go kart engine mod

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Converting a honda gx390 head stock size valves to a big valve head w/ increased compression.First, clean, prep, and preheat.  Then add filler. Attached Images
Reply:more filler added need to make sure there's enough. Attached Images
Reply:leveling everything off Attached Images
Reply:mill deck,  guides prepped, porting complete, seats opened and cut, checked with  blue. Attached Images
Reply:Looks good, did you give it a port & polish too?If you don't want to stand behind our Troops, feel free to stand in front of them.
Reply:side by side mod vs stock.  Just add carb, cam, exhaust, valve train, and that's pretty much it. Attached Images
Reply:How much were you aiming to bring up the compression? Stocks 8.2:1 so go for 10.5 or so?Whats the rpm range the modified engine is going to run?
Reply:Originally Posted by SWellsLooks good, did you give it a port & polish too?
Reply:Originally Posted by Crash5291How much were you aiming to bring up the compression? Stocks 8.2:1 so go for 10.5 or so?Whats the rpm range the modified engine is going to run?
Reply:This is not the modified head pictured above but is more or less the same when finished.   stock unported versus ported.Last edited by olajoe808; 01-27-2013 at 02:52 PM.
Reply:You haven't only increased the compression with that welding, you have also created a squish area opposite to the spark plug. It has reduced the distance the flame has to spread from the plug during combustion, and the turbulence it creates helps the flame spread faster too. Should make a nice improvement over simply machining the head to increase the compression.Don't forget to give us a report of how it runs! And I'm a bit curious about what changes you need to make in the ignition setting too.
Reply:Hi son,i don't give reports , but i do aim to provide the best bang for the buck .  If you search the www you'll find the cheapest bvh with a similar configuration will run you $300+ dollars.  But at that price you'll be limited on flow and compression without needing further extensive  work done to increase performance .  When I did give reports, I got tired of it quick, it wasn't for me and finished my elementary education when most people would have begun to have their first experience behind the wheel of a car .  But fwiw, when I was younger I had known a guy that would walk around with a college diploma shrunk down to a wallet size so he could carry it around and show everyone .  That sort of srtuck a nerve with me, if he could do it surely anyone else could .  This project is something that anyone with the means to weld can tackle.  Would make a nice project for all ages.  And the specific tooling is not entirely necessary as local automotive shops can address those needs, albeit at a price.  Just don't let them bully ya... Thanks for commenting.Cheers
Reply:The build up looks good, I just hope that the crocks werent being worn while welding.  Could cause the toes to get alittle warm. lolJobSmart MIG125Lincoln AC225-SLincoln Pro-Mig 175Dewalt GrindersRidgid ChopsawIR Garage Mate CompressorAny thing worth doing, is worth doing right.
Reply:Is it the stock seat just been re cut and opened up? Your in risk of the seat falling out. Because the head has been heated up and now the seat loose. Not good. Won't be pretty when it falls out at 8k. I'm hoping nobody bought your head. Because they just got screwed. Also the welding needs to be grind down some more until it blends and has a nice radius and it's smooth like a baby's bottom.
Reply:Originally Posted by Pulling123Is it the stock seat just been re cut and opened up? Your in risk of the seat falling out. Because the head has been heated up and now the seat loose. Not good. Won't be pretty when it falls out at 8k. I'm hoping nobody bought your head. Because they just got screwed. Also the welding needs to be grind down some more until it blends and has a nice radius and it's smooth like a baby's bottom.
Reply:I recognize that head design. Looks the same as the Honda power equipment I keep fixing after my dad get ahold of 'em.What would that mod do for a 5KW genset? Or a riding mower?Be wary of The Numbers: Figures don't lie,. but liars can figure.Welders:2008 Lincoln 140 GMAW&FCAW2012 HF 165 'toy' GTAW&SMAW1970's Cobbled together O/A
Reply:Well it might do this to your riding mower but I doubt itMillermatic 30aMillermatic 210Miller thunderbolt 225 ac/dc/ccMiller HF15-1-wg tigLincoln ranger 10(honda powered)Cebora 175 mig Too damn many tools but oddly not enough......
Reply:Oh and by the way olajoe, nice work!Millermatic 30aMillermatic 210Miller thunderbolt 225 ac/dc/ccMiller HF15-1-wg tigLincoln ranger 10(honda powered)Cebora 175 mig Too damn many tools but oddly not enough......
Reply:Originally Posted by cowboy181dWell it might do this to your riding mower but I doubt it
Reply:Originally Posted by mike837goI recognize that head design. Looks the same as the Honda power equipment I keep fixing after my dad get ahold of 'em.What would that mod do for a 5KW genset? Or a riding mower?
Reply:Originally Posted by ironmangqYup, the GX390 is used in a ton of stuff, all the GX series heads look about the same and they are about as universal an engine as you can find. Riding mower would benefit the most (think Tim the Tool Man Taylor in his prime). The genset wouldn't gain a whole lot as spinning it faster will really cause issues with the electronics, they need to spin at one speed to put out a good power source at 60hz, faster or slower and your going to have problems.
Reply:Nice workNow, lets see what this motor is going in
Reply:I do not see the mistake with "too big of an engine on a lawn mower" ?miller syncrowave 250hobart handler 140home made 400 amp engine driven in progress...
Reply:Originally Posted by jdchmielI do not see the mistake with "too big of an engine on a lawn mower" ?
Reply:Why change any pulleys on the new motor ? was it not that same RPM governor?miller syncrowave 250hobart handler 140home made 400 amp engine driven in progress...Same pullies all around. The 36% more powerful engine operated in a much lower rev range to produce sufficient power to get the job done. That meant that the transmission gearing was 'all wrong'. And the power pulses (remember that a 1 cylinder engine is producing power for 1/2 of a revolution out over every two) caused the mower drive belt to jump as soon as there was any misalignment or loading.Like I said, the basic engineering on the engines was nearly identical. The only real difference was the larger engine had pre-tapped holds for 3/8-18 bolts and the old engine had smooth holes for 5/16 bolts. The drive pully and PTO clutch slide on and bolted up wonderfully! Even the choke and throttle cables located within an inch on both engines.Be wary of The Numbers: Figures don't lie,. but liars can figure.Welders:2008 Lincoln 140 GMAW&FCAW2012 HF 165 'toy' GTAW&SMAW1970's Cobbled together O/A