Carb got me so mad...

[TSnyder]

Last week i posted a message asking for some help with my original MS carb on my 52 8N. The tractor was completely rebuilt and the motor has been broke in but i can't seem to get it tuned right. I did tear down and rebuild the carb and then tore it apart again over the weekend, soaked it in carb cleaner, fed phone lines through almost all the passages (some were even to small to get a wire through) and blew everything out with carb cleaner and air. I put everything back together but i still seem to have the same issue i was having. If the choke it held out a little bit it runs good (sounds good) but i still lack power. I can't enrich the mixture enough with the main mixture screw to make it run smoothly and have power. I can screw the darn thing all the way out and it wouldn't make a difference. I also get some backfiring through the carb from time to time.

I'm going to check the timing again tonight with a timing light and maybe put in some new Autolite 437 plugs but i can't understand whats wrong with this picture.

I am just about fed up with it to the point that i may get a replacement Zenith carb.

Any ideas what else to look at???

thanks,

Tyler (PA)

 

[Bruce (VA)]

Did you replace the throttle bushings? Most kits don't come w/ them.
50 Tips

 

[HCooke]

How's the spark? Having to use the choke could be the result of a weak spark. Also, air leaks (carb to manifold gasket, manifold to block gasket, and the throttle shaft in the carb could be leaking air.

 

[Dell (WA)]

Tyler.......no more than 3-turns (MAX) on yer down-pointing mainjet. Understand???

Check yer sparkies firing order' 1,2,4,3 CCW. The 5-nipple sidemount can gitt sparkies crossed. Usually sparkies 3&4. (swapp'em fer grins) These N-Engines are SOOOoooo GOOOooood they will start and run on just 2-sparkies but won't have enny power.

Holding the choke out, tells me you may have "leakage". Probably around the throttle shaft. I like to spray WD-40 around possible leak sources as the WD-oil will seal the leaks for a little while. I think it is better and safer than waving an unlit propane plumbers torch around.

I do NOT recommend the Zenith carb. The M/S is emmently rebuildable. ........Dell

 

[rustyfarmall]

(quoted from post at 07:45:44 06/06/11) Last week i posted a message asking for some help with my original MS carb on my 52 8N. The tractor was completely rebuilt and the motor has been broke in but i can't seem to get it tuned right. I did tear down and rebuild the carb and then tore it apart again over the weekend, soaked it in carb cleaner, fed phone lines through almost all the passages (some were even to small to get a wire through) and blew everything out with carb cleaner and air. I put everything back together but i still seem to have the same issue i was having. If the choke it held out a little bit it runs good (sounds good) but i still lack power. I can't enrich the mixture enough with the main mixture screw to make it run smoothly and have power. I can screw the darn thing all the way out and it wouldn't make a difference. I also get some backfiring through the carb from time to time.

I'm going to check the timing again tonight with a timing light and maybe put in some new Autolite 437 plugs but i can't understand whats wrong with this picture.

I am just about fed up with it to the point that i may get a replacement Zenith carb.

Any ideas what else to look at???

thanks,

Tyler (PA)

That telephone cord wire is some very small diameter stuff. I don't think there are ANY passages in that carb that are too small for the wire to fit through, so either you are trying to poke the wire through a blind hole, OR that particular hole is still packed full of crud.

Personally, I have given up on the carb cleaner that you soak the carb in to get it clean. That stuff just isn't worth a hoot anymore. Instead, I use a small bucket with a lid. Fill it about 3/4 full of water, add about 3 cups of liquid laundry detergent, put the carb in it, set it on a hot plate and let it boil for an hour or longer. Rinse it in clear water, blow it dry, and then finish up with a can of aerosol carb and choke cleaner. Stick the plastic nozzle right down into those passages and look to see if the spray comes out somewhere else.

 

[TSnyder]

Firing Order is correct... 1,2,4,3 CCW. I am guessing it is more likely the leakage problem if anything. The rebuild kits are sorta cheap and dont' come with a good seal for around the throttle shaft. The kit i used just has a real cheap small rubber boot that doesn't seem to be a real good sealer. Any suggestions for what to use?

What are the throttle shaft bushings?

Also screwing in the idle mixture screw seems to not have much of an effect, it will run completely screwed in.

Is it possible that i didn't get all the seats in all the way?

Also is there a replaceable seat under the main mixture screw?

 

[Dell (WA)]

Tyler........heres the deal on throttle shaft bushings. After many years of use the throttle shaft hole in the carb gitts "egg-shaped" and fer some reason, round seals don't seal the egg-hole, eh? You drill out the old hole and install throttle shaft bushings (they are brass I think) This is a simple machine shop procedure that competent shadetree mechanic can do. I believe instructions are included.

Did you read my side-pointing idlemix instructions? The idlemix is BASSACKWARDS; out for lean, IN for ENRICH. When you screw yer idlemix all the way in, you are ENRICHING yer idlemix. So yes, you could run with it completely screw in. Again, adjust yer side-pointing idlemix for FASTEST idle. Understand??? ..........Dell

 

[ZANE]

I would go back and make sure that economy valve orifice is clear.

Here is a way to see if the ecomomizer is blocked. Completely remove the large down pointing high speed adjusting needle. If it runs OK now the economizer is blocked. It is the tiny one closest to the throttle.

Zane

 

[JMOR]

(quoted from post at 11:54:53 06/06/11) Firing Order is correct... 1,2,4,3 CCW. I am guessing it is more likely the leakage problem if anything. The rebuild kits are sorta cheap and dont' come with a good seal for around the throttle shaft. The kit i used just has a real cheap small rubber boot that doesn't seem to be a real good sealer. Any suggestions for what to use?

What are the throttle shaft bushings?

Also screwing in the idle mixture screw seems to not have much of an effect, it will run completely screwed in.

Is it possible that i didn't get all the seats in all the way?

Also is there a replaceable seat under the main mixture screw?

verything is possible, but I say no, the main power adjust seat is not considered replaceable. Smallest holes in those carbs that I know of are larger than 26 gauge telephone wire (0.016 inch diameter). You can get it thur any, except one that makes a 90 to 110 degree turn.......on that you have to approach from both directions & look thru the opposite opening to see the wire. Tricky ones are as the idle port in the throat....bigger at throat, then smaller as enter hole, then larger again beyond the tiny orifice (not removable).

Probably not all clear, yet.

 

[TSnyder]

I honestly would just like to send my carb to one of you guys to check it out. I know it will need new packing put in at the throttle shaft and choke shaft and could need new throttle bushings. Would someone be able to please help? This seems to be what i'm missing to get this tractor finished from the resto/mod that i started at the beginning of the winter.