where can I get high performance parts?

Discussion in 'Mechanic and Repair' started by Four C. Landscaping, Dec 25, 2004.

  1. Four C. Landscaping

    Four C. Landscaping LawnSite Member
    Messages: 76

    I have a 48" Ransoms Bobcat with a 12.5hp fb460 Kawasaki that I have decided to turn into a project mower.Meaning that I watch to much American Chopper and American hot rod.I still would like to do the work myself and not have someone else do it.
    I would like to bore out the cylinder .01-.015 over and go to a performance carburetor.I know that it is torque that I would like to maximize so RPM should stay about the same.Any help on part location would be appreciated.This may seem foolish to some but its a project that I will enjoy over the winter.
  2. mikemerritt

    mikemerritt LawnSite Member
    from MS
    Messages: 42

    First, you can't watch too much AC or MG unless the lady in your life says you spend too much time watching the tube. Kaws are not really the top choice of people who modify engines for fun, my guess is the stock parts that are needed are high as hell and the fact that the Kaws are metric further complicates matters. I don't know of off the shelf performance parts for these engines but there could be some out there somewhere. Some simple things to consider would be porting of the intake and exhaust. Maybe some kind of free flowing muffler/header pipe. You sure need a carb that is not fixed jet. Maybe some kind of Tillotson or even an old Carter or Mukuni off of something. Anything that would give you adjusting screws. What about a carb from an fb19 or whatever the model is and run it on alcohol. That would still be fixed jet but it would get the air. I would think getting all the air to it you can and then match the fuel to it. It may be that you can get to the main jet on the carb you have and open it a bit at a time until it is getting enough fuel to match the extra air the porting gave it. A little looking into on the timing is in order. Some of the Kohlers alter the timing on startup for easier starting so this could be an issue with advancing the timing. Timing can play a big part in what you are wanting to do. Timing on some models can be played with by removing the flywheel key and advancing the flywheel a degree or two. Just torque back down and go ahead. I think this engine has a firing module or rectifier system of some sort. All of these things are simple, most reversable and not likely to hurt anything. The alcohol would help keep things cool while your giving some 3 foot grass a hard time. Remember, this thing will only cut what the blade drive system can handle so a Chevy 350 wouldn't help a bit but half of the fun is making it look and sound great whether or not it cuts any more grass. Now you can hop up a push mower with the blade directly on the shaft and cut some serious grass and throw it in the woods at the same time. Here is a link that is good reading on pulling engines though most of it won't directly help you I think there are some forums. http://members.aol.com/pullingtractor/tips.htm Got a Kohler side shaft to hop up, this is your site. One more thing, boring is the most expensive thing to do and will give you the least from it. You would have to go to .100 to see any gain and I doubt much at that. If you going to bore it anyway, the bigger the better.

  3. CCWKen

    CCWKen LawnSite Member
    Messages: 113

    I'll agree with most of what Mike mentions; However, for a hop-up you'll want to bore it out and take a little off the head too. Boring not only increases the cc's but also increases compression. Milling the head will also increase compression.

    To increase torque and keep the rpm near stock, you can increase the length of the intake and exhaust runners. DO NOT increase the the size of the ports--Just remove any flashing or sharp edges and polish.

    If you raise the rpm, you'll need a heavier rod. Off the shelf racing parts for a Kawasaki are going to be hard to come by. I don't know of anyone making them. That's not to say they're not out there somewhere. I'd imagine they'll be high dollar though.

    UNISCAPER LawnSite Bronze Member
    Messages: 1,426


    If you want to make one go, you will need to go to an aftermarket custom piston builder, such as Jans, Weisco, Arias, etc. They will take the specs from your engine and turn one down and forge it. Then take a forged connecting rod, and you will need to do some crank work.

    The best way to give yourself a quick cheap boost is to remove the valves, and match all the ports to the gaskets and manifold with a Dremel tool and a small mirror. Make one breathe better, you will improve alot of things.

    Let me caution you if you are going to run the mower every day. Blades and spindles are onle designed to turn a certain RPM without self destructing. Sure, you can make your machine run faster, but, you will also need to beef up the other parts in order to do so.

    I have what once was a 23HP Kohler, fuel injected, turbo charged, roller cam, roller crank and rod bearings. Lots of special parts, dynoed at over 80 HP. It will red line at 8800. I plan to install it in a Wright stander when I can find one that is wasted enough, I will need to put wheelie bars, high speed tires, and a special transmission, hydro motors won't werk for what I want to do with it. If all pans out it will be the worlds first lawn mower to run a 10 second quarter mile. Ity has been a very long involved and drug our process that hopefully, I can resume in a year or so.
  5. out4now

    out4now LawnSite Bronze Member
    from AZ
    Messages: 1,796

    Maybe check out that Lawnmower racers association and see if they have links or advice. I'm sure a search will turn up the link for their homepage.

    HOOLIE LawnSite Gold Member
    Messages: 3,981

    Oh...I thought this thread was entitled "Where Can I Get High"

  7. mikemerritt

    mikemerritt LawnSite Member
    from MS
    Messages: 42

    I suppose I have thought about the comment against porting and was curious why that wouldn't be a good idea. No doubt, you can maker a screamer out of something with all of the internals etc. mentioned here without porting. We take 5 HP B&S L heads and get all out of them we can without blowing a bundle and sacrificing too much durability and porting is one of the best ways to enhance power for almost nothing. Also, we have dyno'd engines before and after going over.100 bore and the gain is a fraction of a horsepower. I know on an old Ford you can bore it over .080 X 8 cylinders and you have added some cubes but on single cylinder engines the gain is hardly worth the parts.


    UNISCAPER LawnSite Bronze Member
    Messages: 1,426

    If you open port size, you will need to match the cam and aspiration system to the new diameter of the ports to take full advantage of the additional capacities.

    By removing casting burrs, and gaskets that stick down past the aluminum housings, and rouding corners where fuel/air hit as it is comming into the combustion chamber, you add power by maximizing the resources the engine already has without needing more to compensate the larger hole size.

    If you put bigger valves in, you will need a bigger cam with a different overlap, and, ultimately, have to add an I beam rod of some sort. We once supercharged a 4 HP Techumseh by using a smog pump from a 350 Chevy, and had to have a titanium rod made in order to hang together with the added compression. WE also took .120 off the top of the head, and had to countersink holes where the valves opened so they would clear the head. Later we welded a water jacket around the head and used a heater core from a '68 Chevy truck as a radiator. Cooling the heads brought more usable HP because we could then advance the timing farther as needed without melting the piston. For a carb, we used a two barrel from one of the jugs of an 85HP Johnson outboard motor. One ventura was used to flow air, the other let the fuel mixture (Blue Sunoco 260) into the engine. By separating the air from the fuel, we had a better chance of vaporizing the gas mixture and set off a hotter explosion inside the engine.

    I will leave you with 2 statements that my father and grandfather always made.....Speed is money, how fast would you like to go?, and, there is no substitute for cubic inches. Bigger is always better and size defintiely matters.

    It equates to if you want to play, you will have to pay. It is fun to play with these toys, but, when it is all done and over, are you really going to make any more money cutting lawns than you did before all the modifications?
  9. Four C. Landscaping

    Four C. Landscaping LawnSite Member
    Messages: 76

    As an update on progress I have called three different lawn mower racing groups with no real success,four junior drag racing catalogs who seem to only have Briggs and Stratten parts,I am still waiting on a e mail from Kawasaki.The project will go on but the lack of parts will effect the build.There are ring kits for .020 over on the bore and new valves will be installed.Tighten up the engine.The carburetor is still up in the air(new performance carb. or rebuild the old one).polishing the ports will be done.The less restriction of gas and air the better.Since the engine is only a 12.5HP. to start with having pistons made and changing internal parts with one of a kind parts would only make me not want to risk using the mower on the job and blow a engine that would then be trash.This is a first time project so minimal machining will be done this time around.I am still going to look around for more bolt on parts like racing exhaust that I saw on one of the Jr. dragracing web sites that they said might fit and what ever else I can find.
    Thanks to all. your response was great I will let you know what I find.
    Have a happy newyear :D :D

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