grandpas 39 B update

[RyaninKS]

Ok everyone, here is an update. I did everything you guys mentioned. I had the entire carb apart once again, just to double check all my passage ways. Again, the Nozzle is brand new, and clear. The float is new, but i figured id check it for leaks anyway, it is fine. Throttle and choke shafts are nice and tight and are flush on the inside of the carb throat. I don"t have an air stack on it right now as it is sitting on a stand in the shop,waiting for paint i didn"t bother putting it on yet. Good flow of fresh gas. I put the governor back where it is supposed to be and it does run better, now if i control the throttle by hand and slowly open it up it will speed up, but it still misses and pops, if i open it up quickly it dies. I now believe that the problem lays somewhere in the mag or timing. I am getting a blue spark, and i can get it to jump a fairly large gap. ( I forget what exactly i set it at) but it doesn"t seem to be "consistent" sometimes it seems to be stronger that other times. I have new plugs and wires, cap, rotor bug, and the points are new and set at .015. Could the coil or condenser be bad? I timed it exactly as you guys and my IT manual stated to. My valve timing is dead on, but one thing i started to wonder about while i was messing with it is the possibility of weak valve springs. (or maybe i"m still just used to high rpm engines lol) Is there anyway to test the valve springs? Would springs off a 41 head work? I have a set that i know the tractor ran good with.

Thanks everybody for all of your help and happy holidays to all!

Ryaninks

 

[ET]

A bad condenser could cause that, and would be cheap to change first.

 

[PBrowning]

Hi Ryan -- -- hand in there. And by all means install a new condenser NEXT. You should be able to grasp the throttle lever – open it up and see the engine accelerate immediately without hesitation. When fooling with an old car, we used to call this “gunning it”. Lack of this response will generally be lack of fuel or an ignition issue.

Do not worry over the valve springs -- They would have to nearly non-existent to make an engine fail to accelerate. They are most likely quite okay.

Also – when the tractor is idling, take a small piece of tubing or hose – wand it around the manifold gasket area to see if you hear any “sniffing” sounds – just to be sure!

Thanks for coming back. (PatB)

 

[johndeereman]

i had that problem once turned out to be one of the tabs on the inside of the rotor was broke letting the rotor rock back and forth pull the plugs and see what color they are you want a grayish color if its white not enough fuel if its black too much fuel or not enough spark. kinda sounds like its running lean by what you describe but if you pull a plug and its black you can narrow it to a spark problem

 

[john n myles]

I have 39 B. it would do the same thing your 39 B is doing. I was plowing with my and it would stop runing let set for 10min and start back up the condenser would get hot and open up change it back plowing

 

[Earl -IL]

Which magneto do you have?With engine off have you checked the fuel level in the bowl with the clear plastic tube in the drain. Turn on the fuel & hold the tube beside the carb bowl it will tell you the fuel level. Did you check the intake manifold good when you had it off.Burned through on the intake next to exhaust or Coked up restricting flo? Like a previous post Sometimes you have to go back to all the basics & check everything. Keep us informed. I bet you will find it. Its man made & subject to error. Earl

 

[WTW]

Ryan,
A bad condenser is hard to diagnose and very well could be what you are fighting. Just because it will throw a "wide" blue spark doesn't mean the condenser is good. Check the spark at the spark plug grounding the body of plug. You may see that the nice blue spark you seen jumping a 1/4" before is now yellow jumping at .030 gap. That is more the characteristic of a bad condenser. If it is yellow change the condenser. Too bad you just didn't have a known good mag from another tractor to slip on it before you swapped the condenser but if you do not try another condenser. I also would not rule out a air leak on the intake side of manifold. I have seen holes burnt through the intake manifold runner into the exhaust chamber on these old all fuel type manifolds. Look down her throat with a flash light with the carburetor removed to inspect the intake runner for a hole into the exhaust chamber. I do not think your problem is timing as it should idle and accelerate whether the timing is at 10 degrees or 35. Timing will affect it performance but not to the existent where it won't idle half way decent. Good Luck, DW

 

[johns48jdb]

if you can get a straw in the end of a nozzle on a spray can of ether you can use it to spray around the intake manifold to see if there is any leaks there. it might work with wd 40 even. i never change the points without changing the condensor too. my father in law put in a set of points once and couldn't get it to fire at all, his grandson happened to come up and ran a piece of course paper through the points and it started right up. be sure you have the hole in the bottom of the air intake cleaned out. i'm not sure that there is one on your tractor, but there is one on my 48 b. it was stopped up and had to use a drill to get it clean. without that hole being cleaan water can get into the oil bath air cleaner on my tractor at least.

 

[Vern H]

Hi Ryan,
Looks like you re getting a lot of good advice. Are you using good , solid wire to the plugs? Bad wires sometimes will break down under load/acceleration and cause similar symptoms. Just keep tinkering and it will run. Ain t John Deeres fun? Good luck, VH

 

[gtx1967jewison]

well nobody mentioned float level. very important for acceleration more so than running as running under load or isle can be greatly compensated for with needle adjustments. also nobody said check the shaft in mag for wear/play. very common issue, will cause erratic spark that's weak/strong. point gap & rotor gap vary. it needs to be without looseness. the shaft & /or bushing in the mag could be worn. the other advice is all good too. just remove cap, rotor, wiggle shaft. Q will be answered.