29 John Deere D backfire

[Coltond202]

Got the 29 D running for the Nebraska tractor test museum. The timing is spot on but it sure like to back fire its kind of scary when you can get flames out of the air cleaner at higher rpm's. I tried for about 2 hours to set the carbureter but it still likes to backfire pretty often. I tried the spark advance to but it made no difference. Any suggestions?

 

[rustyfarmall]

I don't know a lot about those old two cylinders, but I know that there is not supposed to be flames from the intake, EVER. How good are the valves? Are they adjusted to the proper clearance? Is there a chance that the magneto distributer cap is cross-firing inside? Are the plug wires coming into contact with each other, causing cross-firing?

 

[IH2444]

Just put some alcohol in the air cleaner, problem solved.

 

[IH2444]

I was just kidding of course. Do not try this at home.

 

[Mike M]

How does it run under a load ?

I had a 1927 D and that thing popped and banged around and shot flames out the exhaust at idle but ran fine with a little load. Didn't run near as good as any of my later Deere's I think they were just not made as well. Very crude.

 

[riverbottom]

I have never had a j.d. in the shop that didn"t need a valve job. This is the first thing I would do.

 

[Coltond202]

Everything in the magneto is new, The valves were sopposed to be reworked along with new rings. When I got there however everything was put together but they couldnt get it running. I reset the valve clearences. The new wirs dont cross and its got new plugs. Im not going to do the alcohol thing, at least not while Im starting it. The air filter is pluged so I have been leaving it off but that shouldnt make a difference.

 

[Anonymous-0]

MY 29 WILL POP FIRE OUT THE SHORT EXHUAST UNTIL I PULL BACK ON THE SPARK ADJUSTER

 

[Coltond202]

We havent pulled it but I did drive it up a steep hill and it smoothed out but I still dont like flames in the air cleaner. At idle its pretty good but when you push the throttle ahead its sounds like a drive by shooting coming out of the exhaust and the air cleaner.

 

[Coltond202]

I checked and it only sparks on one plug at a time. I did notice that when its running there is a spark between the two magneto caps. It is a splitdorm mag. The spark is between the magneto cap and the cover for the points. I took off the main cap and there is a large copper wire about a half inch long that the spark comes from. Its a new cap. What does this copper wire do.

 

[Earl -IL]

Colton,Sticking valves, weak springs? I would start with a cyl. leakdown test.If you don't have the equipment just knock the center out of a old spark plug & braze a air hose adapt into the plug & get a pressure reg ,roll up on tdc & put about 50-70 lb. of air into the cyl to see if you have any intake valves leaking.I have found very few that can grind valves on our old tractors.If that checks out then check the valve timing by the old deere book. What magneto are you running? I like to run a mag that only fires on compression .If you need more help email is open. Earl

 

[Mike M]

Wonder if the cam is in right time ? Use the fylwheel mark LH Exhaust and check. Within 1" of this mark either way the LH EXH. valve should just start to open.

 

[Coltond202]

checked the timing the other night and it was almost dead on the mark

 

[Coltond202]

the valves look to be just fine. As for the air test it sounds like alot of work for a tractor that will run about 2 hours a year in a museum. But I hate knowing that somethings wrong with it so Ill probly try it. The mag is a splitdorf that only sparks on compression strokes although I would like a wico better, but its not my tractor.

 

[LEH]

Erl in Ill. is right to suspect sticking vales as the cause. If the head has new guides, they may not have reamed them for proper stem clearance. The hotter the engine gets, the more they will hang up. It is normal for an engine with some wear to pop out the exhaust pipe. My 28 is pretty well worn & will give you a warning shot to keep you awake.

 

[Coltond202]

It doesnt seem to change when its hot. Everything looks good in there. I know it has to be the valves though. Ill look at it some more tomorrow but I doubt the museum will let me tare into it farther than I have already when it will probly cost them more money.

 

[DRL]

Probably the valves, but they will pop and carry on if they are running lean also. Might try opening the load needle a notch or two and see if it makes any difference. If it is shooting fire out the intake, though, be careful.

 

[Coltond202]

I opened it up quite a ways when it was running with no change

 

[Anonymous-0]

intake out of time. remove crankcase cover and carb.rotate crank throws to vertical position ;check valve cleance . hang a piece of seran wrap over intake;crank engine,when wrap is blown out of intake,stop. look thru crank cover, see if intake is opening remve cam bearing cap screws remove left cap. set cam so intake is not open.repeat seranwrap test until you get it right. check left hand ex open.