Piston doesn't move when spark plug is in

[cloakedvillain]

Most are trying to increase the compression ratio. It's around 6:1 but extreme modding can raise it. I think I've read 7.5 to 1 on here, but Pinocchios are a plenty on the internet.

This is a very stupid question, but with trouble shooting you have to start with the stupid questions: have you tried slipping the clutch? Try experimenting with how far you can release it while still pedalling.

There is always drill starting. I use the Grubee OCDT.

 

[oscar_0]

Most are trying to increase the compression ratio. It's around 6:1 but extreme modding can raise it. I think I've read 7.5 to 1 on here, but Pinocchios are a plenty on the internet.

This is a very stupid question, but with trouble shooting you have to start with the stupid questions: have you tried slipping the clutch? Try experimenting with how far you can release it while still pedalling.

There is always drill starting. I use the Grubee OCDT.

I tried drill starting it and it almost worked, I smelt burnt petrol. I tried again and I stripped the bolt a little bit, the drill was making screeching sounds so ill have to change the nut and try again.

 

[cloakedvillain]

No no no no. You need a freewheeling driver. Once the engine starts the the engine will start loosening the magneto nut.

 

[oscar_0]

I got the engine running with the drill, I will be purchasing a pull start soon.

 

[ImpulseRocket]

I got the engine running with the drill, I will be purchasing a pull start soon.

Those pull starts are notorious for breaking on standard engines. They are guaranteed to break if you have done anything to increase compression.

 

[oscar_0]

Those pull starts are notorious for breaking on standard engines. They are guaranteed to break if you have done anything to increase compression.

Then how should I start my engine if I can't pedal to start it?

 

[ImpulseRocket]

Then how should I start my engine if I can't pedal to start it?

Figure out why you can't pedal start it, and if it is because the compression is so high you may want to look into dropping the compression ratio. It also may be just your technique for pedal starting. Jackshaft kits are known to be harder to pedal start due to all of the added gear reduction in the system. What gear are you trying to pedal start in?

 

[oscar_0]

Figure out why you can't pedal start it, and if it is because the compression is so high you may want to look into dropping the compression ratio. It also may be just your technique for pedal starting. Jackshaft kits are known to be harder to pedal start due to all of the added gear reduction in the system. What gear are you trying to pedal start in?

I tried the lowest gear and it didn't help, surely there shouldnt be a problem with the compression because the engine ran normally.

 

[ImpulseRocket]

I tried the lowest gear and it didn't help, surely there shouldnt be a problem with the compression because the engine ran normally.

Being able to run, and trying to start it with pedals are 2 different things.

On a direct drive setup with say a 10 front and 44 tooth rear, you are translating your foot power through the pedal sprockets to the wheel, and that wheel rotation then applies torque through the 44 tooth sprocket to the 10 tooth, through the 82 tooth clutch gear to the 20 tooth crank gear. That pedal - wheel - driven sprocket - drive - engine setup gives you a lot more mechanical advantage over the engine. Plus, with your weight on the bike adding momentum to the force trying to turn the engine over.

Jack shafts cut out the pedal sprocket drive ratios and the mechanical advantage they offer with the rear wheel radius acting as a lever arm, so you are losing a lot of assistance with starting. You are using your pedal RPM directly from the chain ring driven sprocket throguh the jackshaft ratios to the clutch and crank, and you don't gain any drive momentum from your weight on the bike turning the wheel because the cassette/freewheel have a freewheel ratchet that allow it to coast. Even if the rear wheel did add any assistance, the ratiosare backwards, with the small sprocket being on the wheel driving the larger front. Then you add in 2 more ratios from chainrong to jackshaft and jackshaft to drive sprocket.

 

[MinimumVK]

When i was using my jackshaft kit on a YD100 it was also really hard to push start. It could be done but even with my big legs it was tough. I just lifted the rear wheel and "kick started" the bike. I now kick start all of my bikes since i can warm them up before a ride and it also looks like starting an actual motorcycle.