This is how you Modify an engine....

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This is how you Modify an engine....

Postby Red-85-Z51 » Tue Jul 29, 2008 10:24 pm

Take a Stock Honda GX-200...

Take off the gas tank.
Remove the flywheel and fan
Remove all tins.
Remove sidecover
Remove head, valvetrain.
Push out rod and piston
Remove crankshaft.

okay, you got a bare block...nice.

Now, pull the governor gear out, and get the little washer behind the gear. Next pull the governor rod, and cut it off at the bend, and put it back in.

Put the crank back in.
Take some 400 grit sandpaper and carefully polish the stock con rod, making sure to smooth all rough edges..finish it off with some 800 grit. Clean the rod in solvent to remove grit.

Next order these parts..

OEM flat top piston
18lb G200 springs
Billet spring keepers.
1.3:1 rockers

Find a 14cc old style GX-160 cylinder head..Clean up the transition between the port and the bowl, massage the shortside radius and smooth it all out, maintain the D shape. Send it off to a shop and have it milled flat, have Stainless vlaves installed, undercut and swirl Polished, 3 angle valvejob.

Put the rod and piston back in...

Put the head on.

Order a Tillotson HL-314G carb, and an EC honda billet intake with pulse fitting. K&N air filter with Velocity stack.

Put the carb/intake on, and use an EC up-pull throttle kit.

Put the head together, valves, rockers, etc..and put it on the block.

Assemble using Studs, or Grade 10.9 bolts. Set valve lash to 0.002" on both valves.

now put the sidecover on.

Find a GX-160 flywheel, itis set for 4* timing advance. Take the plastic fan, and cut off every other fin.

Put the flywheel and fan on.

Cut the wires off the oil alert.

Set coil gap to 0.015".

Install recoil.

Order a Mikuni Round body pulse fuel pump..

Install it, using 2 bolts to the bottom of the lower cylinder shield, with the pulse side to the fin, and the outlets to the carb side. Inlet to the PTO side.

Now run some thick walled fuel line (transparent) to the pulse fitting, fuel inlet, and run the last one to your remote tank.

install a chainguard/clutch guard.

Lastly, install an RLV 12" Open header.

Run 93 octane fuel...

There you have it...I just built this monster...Hope to run it this weekend on my old Emmick Flat Kart. Ill grab some pics of the engine and Kart when it's all together.

Oh, and run a race oil...Im using Briggs/Valvoline Kart Racing oil.
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Postby nvmyengine » Wed Jul 30, 2008 5:16 pm

and the grand total is?? ha sounds like it will run like a rapped ape
my rides-
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can you believe that i have over 2000 posts
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Postby Red-85-Z51 » Wed Jul 30, 2008 7:23 pm

Total cost to this point in about 500 bucks just on the engine.

Power output should be in the area of 20-25 around 4800. Ive got the Digitron GT-52K tach on it with the warning lights set to o come on at 6K. I can also monitor engine temp..Im shooting for 370
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Postby hitm4n666 » Thu Aug 28, 2008 11:23 am

hmmm lol this sounds fun were do i order all these parts off? and do u have any pis of the engine?
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Postby theo » Thu Aug 28, 2008 7:01 pm

Have you tried the engine Red, how did it go?
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Postby hitm4n666 » Fri Aug 29, 2008 8:48 am

yea i read in soe post that he already blew the engine
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Postby Red-85-Z51 » Sat Sep 20, 2008 10:15 pm

hitm4n666 wrote:yea i read in soe post that he already blew the engine


Close. The rod bolts didnt hold torque, started rattling with the kart still on the bench...stopped it before it got too bad. But I confirmed that the valvetrain is right, compression isnt too high, and the intake is perfect...

Billet rod and flywheel are on their way down VIA Fed-Ex right now.

Total cost for the engine has now jumped to nearly 900 dollars however...But now there isnt much else that can break, except for the crank and the block...so it should be fun.

It was nice when it ran though, throttle response was crisp, the Tilly will take some time to get used to...but it will be the best in the long run Im sure.
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Postby kliff » Wed Mar 17, 2010 6:42 am

I know this is digging up the past, 6 months back...but whasssup? New rod & crank, how'd she run? How has she lasted, longevity??

Where you buying all those parts?
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Postby Red-85-Z51 » Thu Mar 25, 2010 9:13 pm

kliff wrote:I know this is digging up the past, 6 months back...but whasssup? New rod & crank, how'd she run? How has she lasted, longevity??

Where you buying all those parts?


I could never make the Tillotson HL314G tune in, I could getit close, but never right. I picked up an F200 spec Tillotson carb, and it was slightly better at times, but its a top end carb, it made the engine a pig until about 4000 rpms, then it launched like a rocket...throttle response was weak.

I had it sustained as high as 8200 rpms, for about 45 seconds, long enough to make 1/2 the pipe cherry red, and the inside of the silencer "hold a flame"....motor just gets stronger and stronger.

My plans are to take a step back, and move away from the race type tillotson carbs, and try a 24mm Mikuni slide carb, such as found on dirt bikes.. These are a better all-round carb.

But Im so busy lately, between restoring my old vette, and keeping my old jeep running...Just havent had time to mess with the Karts lately. In fact, I know right now Ive got to drain old gas out of the Invader's gas tank, put on new lines, and clean the carb, before it will even run...its been nearly 1 year since Ive run it.

The Emmick, and its Honda, the carb probably isnt even "workable" at this point, its been sitting so long.
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Re: This is how you Modify an engine....

Postby Pancake » Tue Apr 28, 2020 3:59 am

I'm also studying this subject.
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