[FORDLT75]

Well i hit a road block with her. Not sure whats going on. Its runs fine at idle but when you throttle up it starts shaking like mad and acts likes it is misfiring and stumbles real bad. When it does this it will backfire through the carb and dies. I replaced points condenser coil keyswitch. Has me and my john deere mechanic friend puzzled. He thinks maybe the cam we switched (mine had bad loob on it) was a 14 hp cam instead of a 10,12,16 cam. Not sure what else it could be. Rebuilt the carb (set it to the book with float) also tried different carb same thing. Any suggestions guys? Motor had less then 5 hours run time on rebuild. We checked timing good there. Valves were set to specs. Also put new governor gear in it to. Any ideas would be great as this is very irritating to say the least. Never had a rebuilt motor do this. Has a aftermarket piston not a stens or kohler but i heard that not the problem. Block was honed to the piston. Crank was turned and polished to.

 

[poncho62]

You are saying that it has ran for 5 hrs.....Was it running good then suddenly started running bad or was it running bad all along?

 

[FORDLT75]

Running bad all along. Been trying to figure out why so i could fix it.

 

[poncho62]

I am sure you tried a new spark plug......
Back firing through the carb kind of says its a timing issue.....not a tooth out on the cam timing are you?

Points are set at .019-.020....valves are set at .010 intake and .020 exhaust?

Tried turning out the carb adjustment screws a bit?

 

[FORDLT75]

Yep timing dead on. Points set. Spark plug is good. Adjusting the carb doesnt seem to yield much improvement. Valves set max.

 

[Rohan]

I would try another plug for giggles. I had one that would fire great and then nothing as rpm went up.

 

[oldsarge]

Open it back up!!!! I swear you have the cam/balance gears out of time.It's easy to do even if you swear you've got it right.Ask me how I know,I dare ya.

 

[FORDLT75]

Ok no balance gears so i guess the cam. Could a 14hp cam cause this issue? I know only 10 12 16 work properly in the k341.

 

[tomw0]

Description reads like a worn exhaust valve cam lobe to me. Did you compare the lift of each lobe? Do the valves open fully, or is is just a narrow opening?
A second thought would be a stuffed muffler, causing back pressure, and thus keeping the intake gas from being drawn into the cylinder. If you feel a good strong exhaust pulse from the muffler that slowly drops, deeper inspection might be worthwhile. Or a weak exhaust that stays that way, also.
tom

 

[FORDLT75]

Yeah were going to replace the cam and go from there

 

[110Driver]

factory carb or walbro? I had brand new walbro, couldn't get to run right bought nos carter carb, ran great after that

 

[FORDLT75]

Factory one that came on motor

 

[WNYTractorTinkerer]

Open it back up!!!! I swear you have the cam/balance gears out of time.It's easy to do even if you swear you've got it right.Ask me how I know,I dare ya.

DITTO!! I wasn't so lucky when I did it the piston blew apart when it backfired.. One little tooth off and BLAMMOOO! :banghead3

 

[FORDLT75]

Ok here is a quick question do you need to use a K341 cam or will cams from 10-14hp work in it?

 

[poncho62]

Ok here is a quick question do you need to use a K341 cam or will cams from 10-14hp work in it?

I just rebuilt a 16hp....used a cam out of a 10hp....my 16hp cam was cracked

What you were saying about the 14hp being different?....I have never heard that.

 

[FORDLT75]

only going by part numbers for each motor. The 16 is different then 10-14's.

 

[rhenning]

The 16 HP cam has slightly longer duration the the 10 to 14 HP cams. Stock tractor pullers trick to use it for a bit more HP for pulling. Not worth doing for normal purposes. Roger

 

[FORDLT75]

Thanks for the info.

 

[Tractor-Holic]

I would try another condensor before ripping it apart again..

I have had a few that would only let the engine idle,and the engine would want to backfire and shake if you tried opening the throttle...

 

[FORDLT75]

Its brand new though.