How many RPM can stock GX340 handle?

#1
I have two electric-start GX340s. How many RPM can the stock Honda flywheels and connecting rods handle without failing?
I'm wanting to build a fat tire woods bike and MAYBE remove the thing that shall not be mentioned here.
I'm not wanting to run 8,000 RPM or anything. I don't want to drag race it.
I can make a throttle stop that will limit max RPM.

I don't want to swap to billet rod and flywheel if I don't have to, because I want to retain the electric starting/charging systems.
 
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CarPlayLB

Well-Known Member
#2
3800 RPM is what it is designed for

...and a throttle stop will not limit RPM! That is why we have governors.
 
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#3
Jaymo,
The answer to your question reminds me of a very famous scene and quotation from the Movie "Dirty Harry" staring Clint Eastwood:
"You have got to ask yourself a question- Do I feel lucky? Well, do you punk?"
Maybe someone more computer-smart than I can post the video link to that scene...
Michael
 
#5
Thank you very much for posting that Twid! Scroll to the 1:50 point in the video to see the scene and quotation I was referencing.
To jaymo: Think of the 44 magnum gun as your engine, and the "possibility/chances" of any bullets in the gun as your governor removed. Simply stated, do you want to take the chance to find out?
Michael
 
#6
Yeah, that doesn't work for me.
Several of the parts sites I've visited state that you need to use a Honda flywheel or a billet flywheel for governor removal.
I'm wanting to run about 5,000 RPM with it, while keeping the electric start and charging. function. 6,000 RPM, max.

IS the Honda flywheel only designed to run 3,600?
Seems to me, Honda would design a serious fudge factor into it. They have a reputation to uphold.
i can see the clones easily failing at higher RPM, since they're cheap, Chicom crap.

Not discounting what y'all are saying. I question everything.

Anyway, I wonder how fast I can make my project bike with a TAV and the stock, governed GX340.

I guess I need to try to buy a few more of these engines from work and do some flywheel/connecting rod destructive testing.
They only cost me $25.00, so it's not like I'm out a big chunk of money.
 
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#7
So, how much power can this engine make (with mods), while retaining the 3,600 RPM governor?
Maybe I can make enough power within this RPM range for excellent climbing/pulling while gaining top speed through use of the TAV?

Now, I'm wondering if any new or vintage motorcycle engine flywheels/stators could work or be made to work with this engine.
 
#10
I'll check with my boss next week and see if they have any more available.
I still think I need to graft two of them together and make a parallel twin.
Phase them so they fire about 360 degrees apart.
Would make for a beast of an adult minibike motor.

Anyhoo, no I don't feel lucky. My luck would be the flywheel would grenade and sever my femoral artery.
I wonder if the stock flywheel can be lightened a little bit and dynamically balanced for better durability at higher RPM?

I wonder what thickness steel or Lexan would be needed for a scatter shield?
 
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#13
I drag raced a gx340 back in the mid 90's before anyone really made parts for them. I had a billet rid made but no flywheel. The bike ran about ten years reving somewhere between 6-8000rpm. Then it happened. One day while going for a test run the flywheel exploded and took out pull start housing, could, and a little piece of my cousins leg.
 

CarPlayLB

Well-Known Member
#15
I drag raced a gx340 back in the mid 90's before anyone really made parts for them. I had a billet rid made but no flywheel. The bike ran about ten years reving somewhere between 6-8000rpm. Then it happened. One day while going for a test run the flywheel exploded and took out pull start housing, could, and a little piece of my cousins leg.
Yet you were still OK with encouraging Danny to run his stock flywheel on an ungoverned clone engine...was not even a Honda! I guess that's OK if it's just a "little piece" of his leg! I struggle with your advice Stephen!:doah:
 
#16
Yet you were still OK with encouraging Danny to run his stock flywheel on an ungoverned clone engine...was not even a Honda! I guess that's OK if it's just a "little piece" of his leg! I struggle with your advice Stephen!:doah:
Clones take bites out of ball sacks. Honduhs take little pieces of leg. Tecumseh's make oily windows. Briggs Flatheads just keep running. I SO have this fingered out.

:ban:
 
#17
Yet you were still OK with encouraging Danny to run his stock flywheel on an ungoverned clone engine...was not even a Honda! I guess that's OK if it's just a "little piece" of his leg! I struggle with your advice Stephen!:doah:
Why are you struggling with my advice? It's all there. They all break and will eventually blow without a governor, you just never know when. Not once did I tell him to do it or made him think it was okay. Back when I did it there were no parts made. That engine is sitting on my bench waiting on a billet flywheel, oko intake, and a 32-34 oko flat side.
 
#18
I would love to see this!
I also want to graft three together and make a triple, and I want to make a V-twin out of two.

Too many ideas, to little time and money.
Time for some :hack: and :weld:

OK, if that Honda ran ten years before it shat the bed, I wouldn't be able to complain.
I'm not wanting to drag race it or run 8,000 RPM.
I want to build a two-wheeled mountain goat crossed with a two-wheeled pack mule.
It would rarely ever see 6,000 RPM. Only when riding down the logging roads, to the hunting trails.
Well, maybe also around camp.:pimp:

I'm not trying to be an:asshole: and I don't want to be on the receiving end of the :ban:hammer.
Nor do I want to my engine to :001_9898:all over me.
I enjoy it around here and see a lot of good ideas on this forum.
I just wonder how much RPM fudge-factor Honda built into their factory flywheels.
And, I want to be able to keep my electric starting and charging systems.

Remember, I'm not going to be anywhere near as hard on it as the mini dragbike crowd is on their engines.
I'm looking to build a Rokon without the driven front wheel, with more power and on the cheap.


BTW, that Model 29-2 used by Clint sure was a gorgeous revolver.
 
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#20
I wish I could tell you what the margin of error for the rpm is.
I wouldn't go over 4500-5k on stock parts honestly. And that would be very few and far between. That's just me though. With that said a stock governed gx340 has enough torque that you could gear it to run and pull really well with a 40 series torque converter.
 
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