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Dose any one have Blueprints cut out picks parts diagram for the 40 cc 4 stroke clone and or how how close it is to a real Honda in design
the honda gx35 runs a wet timing belt the pocket bike engine is a push rod engine but they use that engine on all kinds of stuff little post hole diggers portable water pumps and such.
 

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Discussion Starter · #42 ·
the honda gx35 runs a wet timing belt the pocket bike engine is a push rod engine but they use that engine on all kinds of stuff little post hole diggers portable water pumps and such.
Thanks I got out of small engines right as the the mini 4 stroke was being interduced to the market ...so have not had the pleasure of working with to many .....that information helps a lot knowing it's (OHV)vs(OHC) completely different
 

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Discussion Starter · #43 ·
Sounds great, it’s about time people try to make gains on those small 4 stroke engines. And not only put on an oversized exhaust and the biggest carburetor they can find.

I’ve been porting twostrokes I used to never touch the 4 stroke engines.
But now I had a lot of small 4 strokes that I’ve been fixing and then selling.
So naturally I’ve been like a sponge about 4 stroke porting and trying to get as much knowledge as possible.

I have a few heads with bent valves. So I’ve ordered new valves, and I’ll do some porting.
Mostly blending for now, I’m also interested in filling the intake with jb weld in the right spots, I’ve heard that on some small 4 stroke engines the intake volume are too big and they benefit from making it smaller and not bigger as most seem to do.

Without a flow bench and knowledge for the different data you get from that, then trial and error will be my only bet.
Not sure if I have 3 heads unfortunately, cause it would be fun to see the difference if

one is only blended and casting errors is removed,
one with blending,removing casting errors and making intake volume smaller
and last head with blending, casting errors and making intake volume bigger
Then test them all and see which performs best
You say you have a few heads with bent valves ?
Do you know why that happened? Was it something modified or is this a common problem???
 

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Discussion Starter · #45 ·
it has a weakness the plastic cam gear but all so an advantage of being easy to change the shape of the lobe
Got you. so plan on reinforcing and make the cam gear adjustable wile I'm their......and as (always check value clearing with the piston when altering valve timing lift our in any other way for any one trying this a extra 15 minutes of work will save you money and a week of shipping )!
 

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What's your poison? Mine is 40:1
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Interesting because I have been waiting for someone to post (in my area ) a 4 stroke, and I wanted to scoop.it up for tests, stock, then a few mods, see where I end up. Only because thats what most people have these days.
 

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This should answer a lot of questions just remember there is no head and it is a one-piece design...

Just remember that the genuine Robin/Subaru engine and the china copy although they are the same 4 stroke design the parts will not interchange...
 

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Discussion Starter · #49 ·
This should answer a lot of questions just remember there is no head and it is a one-piece design...

Just remember that the genuine Robin/Subaru engine and the china copy although they are the same 4 stroke design the parts will not interchange...
Thanks and that answers all the ?s about the basic design.... the only ?s left I'll have to answer myself ... but now I have a ida on what things look like I can start planning on modifying
 

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This should answer a lot of questions just remember there is no head and it is a one-piece design...

Just remember that the genuine Robin/Subaru engine and the china copy although they are the same 4 stroke design the parts will not interchange...
Oh yeah. I will "try" to do basic bolt ons. But maybe some easy internal work too.
 

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Discussion Starter · #52 ·
Oh yeah. I will "try" to do basic bolt ons. But maybe some easy internal work too.
Nice I'm going to grab a old o2 sincer from work and try to make a o2 Monitor for less time spent reading plugs ...
ATV....you say you have a tread on the 4 strokes ?? If so we can move this conversation their if you want.

Mr kitty thanks Sadly the Unicase change some of my ideas but Seeing the basic design of the valve train Has given me countless ideas!!!

Somewhere I read that these engines are bad about GRENADINE Somewhere around 9 TO 10 I'm guessing that happens because this of valtrain a Is failure????
 

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Nice I'm going to grab a old o2 sincer from work and try to make a o2 Monitor for less time spent reading plugs ...
ATV....you say you have a tread on the 4 strokes ?? If so we can move this conversation their if you want.

Mr kitty thanks Sadly the Unicase change some of my ideas but Seeing the basic design of the valve train Has given me countless ideas!!!

Somewhere I read that these engines are bad about GRENADINE Somewhere around 9 TO 10 I'm guessing that happens because this of valtrain a Is failure????
Generally they are excellent free spinning high revving engines designed for commercial brush cutters.

The four-stroke engine is actually really good for children riders under 120 LBS.

But yes the plastic cam gear is the weakness as the engine begins to heat up from the load of a heavy Rider trying to go up hills and such the valve clearances in the guides starts closing up putting a heavier load on the plastic cam gear once a tooth snaps off there goes the timing.

I have thought long and hard about modifications for these engines I just haven't come across a running one the only ones I have seen are either working and the owner is not willing to part with it or it already has the striped cam gear with bent valves and such.

The mods are really simple the cam gear is the secret in my opinion and making one on a 3D printer to advance or retard the timing then shorten the open duration to increase compression and selling different cam gears for different applications would be the fun part of tuning of course the 3D printed part would have to be molded/sand casted/CNCed made out of aluminum valve guides would be lightly honed port and polish the flow path then modify or change the carburetor to support the modifications.

Then to make good power you add a CDI to the mix.

The problem is the complexity of the four-stroke engine will make it hard for beginners to repair when things break down. And more advanced builders are demanding 2 stroke pocket bikes mini bikes with the bigger predator style engines Honda or cloned pit bike engines.

With all of that said it's still very surprising to me all these years the four-stroke has been out and there is still zero aftermarket parts for it.
 

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Discussion Starter · #54 ·
Casting an aluminum gear and cam was on my list along with or the lifters as well ... that would also allow to change the ratio of them For either getting more lift Out of the valves or slightly less Is lift But reducing pressure on the Cam gear And making up for the lyft with the Cam lobe ... the aluminum gear might be a bit heavier and not make as much power as a plastic 1 ....BUT MAKING BIG POWER FOR 1 PASS IS EASY! MAKING POWER THAT RUNS THE NORMAL LIFE OF THE ENGIN IS MY MAIN GOAL!!
 
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