Was thinking of converting a Ryobi but after reading threads about Echos, went out today and bought 2 used echo string trimmers to convert for 10 bucks at mower repair shop.
My question are:
What size (cc) are these two engines?
Are they worth converting?
Where can I buy prop shaft hubs for them?
1. SRM 2100 in a gray plastic case
2. SRM 302 ALX in a orange metal case alot of trimming will be required.

If they are worth converting will probably remove flywheels and coil and replace with TIM6 electronic ignition from Jerry E. Howell
Thanks in advance for any help/info.

Just checked my book. The SRM 2100 is 21cc . The SRM 302 ALX is 30cc . The 2100 is a little on the small side, But the 30 would work well. They are a quality built engine.