420 crawler engine surging

General help and support for your Lindeman through 2010 John Deere crawler
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lurch85
430 crawler
430 crawler
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Post by lurch85 » Tue Feb 04, 2014 10:35 pm

I've caused myself a lot of headaches with inline filters that were too restrictive... found some that seem to do ok in the marine area of Walmart... its more of a screen than it is a filter. The one i'm thinking of is clear with a white plastic screen inside..
John Deere 420C, John Deere 350 straight with Gafner loader, John Deere 4020

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traber1
MC crawler
MC crawler
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Joined: Wed Dec 14, 2011 11:21 am
Location: Albany, NY

Re: 420 crawler engine surging

Post by traber1 » Tue Aug 15, 2017 4:55 pm

Can any of you provide an audio snip of what a good, smooth running 420 sounds like?

I've been fighting multiple issues and am now concerned I burned the exhaust valve on #1. Unit ran fine for an hour yesterday, moving brush and pulling trees. Shutdown to cut more trees and after setting for about 30minutes, I could not get it restarted. Noticed it was back puffing through intake while trying to start and suspected a valve leak. Found #1 exhaust with only 0.003"tappet clearance. I adjusted all valves back to spec and can now restart hot, but engine still sounds like it is skipping every 3rd or 4th cycle. Timing is dead on according to timing light. What am I missing?
I have unplugged the inline fuel filter and filter bowl valve, cleaned all passages of carb (could not get main jet out) replaced condenser/points /plugs. Checked /replaced ignition coil, plug and coil leads, cleaned the flyweights in distributor. Ignition key switch test alright (hot or cold). Unit 420 gas, 6V NEGATIVE ground (alternator installed) and ignition coil wiring changed accordingly.

SUGGESTIONS APPRECIATED. Where can I order carb parts?

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Lavoy
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Re: 420 crawler engine surging

Post by Lavoy » Wed Aug 16, 2017 9:20 am

Do a compression test, that will tell you if a valve is leaking.
Lavoy
Parts and restoration for antique and late model John Deere crawlers.
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traber1
MC crawler
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Re: 420 crawler engine surging

Post by traber1 » Thu Aug 17, 2017 7:23 am

Compression test cold was about 55psi for both cylinders. Not sure how accurate the gauge is, but at least they were the same when cold. Did not check hot. Since I adjusted valves already, cannot tell.

Ran for another 20minutes in driveway, shutdown and let set for 30minutes. A quick pull on choke and fired right up. Hope I don't have to tow it home again.

Wish me luck. Taking out to do more trees today. Where can I order carb rebuild kit to have on hand?

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notmeu
1010 crawler
1010 crawler
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Re: 420 crawler engine surging

Post by notmeu » Thu Aug 17, 2017 10:21 pm

If I remember correctly the cold compression test should be around 100 - 130????
1956 JD420, gearmatic 8a winch, custom 6 way blade and FOPS.

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Lavoy
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Re: 420 crawler engine surging

Post by Lavoy » Fri Aug 18, 2017 8:55 am

Yeah, you are way light on compression. Squirt some oil in each hole just to verify it is valves, but that is way too low.
Lavoy
Parts and restoration for antique and late model John Deere crawlers.
Owner and moderator www.jdcrawlers.com

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shinnery
350 crawler
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Re: 420 crawler engine surging

Post by shinnery » Fri Aug 18, 2017 5:00 pm

Be sure you have the throttle plate and choke plate in the carb. wide open for no air flow restriction. Possibly even remove the air cleaner. For Compression tests. The added oil in cylinders helps the rings to seal, if compression stays the same after adding oil it indicates the leak is at the valves.
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But, many electrons were terribly bothered.

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