And you didn't realize this BEFORE you forked over the money ??Well I just bought my first bike
odd ya'd think the katana would want super unleaded but the service manual says regular .And stop paying for octane that you don't need.
The real reason is most likely a K&N air filter, followed by limited fuel flow from a kinked fuel line or a petcock issue.And you didn't realize this BEFORE you forked over the money ??
Alas, this might turn out to be a bad move and not a good first bike choice.
Could be simple or could be a major problem.
I'd first suggest draining the tank and float bowls and then fresh gas with a healthy dose of carb cleaner.
THEN.....other routine maintenance that you SHOULD HAVE insisted on being done before the sale.
Like plugs and valve check.
There always is a chance of something major......like bent valves, stuck rings or a blown head gasket.
Since the tach is jumping around, it could be that the ignition module is going bad......or something like a crank position sensor.
Let's hope not.
Life's lesson: NEVER buy a used vehicle that is not running right....IF you don't have the skills to fix it yourself.......and then only if it is REAL cheap.