Motor hits a wall at 20mph?

BADBOOH

BADBOOH

New Member
Hello, I have a new motor with 115 miles on it, the motor runs great, until it hits 20mph, than it backs off, like it has a rev limiter. I'm running 4oz of semi- synthetic 2- stroke oil to every gallon of 91 octane gasoline. Another MB told me this is to much oil and that if I run a 50/1 mix this problem will go away. Any thoughts?
 
If you go 50:1 i would use full synthetic myself, i know there are people who will say they run 50:1+ ratio without it being full synthetic but I think that could be a little risky with these motors, but I could be wrong so you go with what ever you are comfortable with in this area.

Question: Has your motor run the way you described from the very start or did it just start acting this way?

If it has run this way from the very start I would say there is a good chance that it is running to rich on fuel but that doesnt mean you need to cut back on the oil in the fuel/oil mix, 4OZ per gallon is not a but load of oil so I'm not sure that cutting back would change much but, you can try and see what happens and if it does get better then by golly your friend was right ... but if it doesnt make a diference I say you need to solder up your main jet and then redrill to the next smaller size and then repeat this proccess until it is running in a way that leaves your spark plug a nice lite to medium brown color, if you run it and it looks real white then you are to lean on fuel and this will cook your engine if you run it for very long this way.
 
Last edited:
mapbike said:
If you go 50:1 i would use full synthetic myself, i know there are people who will say they run 50:1+ ratio without it being full synthetic but I think that could be a little risky with these motors, but I could be wrong so you go with what ever you are comfortable with in this area.

Question: Has your motor run the way you described from the very start or did it just start acting this way?

If it has run this way from the very start I would say there is a good chance that it is running to rich on fuel but that doesnt mean you need to cut back on the oil in the fuel/oil mix, 4OZ per gallon is not a but load of oil so I'm not sure that cutting back would change much but, you can try and see what happens and if it does get better then by golly your friend was right ... but if it doesnt make a diference I say you need to solder up your main jet and then redrill to the next smaller size and then repeat this proccess until it is running in a way that leaves your spark plug a nice lite to medium brown color, if you run it and it looks real white then you are to lean on fuel and this will cook your engine if you run it for very long this way.
Click to expand...

Agreed on the aforementioned
 
Look at your plug to determine what the mixture is before making any changes.
Black and oily= too rich.
White or light grey= too lean.
Brown to light carbon/oil is A-O.K.
 
I'm on my way home to check on my carb, however, if my memory serves me, my carb has never opened all the way. I'll have to adjust it. And lean out fuel cause my spark plug is black and oily. Thanks!!!!!! Let you know what I find...
 
OK, unfortunitly its been raining all day. I checked if my carb slide moves completley out of the way when full throttle is applied, and it does. So i thought lets take a look inside the float bowl, when I removed the bowl I found the jet that sits in between the float was not conected to the carb, just sitting there where the needle comes in. I then screwed the jet into place and put everything back together, but havent been able to try her out due to rain. Think this could be the reason for the problem? Since my spark plug is black, I will also lean her out just a little. Thanks!
 
After srewing the jet onto the carburator, instead of just hanging out next to the float solved the problem! BOY does she go now! Unfortunitly the rain made the test ride only last a couple of miles before heading back in the garage, Thanks guys, the 4 stroking link lead me in the right direction to finding what was wrong. Once again THANKS, to all of you!!!!!!!
 
I would screw the jet back in, run it awhile and then check the plug before you change any settings.
 
OK, shes running better now that i have screwwed the bowl jet back in, however, its only a couple of miles per hour faster then the same thing. When I turn off the fuel valve it goes real fast! How would I decrease the amount of fuel going into the engine?
 
Do I need a smaller hole in the bowl jet? and if so how? I was wondering if I should just buy a speed carb from spooky tooth? and if so, could this help?
 
AFAIK, you could turn off the fuel valve partially, thereby reducing fuel going INTO hte engine. seems doable, i dont know if it will help though to be honest. might beworth a try
Aaron
 
Try moving the C clip on the needle up one notch first, check your plug, then let us know what you get.
 
I moved the C clip up one notch, at first a massive improvement, but then this morning, back to the same thing. The plug color is a faint tan, but not white or gray. One more notch? or do you think my jet hole is to large?
 
No crack in the float, and the inlet needle is not sticking. At a lose. Besides this problem she is running very well. Any more ideas would be greatly appreciated. Thanks!!!!
 
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