420 crawler engine surging
420 crawler engine surging
looking for some advice. Rebuilt my carberator in 420 crawler and now i cant get engine to run smooth . it surges up and down. It is a little better with more throttle and worst at idle any suggestion out there would be helpful
This sounds like an adjustment issue on the carb. I am assuming this is a Marvel-Schebler carb which is linked to the governor. I have some familiarity dealing with them on my 1952 Ford 8N tractor. It sounds like your governor (which is linked to the carb) is kicking in and out to compensate for the mal-adjusted carb, causing the surging. You should be able to watch at idle and see if the governor linkage is moving in and out with the carb when it does this.
If so there are usually three external screw settings that can be adjusted and if not done according to spec and in the proper order it will cause issues with surging. It is not an exact science on those adjustments but they need to be reasonably close to what is in the manual or you will have problems.I can't speak to the specific procedure as I am not sure of the exact M-S carb model that is on the JD crawlers, but it should be in your manual.
A mal-adjusted float in the carb could also potentially cause that issue, but I am assuming you adjusted that during reassembly.
If so there are usually three external screw settings that can be adjusted and if not done according to spec and in the proper order it will cause issues with surging. It is not an exact science on those adjustments but they need to be reasonably close to what is in the manual or you will have problems.I can't speak to the specific procedure as I am not sure of the exact M-S carb model that is on the JD crawlers, but it should be in your manual.
A mal-adjusted float in the carb could also potentially cause that issue, but I am assuming you adjusted that during reassembly.
(1) JD Straight 450 crawler dozer with manual outside blade; (2) JD 2010 diesel crawler loaders; (1) JD 2010 diesel dozer with hydraulic 6-way blade; (2) Model 50 backhoe attachments, misc. other construction equipment
engine surging
OK thanks it will smooth right out if I pull the choke out just slightly also really appreciate you help
- Paul Buhler
- 350 crawler
- Posts: 991
- Joined: Wed May 21, 2008 6:25 pm
- Location: Killington, VT
Send me an email, and I can send you a copy of the M/S carb manual as a .pdf.
Short term, try one turn out for the idle screw, and 1 1/2 for the load (if you have one) then tweak as needed. On my old, but rebuilt carb, I actually have the idle screw turned in completely to get a slow idle (air leak somewhere), but I've found that I had to spend some time finding the sweet spot with the load screw - too rich, ran rough (surged), too lean, no power or pickup under load.
Short term, try one turn out for the idle screw, and 1 1/2 for the load (if you have one) then tweak as needed. On my old, but rebuilt carb, I actually have the idle screw turned in completely to get a slow idle (air leak somewhere), but I've found that I had to spend some time finding the sweet spot with the load screw - too rich, ran rough (surged), too lean, no power or pickup under load.
Paul Buhler
Killington, VT
420c 5 roll with 62 blade, FOPS, and Gearmatic 8a winch
Killington, VT
420c 5 roll with 62 blade, FOPS, and Gearmatic 8a winch
What all did you do when you rebuilt it?
Lavoy
Lavoy
Parts and restoration for antique and late model John Deere crawlers.
Owner and moderator www.jdcrawlers.com
Owner and moderator www.jdcrawlers.com
carb ajustment
Lavoy I put the basic kit in. Clean and blew all ports out. Going to checkout throttle shaft for wear next. Adjusted float to proper height. Cleaned complete fuel system. If I pull choke very slightly it will smooth out. Any tips for me!
- DukeofDeere
- 1010 crawler
- Posts: 443
- Joined: Wed Oct 26, 2011 7:12 am
- Location: Hudsonville Michigan
As has been mentioned, you need to pull all jets and the nozzle. Then soak in a good carb solvent, no just spray carb cleaner through. Once done soaking, rinse with water, blow out with air, then with the little tube doohickey on a can of carb cleaner, blow carefully through every passage on the carb, and observe very carefully if spray comes through. Inevitably, the ends up being one passage with crud in it.
Lavoy
Lavoy
Parts and restoration for antique and late model John Deere crawlers.
Owner and moderator www.jdcrawlers.com
Owner and moderator www.jdcrawlers.com
- DukeofDeere
- 1010 crawler
- Posts: 443
- Joined: Wed Oct 26, 2011 7:12 am
- Location: Hudsonville Michigan
engine surging
OK guys I will tear down and do a try this again taking much more care and detailed job. Thank you so much for your advice. Rest of tractor is complete and I guess I was hurrying a little to try this thing out.
engine surging
Oh and I also installed a new inline fuel filter in the fuel line ( and correctly) would this be to much restriction?
- DukeofDeere
- 1010 crawler
- Posts: 443
- Joined: Wed Oct 26, 2011 7:12 am
- Location: Hudsonville Michigan
- gregjo1948
- 350 crawler
- Posts: 1000
- Joined: Mon Aug 30, 2010 5:58 am
- Location: Newark Valley,NY,USA
Seems to me that, the rebuild kits come with 2 idle jet screws and possably the wrong one was installed. gregjo1948
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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