8n hesitates with throttle

[kozz]

Hey guys sure need soom help! Got a 51 8N had it for over 30 years and has run great. Yesterday did some rolling with a heavy roller for about 4 hours ran fine than put on a two blade plow and started working fine , Than I dropped the plow deeper and the tractor started to stall so I gave more throttle fast. The engine picked up speed than put out a puff of black smoke from exhaust and tried to stall. After that it starts ok but when I advance throttle it starts hesitating. put in new plugs, checked points, checked gas flow and filter , cleaned air filter, and tried to adjust carb. all OK. Engine compression 90,90,85,90 been near that for years now. It sill starts fine and idles fine but when I drive it I advance throttle it hesitates steadys out than seems to hesitates again like its running out of gas than steadys out again. I don"t know what the heck to look at.

 

[Tom N MS]

You said "checked points"..Did you clean them and reset them? At least run a crisp new dollar bill between them several times or brown paper bag and reset. What does fire look like when you gap an old plug to 3/16" and ground it against a clean(no paint) spot on the head?? Need strong blue fire, not yellow..

 

[kozz]

Tom , on the points I checked gap .015 and cleaned with a piont file sparkn looked strong.
was just working on it again and noiiced that I can run throttle up faster if I pull the choke out part way. Now I'm wondering if it the carb

 

[Dean]

Kozz:

Point gap should be set to .025" on your 51 8N with side mount distributor, however this is not likely causing the symptoms that you describe.

If the engine runs better when the choke is partially closed, it is not getting enough fuel. Verify that all 3 fuel screens are clean and that there is an adequate flow fuel from the bottom of the carb when the plug is removed.

Dean

 

[kozz]

Tom,
Just came back in , pulledb the point cover again and cleaned again, did not resety to .)25 but will next time . but did put a spare plug in with a 3/16 gap and have very good spark. Did notice that the engine will rev up nicer with the choke pulled partway. the sceeen at the carb. enter was perfech clean and the bowl looks clean did not pull bowl from the bottom of tank yet. but the tank looking in with a flashlight is as clean as new.

 

[kozz]

Dean, the trouble with pulling the plug on the bottom of my carb. is , there is none on this org. marel carb. but I guess I will have to drain the gas tank and go that route. thanks

 

[old]

You most have an odd carb or you just are not seeing the drain plug. I have never seen a M/S carb that did not have a drain plug. As for the points as Dean said they need to be set at 0.025 not 0.015 the 0.015 if for the front mount distributor 8Ns and does funny things on the side mounts

 

[kozz]

Old,
I'm draining the gas tank right now, but just went out and looked again. this old Marvel carb. does not have a drain valve on it, it has a flat spot in the casting but no hole . the only thing on the bottom is the bronze filter. I rebuilt this thing a few years ago and noticed it did not have a drain like I was seeinng in pictures. You bet if I have to take this apart again it WILL have a drain drilled and added. Thanks

 

[old]

I don't think I would try to drill and tap it for a drain but I would look for at least the bottom part of a carb. Shoot I might even have a good bottom laying around here.

 

[kozz]

Old,
Just came back in , totaly drained gas tank and removed bowl filter all clean, regaped points to .025. no luck it still hesitates when advancing throttle. but seems a lot better when I put the choke a litte, think I should rebuild carb? If you do find a bottom let me know please.

 

[Dean]

Kozz:

Check the fuel adjustment. Perhaps it is set too lean. About 1 1/4 turns out from seated should be close.

Dean

 

[old]

If choking it helps and you have a good spark then yep carb rebuild maybe in order. I will have to go out and look to see if I still have a carb bottom. I do so much buying, selling and trading of stuff it is hard to keep up with what I do and do not have for day to day

 

[Bob Harvey]

Tom, for gosh sakes............WHEN did you see a 'crisp new dollar bill' (unless you're printing you're own!!) grin

 

[Bob Harvey]

Forgot to add that that deal won't work here, our 1's & 2's are coins and who's got a five ??

 

[Tom N MS]

Both points you made are good ones..Guess you'll have to do like I do and use a piece of brown paper bag--that is, if you can find a paper bag--they are almost extinct too..

 

[Anonymous-0]

Sounds to me like you may have an air way restriction,simulating choking down the motor.That's what happened to mine.Soon as it got air ran like a different motor.I just thought my filter was clean.Check for dirt dobbers lately. Fred