Go Bottom Go Bottom

MF135 Zenith Carburetor Problems and adjustment

View my Photos
ulav8r
Join Date: Dec 2010
Posts: 4 Arkansas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2010-12-11          175669

Just joined to get help with adjustments to a carb on a MF135. It is a '73 or '74 gas with a Zenith #013338 carb. Was bush hogging earlier this fall and could just keep pto at 540-560 rpms, engine maxed out at 2000 rpms. Things got worse and inspection found the sediment bowl screen covered in rust and the bowl about 1/2 full of sediment. The filter at the carb was also full of rust. Managed to break of the brass elbow the filter was screwed into, so had to remove the carb to get the broken part out. Got a carb rebuild kit to get replacement gaskets. Cleaned the carb thouroughly, and replaced the float shaft and the brass seat and needle that is operated by the float. Left the other jets and components alone. Just got it back on and started. The engine revs to over 2500 rpms and the throttle will not slow it down. I re-checked the linkage and it is hooked up properly. The throttle butterfly was not removed while torn down, so it should be OK. The choke linkage also works as it should. I tried closing down the screw(needle valve) just below the throttle shaft and that had no effect.

I have a little experience working with engines, but need guidance.

This is my Dad's tractor but he is in a rest home with Alzhiemers and was not any better at mechanic-ing than me. I have the operator's manual but it is no help.

Thanks in advance for any help you can give.


Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2010-12-11          175683

Ulav8r,

From the description you provided, I'm all but certain that you have a bad seal between the carb parts.

Here's a list of possibilities:


1: At least one of the replacement gaskets isn't seated properly, or the carb wasn't assembled properly.

2: You may have damaged a gasket when you installed it.

3: Maybe you forgot to tighten a screw.

4: You may have over-tightened a screw and stripped the threads.

An old friend of mine has a neat little tool for checking this sort of thing. It makes white smoke..much like diesel does when a drip is applied to a hot soldering iron....and the smoke gets sucked in any place there's a vacuum leak.

Please see the link I posted below.

Joel ....


Link:   Engine Vacuum Leaks

 
Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
ulav8r
Join Date: Dec 2010
Posts: 4 Arkansas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2010-12-12          175687

Did not strip any screws, am quite familiar with those! I will be working on it again in the morning and will keep your suggestions in mind.

Thanks. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2010-12-12          175692

I find the handiest thing for finding vacuum leaks is a propane torch like you'd use for soldering copper pipe.

I take the tip off the torch (the O2 mixer part) and with the engine running open the valve and start pointing the torch tip near all the suspect places. If you get to a vacuum leak the engine will ingest the propane and that will cause the RPM's to rise from the extra fuel.

For confined areas I slip a piece of rubber tubing over the end of the torch to make it easier to get into the tight spots.

Best of luck. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
treeman
Join Date: Feb 2002
Posts: 251 Wisconsin
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2010-12-12          175694

Murf...good idea on using propane as a vaccuum leak indicator. I have always used a flammable contact spray. ulav8r...make sure the throttle plate is able to close all the way (look at it in the carb). When it is running, with your hand, close the throttle AT THE CARB. Does the RPMs drop to where they should be? Yes, something is wrong with your linkage or governer. NO, you have a vaccuum leak sucking air. If the throttle plate IS closed all the way but is still reving, it's getting air from somewhere else. The air leak has to be between the throttle plate and the cylinder. That's when you start using the tips you have heard from the other guys here. good luck and post back! ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
treeman
Join Date: Feb 2002
Posts: 251 Wisconsin
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2010-12-12          175696

ulav8r...is all the rust coming from the fuel tank? Is the tank rusty or is the rust coming from the bulk tank? When I am comfronted with this problem in the shop, I will clean the ENTIRE system to ensure the customer is free from future problems. I have seen farmers buy a ATV and find out their bulk tank has rust in it. The carb jets in a ATV are much smaller than their tractors so the ATV suffers the problems. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
treeman
Join Date: Feb 2002
Posts: 251 Wisconsin
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2010-12-12          175697

"Left the other jets and components alone" The problem is those small passages around the jets and adjustment screws are where the dirt will make the most difference. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
ulav8r
Join Date: Dec 2010
Posts: 4 Arkansas
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2010-12-15          175783

This is the original carb, ran fine last year for about 5 days worth of bush hogging. Ran for a day and half this year before the rust clogging the system was found. Loosened the clamps on the fuel filter and broke off the fitting the filter screwed into the carb. Then disconnected the throttle/governor linkage at the carb and the choke cable at the carb. Took off two nuts and dropped the carb off to get out the broken end of the fitting. Split the carb to be sure there were no parts of the fitting inside. Used carb cleaner to remove soot and flush out all passages. The governor spring and and connections were not touched. Then reassembled and installed, ran too fast.

When I get back to it, I will pull the carb again and re-check everything there. Then I will check the governor adjustment. The last time I tried it, I also noticed the the exhaust manifold gasket is leaking, so I will also replace that before it causes further damage.

It seems to me that if there was dirt in the carb it would run rough or slow, not fast.
....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
leejohn
Join Date: May 2007
Posts: 71 Doniphan, Missouri
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2010-12-16          175796

On some of those old carbs. the throttle plates when open all the way can hang up on the intake. Make sure it is in the middle of the intake. When taking the 2 mounting bolts loose you might see if throttle plate shaft turns any. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
shona13
Join Date: Mar 2012
Posts: 32 Western Australia
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2012-03-21          182833

Hi .
Interesting !.
First before starting the engine ie cold so you dont burn yourself with the engine stopped close the throttle that is set it to slow or idle and put your hand around the back of the carburetor and feel if the throttle lever is hard against the idle adjusting screw ,it should be, next still with the engine stopped open the throttle up to max or high and the throttle lever to the carburetor should be fully open and you should be able to push the lever back a little bit against the spring.
I think you know how to clean out the fuel system so i wont talk about that.
This is a start and if you still have no joy let me know and I will tell you how to set the governor assembly.
The carburetor main jet adjustment the one with the knurled knob should be roughly one turn out and the air screw ,the one with the screwdriver slot should be say one half turn out, Warning When you screw the screws in screw in only till you feel them touch bottom dont force them they are only brass and will deform very easily this will give you a start point when the tractor is idling you can fine tune it.
Have fun
Happy days
Hutch.
P.S.
the most commom air leak is the carburetor throttle butterfly shaft if you put you hand around the back and give the throttle shaft a wiggle you will feel the wear I cant afford gas etc I just get a coke bottle full of water and pour it arounfd you will soon hear where the problem is and it is real cheap.
See Ya.
....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



MF135 Zenith Carburetor Problems and adjustment

View my Photos
DennisCTB
Join Date: Nov 1998
Posts: 2707 NorthWest NJ
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2012-03-21          182834

Quote:
Originally Posted by Murf | view 175692
I find the handiest thing for finding vacuum leaks is a propane torch like you'd use for soldering copper pipe. I take the tip off the torch (the O2 mixer part) and with the engine running open the valve and start pointing the torch tip near all the suspect places. If you get to a vacuum leak the engine will ingest the propane and that will cause the RPM's to rise from the extra fuel. For confined areas I slip a piece of rubber tubing over the end of the torch to make it easier to get into the tight spots. Best of luck.


Murf I know this is an old thread but I must have missed it when it was posted in 2010. That is one neat tip !

....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo


  Go Top Go Top

Share This
Share This







Member Login