Yd100 performance issues

ETHAN5438

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Feb 18, 2019
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My yd100 seems to not want to get to its power band or higher rpms for that matter and has very little low end torque. Did I mess something up? Or do I just need to tune my carb with a different jet?
 
Try moving the clip on the needle down one notch and see if that helps first. But it probably needs a bigger jet.
 
Those YD's are a hit or miss when it comes to power. I've several 66/80cc that are stronger. That said, you might try a #65 jet.
 
Before making any adjustments to the carb, verify that you have good compression and ignition. What is your fuel mix? What spark plug are you using and what is the gap. What does the plug show you about how the engine is running? Is the engine broken in, and do you have good compression? What is your wheel and sprocket size? Check the float level before adjusting the needle or jet.
 
What does the engine sound like at low RPM, does it blurble and 4 stroke? Make incremental changes so that you can identify the corrective cause.
 
Before making any adjustments to the carb, verify that you have good compression and ignition. What is your fuel mix? What spark plug are you using and what is the gap. What does the plug show you about how the engine is running? Is the engine broken in, and do you have good compression? What is your wheel and sprocket size? Check the float level before adjusting the needle or jet.
The engine is pretty new been threw a few tanks at 40:1 using b5hs plug ngk, 36t sprocket. Don’t have a comp testing but the pressure isn’t weak from putting my thumb over the hole and having my friend turn over engine with rear wheel.
 
What does the engine sound like at low RPM, does it blurble and 4 stroke? Make incremental changes so that you can identify the corrective cause.
Slight miss it seems at middle throttle but 3/4 is pretty smooth no four stroking that I can tell
 
The engine is pretty new been threw a few tanks at 40:1 using b5hs plug ngk, 36t sprocket. Don’t have a comp testing but the pressure isn’t weak from putting my thumb over the hole and having my friend turn over engine with rear wheel.
B8hs plug my bad
 
So, if compression seems good, look at fuel and ignition. NGK recommended gap for that plug is 0.6mm (.024"). Check the spark, is it bright and makes a crisp snapping sound? Stock CDIs may not have enough output to make a snappy spark at a wider gap. How does the plug look? Check out the plug chart in the Resources section of this forum and make a comparison that we can see.
 
Even recommended makers make a bad plug from time to time. That one you have is in the wrong heat range, try a B6HS, with the gap set at .025-.028
 
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