Pronounced engine noise and you're discussing mapping and mufflers?

You added incorrect viscosity oil for the Rotax twin in the 1125.
You state you can't find an oil filter.

A sound investment, cheap money, peace of mind...change the oil and filter to definitively eliminate the lubricant as source of excessive engine noise. The below should help.

OIL CAPACITY WITH FILTER CHANGE---3 US quarts
Stock oil filter H-D part # Q1064.1AM
""""""""""""""" Rotax part # RB-X341
K&N oil filter part # KN-556
HiFlo oil filter part # HF564 ( HiFlo one of the finest filters on the market)
The HiFlo and K&N part numbers readily available on Ebay and priced right.

Use a quality conventional non-syn 20W50 your first oil change. Must be motorcycle specific and meet JASO-MA ratings. Most run a quality 15W40 in these motors. A quality 20W50 will quiet the typical Rotax engine racket.
And check the drain plug sealing washer. Replace if required.


18mm x 24mm x 1.5mm
12mm x 18mm x 1.5mm