If that hole circled in red has a pathway to the combustion chamber, then that's not normal..

As for oil into the valve cover? Look where the fuel is being injected (brass nipple in this head) and notice that ring of 6 holes around the intake valve. The fuel/oil dribbles out the injector and most of it gets sucked in past the intake valve and then blown out the exhaust (or a bit past the piston). Some fuel/oil dribbles back down the valve stem (if inverted) and into the valve cover through those 6 holes. From there the methanol evaporates out and for the oil mist it's a trip down the exhaust pushrod into the cam area, along the crank to the rear bearing and out through the crankpin/conrod big end bearing to get sucked up to the top again and hopefully make it into the combustion chamber and then out the exhaust. With luck the constant air swirl inside the valve cover prevent too much oil from pooling there when running inverted at idle for long periods. Those six holes allow the valve cover volume all the way to the cam gear area to form a plenum chamber for the engine to pump up and supply air to the intake valve.

https://cimg1.ibsrv.net/gimg/www.rcu...4586ce1dbe.jpg
Rear valve cover bolt hole

YEP that's where the oil is coming out from..........

I didn't think that was normal......I tried putting a drop of oil in the hole and turned the prop to my surprise oil squirted out.

This means that fuel is getting pushed up through the hole by the piston which would explain why a brand new engine will not run....
I am suspecting a defect in the head casting or porosity as Claude mentioned before.
I have emailed YS Factory and waiting for advice.Will keep you posted.

Thanks to the bloke from Toowoomba....great knowledge mate.

regards

So further to my predicament I conducted the YS factory and they were more than helpful in rectifying the situation.
A new head was received under warranty ,,,,send by FEDEX Express.

The new head installed no further issue.

Thank you mr Yamada .

Good news.

As expected from Mr. Yamada,like the Mandalorina will say "This is the way", Yamada is very serious (no kidding, hasn't seem him smile yet hehe), but I cannot deny I do hate when people go into a rampage on social media talking crap about companies where their own ignorance is root of their lake of problem solutions.

FWB I am glad you your problem solved and Yamada tool care of you.

Regards

By the way is Mr Yamada first name Naohisa ???

Yes,

and he is the one that sends parts, warranties etc. His brother works with him too as far as I know, but know Naohisa only.

His brother is Chizuko

Thanks its good to know.
A very good company to deal with always prompt and polite.

I hope they develop a contra engine next........that will put the cat amongst the pigeons !!!!

Which, going by electric contras will at least double the price of the engine.

A YS two-stroke/electric hybrid would make a lot more sense if one must fly IC, and if YS had R&D money to waste.

With the right electronics, the torque curve could be whatever you want and the torque profile during each revolution could be as flat as a mill pond on a calm morning. This would enable weight reduction in airframe and propeller construction plus it'd be self starting too.

Interesting..........so how would that work ??

Way off topic, but here goes.
Rear induction, rear exhaust, mount a stator to the front housing where the crank passes through and connect the outrunner bell to the crankshaft at the prop driver I'd suggest for extra bragging rights a planetary gearbox (it can be contra if you wish?) on the output to let the two-stroke rev a bit and to minimise the outrunner diameter wouldn't hurt either. It'd have to be a "solid" connection between the electric and IC part with no belt/gearbox backlash between the two so the electric part can effectively operate like an electronic flywheel or harmonic balancer, as well as a drive and a brake.

Total pie-in-the-sky and will never happen, but then again I never thought the price of an off-road push bike would exceed the price of a dirt-bike either.

Keep us informed of your progress Brett 😉😃

Inovation is the mother of all Inventons........

Isn't it, necessity is the mother of all invention.

Not sure...............Smile

Sometimes it's a bit of both.
I built these at the end of 2000 for my 2001(plus a few more) season. Just some country hick in rural Queensland who looked at the tyre warmers of the period, didn't like what he saw, and had been playing with composites in toy aeroplanes for a few years previous.
https://cimg2.ibsrv.net/gimg/www.rcu...5397154ba3.jpg
During construction, carbon element sandwich between glass. Thermostat controlled, 300W @ 50Vac.
https://cimg2.ibsrv.net/gimg/www.rcu...7d05701549.jpg
Controller just visible under stand. Also note how far they wrap around the tyres for heat retention.

Check out the dates when this UK company started working with the same idea and when it became a "product".
https://kippax-moto.co.uk/brands/thermal-technology/

I won't be making an IC/Electric hybrid any time soon though :)

Why not?

Is the 200s an accurate drop in instead of the 185, 200?
Thanks.

Yes.

Thanks a lot.

Why does my YS200s make a clicking noise when I rock the prop back and forth.....??

All mine do the same.

The clicking noise might come from the pushrod hitting the valve rocker.