Honda GX390 Stroker Build
- Thread starter KartFab
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KartFab
Active member
So I went over to Dennis's garage and he milled my piston down 44 thousandths and I have some more parts on the way. I hope to be able to get a lot more accomplished over the christmas break.
Here is a little video I made while I was over there checking out all his go karts.
https://youtu.be/rDhDpHTrKoc
Here is a little video I made while I was over there checking out all his go karts.
https://youtu.be/rDhDpHTrKoc
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Mr. Spindle
Senior Member
..Kart Its' gonna have a kick outta that!!!
Don't kill yourself!
Don't kill yourself!
gman3850
Member
Hey kartfab. I was wondering what length rod they made for you
KartFab
Active member
I want to stress that this was a one off rod that ARC made during one of their batches of rod milling, and that they specifically told me that they wont do this for anyone else, so don't expect to call them and have them do this for you.
ARC made it shorter (I forget by how much- I want to say 50 thousandths?), but after installing the new rod, checking my pop up at TDC, selecting my head gasket, and checking out the compression ratio recommended by my cam, I cc'd my head, and did some fancy math to end up needing to take 44 thousandths off of the piston, putting the piston in the hole 5 thousands at top dead center to get exactly 10.2:1 static compression ratio.
ARC made it shorter (I forget by how much- I want to say 50 thousandths?), but after installing the new rod, checking my pop up at TDC, selecting my head gasket, and checking out the compression ratio recommended by my cam, I cc'd my head, and did some fancy math to end up needing to take 44 thousandths off of the piston, putting the piston in the hole 5 thousands at top dead center to get exactly 10.2:1 static compression ratio.
gman3850
Member
Alright. I was just trying to see the length difference between a stock rod. I am looking at maybe going with the 88mm and a 66mm stroke
Pardon me ..
What is wrong with runnig a stock gx 390 with the gov tied back..
It is 2 or 3 times stronger than a stock 5 or 6 hp engine .it is a honda so it is durable and reliable.
And if you just re gear it i will take off fast and have top end as well..
I am just not seeing putting all that time and money in an already bad *** motor and losing it reliabilty....
Audience of one...
What is wrong with runnig a stock gx 390 with the gov tied back..
It is 2 or 3 times stronger than a stock 5 or 6 hp engine .it is a honda so it is durable and reliable.
And if you just re gear it i will take off fast and have top end as well..
I am just not seeing putting all that time and money in an already bad *** motor and losing it reliabilty....
Audience of one...
Kartorbust
Inmate #627
The govenor gear may end up breaking apart, sending the weights inside of it everywhere, potentially getting into the cam and crank gear, which will grenade the engine. You're better off either leaving it in or removing it completely to prevent such a disaster.
KartFab
Active member
1) because I can
2) one doesn't lose all reliability because of some performance modifications, but one would potentially blow their motor up or gall the cylinder wall if the governor was just "tied back"
3) besides because I can, the goal is increased low end torque and a much higher target rpm. Some engines push upwards of 20hp after these modifications... Not only am I making it more reliable, I am actually making an engine that was otherwise completely useless, work much better. I don't know if I posted it here, but the cylinder wall was shot, and the engine had so much blow by it would not even run past idle under load, so rather than just tossing it, I had the cylinder bored and am going to have a nice little toy to play with this summer.
gman3850
Member
any updates on the motor
KartFab
Active member
1.2 ratio rockers, valve cover spacer, balanced piston,rod, crank assembly, putting it on a Baja warrior mini bike.
gman3850
Member
Where did u get your assembly balanced at. And how much
KartFab
Active member
Nr racing ~100 iirc
KartFab
Active member
Okay, so I am going to start assembling everything now. and im looking at the carb mounting studs on the head. The studs have got to go. I also am thinking how am i goign to remove them? They seem like they are stuck on there really really REALLY tight.
The thing I am putting on there is below
http://www.vegascarts.com/32mm-billet-intake-manifold-adapter-p/inman.htm
Also, wondering what size the thread is and what size bolts to get. eyeballing it, i want to say 8 mm, but who knows about thread pitch.
The thing I am putting on there is below
http://www.vegascarts.com/32mm-billet-intake-manifold-adapter-p/inman.htm
Also, wondering what size the thread is and what size bolts to get. eyeballing it, i want to say 8 mm, but who knows about thread pitch.
bob58o
SuckSqueezeBangBlow
Tighten two nuts together on the stud. Then put the wrench on the back one and turn it out.
There is probably some loctite on them, but that has worked for all my intake and exhaust studs so far.
https://www.youtube.com/watch?v=8qYKMtb3Jpo
There is probably some loctite on them, but that has worked for all my intake and exhaust studs so far.
https://www.youtube.com/watch?v=8qYKMtb3Jpo
KartFab
Active member
okay, when i get home tonight ill have to see about this. Last time i tried to remove them i just felt like i was going to shear the stud. Ill do the two nut thing again, but also spray where the stud enters the block with PB blaster.
KartFab
Active member
got the piston, rod, and crank in last night. Removed the studs. PB blaster really helped with that. also, as an FYI the carburetor bolt size is standard metric (not fine) 8mm. I used allen head bolts and you can get the 25mm length for that specific intake manifold so the threads sit at the same spot.
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bob58o
SuckSqueezeBangBlow
what carb? 32mm? Mikuni? Keihin? knock off?
KartFab
Active member
mikuni tm32-1 gravity fed
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