70cc DAX motor only going 15 mph need help

Skyline PDR

New Member
May 14, 2008
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Hello eveyone, this is my first time posting I hope someone can help. My bike is only getting up to 15mph. I have tried a few things but it still not getting the full power. It is a dax 70cc. It starts up fine but when it gets to full throttle it just seems like it can go faster but something is holding it back. My next thing I guess I could do is clean the carb and gas tank.
 

Ilikeabikea

Active Member
Jan 27, 2008
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Welcome to the forum, You'll like it here. Lots of motorized bicycle enthusiasts. Do you have an inline fuel filter between the tank and the carb? If you don't that would be the first thing I would try. You might try a different plug and plug wire. If that don't work let us know. It'll go faster than 15 mph when you get all the bugs worked out.......................
 

paul

Well-Known Member
Dec 23, 2007
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Kalamazoo, MI
also make sure you do not have any air leaks to the bicycle motor from the carburetor. a way to check that is spray a little starter fluid around the intake manifold where the carburetor bolts on. just a little and if it revs up you know where the problem is
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
Skyline- Welcome to the place.

Places to start- Check your spark plug- should be a chocolate brown, not oily and black or grey/white.

Double check the tightness of the manifold bolts and the carb clamp.

Post back here when you do those things and let us know what you find....we'll get yer' motor runnin'!
 

deacon

minor bike philosopher
Jan 15, 2008
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north carolina
If i were a betting man I would bet on an air leak at the car manifold connection is by far the most common first problem with a build. It would also act as you describe.
 

Norman

LORD VADER Moderator
Jan 16, 2008
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your chain isn't too tight is it? what size rear sprocket you running? your brakes aren't dragging? tires inflated to the proper pressure? axle bearing greased and adjusted so they aren't too tight? also the dax will need to be broken. All of these 2-stroke engines will run poorly until they get about 2 or more tanks of fuel run through them. I'll run about 20 to 1 for the first tank then I go to 30 to 1 after that. My dax engine had 2 base gaskets and I removed them and played with the thickness of the base gasket to make it run bettee along with that you will have to make sure you don't hit the head with the piston.
 

Skyline PDR

New Member
May 14, 2008
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Thanks for all your input. I did everything that yall suggested and you know what the problem was. My air box on the carb was to close to the frame so I put the filter right up against the carb without the box and it was flooding it when I had it throttled. I did not think that the filter could block it that much to make it flood. It is a new motor but I just couldnt resist full speed. The mixture right now is still 20 to 1. Thanks everybody
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
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north carolina
I think all the motors are about the same so this is generic advice... When i broke mine in I ran it half throttle on the flat and downhill and wide open to climb the hills. which made it run wide open about ten to fifteen percent of the time. i seemed to have worked out well enough.
 
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Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
237
63
up north now
Avoid no throttle downhill operation for extended periods..."blip the throttle" once in awhile when going down hill, even after break in. These engines are lubed by the oil in the fuel that is drawn in through the carb. When you are going down hill for extended periods, the engine is not getting much oil.

15 mph is O.K. for a frame mount engine for a bout the first 15 minutes, after that it should be able to pull up to 25 or better, if it doesn't, something is wrong.