Motorcycle Repair: 1999 jr50 suzuki kids dirt bike, brownish gray color, cylinder compression

Question
I have changed the spark plug, checked to make sure the restrictors are out of exhaust system but I continue to have power issues when applying a strain or load to the bike.My son is not oversized and the bike preformed well to this point.At high rpm,s while revving the motor it sounds like someone pulled out the choke,the idle is ok however, I have no problem starting the bike I have considered buying a new carb. but thought I should get another opinion.The old plug that I removed looked very dirty but it was an odd brownish gray color, Is there any control on the oil that is injected with the gas? Hope I gave you enough info.// confused in Pa.// Auckerb@aol.com

Answer
Hi Matt,

Is the air filter clean and in good condition?

Has the exhaust been decarbonized lately?

What is cylinder compression?

Hold off on buying a new carburetor. Find the defective part, if any, before replacing parts.

I'll send tech files to your email address.

Respectfully,
Mark Shively