8n will start and idle fine but missfires at half throttle to full! PLEASE HELP

[Rod in Forfar]

Recently my uncle and I took on the project of a 8n which had been sitting for several years while the tractor had not been stored properly we do know it ran great up till the electronic ignition had fried.

First we replaced the fuel tank, petcock and fuel line. The carb, which was a aluminum aftermarket version, was soaked thoroughly and rebuilt. We relaced the complete ignition system with new points setup, coil, ballast resistor, wires and plugs. The flyballs in the governor was also replaced. We also have replaced the intake gasket.

Now the tractor starts and idles perfect but will consistently hesitate or missfire once the throttle is adjusted to half throttle or above. We have taken the tractor to the only shop in our area but only to confirm the points was set correctly and the carb was adjusted, but the guy did not like the aftermarket carb so he set us up with the cast iron Marvel carb which I also put a kit in only to run exactly the same. Occasionally the tractor will act as if it wants to run correctly but then goes right back to hesitating.

I don't know how the air cleaner is set up on an 8N, but I had the same problem with my MF35 Perkins diesel and it was the oil bath air cleaner flooded with rain water.

 

[Soundguy]

Oh, I definitely believe you when you say that it's not common to be running a dwell check on a set up like that.

Other than point gap though you're not looking at timing with a dwell reading, you're watching the operation and performance of the distributor relative to the points and visa versa.

and if the parts are good and the advance works, and the bushings are good.. it is less needed. that is a pretty odd dizzy.. unlike most other normal car dizzy's. 99% of the time, you put in new points, static time with a straight edge .. can use an ohm meter or test lamp to check points cracking... and go.

 

[rsallen]

I think it's cool the dam thing has gotten fixed.

The distributor should've gotten fixed right the first time it was taken apart to replace the bushings.
Is a touch of oil or grease on the cam lobes advisable for point longevity?

 

[Soundguy]

I think it's cool the dam thing has gotten fixed.

The distributor should've gotten fixed right the first time it was taken apart to replace the bushings.
Is a touch of oil or grease on the cam lobes advisable for point longevity?

cam lobe lube.. a lil dab on the lobes for the rubbing block to distribute. a lil dab will do ya.

 

[Midniteoyl]

First thnx to everyone who replied with suggestions! Now for the results, it ended up being the advance springs, which we was told by our parts supplier/tractor shop that the advance was fine! Being he has 40 yrs of experince and specializes in 8n/9n/2n tractors I took his word and went with it, also I absolutely refuse to just unnecessarily throw parts at anything. We will also replace bushings for good measure.

Conclusion is trust your instincts and go with what you know!

Again thnx for all the replys!

Thank you... Glad its fixed!