My Tractor Forum banner

1 - 20 of 20 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1
I rebuilt the carb and set things according to manual. Starts fine. At high throttle, it conks out after about 20 seconds and it feels like it's starved for fuel. (I could be wrong on this interpretation.) Lowering the throttle or playing with the choke at that point doesn't help. Inline fuel filter is good. What would be a good sequence of things to try to fix this. I don't want to screw up something else.

I like the machine and the idea of keeping the old thing running, but it's one problem after another and getting frustrating. Started looking at Craigslist last night for another mower.

Thanks for any advice.
 

·
Premium Member
Joined
·
3,028 Posts
Try removing the plug in the bottom of the carburetor bowl and using a clean container catch the gasoline draining out. See if you really do have good fuel flow. I would suspect the screen on the fuel shut off valve if that is what your tractor has. Have you tried loosening the gas cap, they are supposed to be vented, maybe yours is blocked.
 

·
Registered
Joined
·
532 Posts
It might also be the magneto. Try cleaning adjusting the points and see if that works. If it doesn't, replace the condenser. Part number is RR175 from NAPA for Wico, Fairbanks, Eisemann, and Bendix magnetos. Condensers for Edison magnetos are no longer produced. Also check if the coil is cracked. On my Gravely, a cracked coil caused a similar problem.
 

·
Registered
Joined
·
695 Posts
I second double-checking the fuel=flow...

Condenser, and point gap are also possibilities.


in reasonably decent running order, an old model L should be capable of running fast enough to hurt itself. ( Not that I'm encouraging "destructive testing" ! )

Could also be that there is some crud / flaky-rust floating around inside the tank, which is restricting the fuel-flow ?

Hang in there, be methodical... yes, an old machine will try your patience (especially a Gravely), but they're worth the effort, and will pay-back your investment.
 

·
Registered
Joined
·
695 Posts
I would think that too low a float would cause surging once the fuel=level were drawn down, but complete die-out at High Speeds sounds like either cessation of fuel supply or spark.
 

·
Registered
Joined
·
695 Posts
Charlie,

When it dies-out like this, pull the spark-plug and check for spark as follows:

a) turning engine over by hand until the impulse snaps

b) pulling it the engine over with the strap or starter

Note quality and quantity of spark.

In both cases, ideally, it should be bright blue-white and "snappy".

If it is yellow-red, or when turned-over fast, snaps once then stops sparking, that indicates trouble in the mag.

If it has good spark after it dies, then we're back to fuel, or possibly an exhaust valve sticking open.

Does it have good compression when it quits ?

How long does it take / how hard is it to re-start ?
 

·
Registered
Joined
·
20 Posts
Discussion Starter #8
I appreciate all these suggestions. I will be back to my camp on Sunday, also with a new battery for the electric start, and will go through these suggestions systematically. I'm surprised that no one mentioned adjusting the main jet. I'm also trying to understand why I might only get spark problems at higher speed. It does start right up after I and it take a break. (I take a lot of breaks when all my old equipment gets me depressed.)
 

·
Registered
Joined
·
695 Posts
Charlie,

First of all, taking breaks is a good thing - it keeps us from hurting ourselves, and from going on a destructive rampage with a B-F-H ! :hide:

Regarding the main jet, if it were too lean, partial or complete choking should over-come that... not that you'd want to keep running things that way.

You could certainly try turning it out ( counter-clockwise ) 1/2 turn at a time, and see if things improve.

The phenomenon of spark disappearing at higher engine speeds, is usually caused by one or all of the following: oxidized points, points gapped too close, failing condenser.

When the engine is stopped, the mag can build-up enough charge for one fat spark off the impulse, which will fire the engine, spin it fast, and then the mag can't keep-up with the rpms, and the spark dies.

I'll bet every guy on the forum with a Gravely engined-L has stories about a tractor that would "pop once, then die ! "

Not knowing the history of your particular machine, but having resurrected quite a few neglected Gravelys in my time, a couple of big culprits in the fuel system are: dirt, insects ( especially mud-dauber wasps ! ), and rust. Any or all of these can block-up or restrict fuel passages and cause a lot of head-scratching.

If you get a chance, snap some pics when you visit it, and let us see what your're working on... :fing32:
 

·
Premium Member
Joined
·
3,028 Posts
Charlie,

You did say you rebuilt the carburetor and set things according to the manual. If you did do that, then questions about main jet and idle jet settings would be redundant.

Can you give us a year on this problematic Graveley?

Have you ever set the valves?

Roger,
 

·
Registered
Joined
·
2 Posts
Charlie,

Where in NH are you located? I'm in southern NH and I have rebuilt several of these machines. I would be more than happy to take a look at it with you if you are reasonably close.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #12
Well I just got back to my camp, checked the fuel flow, put in a new battery so I don't have to keep jumping it when it conks out, and started it up. It started and then ran fine at all speeds. Pouring rain today so I can't try under load conditions, but maybe the problems I had were due to it being the first run of the year. For reference, it's the LS model, Serial 2M33215, Manufacturing number I11754, which I think is 1965. 6.6 HP.
Thanks for all the suggestions, which I will return to if the problem persists.
 

Attachments

·
Premium Member
Joined
·
1,987 Posts
I too have suffered from Magneto issues....

Older Gravely L with original Bendix Mag, freshly rebuilt engine and carb. Fires off on the first pull, makes powere, after about 30 minutes of use the power drops then the engine stops, very similar to running out of fuel, only there was nearly a full tank. Try for a restart and nothing, not even a pop! After a few hours of setting the engine would fire right off, then die 20-30 minutes later. I rechecked valve clearance, carb settings even timing, then I remembered talk about how the coils in the old Bendix Mags suffered from cackling, bad epoxy I guess. Sure enough after I replaced the Bemdix mag with a known good Wico Mag the engine fired off and ran like a champ! Still does. Below is a photo of the coil taken from the Bendix Mag, not good!

ImageUploadedByMyTractorForum Free App1435767483.145218.jpg
 

·
Premium Member
Joined
·
1,987 Posts
I think this has been mentioned but in case it has not here is a good check to see if fuel starvation is an issue.

After the engine quits shut off the fuel, then unscrew the drain plug located on the bottom of the carb, if little to no fuel drains out I'd say it's a fuel delivery issue, wether it's a stuck needle or a clog. If there was a clog in the main jet then closing off the choke should somewhat keep the engine running, however if fuel is not getting to the main jet then the choke method would not work.

Typically when an engine starves its self of fuel as the engine leans out the RPM should increase as the last bit of fuel is consumed. How easy does the engine start up for the first time, a properly tuned L should fire off on the first to second pull 3 to 4 pulls, in my opinion, indicates something not in tune.

I'm of the opinion that fuel is not your issue, I agree with the others who feel you may have and ignition problem.

Don't give up, you'll get it all worked out.

Oh....all my BFH's are under lock and key as I tend to use them in inappropriate ways when I have refused to take brakes from fixing confounding machinery that seem to exist to puzzle me.

Good Luck!
Corey
 

·
Registered
Joined
·
1,053 Posts
Oh....all my BFH's are under lock and key as I tend to use them in inappropriate ways when I have refused to take brakes from fixing confounding machinery that seem to exist to puzzle me.
LOL, might also be a good idea to lock up the gasoline. :thThumbsU
 

·
Registered
Joined
·
532 Posts
I too have suffered from Magneto issues....

Older Gravely L with original Bendix Mag, freshly rebuilt engine and carb. Fires off on the first pull, makes powere, after about 30 minutes of use the power drops then the engine stops, very similar to running out of fuel, only there was nearly a full tank. Try for a restart and nothing, not even a pop! After a few hours of setting the engine would fire right off, then die 20-30 minutes later. I rechecked valve clearance, carb settings even timing, then I remembered talk about how the coils in the old Bendix Mags suffered from cackling, bad epoxy I guess. Sure enough after I replaced the Bemdix mag with a known good Wico Mag the engine fired off and ran like a champ! Still does. Below is a photo of the coil taken from the Bendix Mag, not good!

View attachment 1338353
I had the same thing happen with a Wico mag. I found an interesting solution to this problem after I had an Eisemann magneto on a Wisconsin engine do the same thing. Painting the coil with "liquid electrical tape" or red RTV seals it up , and the coils work perfectly after that.
 

·
Registered
Joined
·
318 Posts
I replace the carb drain plug with radiator petcocks.

Makes it easy to check fuel flow or drain the carb at storage time.
 

·
Registered
Joined
·
3,013 Posts
I replace the carb drain plug with radiator petcocks.

Makes it easy to check fuel flow or drain the carb at storage time.
I was thinking of something like this. Have a part number or where you got it by any chance?
 

·
Premium Member
Joined
·
226 Posts
My C8 did the same when I first bought it. I eventually traced the problem to a small round stone in the fuel tank sitting right on top of the fuel outlet. Fuel would trickle by the little stone so the C8 would start and run for a half a minute then die. Then it would not restart until it had sat for a while. I replaced everything in the fuel system before I found that little stone. I would have replaced everything anyway but it was still annoying. :mad:


Matt
 
1 - 20 of 20 Posts
Top