90 Sized Pull starts?

[lu wei yao]

Hey guys.

Im now designing and fabricating a large scale heli project.
Need to know if OS (or any other manufacturers) offer 90 Sized Pull start engines.

Better if theres an option or conversion kit for direct replacement on a OS91 SZ.
Design would be similar to current pull-start engine assemblies where pull-start crank directly rotates crankshaft of engine.

Any input welcomed.

Thanx!