83 marathon with robin 244 slow to get going, if at all

[naga77777]

Hi all,

recently bought an '83 marathon, and she won't take off without choke.


details:

-compression peaked at 120

-replaced starter/generator

-new 4ga wires from starter/gen to f/r selector and the ground by the microswitch

-new fuel pump

-new fuel line from pump to carb, and took out water separator

-new fuel filter

-new carb

-new spark plug, NGK 3611



the fuel filter will be about 3/4 full after she sits, but when we jack up the rear end and get her going, the filter empties. we still see a small stream of fuel going in/out of the filter, but it's not holding any.

before carb and fuel filter replacement, i would have to choke it to get it going while cold. after warm, i'd either have to 1/2 choke it to get going, or it MAY go with no choke after riding around 20min or so. (most of time had to at least pull the choke once to get her to take off).

We could be driving along pretty steady, and it'd just die out like starving for fuel. I could either pull choke all the way and release, or hold 1/2 choke, and she'd take off again. this got better, and less frequent, the warmer she got. still would stall on hills sometimes, or for no reason at all. Pull choke, takes off again.


on the new carb, i have not fiddled with the fixed jets. the low speed air mixture screw is set at 1.5 turns out. the throttle butterfly is all the way closed, but has like a 16th" or a 32nd" of play in it, due to slack in the line that runs to the microswitch.

so NOW, it won't take off without pulling the choke. we've been testing enough with the rear end jacked up, I KNOW the engine is hot. and now she won't get going without choke no matter what. Even seems like the choke is slower to get the engine running now (instead of just being spun by the starter).

Fuel lines are clear, pickup tube is clear, removed water separator from fuel line between pump and carb. Carb mounting gaskets look good.


Kinda at wits end here, not sure what else to do? The cart is ridable, but it's really annoying to have to choke her EVERY SINGLE TIME you wanna take off.....and sometimes for no reason at all when she stalls out during riding (just sits there being spun by starter).

at least with the old carb (which we destroyed by accident), it would take off without choke after getting hot. It's even a little slower now to get running WITH the choke.

[TheGDFP]

How strong a stream comes from the fuel line, when unhooked from carb?
I'd look at that and the float height, first.

[cart around]

I'm leaning towards worn crankshaft seals, or plugged muffler.


120 compression is great.

All of the fuel filters drain like that.

Take up the slack in the throttle cable by sliding the spring from an ink pen over the throttle cable.

Look at the pictures in this thread. http://www.buggiesgonewild.com/gas-e...s-hook-up.html

[naga77777]

Originally Posted by TheGDFP

How strong a stream comes from the fuel line, when unhooked from carb?
I'd look at that and the float height, first.

i think this is the issue.... Yesterday we replaced all the fuel line from the tank to the carb. Also put a new starter solenoid on there, which helped A LOT. I got excited, thinking I had fixed the problem, but not yet. It does spin faster with the new solenoid, as my positive battery cable was kinda rusted up on the old solenoid terminal.

the fuel pump just kinda dribbles fuel with each engine pulse, and I just read in another thread here that it should shoot something like 1oz per pulse. (per dave box i believe, but mine does not shoot NEARLY that much per pulse.)

someone else was kinda having same symptoms, and they were saying it was prolly his crank seals. Guess I need to look into whether or not my crankcase is keeping pressure. Any ideas how to test this?

On the float, does it pivot in-line with the throat of the carb, or does it sit perpendicular to the throat? I havent taken the old one apart yet, and its at home so I cant check till this evening.
I was thinking in my head that if it sits perpendicular to the throat, it could explain all the hesitation when going up hills. (like if the fuel was so off-level in the bowl, it could trick the float into being shut maybe?)

Originally Posted by cart around

I'm leaning towards worn crankshaft seals, or plugged muffler.

120 compression is great.

All of the fuel filters drain like that.

Take up the slack in the throttle cable by sliding the spring from an ink pen over the throttle cable.

Look at the pictures in this thread. (carb thrad)

THANK YOU For the link to the carb thread. I had never seen the ink pen spring trick.

And all fuel filters drain like that? Good to hear, puts my mind at ease with regard to the filter.

We disconnected the muffler yesterday evening, put about 1/2" gap in there, and it ran no better. Was VERY loud, though Had never heard a cart without the muffler before, those little engines can scream.


According to everyone's posts, along with the other threads im reading, looks like i need to take a look at crankshaft seals. Off to find testing procedures for these.

[ksmechwannab]

OK here it goes. Long time reader, but I think my first time posting. CRS If I'm in the wrong section I do apologize. If a new post, I can try.

I had the same problem as going slow, or sluggish starting, after rebuilding the engine: new crank, bearings, top-end, seals, the whole shebang.

Anyhow, I discovered that with the DF wire disconnected from voltage regulator, she starts and runs well (on blocks) after a few timing adjustments; go figure.

Yes, initially I had the wet spark plug Dave B. had commented on in another post, which was very similar to my exact problem, and I can assure you I cleaned the snot out of the ole carbx3 and changed plugs.

I did check all the ignition components, noticed values differ than what the manual states for the resistance between high tension wire & orange wire, I got "0"ohms (nothing), but with spark gap set at .23-25 it runs with original coil.
As best I can tell S/G checks OK, nothing shorted against housing with all wires removed.
I even swapped in a new igniter, new ign coil, 2x new plugs, pulsar at 157 ohms, but the only thing thus far that seems to help the old girl run smooth with decent acceleration is leaving the DF wire disconnected from the VR. Don't think this is advisable, but...

At my wits end, and am hoping someone has come across this issue noting all the HEI mod and weak spark discussions on Marathons, which I thought seriously about going this route until I discovered the issue with the DF wire.

Thanks for your feedback

[ksmechwannab]

UPDATE: whether the DF wire is attached in combination with the red wire, or red & blk wire connected to V/R, cart will run, buuuut when all three wires are connected to V/R, engine does not start.
I removed the black wire and whilst the engine was running I attached it to ground and the engine immediately started dying. It was like I was attaching the spark plug to ground with little sparks about 1/8" away from metal; go figure.
I did check voltage and had battery voltage across all 3 V/R terminals (w/ground wire removed) while she was running. Totally stumped!

Leaning toward S/G, but then that's an expensive what if probability. I will disassemble it anyway and see if there's anything obvious causing my problem. Doubtful, noting it ohms out OK, with nothing shorted.
Most all wiring is near identical to schematic. I even wired igniter to V/R as it shows in the manual, then over to solenoid, then to GRND, but this did not help.

Does anyone know if there is an automotive V/R available??? I'll try the original V/R tomorrow and see if I get the same results or differing results. Could be an incorrect aftermarket S/G (label shows PN# 1427060200, GSB107-03)??? More research needed.

Here's one thing I did notice, the engine appears to be spinning reverse of what the F&R lever position, could just be allusion (drive belt is removed, so I don't see which way they would be turning). Cables are marked and attached to corresponding S/G terminal.