general tuning questions?

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Jesse002100

Member
May 1, 2010
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Parma Ohio
he again everyone.
i have built two bike in the past few days and both run ok but i guess it called 4 stroking both at any speed unless full throttle sputter one exhaust tip fell off and gave it alot more power and it pulls hard but wont beat 20-25 mph.
i raised the needle one click on the one where the cap on the exhaust fell of and put it about 6 turns out on the mixture screw and it runs better but no where near right.
any basic tuning tips??
i am comfortable drilling jets or closing them and re drilling them if needed i have a dremel drill press and have done this before on my gsxr for tuning.
thanks, Jesse
 
Bikeguy Joe

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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If it was 4 stroking, and you raised the needle and it ran better, you have one **** of a unique carb there. Raising the needle make the carb richer as you should know from tuning your gixxer.....you would also know that that screw is an idle speed screw, not a mixture screw.
 
J

Jesse002100

Member
May 1, 2010
48
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Parma Ohio
well i have never worked on a 2 stroke before and it pulls harder with the needle raised compared to stock height. i thought that my other one is better running with a higher top speed by alot so give it more gas to see if it made it better or worse and seemingly its a bit better,
four stroking in theory is where it only fires once every two rotations and thus is why its sputtering and i though it was because of a lean condition from what your saying it could be both ways?
 
BarelyAWake

BarelyAWake

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Jul 21, 2009
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Usually four stroking in a two stroke is caused by a rich condition...

"unless full throttle - exhaust fell off"

The exhaust "falling off" would lean the mix a bit... but all these somewhat primitive two strokes will four stroke a bit unless under load, if it goes away "full throttle" your prolly pretty close.

Thing is I bet it's mostly this: "built two bike in the past few days" - these 2 smokers run poorly for the first few tankfulls/coupla hundred miles. I'd recommend fixing your exhaust, placing the clip on the second notch down on the needle (keeping an eye on plug coloration ofc) and leaving the carb alone for a while, just ride the bejabbers out of 'em - they tend to sort themselves out after 200 miles or so as the rings seat and everything wears in ;)
 
J

Jesse002100

Member
May 1, 2010
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Parma Ohio
well i thought id pull the plugs on them and post here for opinions.

this is the one were the baffle cap fell off and i raised the needle it seems fairly clean this one has about 30 miles on it

this is the one all stock runs better then the other but the plug seems a bit blacker this one has about 100-150 miles on it

and here they are
 
flybytaco

flybytaco

Metal Molding Madman
Oct 17, 2009
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this is how it should look i'm sure you know but this is from one of my bikes i consider to be tuned well see how its dry
 
J

Jesse002100

Member
May 1, 2010
48
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6
Parma Ohio
well one just took a crap about 5 miles from home. petaled a long way and checked for spark no spark changed the cdi no spark changed the plug no spark.
im guessing its something to do with the magneto? any thoughts or how to check it or service it?
it was all good about 25mph 3/4 throttle then i stopped and it just died and wont start again.
 
J

Jesse002100

Member
May 1, 2010
48
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Parma Ohio
alright i fixed it. the copper spool forget the name in the side cover was broken re soldered it all up with silver solder and now its back running.
 
J

Jesse002100

Member
May 1, 2010
48
0
6
Parma Ohio
thanks... i got the needle 2nd clip from bottom and its best it doesnt 4 stroke execpt when comming off the gas and a bit every few seconds . and the other one is in the stock position with the carb mod small hole drilled in it and it helped idle alot and made it smoother. im learning these 2 strokes slowly but surely.
 
T

Techbiker

New Member
Oct 27, 2009
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My spark plugs were that rich until I rejetted my carb to a 72. My plugs are still too rich so I will move to a 73 and then maybe a 74 jet. Just wait until your engine has a few hundred miles on it, and then play with the c-clip and jets. Good luck.
 
J

Jesse002100

Member
May 1, 2010
48
0
6
Parma Ohio
Techbiker said:
My spark plugs were that rich until I rejetted my carb to a 72. My plugs are still too rich so I will move to a 73 and then maybe a 74 jet. Just wait until your engine has a few hundred miles on it, and then play with the c-clip and jets. Good luck.
Click to expand...
the bigger the jet the richer it is... so you might want to go down a size or two....
 
W

wildemere

New Member
Feb 12, 2008
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Newcastle
With motorbikes, jets are measured in mm.

The HT takes a .65 or .70mm jet.

Dellorto 5mm jets fit. You have to order them by mm not drill size or the wrong ones will arrive.

There is also a cure for 4 stroking I posted here.

http://motorbicycling.com/f4/30-miles-wt-17072-5.html#post179241

A perfect tune up is possible, with no four stroking anywhere.

Like a real motobike,

Even with the stock HT carb.

You want a lean idle, a slightly richer midrange and a fat full throttle for the hills.

Fuel is the main coolant system on small two strokes.

I have achieved this with 2 mm ground of the bottom of the slide, then adjusting the cutaway to 1.2mm or 1.5mm, ( stock is 1.0) then running a 0.65 or 0.70 main jet.

This setup gives 2 full throttle positions, level with the bore of the carb for the flats (lean) and then 2mm more slide travel gives more fuel for big hills, high loads.

A setup like this setup runs clean on the flats then powers up hills.

No 4 stroking anywhere, and good pickup from low speeds.

Its trial and error but perfect tuneup is posible.

No more 4 Stroking ever.

Tune the needle for a nice mid range.
 
S

slowpoke

New Member
May 12, 2010
14
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0
North Texas
Wildemere, if you explained already, forgive me... what's the reason for the ground-down bevel on the end of the carb slide in your mod? Obtw, my motor is a 66cc Grubee Skyhawk purchased 04/01/10 and the carb slide looks like plastic. It's black. I saw on thatsdax website where he has a teflon coated slide reasonably priced, I may order one. I'd like to minimize the 4 stroking. Thanks.
slowpoke
 
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