40c
40c
ok, I've been trying to find out what is wrong with this JD, we got a backfire in carburetor problem, did everything people told me on this forum. brand new firing system, overhaul carburetor, still the same problem. works OK when cold, has soon its coming hot, its starting to backfire in carburetor. anybody could help me please. really need to fix that thing. thanks
- gregjo1948
- 350 crawler
- Posts: 1000
- Joined: Mon Aug 30, 2010 5:58 am
- Location: Newark Valley,NY,USA
I'd check compression when first started and then when it starts firing thru the carb. It sounds like you may have an intake valve issue. Check the bushing in the distributor for wear. If it's worn excessively, it alters the points, which changes when the plugs fire. If firing too soon, (advanced) it is firing on the end of the intake stroke. I really don't know why it matter if it's cold engine or up to running temp...
JD 350B diesel 6way blade, Case 580B Loader/backhoe, Farmall 504 high crop w/ flail boom mower, International 404 , International 284 diesel w/belly mower, 1972 Ford F600 dump truck, Galion 3-5 roller, Allis Chalmers D17, 1620 Ford
40c backfire
When it is running and backfiring, try holding spk plug wire off but close to the top of plug and see if it is firing consistently or missing one and then firing the next, try this on both plugs one at a time. Just a thought
- Stan Disbrow
- 350 crawler
- Posts: 2898
- Joined: Fri Jul 15, 2005 3:13 pm
- Location: Raleigh, NC
Hi,
Cold OK, warm backfiring would have me looking at intake valve clearances. They close up as they warm.
Of course I would then take the time to set all the valve clearances. I mean, once the valve cover is off, it is worthwhile to check everything under it.
Stan
Cold OK, warm backfiring would have me looking at intake valve clearances. They close up as they warm.
Of course I would then take the time to set all the valve clearances. I mean, once the valve cover is off, it is worthwhile to check everything under it.
Stan
There's No Such Thing As A Cheap Crawler!
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
- mapaduke@yahoo.com
- 1010 crawler
- Posts: 420
- Joined: Sun Sep 13, 2009 6:27 pm
- Location: Rochester N.H.
ok, got more info from my dad,he did put some new point, rotor, distributor cover, leads and spark plug in new. compression check cold, above 100 psi, valve clearance check and are ok. what he's telling me is that its work good at idle when its cold, after 30 minutes about, it will run good when working with it, but as soon he put it in idle to go do something, its start backfire and sometime almost stop. if he goes back full throttle and work, run great. the carb is overhauled. any anything. thanks
- gregjo1948
- 350 crawler
- Posts: 1000
- Joined: Mon Aug 30, 2010 5:58 am
- Location: Newark Valley,NY,USA
If there is an auto advance in the distributor, that's what I would suspect is not functioning correctly. Just because the carb was "rebuilt", doesn't mean it isn't worn out. Check for possible vacuum leaks. The carb might be a little too lean... try adjusting...
JD 350B diesel 6way blade, Case 580B Loader/backhoe, Farmall 504 high crop w/ flail boom mower, International 404 , International 284 diesel w/belly mower, 1972 Ford F600 dump truck, Galion 3-5 roller, Allis Chalmers D17, 1620 Ford
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- 420 crawler
- Posts: 38
- Joined: Sat Sep 23, 2006 12:20 pm
- Location: Columbus, Ohio
Carburetor
Also check the venturi in the carburetor for a good seal, it can suck air in, causing a lean condition. To test, try closing the choke when it backfires.
1960 440 ICD with 602 blade
1960 440 ICD with 831 bucket
1960 440 ICD with 831 bucket, center throttle
1960 440 ICD with 831 bucket
1960 440 ICD with 831 bucket, center throttle
jd 40c 1954 distributor
what direction does the distributor turn in my 40c clockwise or counter
clockwise .....had to repair oil pump new piston rings and rod bearings
now get it started
clockwise .....had to repair oil pump new piston rings and rod bearings
now get it started
- gregjo1948
- 350 crawler
- Posts: 1000
- Joined: Mon Aug 30, 2010 5:58 am
- Location: Newark Valley,NY,USA
Leave the distributor cap off and crank it over while watching the distributor shaft.
JD 350B diesel 6way blade, Case 580B Loader/backhoe, Farmall 504 high crop w/ flail boom mower, International 404 , International 284 diesel w/belly mower, 1972 Ford F600 dump truck, Galion 3-5 roller, Allis Chalmers D17, 1620 Ford
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- 1010 crawler
- Posts: 258
- Joined: Wed Sep 11, 2013 3:34 pm
- Location: Shiner, texas
40's are famous for backfiring if they get a too-lean mixture. They don't fire on one stroke because the mixture is too lean, and then the missed fuel ignites on the next exhaust stroke. Look for any way it can get too much air or too little fuel. The throttle butterfly shaft is often overlooked, and the felt washers on them deteriorate, allowing lots of air in.
Early 40C w/Yakima toolbar and homebuilt ripper: 350 w/6-way
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