So close, almost right, need advice

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goofyfoot2001

New Member
Aug 16, 2012
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South Carolina
So here;s what I have going on, the bike has great low end all the way up to say 22 mph. low end in fact is lovely and fun especially coming out of corners. However, she only gets to about 25mph WOT and sounds way whiny.

Spark plug looks damn near perfect in color.

I have a Dax RT Carb with #70 jet (I've tried them all and maybe I cleared up a vacuum leak along the way).

Idle is perfect, no racing (I think the vacuum leak was causing that).

I took a close look at the Chinese sparkplug wire as opposed to the one on my mower and man that Chinese stuff is total crap so will replace. Have an NKG sparkplug in it FYI.

Oh and with the original NT or CNS carb I had been getting close to 30MPH but it was an ugly loud 30MPH. The DAX is the bomb power wise but gets lame near the top.

Any Ideas would be welcome.
 
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bigbutterbean

Active Member
Jan 31, 2011
2,417
3
38
Lebanon, PA
50 miles aint broken in, considering these engines get 100+mpg, you havent even run half a gallon through it yet. general rule of thumb is you wont know what kind of powerband you really have until its fully broken in, which your engine is not.
 
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goofyfoot2001

New Member
Aug 16, 2012
75
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South Carolina
It does seem to get better each time I take it out. The hill climbing is much better than I thought it was capable of. Four stroking is annoying at the top end if that is what is actually happening.
 
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bigbutterbean

Active Member
Jan 31, 2011
2,417
3
38
Lebanon, PA
if you have more than one position on your needle clip, you can try adjusting that, but keep an eye on your plug color. Needle adjustment is only effective to 3/4 throttle, so if you are wide open and still 4 stroking, then you need to re-jet. However, if you are still running break-in mixture, wait until switching to regular mixture before adjusting anything. the engine always runs rich during break-in, no way to avoid that. but with probably about only half the oil being used after break-in, it may not run rich anymore. In fact, if you have already adjusted your needle during break-in, it may run lean on regular mixture. just be sure to keep an eye on your plug color.
 
Ludwig II

Ludwig II

Well-Known Member
Jul 17, 2012
5,071
783
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UK
One mechanical safety trick to remember is to use a slightly harder/cold rated plug. It might oil up, but this is better than having a soft/warmer plug cause the engine to seize when placed under load. Ask me how I know.
 
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bigbutterbean

Active Member
Jan 31, 2011
2,417
3
38
Lebanon, PA
I run a slightly hotter plug (most here run a 7, I run a 6), and have had no problems doing so for over a year. As long as you check your plug color and adjust your fuel mixture as needed, there is no reason to say a warmer plug will cause your engine to seize. Now, I wouldnt go any hotter than a 6, but I wouldnt go any colder than 7 either. If you are having problems with 4 stroking, a cooler plug is not the answer. adjusting the needle and/or re-jetting are the best solutions to 4 stroking.
 
Ludwig II

Ludwig II

Well-Known Member
Jul 17, 2012
5,071
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UK
You'll have to excuse me, I'm just paranoid. Years ago I had a 2 stroke seize in the outside lane on a busy motorway, entirely down to the wrong plug being fitted at the dealer's.
 
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ivan H

Member
Oct 8, 2011
622
1
16
australia
I think some people misunderstand the heat rating of plugs. The range is like a scale of the plugs ability 2 transfer heat to the cylinder head, while maintaining the correct operating temperature so as to burn oil & other deposits off. A hotter plug transfers less heat, a colder plug transfers more. A rule of thumb guide is to look at the threaded portion of the plug. If the end 3 threads show blackening from heat, ur using the correct heat range. Cheers
 
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goofyfoot2001

New Member
Aug 16, 2012
75
0
0
South Carolina
I replaced the spark plug wire with a fairly new spare I had from my Volvo (the one from the distributor to the ignition coil) You really do just unscrew the spark plug cable from the CDI. It looks like a common wood screw inside there. The spark plug cap also has a wood screw in it. The screw just screws into the cable end.

I had good uphill torque before but now there are intermittent spurts of real power. There is also some intermittent missing too I think but the power is incredible for a second.

Any ideas how I keep that power goodness? I got a real taste of what these little bikes are capable of and it would exceed my expectations.
 
Ludwig II

Ludwig II

Well-Known Member
Jul 17, 2012
5,071
783
113
UK
Interesting. Have you got a spare plug cap by somebody reliable like NGK to try as well? There's an intermittent contact there somewhere from the sound of it.
 
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goofyfoot2001

New Member
Aug 16, 2012
75
0
0
South Carolina
I replaced the spark plug wire with a fairly new spare I had from my Volvo (the one from the distributor to the ignition coil) You really do just unscrew the spark plug cable from the CDI. It looks like a common wood screw inside there. The spark plug cap also has a wood screw in it. The screw just screws into the cable end.

I had good uphill torque before but now there are intermittent spurts of real power. There is also some intermittent missing too I think but the power is incredible for a second.

Any ideas how I keep that power goodness? I got a real taste of what these little bikes are capable of and it would exceed my expectations.
 
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ivan H

Member
Oct 8, 2011
622
1
16
australia
Hi Goofyfoot2001, have u replaced the bakelite cap that attaches the lead 2 the plug. When I first got my kit I had problems with bursts of good running & bursts of intermittent low power/rough running that turned out 2 b the bakelite cap/plug attachment. I replaced with 1 off an old dirt bike, same design but better quality. Its been good ever since. Cheers
 
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goofyfoot2001

New Member
Aug 16, 2012
75
0
0
South Carolina
I unscrewed tthe cap thing off my lawnmower. Contact isn't the problem. Now I'm thinking maybe its the position of the bowl. the intake extention I had to use puts the carb at an angle slanting forward. So maybe I need to figure out how to bend the pipe to make it sit more level. Maybe going up hils makes it level and gives it the power it should be getting on level ground.. jst woke up fyi.
 
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