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Discussion Starter #1
I got this old scooter, it was sitting around for a bit from what I could guess....

I threw a new battery, spark plug, and drained the old gas/oil for new stuff.

I was ripping around the block on it for a few days, and all of a sudden it lost a lot of power when i was riding it.

I haven't dealt with many 2 strokes yet, but the new spark plug is starting to look a lot like the old one. all wet and sutty.

I have a suspision that it needs more spark, possibly a new condenser, but I wonder what you guys think. (it's been a few days, and it constantly has less power)

What would cause my scooter to lose all that power? Full throttle used to mean 35kmh-70k now full throttle is 20km to 45 going downhill.

The only thing I've done to it otherwise is tighten the throttle cable, and adjust the idle screw.

So what do you suspect went wrong?

I'll be throwing another battery in it tomorrow to see if the existing one is faulty... it's a 4amp, but I don't see anything in the manual that says what amperage of battery it needs.
Here's a link to the manual. http://www.motorscooterguide.net/Manuals/Yamaha_SH50_Service_Manual.pdf
 

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I don't think you are losing spark, it's likely that you have excess gas......or oil.

The reed valves tend to get weak over time and may need to be changed.
Putting a little carb cleaner in with the gas might help......but I wouldn't hope for too much.
 

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Discussion Starter #3
I don't think you are losing spark, it's likely that you have excess gas......or oil.

The reed valves tend to get weak over time and may need to be changed.
Putting a little carb cleaner in with the gas might help......but I wouldn't hope for too much.
Any idea as to what issues it specifically could be?

it runs the exact same as when I first got it running, except it doesn't go nearly as fast.

I literally just finished ripping around the street when all of a sudden it had a lot less power.
 

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I literally just finished ripping around the street when all of a sudden it had a lot less power.
If the problem is intermittant, then it likely would be restricted fuel flow or a plug shorting out when it gets hot.......or the afore mentioned reed valves.

I would first change the plug and put some carb cleaner in the gas........and when it starts running bad, crack the gas cap open to be sure you don't have a tank venting problem. If there is a fuel filter, change it even if it looks good.

Except for the plug and filter, I am NOT going to tell you to start changing out parts just on a wild guess.
 

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Discussion Starter #6
did you bleed the auto oiler after you drained it?
Auto oiler?

Also. to make it 100% clear. it's NOT an intermittent issue.
 

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I literally just finished ripping around the street when all of a sudden it had a lot less power.
Also. to make it 100% clear. it's NOT an intermittent issue.
Well I know you are trying to make this clear but...........
When it works right sometimes and not others, that is the definition of "intermittent".

So, if your first statement above is right, then it IS intermittent.

As for the oiler question, do you mix oil with the gas or does it have a separate little oil tank ?
 

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Discussion Starter #9 (Edited)
did you bleed the auto oiler after you drained it?
I didn't bleed the auto oiler... but I didn't think that'd effect the engine much... shouldn't the scooter just be running too lean if anything? because it'd be going through an air bubble without as much oil?

By drain the old gas and put in new stuff, I meant disconnected a gas line to the reed valve. therefore removing all the gas from the tank.

also, I disconnected directly from the oil tank to drain that.

What do you think went wrong by not bleeding the autolube pump?

it would've been a pretty small bubble because I drained directly from the oil tank...

My neighbour has a lot of experience with 2 strokes.

He claims it must be the piston rings. but to truly test whether it is that or not, I should follow the compression test measurement on page 2-11.

P.S. Bravada seems to know his stuff here. he or she talks about the purpose of bleeding the autolube pump.

http://www.advrider.com/forums/showthread.php?t=726006

Also, here's a good page about oil pumps.

http://www.dansmc.com/2_stroke_oilpump.htm
 

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Discussion Starter #10 (Edited)
Well I know you are trying to make this clear but...........
When it works right sometimes and not others, that is the definition of "intermittent".

So, if your first statement above is right, then it IS intermittent.

As for the oiler question, do you mix oil with the gas or does it have a separate little oil tank ?
I never said it worked sometimes and not others.

the definition of intermittent is "occurring at irregular intervals; not continuous or steady."

The engine was continuously providing enough power to go 50KmH when needed.

The engine is now continuously NOT providing enough power to go more than 40KmH.

Therefore this issue is NOT intermittent at all.

ALSO - As mentioned above, it does have a separate oil tank. Perhaps you could look more at the manual I have linked.
 

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I never said it worked sometimes and not others.
I am sorry that I misunderstood.
Once it lost power, it has never run at full power again, right ??

I think we've about exhausted the help that we can provide without being there.

If the oiler isn't working right, you might be burning up your rings and cylinder walls.
 
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