851 DISTRIBUTOR / TIMING SANITY CHECK

PAVLOCK

Member
Looking for a sanity check. Tractor starts up great and runs around great but the higher RPM is off. Timing/Carb or both.

Checked timing on my tractor from previous owner, and at idle i am seeing 24* and once going up slowly to max RPM timing is all over the place. I marked the 4* and 24* lines on the flywheel but the timing is unstable enough for me to see anything useful. Assuming weights could be stuck?

After finding TDC on compression stroke and turning the fly wheel to 0* I noticed that the rotor and cap on #1 do not line up.. I need to go back and verify here in a bit, but I ("think") once I get to the 24* mark the cap and rotor lined up.. I see some manuals saying to turn fly wheel to 4* and stab distributor and another saying to turn flywheel to max timing at 24* and then stab the distributor.

Here are some pics for reference and appreciate any advise in advance!
mvphoto11168.jpg


mvphoto11169.jpg



Red asterisk is where number 1 nipple on cap lays once clamped down at the 0* mark on flywheel.
mvphoto11170.jpg
 
Ignition timing should be 4 degrees BTDC at 400 RPM or less. Your numbers do not make sense.

Are you using an inductive pick up timing light? 12V or 6V?

Check operation of the centrifugal advance mechanism.

Dean
 
Like Dean says, before you pick up your timing light you have to check those advance weights, springs and pins.
I go thru a lot of old junk here and all advance mechanisms are a cruddy, rusty mess, a high percentage are stuck completely.
Just got a JD with the initial run around the yard to warm the oil for changing showing symptoms of retarded timing, running hot, very loud exhaust, muffler too hot.
Pulled the cap and tried to turn the rotor a little. yep, advance stuck.
Also had one with very erratic timing, advance was sticky, not quite stuck yet.
big delay in the advance coming in when revving up, and dropping the throttle quickly, another big delay before the advance dropped back. poppoppop
 
Your rotor is pointing to #4.In other words you are 180* out from what was delivered from the factory.The tractor will run fine that way provided you have the correct fireing order.
I'd say you have worn distributer bushings or the mechanical advance is not working the way it should.Could just be dirty or the springs could be broken.










 
Thanks for all of the responses and I am using an inductive timing light Dean.


**Below are updated pics of turning the flywheel to 24* and now the cap and rotor line up with #1.

Did the previous owner stab this in correctly?


Confusion is the difference of I&T manual and what I have read on the forum.

[b:f4d2c27d1e][u:f4d2c27d1e]I&T manual[/u:f4d2c27d1e][/b:f4d2c27d1e]- Stab dist. at 24 degrees and mentioned that if it will not idle at 4* then mechanical advance could be faulty.

[u:f4d2c27d1e][b:f4d2c27d1e]What I read on forums[/b:f4d2c27d1e][/u:f4d2c27d1e]- Stab Dist. at 4* and it should advance to 24* at upper RPM.

http://forums.yesterdaystractors.com/viewtopic.php?t=1148041&highlight=distributor&sid=50f3a7e03d709aeb94161b24f2a42d0b


Which way is correct?

Is it possible to put a little oil on the advance weights and try to free it up with out removing points etc?

Thanks again and sorry for the dumb questions.





mvphoto11171.jpg


mvphoto11172.jpg


mvphoto11173.jpg
 

Can you explain this a little more..

My #1 faces in between 4 and 5:00 like in my pics.

Where does it face from the factory?
 
(quoted from post at 14:29:17 09/18/14) Thanks for all of the responses and I am using an inductive timing light Dean.


**Below are updated pics of turning the flywheel to 24* and now the cap and rotor line up with #1.

Did the previous owner stab this in correctly?


Confusion is the difference of I&T manual and what I have read on the forum.

[b:2656e9c410][u:2656e9c410]I&T manual[/u:2656e9c410][/b:2656e9c410]- Stab dist. at 24 degrees and mentioned that if it will not idle at 4* then mechanical advance could be faulty.

[u:2656e9c410][b:2656e9c410]What I read on forums[/b:2656e9c410][/u:2656e9c410]- Stab Dist. at 4* and it should advance to 24* at upper RPM.

http://forums.yesterdaystractors.com/viewtopic.php?t=1148041&highlight=distributor&sid=50f3a7e03d709aeb94161b24f2a42d0b


Which way is correct?

Is it possible to put a little oil on the advance weights and try to free it up with out removing points etc?

Thanks again and sorry for the dumb questions.





mvphoto11171.jpg


mvphoto11172.jpg


mvphoto11173.jpg
hey are both correct, when you read in their entirety. At least in my I&T FO-20, there is more than you quoted. The remainder is significant! "Rotate the breaker cam in the normal direction as far as it will go and while holding the cam in this position (my words:this is against advance springs & has full advance engaged), turn the distributor body in the opposite direction until the breaker contacts just start to open, then tighten distributor clamp securely."
 
It makes no difference.

Spark plug wires can be placed in any cap tower so long as the fireing order is correct and the distributor is installed such that the timing can be set properly.

Dean
 
The cap and rotor just need to be close some are not dead on. It's when the points open that count. Grab the rotor turn it in the direction of rotation it should move a 1/4 inch or so and spring back. also check for side to side movement of the shaft.
 
10/4 guys.. Thanks for the responses..

Setting baseline to 4* and mechanical advance advancing an additional 20* makes more sense to me but I suppose I have it all wrong..
 
I went through a similar situation recently with an 861:

http://forums.yesterdaystractors.com/viewtopic.php?t=1152148&highlight=861

Essentially, I put away the timing light, pulled the spark plug wires, made sure the carb advance was working and found TDC. Then I wired from there. Ran beautifully! Set final timing by ear, confirmed with dwell meter.

Not sure what is wrong on the 861, but doesn't matter because it runs so well. When I have nothing else to do I might investigate.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top