Jeff jet 1750

[Jeff B]

Little project to use up some of the offcuts around the place.

[Jeff B]

Had a yz125 with blown gearbox, split casing.
So I chopped the gearbox off, just left with the crankcase and top end.
A Kawasaki 750 pump highly modified....

[Jeff B]

Engine mounted straight to pump, couple bearings and seals to take the side load of Honda timing pulley drive....

[Jeff B]

Got plenty of room (for a tiny hull)
Still a lot of finishing to do but pretty lightweight so far.
I have 46kg for,
Hull, engine, exhaust, pump, driveshaft
Should be able to keep it under y0kg total if I'm careful

[Kakapo76]

That's a very cool little boat- whats does the engine rev out too? And have you worked out the reduction ratio on the honda pulley?

[Jimmy Jet]

Cool Jeff. Any idea of the hours to get to this point? You sure churn em out.
Very creative.

[Jeff B]

That's a very cool little boat- whats does the engine rev out too? And have you worked out the reduction ratio on the honda pulley?

I have worked out the optimum ratio at about 2.2:1
The cam pulleys are obviously 2:1 so not exactly ideal.
I have ordered a bigger pump pulley to take it to 2.3:1 but it hasn't turned up yet. Engine just pivots like an alternator tension setup.
Engine needs 11,000rpm to make peak power (33hp) so gearing is quite important as there is not a lot of power below that...

[Jeff B]

Cool Jeff. Any idea of the hours to get to this point? You sure churn em out.
Very creative.

Ummm not sure sorry, the hull is pretty easy/fast, about 1 day.
Pump setup roughly another day.
Just been doing little bits here and there between work.
It's all the little things that suck up time, steering, cooling, throttle etc....

[Jeff B]

Steering is simple push/pull cable.
Offset column so 2x kids can fit....or one big fat kid.....

[Jeff B]

38mm Mikuni flat side.
Should feed a heap of air and fuel into the puny 54mm cylinder
Most of which will blow straight out the exhaust....

[Jeff B]

Chopped and changed the chamber to fit better, should just have enough room for factory muffler in behind.
I think I'll just wrap it, Rogee style for testing purposes.

[Jeff B]

Fuel tank fitted. Got a cap with gauge built in.

[Ross Goldsack - JBNZ Immediate Past President]

So your ride-on lawnmower is now missing a fuel cap?

[Warwick Marflitt]

Have you calculated the belt speed isnt too fast? They're measured in meters or Feet per second? There's a formula for it.... Not that it'll cause any issues if it fails  unless you're in the middle  of your favorite Waikato test rapid.....

https://www.sdp-si.com/D265/PDF/D265T146.pdf

[Jeff B]

Na I haven't calculated belt speed, should be ok as I'm only turning it twice as fast as factory Honda cambelt...
Plenty other modified parts to worry about first...