Hi Experts,
Need your advice !
My Toki 15 (2.5 cc nitro) bought for a 15 class model is giving trouble....
The shaft extender (necessarily required for mounting props)  screws clockwise to tighten on the shaft-stub. However, for starting the engine, we got to flick the prop anticlockwise.
After a couple of flicks, the prop shaft extender unscrews !! No amount of tightening resolves the problem. Even when the engine looks like starting and fires, the shaft extender unscrews and spoils the show ! (I have checked, the screw threads look ok) .

Is there any mechanical solution to lock the extender to the shaft-stub of the engine ? Should I go for welding ??

All ideas welcome !

three things


put thread lock on the shaft and tighten the nut . do not overtighten

use a engine starter,

use a lock nut - with a nylon insert.

most likely - doing the first is good enough.

what plug and how much nitromethane are you using ?

The Toki 0.15 shaft has a hole at the back (look at the back of the engine where the shaft sticks out. Put a thin screwdriver or hardened steel wire in the hole to stop the shaft from moving, put some threadlock and tighten the extender. When it's tight halfway, put the spinner, prop, prop nut and tighten further. Bear in mind, you will not be able to open the extender easily once the threadlock dries up

Thanks for the suggest...
But some things still unclear :
- How can a locknut be used when the shaft extender screws into the engine shaft stub ?
-  Fuel used is a home mixed brew methanol, Castrol and engine additive (the engine did run a couple of times on the fuel mix)
-  Most hobbyists advised me against using an electric starter for so small (2.5cc) engine. The Toki 15 has an adaptation for "pull-start" at the rear of the engine if it is used in a RC car/truck, but I don't have that and it is impractical when mounted on an airframe.

Aero,

The little hole you see in the shaft in the picture is where you need to insert a bicycle spoke or something similar and tighten the extender

These engines can be started with a chicken stick easily, once they're broken in. Till then using a starter will make life a little easier..



these engines do not have great compression but once tuned, they perform just ok ok,  can be good for small builds. Here's is a 2 stroking toki at full throttle. I use home brewn fuel. This engine is running without nitromethane

These engines need a lot of runningin to break-in completely

Girish has mastered these Toki 15s

But why is this thread in Electric Planes?

Thank you everyone for the suggestions.
Fixing (tightening) the prop extender by jamming the rear end of the shaft (using the hole and screwdriver ) and tightening the prop nut has resolved the issue  !  Now the shaft extender no longer comes loose !
I have also changed my fuel (5 % nitro from a Danish brand....) but tuning it is still in process.
All my other components are ready : airframe, radio, servos, etc. Just now struggling with the engine !
(however, I love the struggle, especially when RC-wife is not around !!!)

use 20% nitro and you will love them. These are car engines to begin with. They'll play along well with 20% nitro

Thanks Girish.
I'll switch to 20 % nitro pretty soon.

Hope it'll run better ....