Gx200 clone (S170F) block preparation advise?

#24
Hey... Thanks, Ole4!

So, I did go with a PWK24 style carb/intake setup.

Also, I got the head roughed in as far as porting and started roughing out the combustion chamber.

Which lead to me ordering a new ducar 14cc 27/25mm bare head casting. The 14cc suggestion is appreciated!

Also, received some flat faced stainless valves. And, I ordered a .027 70mm predator mls gasket. If there is a dowel pin discrepancy, I need to drill the castings now to use the most easliy avaliable parts anyway.

Piston in the hole is undetermined still. Just received some plasti gauge for final check before reassembly. I suspect it to be .020 or flat. Original as disassembled was slightly out of the hole, to my surprise. I do not know how much. It caught my 6 inch stainless machinist ruler, and I tore it apart.

Any other suggestions are welcome! Thanks.
 
#26
what are you doing to the head? What are you doing to port it? Is it a 22cc head with a bathtub chamber?
Originally, it was a 22cc. I started cutting around the valve seats to unshroud them a little and realized this was quickly gaining cc's. To be enough to warrant some milling to salvage compression.

So I backed up, and will start over with the 14cc casting. No local machinist, outside of industrial only settings locally.

I was working on widening the intake port floor to match the bowl width and smoothing out the sharp lines on the roof, walls and inside radius at the valve seat. The rest was just general blending and straight lining walls.

The exhaust side, I tried to ramp the bowl roof into the port casting with a gentle curve. As in, each side of the valve guide blended into the port roof. I did not raise the roof, I may have slightly widened the roof of it, but only because of my bit size.

Mainly because after working the inside radius gently to remove the square edge, I could see the entire valve seat through the port. Again, gentle straight line blending of the port into the bowl.

Both ports had some material removed from the port side, in front of the guides also.

I did not get past roughing it all in with carbide reamers. Before deciding to go to a 14cc casting.

I also picked up a much smaller set of 6mm dremel carbide bits as most of my stuff was too large to work comfortably. Death grip cramps.

This 22cc head will go on another motor after I locate a machinist. Into the "later" pile, with it! 17118374567722472879883732534425.jpg 17118375960661980894960389934342.jpg 17118376566506956250906756438221.jpg 17118377263934117354981158619184.jpg 17118377693705076426326866287004.jpg

This is where I stopped. Funny how choppy the grinding looks in the light.

Anyway, to give you an idea of where I was working.
 
#27
Head mods otherwise...

Stainless 27/25mm flat face valves, valve stem seals on both, aluminum retainers, automotive style keepers, lash caps, 26lbs springs, champion style forged rockers, pushrods to be determined, black mamba jr camshaft in hand.

No three angle, would cost too much in my area to justify.
 
#29
You went a bit overboard with your valve unshrouding.
Thanks again, Ole4! I greatly appreciate the tips.

Unfortunately, I have no experience with these gx styled engines. And I am left to my own devices...sheesh! My gut told me to order another casting. Secretly... I think I wanted to see if it would punch through. Ha Ha! Maybe I will drill probe it just to learn something. Or use it in a ultra hot setting/timing experiment sometime.

The work I was doing, I believe, came to negate my end goal. I am targeting 2000-6500 rpm. 20" tire, CVT, mini bike. Left side chain. Undetermined gear, just like the pushrods.

Thanks for the input!
 

Davis

Well-Known Member
#30
Thanks again, Ole4! I greatly appreciate the tips.

Unfortunately, I have no experience with these gx styled engines. And I am left to my own devices...sheesh! My gut told me to order another casting. Secretly... I think I wanted to see if it would punch through. Ha Ha! Maybe I will drill probe it just to learn something. Or use it in a ultra hot setting/timing experiment sometime.

The work I was doing, I believe, came to negate my end goal. I am targeting 2000-6500 rpm. 20" tire, CVT, mini bike. Left side chain. Undetermined gear, just like the pushrods.

Thanks for the input!
@ole sells heads check em out.
 
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