Engine Size 48cc Vs. 80cc King difference

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Kielohawk

Guest
I was curious what the difference besides the CC rating on the King 48cc and 80cc engines. I know a big selling point was that there were no stampings or markings on the engine to tell what size it was due to legalities. Are they just bored differently? What is the piston diameter for a 48cc vs. 80cc? I wonder what the top end speeds are for both? I ordered the 80cc engine and I can get up to about 32Mph on flat ground running 25:1 fuel. I weight about 200 Pounds and my bike is prolly around 50 Pounds.

Dan
 
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lotsa_mpg

Guest
The manual that came with my Power king 80 states the following bore sizes. 50 cc=40mm 60cc=45mm 80cc=47mm I know there has been some controversy over the 80cc mill not actually being 80cc and I'm not sure if it is or isn't. My bore size is just a few thou short of what the manual states. The stroke on the 80 is listed as 40mm, but I forgot to measure it before I reassembled the engine. One of these days, I'll have my PK "80" installed and see how it fairs against my Dax 70.

I did pull my engine partially down in order to paint the crankcase and cylinder and I measured my bore size to be 46.95mm. I'm really glad I decided to strip it down before I used it because the piston was installed backwards with the arrow on the piston dome pointing towards the carburetor and the ring end gaps on the exhaust port side. Probably wouldn't have lasted a mile. I guess somebody wasn't paying attention on the assembly line. I almost wanted to keep the backward piston issue to myself for fear that it might trigger a bunch more PK bashing and I really can't blame the seller for this as I couldn't expect all sellers to dismantle every engine and inspect them. But, since it's very easy to do, I think it might be wise to pop the head off any new 2-stroke Chinese engine to ensure you don't have an improperly installed piston. Hopefully, mine was a totally isolated case.

Pete
 
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gone_fishin

Guest
the ring-gap/port thing is crucial, i think...even if it doesn't arrive "backwards" from the factory, i bet a lot of people who've done work on the top-end don't know about that small detail, including myself...i'm gonna have to tear it down to see if i won the 50/50 lottery.
 
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Kielohawk

Guest
Thanks for the info! A few questions. Which way is the arrow on the piston supposed to point? and where should the gap on the rings be?

I have almost 200 Miles on my engine. If anything was backwards, would it be catastrophic right away?

Dan
 
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lotsa_mpg

Guest
The arrow on the pistons in 2 stroke engines almost always point to the exhaust side (the only exception I know of is on the Fugi engines used in Polaris snowmobiles and ATV's where the arrow points to the mag side). I'd feel very confident that if your engine has run 200 miles already, the piston must be installed properly. Depending on the engine type, they will either fail very early with an improperly installed piston....or on some engines (this comes from my experience with some vintage snowmobiles) they will run for a long time, but perform terribly. I haven't tried running a backward piston in these mills to see what would happen, but my guess is.....a ring would likely snag an exhaust port within the first few minutes....and then the piston and cylinder would pack it in for good.

For anyone removing a piston, be very careful with the c-clips. They are real tiny and tricky to work with....be sure you do the work in a super clean area because the c-clips can go flying across the shop floor when removing them or installing them.....and finding a c-clip on a messy cluttered floor is a real pain (I searched over an hour for one the other day). Technically, you should never reuse a c-clip (even if the engine has never been run). But I took a chance and reused mine as I did not have any new ones and mine did not appear damaged. Also, when installing a c-clip in a piston, it should be installed with the gap facing either the top or the bottom....never have the c-clip gap on either of the sides. Reason being, if the gap is on the side, the constant up and down motion of the piston can eventually cause the c-clip gap to become compressed which will reduce the diameter of the clip and allow it to dislodge itself from the groove in the piston.
 
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lotsa_mpg

Guest
Just a footnote to my previous post. Here's a fun prank you can play on one of your buddies if they've just had their engine apart and put it back together. Find yourself a small c-clip similar to the ones used in the engine...then place it somewhere on the same workbench he/she was using to rebuild the engine. They will eventually stumble upon it and in panic, tear apart the engine again to install the c-clip they thought they'd forgotten. It works almost every time.

Pete
 
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prowler

Guest
piston orientation?

I know that I'm new to this board and not all that familar with these engines, but I'm wondering regarding piston arrow direction? Over the years I've seen them point toward the flywheel or exhaust port or rotating direction (or even front of the vehicle?) depending on the manufacturer. Are you sure that the piston arrow on these motors is not supposed to point in rotation direction? Some motors it just doesn't matter. Not sure on these, never had one apart.
 
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lotsa_mpg

Guest
You make a good point, prowler.....as every manufacturer is pretty much free to stamp their arrows any which way they want, however, I had to assume that mine was backwards because of the ring end gaps being in the wrong place with the arrow pointing at the carb. I jut could not see that working.

Pete
 
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OldPete

Guest
Good info lotsa,
One point. The C' clip's opening faces down because the piston accelerates and decelerates much quicker from TDC than BDC...Think about it. I have installed automotive pistons that use internal snap rings and have rounded their external edges then used it after loosing a C' clip.

1633_snapring_2.jpg


Internal snap ring facing up.

If the barrel if off a new engine, be sure the sharp port edges are broken with a bit of 220 wet or dry. This just ensures a ring does not slightly snag the port. The edge is just broken, like a dull razor, not rounded at all.
 
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OldPete

Guest
lotsa_mpg said:
Just a footnote to my previous post. Here's a fun prank you can play on one of your buddies if they've just had their engine apart and put it back together. Find yourself a small c-clip similar to the ones used in the engine...then place it somewhere on the same workbench he/she was using to rebuild the engine. They will eventually stumble upon it and in panic, tear apart the engine again to install the c-clip they thought they'd forgotten. It works almost every time.

Pete

*wiggles finger* Very poor work practice. Do that to me and I'd Loctite your tool box locks and break off wooden tooth picks in your car's door locks. I have been responsable for the firing of three fellow diesel mechanics (they thought they were) in my 28 years in the industry.

I had a guy weld my lunch box to a bench. He liked sneaking into the foreman's office. So one day a bunch of his victims nailed the door shut with him in there...Worked! :D

Hurt fellings and broken trust run very deep and your so called buddy will get even...Betcha. :cool:
 
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