Lack of power/bursts of power

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Greg58

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May 1, 2011
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As far as the piston goes I trim just enough to fully open the intake port, you won't be changing the rings and because of the end gap pins in the ring grooves of the piston the rings will stay in the same place.
 
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D.Knight

Member
Apr 18, 2017
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D something is holding you back, my 48cc with minimal performance upgrades will do 30 on flat roads, that's with a 44 tooth rear sprocket. I've trimmed the piston for port clearance, a little porting and a modified stock exhaust . This is with a stock nt carb. I have got 32 out of a different motor using the cns2 carb but got tired of the carb bushing problem.
Thank you to you, and again, crassius for mentioning the simplicity of the whole operation and the parts involved. I put the NT carb on and WOW! There was the power I knew was there the whole time. I had never tried the stock carburetor while the bike was running so I never got a read on it. I had tried the stock exhaust while it was running with performance lowering, so I had a pretty good feeling about that. I'm wondering though, what bushing problem can occur? And which is the cns2?

If you are using a stock head sanding it on sandpaper taped to a thick piece of glass will help seal it. I've had a couple that leaked badly. Check both ends of the crank for fuel behind either cover, fuel means a leaking seal. Also look around the base of the cylinder and the crankcase halves for signs of fuel. One of the most common leaks is at the carb to intake.
Luckily I have some mirror cutoffs laying around so I sanded down the head which solved a small leak. As far as the motor is concerned, nothing looks out of the ordinary, but I'll do a more in depth inspection tomorrow.

As far as the piston goes I trim just enough to fully open the intake port, you won't be changing the rings and because of the end gap pins in the ring grooves of the piston the rings will stay in the same place.
I was planning on taking the intake manifold off with the carb, mark the area that's obstructing the flow with a sharpie, and then take it off. Good to know that I don't have to worry about the rings again
 

Greg58

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May 1, 2011
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If its running good now I would ride it for awhile before doing anything to the piston, if you take off too much it will get out of balance.
 

Greg58

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May 1, 2011
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The CNS carbs use a bushing between the carb and intake to adapt a larger bore carb to the 3/4 inch intake, the problem was some of the bushings supplied were not fuel resistant . I ended up making a bushing out of a copper pipe fitting, the CNS has the choke lever on the handle bars(its really a enrichment jet).
 

D.Knight

Member
Apr 18, 2017
82
1
8
CA
If its running good now I would ride it for awhile before doing anything to the piston, if you take off too much it will get out of balance.
Yeah I'm going to run this setup for while since it seems to be performing much better now.
 

KCvale

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Feb 28, 2010
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Phoenix,AZ
Sure, sanding your head on glass and using different types of head gaskets is all well and good, but meaningless if you don't use a torque wrench to put your head back on.

For the unfamiliar...
A torque wrench is simply a socket wrench with an indicator of how hard you are pushing it.

I just use a <$20 cheapie like this.


https://www.ebay.com/i/252137453352?chn=ps&dispItem=1

I usually remove the Real Skyhawk 66cc head, paint it, and remount it with the slant head plug facing forward.

I torque my heads down 5# at a time in an X pattern with a torque wrench until all the nuts are at 20#.

That is far more than the specs recommend but on the real Skyhawk engines I have done ~100 of, none have had head issues.

If you have a cheapo E-Pray engine, use the same procedure, but I suggest stopping at 15#.
 

D.Knight

Member
Apr 18, 2017
82
1
8
CA
Sure, sanding your head on glass and using different types of head gaskets is all well and good, but meaningless if you don't use a torque wrench to put your head back on.

For the unfamiliar...
A torque wrench is simply a socket wrench with an indicator of how hard you are pushing it.

I just use a <$20 cheapie like this.


https://www.ebay.com/i/252137453352?chn=ps&dispItem=1

I usually remove the Real Skyhawk 66cc head, paint it, and remount it with the slant head plug facing forward.

I torque my heads down 5# at a time in an X pattern with a torque wrench until all the nuts are at 20#.

That is far more than the specs recommend but on the real Skyhawk engines I have done ~100 of, none have had head issues.

If you have a cheapo E-Pray engine, use the same procedure, but I suggest stopping at 15#.
I know what it is, but what are the advantages/ disadvantages to over tightening?
 

crassius

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Sep 30, 2012
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over-tightening a steel stud in an aluminum case will often rip all the aluminum threads out
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
Okay, I thought there was something to it other than the normal reasons
There is, it's a 2 piece combustion chamber!
Fuel explodes in there!
You want those 2 pieces perfectly mated and a torque wrench is the tool to do it.

Sure you can guess it by hand, but why?
It's a $12 tool, and if you have been doing mods to your engine do really want to just guess when you put the final piece back on?
 
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D.Knight

Member
Apr 18, 2017
82
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There is, it's a 2 piece combustion chamber!
Fuel explodes in there!
You want those 2 pieces perfectly mated and a torque wrench is the tool to do it.

Sure you can guess it by hand, but why?
It's a $12 tool, and if you have been doing mods to your engine do really want to just guess when you put the final piece back on?
Well when you put it like that... lol
 

D.Knight

Member
Apr 18, 2017
82
1
8
CA
Alright, I got everything working like a charm. I ditched the boost bottle and there went my vacuum leak and idle fluctuation problem. I did notice that I have significantly less acceleration with the stock carburetor over the "high performance" one. I was thinking of getting a velocity stack for the carb, but I'm having a hard time finding a 50mm inner diameter air filter with an angle. Then I ran into this carb setup. Anyone have any experience or insight on it?

NOTE: I am NOT buying this from gasbike.net, it's on kings motors
 

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KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
I ditched the boost bottle and there went my vacuum leak and idle fluctuation problem.
Good, a boost bottle is just a gimmick add-on.

I was thinking of getting a velocity stack for the carb, but I'm having a hard time finding a 50mm inner diameter air filter with an angle.
A 'velocity stack' hehe, don't fall for any more hype like you did for the Boost Bottle.

Then I ran into this carb setup. Anyone have any experience or insight on it?

NOTE: I am NOT buying this from gasbike.net, it's on kings motors
Gasbike and Kings are the same outfit, Nationwide, and they sell the same stuff.

That's not a bad carb and reed setup, pretty much the same thing this $700 7HP racing engines come with.



That bike did haul butt ;-}
 

D.Knight

Member
Apr 18, 2017
82
1
8
CA
I had a feeling it was a gimmick but I wanted to see for myself, I'm still learning.

How come I've had nothing but negative experiences with gasbike but kings has been awesome? Lol

I can dig that bike, and the reed setup with the carb. I'll definitely be going that route
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
How come I've had nothing but negative experiences with gasbike but kings has been awesome? Lol
Different box movers. Maybe the ones at the kings shipping facility actually know what the parts are.

I can dig that bike, and the reed setup with the carb.
I'll definitely be going that route
I didn't have it long enough to do any accurate tests of RPM's, speed, etc. All I can say is that bike hauled ass.