Reversed top end, running

good vibrations

good vibrations

New Member
Just wanted to show everyone what I've been up to. Reversed the top end and cleand up the ports a little better than I did the last time I was in there. Still runs good. Not sure if it's the cleaning or the reversal, but man, she really goes now. Here's some video, enjoy! YouTube - v_00126 - Copy.avi
.xx.
 
I just watched your video....Ya done good...How did you get the sprocket to run in the right direction????? The turn signal deal is cool.....Just kidding about the sprocket thing,lol.....
Cool bike....
 
stuartracing said:
I just watched your video....Ya done good...How did you get the sprocket to run in the right direction????? The turn signal deal is cool.....Just kidding about the sprocket thing,lol.....
Cool bike....
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Norm has a thread on the reversed top end it gives good info. Unfortunately, I had to turn mine back around. Caught a ring. I even turned the piston around like yer supposed to(proper wear, ring port alignment) and it still hung up. I think it has to do with port position. I believe Norm ended up turning his back around as well. Honestly, I think it's a crap-shoot on weather it will work or not. It ran great till' that ring hung.(Might a been 'cuz I was racing a rukus and was close to red for too long=)) I got the turn signals from rite-aid, 8 buks I believe. In the bike section. Did you know that rite aid has a bike section? It also has a running light in the middle that I had rigged up as a brake light, but I broke the switch. I'll show everyone that when I get it hooked up again. I also wanted to mention that if any one has the thumb shifter for their clutch, I can tell you how to fix the ratcheting mech. inside so it doesn't snap in. It wont lock anymore, but yer not gonna burn up yer clutch either.
 
If you do this to a new engine that has not been broken in yet, there should be a lot less chance of a problem. Perhaps the top ring hung up on the port because of a sharp edge or too large a hole that let it ride out of place. Did it sheer or jam into the cylinder wall, or snap and leave debris in one of the ports?
 
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How did you know the ring hung up,did it break a ring and stop the engine or make noises and did you have to replace the ring?
 
i did that to mine back in december: http://motorbicycling.com/f38/backwards-engine-experiment-1939-colson-13458.html.

haven't had any problems with rings yet and i beat the h3ll outta this bike. it's got a few thousand miles on it, and it screams along at 45mph+.

i started with a brand new grubee starfire gt4, and it's still going strong.

i've got another build planned with another gt4 reversed, that's how much i like it.

hopefully, i won't have any probs with that one, either.

on yours, what kind of motor did you use, and was it new?
 
The motor doesn't care which way the cylinder is pointed, it's just a dumb machine it doesn't know any better. Racers have been doing this for years on 2 strokes. They'll even run backwards if you bump start them the wrong way.
 
ruppster said:
The motor doesn't care which way the cylinder is pointed, it's just a dumb machine it doesn't know any better. Racers have been doing this for years on 2 strokes. They'll even run backwards if you bump start them the wrong way.
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That's not entirely true. Because of where the rings on these things sit, you have to make sure that you turn the piston as well. That being said , the edge of the ring still has the tendency to hang up because because of the difference in port height. As far as the thing litteraly running backwards, the magneto would have to be reversed in order for it to fire. Otherwise it would try to fire on the exhaust stroke, no go. If it were able to run backwards, I would have figured out some way to mount that sucker by now=)
 
Yes the ring gap has to clear the ports but it doesn't make a difference which way the cylinder is pointed. Yes 2 stokes will run backwards but the timing will be off but they can and do run backwards. That's how bombardier's and Polaris' (borrowed from ski-doo) reverse system works, the motor runs in reverse so there's no need for heavy extra gears.
 
Is the piston the same on both sides?
Are the rings lower on one side than the other?
Or are they the same height on both sides.
 
Cabinfever1977 said:
Is the piston the same on both sides?
Are the rings lower on one side than the other?
Or are they the same height on both sides.
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Well, again I say it's a little bit of a c**p-shoot on weather it works or not. Were talkin about ht 2strokes here. We all know about the QC over there and that I'm sure is a determining factor. This particular motor, when the pipe and the carb are removed, you can see jus the slighest bit of the ring gap mark inside of the ports. Not alot but it's there. Doesn't matter which way or combo I try to use. I did some VERY mild porting but I suspect it was that way to begin with. So, on my particular ht, when the jug was turned, the leading edge of the ring was exposed just enough to hang up at the top of it's stroke.Also, my piston has two rings on it. Someone posted earlier something about one ring? Do they come with one ring?
 
I have the 48cc Skyhawk made in 2009, from Bikeberry. It has 2 rings. My mistake.

I wasn't trying to play april fools.

It has 2 fat little rings that you can remove with your fingers. They have tiny little guide pins set in the piston too, to keep the gaps staggered.
 
cabinfever, it's where the ring guides are that matters. if you take a look at a piston, there's the two little pins where the ring gaps go. it's not the same orientation if you turn it around.

on my engine, it actually looked like the ring gaps wouldn't be in the ports when i reversed it, but they were close. after reversing the piston, they had plenty of clearance.

like good vibrations said, it may be a crap shoot. it works great on my engine, but i haven't tried any other ones to see what the clearance is.

on another note, i have "fakied" my bike and bump started it backwards, but the engine still started forwards. weird. but i'm glad it did. i woulda hated to flip over the bars with my bike behind me...
 
happycheapskate said:
I have the 48cc Skyhawk made in 2009, from Bikeberry. It has 2 rings. My mistake.

I wasn't trying to play april fools.

It has 2 fat little rings that you can remove with your fingers. They have tiny little guide pins set in the piston too, to keep the gaps staggered.
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Mine are similar, only there's no pin to hold them in place. There's a dot imprinted on the side of the piston were the gap lines up, otherwise you can't squeeze them far enough into the channel to get the piston into the cylinder. I also forgot to mention that this may happen again even with the jug in the right direction. So far, so good, but the way those rings are held in place seems prone to failure anyway after so many miles of wear. CONSPIRACY! Kiddin'. There's no conspiracy..... I KNOW there out to get me.=) xx.
 
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