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Yard Pro Gtk-20 Puller?


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#1 homebuilder OFFLINE  

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Posted January 15, 2013 - 01:02 PM

Hey, I have our old lawnmower, a GTK 20 yard pro at college with me (going to Kemptville College for Diesel Equipment Mechanics)... every spring we do a sort of fair on campus. A couple buddies have pulling tractors and I want to do mine up so we can put on a bit of a show. I'm having a hard time finding out any info on the tractor at all, other than that it's almost the same thing as a Craftsman GT-18. What are some things I could do to the motor (Kohler M-20) to squeeze some more power out of it? I've already deleted the governor, and I'm planning on milling the heads in the next week or so. Probably going to port it, run dual straight stacks and possible dual carbs. Any other suggestions would be appreciated. Thanks! Zack

 


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#2 A.C.T. OFFLINE  

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Posted January 15, 2013 - 03:00 PM

Some of the pro's will be here soon to help you. I just wanted to say:

 

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#3 boyscout862 ONLINE  

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Posted January 15, 2013 - 04:32 PM

Welcome to GTT. Check out the manuals and photos sections. Some of the knowledgable guys will be here soon.



#4 Dieselcubmike OFFLINE  

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Posted January 16, 2013 - 01:19 AM

Hello zack and welcome! First off if you could post a few pics of it that would be great! :thumbs: I have a few questions for you to better help you out. First off, is there a local club you plan on pulling with for fun? if so id check the rules and see what you can and cant do (be a bummer if you did something and turns out you cant run in that certain class) Some things you can do is lock the rearend so its posi. Also get a set of good ag tires. Carlise makes a good tire especially the older ones. As far as dual carbs im not sure if you can do that on the flat heads? I know you can on stock altered engines in the NQS  series. Other than that since your just running for fun id stay with the setup you have. Best of luck to you :thumbs:



#5 1978murray OFFLINE  

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Posted January 16, 2013 - 08:52 AM

it u are just pulling out of a club. I would mill heads, port motor, make main jet in carb a little bigger, no restrictinve exhaust, port match intake, u could do dual carbs, it will just be harder to tune and wat not



#6 JDBrian OFFLINE  

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Posted January 16, 2013 - 09:07 AM

You should look at the drive train and tires after you get the engine sorted. No good having extra power if you can't put it on the ground. 



#7 JD DANNELS OFFLINE  

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Posted January 16, 2013 - 10:36 AM

I'll second Brians reccomendations!! I have found HP is not so much the issue as having a drivetrain and chassis that will Hookup.

The stock engine running well will pull well,  Most Gt's spin out long before they run out of power.



#8 Guest_rat88_*

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Posted January 16, 2013 - 11:10 AM

Can anyone address the removed govorner issue. I have seen this be a problem with the "lesser informed" mechanics removing or bypassing the govonor for racing on the aliminum briggs twins. It usually ends up with a busted rod or exploded flywheel. I dont know how this will effect the cast iron briggs or kohlers to be able to add any valid information.



#9 homebuilder OFFLINE  

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Posted January 16, 2013 - 09:09 PM

I would imagine it has more to do with whoever's behind the throttle, than whether or not the governor is functional. I know with diesels, once you give them an unlimited supply of fuel, the can rev at up to 1000 rpm per second until they go boom. I think a small gasser would have probably the same characteristics. 



#10 homebuilder OFFLINE  

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Posted January 16, 2013 - 09:11 PM

Oh, and I plan on running atv tires on it, and welding the rear diff up. Possibly turning the motor in the chassis so I can delete the fancy set of idlers that make the belt turn 90 degrees twice and maybe put 2 belts on it



#11 skyrydr2 OFFLINE  

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Posted January 17, 2013 - 05:12 AM

Oh, and I plan on running atv tires on it, and welding the rear diff up. Possibly turning the motor in the chassis so I can delete the fancy set of idlers that make the belt turn 90 degrees twice and maybe put 2 belts on it


That's the best thing to do for power transmission, don't rev the engine over 4500 or someone is gonna get hurt when the flywheel blows up!!! Kohler flat twins don't like to rev, Onans and Briggs rev much easier and seemed to do better reved higher.

#12 1978murray ONLINE  

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Posted January 17, 2013 - 08:45 AM

I would imagine it has more to do with whoever's behind the throttle, than whether or not the governor is functional. I know with diesels, once you give them an unlimited supply of fuel, the can rev at up to 1000 rpm per second until they go boom. I think a small gasser would have probably the same characteristics. 

 

gassers will not run away. the governor does not supply push fuel in like a diesel. it controls your throttle butterfly.  plus diesels can not be shut off once they run away unless u block intake. gassers can shut off quickly



#13 JDBrian OFFLINE  

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Posted January 17, 2013 - 09:15 AM

No governor and no tachometer are a good recipe for a unexpected look at the inside of the engine! I'd reconnect it unless you are willing to risk blowing it up. It's going to be really hard to judge rpms by ear when you are in the middle of a pull .



#14 homebuilder OFFLINE  

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Posted January 17, 2013 - 06:08 PM

Okay. I got the heads off and milled this afternoon after class... Just gotta do some final polishing and (possibly) some clearancing. By the time I got them flat I'd knocked .050 off each of them. Going to get some stainless tube for my stacks on monday, and will be port matching/ cleaning and polishing my exhaust ports when I get the stacks built. Then it looks like I can come up with a reasonable way to put a pair of Mikuni VM34's on it. Since the old motor has over a thousand hours on it, I'm thinking maybe I should break it right down and throw a new set of bearings in it, regrind the valve and redo the rings. And there's a custom billet steel flywheel in the works :) I'll post some pictures as soon as I figure out how :S Oh by the way, I will be putting a tach on it. Oil pressure and temp gauges too.


Edited by homebuilder, January 17, 2013 - 06:09 PM.


#15 Guest_rat88_*

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Posted January 17, 2013 - 07:24 PM

It sounds like you know the lingo, but as stated before... HP wont do you any good if you cant get it to hook. What little I know about the GTK 20 yard pro is it looks a lot like a Roper built GT. Good drive train but built kinda on the light side. The weird way the belt runs may rob a little hp, but I dont think you will have a problem with belt slip. If it were me, I would spend the money on weights and tires and a little less on the R&D on the dual carbs. From what I have seen, they are fairly competitive in the stock twin class.

 

Taking 50 off the heads will boost the compression ( maybe too much). With 1000 hrs on the engine, it will need new rings AND pistons to keep from blowing all of the oil out of it. While your are in there, get a couple after market rods if you are still planning on cranking it to 4000+


Edited by rat88, January 17, 2013 - 07:41 PM.





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