3020 timing

cobra1379 · Sep 22, 2014

I have a gas 3020. Just rebuilt the carb and it idles fine but when I hit the gas it dies. I decided to check the timing and it was a little off so I reset it with a light but it still does it. If I set the timing by ear it runs great but ends up being 35-40 (guessing) advance instead of the 20 that the book calls for. The centrifugal advance appears to be working fine but I'm not really sure how to check it. The book gives degrees at different rpms measured at the distributor but I don't know how to test. Test bench maybe? Its been converted to electronic ignition but everything else is stock

Jerry/MT · Sep 22, 2014

If you have a timing light, check the initial timing and make sure it"s correct. Then rev the engine and watch the timing change when iluminated by the timing light. If it doesn" move when you rev it, the cetrifugal advance is not working.If you have the distributor curve spec you can check out the whole curve however you"ll need an rpm measurment. Also and remember the distibutor turns at 1/2 engine speed as most distributor curves are give as a function of distributor rpm.

cobra1379 · Sep 22, 2014

I can set it at 20 degrees (where it is suppose to be) at close to wide open and then when I slow down to idle it comes down close to tdc. When I set it like that though it just dies when I hit the gas again.

Steve@Advance · Sep 22, 2014

Might try riching up the idle just a little, that should help the hesitation and dieing.

If you're satisfied the centrifugal advance is working, and sounds like it is, I would just play with the timing until it runs good with no clatter or starter kick back. As low compression and slow as the engine turns, not likely you'll do any damage.

Bob · Sep 22, 2014

Timing is ONE thing, but tractors are not exactly like high-performance cars that respond instantly when the throttle is stomped on.

That being said, a 3020 carburetor will have a vacuum operated accelerator pump that dumps a shot of gas into the air stream when the throttle is popped open/manifold vacuum quickly drops off.

Likely, that part of the OP's carb is not working properly.

Jerry/MT · Sep 23, 2014

Per your description, it sounds like the centrifugal advance is working because your timing retarded with a drop in rpm.

Are you sure you have a good spark?

I don"t know what kind of carb you have but is it set properly? If it has an acceleration well, make sure the float is properly set and the main jet is adjusted rich enough to allow the accel to be smooth and without hesitation. If it has an accelerator pump, make sure it is working properly and set in the correct hole in the accel pump rod.

cobra1379 · Sep 23, 2014

I did just put an accelerator pump in the carb and I'm not absolutely sure the check valve is working in it. Would the timing being really advanced compensate for that though? It runs great when I set it up like that but you cant start it and I'll bet itll overheat and start pinging. If it jumped time would it have these symptoms?

Jerry/MT · Sep 23, 2014

If this was my tractor, I"d set the spec initial timing at idle rpm.
I"d make sure that I had a good spark(FAT AND BLUISH-WHITE,the color of lighning).
I would make sure that the enrichment system was working properly(".... I"m not absolutely sure the check valve is working in it.")
Then I would check the spark advance to verify that the spec advance curve was being followed.

You have to approach this systematically and not jump from one conclusion to another without verifying the first.

cobra1379 · Sep 24, 2014

Ok but the book says to set the timing at 20 degrees at 2200 rpm. Here is what it says about distributor degrees. 0-2 degrees at 225 rpm;5-7 at 350; 10-12 at 825; 14-16 at 1200. If I understand it right you would double the rpm to match the engine. So at 700 engine rpm it should be between 5 and 7 degrees advance correct? I would think that if it wasn't getting enough fuel then advancing the timing wouldn't affect it. I would also think that I would be able to very slowly raise the rpm regardless of if the accelerator pump was working properly. I'm just trying to understand whats going on in there. I'll check the fire and check valve.

Jerry/MT · Sep 25, 2014

Does the book tell you what intial timing is, usually an nominal idle speed?
Usually advance curves are the incremental advance as a function of distributor rpm. The timing is the sum of the initial timing plus the advances. For example if my intial timing is 5°BTDC at 400 enine rpm and my centrifugal advance is 4°@ 500 distributor rpm (1000 engine rpm) than my timing at 1000 engine rpm =5°+ 4°=9°BTDC

In your case,1100 distributor rpm should give 13-15° advance and if you need timing of 20°BTDC @ 2200 engine rpm, then your intial timing needs to be between 5-7° BTDC inital timing ( 20° -13-15° = 7-5°BTDC).

I don"t know about the innards of your carb to comment but you may correct in your statement that you should slowly be able to accel the engine without utilizing the accel pump.

cobra1379 · Sep 25, 2014

No it just gives what Ive given on here but your math makes sense to me. Only thing is much below 20 degrees it wont run at all at idle and the only marks I have on the flywheel are tdc 20 degrees and 25 degrees.

David G · Oct 10, 2014

20 degrees at 2200 does not sound like a lot of timing, I would want it at 30. I am running my MH at 22 and it runs 1400.

Books tend to be conservative on timing.

3020 timing

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