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nzjetboating.com Forums => Projects => Topic started by: Jeff B on April 29, 2021, 09:05:53 AM

Title: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 09:05:53 AM
Little project to use up some of the offcuts around the place.
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 09:08:30 AM
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....
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 09:10:23 AM
Engine mounted straight to pump, couple bearings and seals to take the side load of Honda timing pulley drive....
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 09:13:10 AM
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
Title: Re: Jeff jet 1750
Post by: Kakapo76 on April 29, 2021, 09:19:59 AM
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?
Title: Re: Jeff jet 1750
Post by: Jimmy Jet on April 29, 2021, 09:55:52 AM
Cool Jeff. Any idea of the hours to get to this point? You sure churn em out.
Very creative.
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 11:29:41 AM
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...
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 11:32:08 AM
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....
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 11:33:32 AM
Steering is simple push/pull cable.
Offset column so 2x kids can fit....or one big fat kid.....
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 12:22:18 PM
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.... ;)
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 12:24:22 PM
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.
Title: Re: Jeff jet 1750
Post by: Jeff B on April 29, 2021, 20:02:59 PM
Fuel tank fitted. Got a cap with gauge built in.
Title: Re: Jeff jet 1750
Post by: Ross Goldsack - JBNZ Immediate Past President on April 30, 2021, 11:31:48 AM
So your ride-on lawnmower is now missing a fuel cap?
Title: Re: Jeff jet 1750
Post by: Warwick Marflitt on April 30, 2021, 19:17:53 PM
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  hhh unless you're in the middle  jaw of your favorite Waikato test rapid.....

https://www.sdp-si.com/D265/PDF/D265T146.pdf
Title: Re: Jeff jet 1750
Post by: Jeff B on April 30, 2021, 22:33:57 PM
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... ;)
Title: Re: Jeff jet 1750
Post by: Allen M on May 01, 2021, 08:03:40 AM
 ???
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... ;)
:o Hmmmmmm!!!! It might only be turning at twice the speed as the Honda cam belt but the load turning the jet pump would have to be considerably more than what was required to turn the said camshaft. Still you don?t know what the limits of something are till you exceed them. pop
Title: Re: Jeff jet 1750
Post by: Jimmy Jet on May 01, 2021, 08:47:27 AM
I think the belt will be fine. Only basing my assumptions on a Harley Davidson belt drive and the torque transmitted in that application. I think you have a bigger proportion of belt area.
Title: Re: Jeff jet 1750
Post by: Jeff B on May 01, 2021, 10:32:51 AM
Basing engineering strength on Harley Davidson equipment is not what I call hi tech.... l-l
Not sure really? Camshafts are pretty tough to turn...2 of them...I'm not sure how much torque they absorb??
Anyway....I could spend a day researching and wondering about it or I can just run it and upgrade to something else when/if it fails....
Destructive testing is much more gun....
Title: Re: Jeff jet 1750
Post by: Ross Goldsack - JBNZ Immediate Past President on May 01, 2021, 12:57:57 PM
I'd be more worried about the dentistry bills after it shakes your teeth out
Title: Re: Jeff jet 1750
Post by: Jeff B on May 01, 2021, 19:39:00 PM
Few mods to engine.
Had to bodge up the water feed Inlet, raw water of course.
Title: Re: Jeff jet 1750
Post by: Jeff B on May 01, 2021, 19:40:11 PM
Assembled top end.
Man the ports are huge! Not much cylinder left with all those holes through it....
Title: Re: Jeff jet 1750
Post by: Jeff B on May 02, 2021, 08:48:27 AM
Fitted pulse line fitting for fuel pump
Hopefully pressure is low enough I dont need header tank.
Title: Re: Jeff jet 1750
Post by: Jeff B on May 02, 2021, 09:23:56 AM
I still need to figure out how to actuate the power valves too...
Maybe another lever or button on steering wheel?
Raises the exhaust port a good 6mm so definitely needs it for power.
Not sure it will idle with them fully open?
Title: Re: Jeff jet 1750
Post by: Jeff B on May 02, 2021, 16:41:09 PM
Finished off the exhaust, managed to tuck the std muffler up under transom with a little silicone water trap on end.
Just gunna wrap copper pipe around the header to pre heat raw water before entering cylinder. Not sure how many wraps I'll need? Will just heat wrap the whole exhaust system (rangi I know)
Title: Re: Jeff jet 1750
Post by: Jeff B on May 02, 2021, 16:44:57 PM
Electrical system installed and hooked up, easiest electric setup yet..a coil and CDI....
Fired the wee stinker up,
Pulse fuel pump is providing too much pressure and flooding carb, needle valve and seat are pretty big, 2.2mm (for gravity feed from tank) might try a smaller needle and seat before rigging up a header tank??
Vibrates a bit...less than the 300 though.... :o
Title: Re: Jeff jet 1750
Post by: Tones on May 02, 2021, 17:31:49 PM
Jeff, Gates make a carbon fibre belt that would be ideal in that drive application. I have used them on forestry equipment and have worked well. The downside is they have to be perfectly alined which shouldn't be a problem for a genius Gates Polychain Belt.
Title: Re: Jeff jet 1750
Post by: Jeff B on May 02, 2021, 18:17:23 PM
Jeff, Gates make a carbon fibre belt that would be ideal in that drive application. I have used them on forestry equipment and have worked well. The downside is they have to be perfectly alined which shouldn't be a problem for a genius Gates Polychain Belt.

Yeah my local sponsor bearing supplier showed me the carbon timing belts, same thing. He said they were quite expensive? Not sure what his interpretation of expensive is.....jet boating has somewhat numbed my cost scale.... l-l
Title: Re: Jeff jet 1750
Post by: Tones on May 03, 2021, 12:08:19 PM
The belt I had was rated to 5000nm torque, cost $1000 O)))) O))))
Title: Re: Jeff jet 1750
Post by: Paul on May 03, 2021, 17:12:06 PM
The belt I had was rated to 5000nm torque, cost $1000 O)))) O))))

How can a belt be rated for a torque?  Surely, that depends totally how many teeth are engaged on the pulleys and the diameter of the pulleys..
Title: Re: Jeff jet 1750
Post by: Warwick Marflitt on May 03, 2021, 23:39:08 PM
Finished off the exhaust, managed to tuck the std muffler up under transom with a little silicone water trap on end.
Just gunna wrap copper pipe around the header to pre heat raw water before entering cylinder. Not sure how many wraps I'll need? Will just heat wrap the whole exhaust system (rangi I know)

Rangi Jeff!
      Now there's an Oxymoron if. ever Ive heard one.....it'll be fine mate....
I'm wishing I'd  00- ma cake hole bout the cam belts service rating... Your on the right verdict though S.I.A.S "suck it and see"? Thinking about your set up... You only have 33hp and that'll only make X amount of torque. So wither it gets to 11,000rpm or not. The pump will resist against only what the engine puts out.... so it's kinda a self full fooling prophetic equation? Limited by the engine more than the unit. Unless the Impellers are too steep. But that wont cause belt failure.... Any hoot OoOoO it gave us all something to bleat and yap on about..... Your a legend Jeff  D_D b_r
Title: Re: Jeff jet 1750
Post by: Jeff B on May 09, 2021, 07:38:28 AM
Manual power valve actuation
Be interesting to see what difference it makes.
Title: Re: Jeff jet 1750
Post by: Jeff B on May 09, 2021, 07:40:23 AM
Copper wrapped I big portion of chamber, then wrapped with fiberglass tape, yucky and itchy.
Pre heat rawxwater around exhaust before entering cylinder
Title: Re: Jeff jet 1750
Post by: Jeff B on May 09, 2021, 07:41:26 AM
Started on engine cover/seat. Plenty room.....
Title: Re: Jeff jet 1750
Post by: Tones on May 09, 2021, 15:44:44 PM
How can a belt be rated for a torque?  Surely, that depends totally how many teeth are engaged on the pulleys and the diameter of the pulleys..
By the width of the belt.
Title: Re: Jeff jet 1750
Post by: Paul on May 09, 2021, 16:59:02 PM
By the width of the belt.
That's not relevant. Belt width would just be proportional to breaking tension

Torque is "force x radius". If radius is unknown, then torque is unknown.  If you put the same belt on a larger pulley, it is now capable of more torque tansfer, hence torque rating on a belt alone is meaningless.
Title: Re: Jeff jet 1750
Post by: Jeff B on May 09, 2021, 18:47:48 PM
Used up all my little offcuts of EVA foam, made seat/engine cover.
Title: Re: Jeff jet 1750
Post by: Jeff B on June 01, 2021, 05:55:55 AM
Few more small things to finish then test time.
Title: Re: Jeff jet 1750
Post by: Henry on June 01, 2021, 10:17:05 AM
Good entertainment value, cant wait to see it going.
Title: Re: Jeff jet 1750
Post by: steelo on June 01, 2021, 11:11:53 AM
Inspirational Jeff. Can?t wait to see some action shots or video
Title: Re: Jeff jet 1750
Post by: Jeff B on June 01, 2021, 12:46:36 PM
I'm hoping that when the belt fails it will just rip the teeth off (when the mighty 125 hits power band) rather than shreds the belt right off, that way I should still be able to putter back to boat ramp....
Title: Re: Jeff jet 1750
Post by: Paul on June 01, 2021, 16:01:28 PM
Maybe a snorkel for the carb intake?  It looks pretty close to the sucking up water from the rear corner?
Title: Re: Jeff jet 1750
Post by: Jeff B on June 13, 2021, 07:03:14 AM
Finished off drive setup, used a keyless taper lock on pump shaft. And welded the honda cam pulley to yamaha drive gear engine side.
Belt is tensioned with slot and thread so whole engine moves.
Hope my drive ratio is calculations are accurate....
Title: Re: Jeff jet 1750
Post by: Jeff B on June 13, 2021, 07:06:01 AM
Got sick of waiting for my new Vespa bevel drive starter to turn up so fitted an old Kawasaki starter, just fits.
A kick start or pull start was not going to be too practical
Title: Re: Jeff jet 1750
Post by: Jimmy Jet on June 13, 2021, 10:24:19 AM
I think the power valve will make a huge difference. Years ago I rebuilt the top end on my 93 CR250 and incorrectly re-installed the PV actuation rod. The bike would rev to about mid-range and then just go flat, full boggy.
Title: Re: Jeff jet 1750
Post by: Henry on June 14, 2021, 08:37:26 AM
Starter motor look heavy tho. Half as much as the engine.
Title: Re: Jeff jet 1750
Post by: Jeff B on June 14, 2021, 11:03:45 AM
Yep the starter is a monster, with the small gear on flywheel it spins the 125 faster than an old Grenada running at WOT.....only have to touch the starter button and it's running.
Weight is piling up though...
75kg all up with big 20ah battery(no charging circuit...yet) and a full tank of premium gas.
Ready for water test....
Title: Re: Jeff jet 1750
Post by: Jeff B on June 16, 2021, 17:58:45 PM
https://youtu.be/BB7hDriCyFo
Title: Re: Jeff jet 1750
Post by: Jimmy Jet on June 16, 2021, 19:41:43 PM
Brilliant. How did the powervalve go?
Title: Re: Jeff jet 1750
Post by: Ross Goldsack - JBNZ Immediate Past President on June 16, 2021, 22:05:07 PM
Looks quite snappy..... maybe I'm just thinking of the belt?
Title: Re: Jeff jet 1750
Post by: Jeff B on June 17, 2021, 09:34:01 AM
Only pushed the power valve lever once, rpm increased but not sure how much, that video is with the low exhaust port mode so there is heaps of power on tap. Waiting on a tacho so I can get some accurate data but promising first run.
The belt, well the belt is holding up fine.....for now.....
Title: Re: Jeff jet 1750
Post by: Henry on June 17, 2021, 09:39:20 AM
Looks like the relatively big pump and gearing worked a treat. Do you think it would work with a putts four-stroke like a Honda XR250?

When customers have an idea to do something a bit tricky i can almost always send them to the relevant Jeff thread now days. The belt drive was the final missing piece.

Maybe sounds even worse than a 300cc tho....
Title: Re: Jeff jet 1750
Post by: Jeff B on June 17, 2021, 12:22:32 PM
Nup the little screaming 125 does sound slightly better than the lugging 3 hunny......slightly.

Henry, the xr250 is a dead duck...air cooled,
Look at the 4 stroke scooters with cvt belt drive...there are some 250cc models that might work, some of the chinasian cvt buggy engines are the same, I think yamaha knockoff?
20hp might be ok?
Title: Re: Jeff jet 1750
Post by: steelo on June 17, 2021, 14:51:52 PM
Thanks for the quick video Jeff. Looks brilliant. More More.
Title: Re: Jeff jet 1750
Post by: Jeff B on June 19, 2021, 18:10:57 PM
Bit more testing today.
After an initial flooding problem, bit of swarf in needle valve, got some data runs in.
Minimum plane, about 6500rpm, 25k
Cruises nicely 7500rpm, 35k
WOT 10800rpm, 55k
Hull sits up and cruises nicely, pulls nose down at full throttle, no porposing.
Can probably bang the ride plate up a bit and get a bit more speed but it handles good now.
The belt is still holding together too....
Title: Re: Jeff jet 1750
Post by: steelo on June 19, 2021, 20:33:42 PM
I suppose you can just vary the sizes of the pulleys to adjust speed / rpm. Something we can't do in our boats
Title: Re: Jeff jet 1750
Post by: Matthewf/Norbert/TuiDog on June 20, 2021, 19:18:07 PM
I suppose you can just vary the sizes of the pulleys to adjust speed / rpm. Something we can't do in our boats
Stick a lathe gearbox in it jeff🤣
Title: Re: Jeff jet 1750
Post by: Jeff B on June 21, 2021, 11:34:57 AM
I suppose you can just vary the sizes of the pulleys to adjust speed / rpm. Something we can't do in our boats

Yes that is the benefit of this setup.
Although I think I have it pretty close first pop with 10,800rpm (goal was 11,000)
Title: Re: Jeff jet 1750
Post by: Jeff B on June 26, 2021, 12:41:56 PM
3mm ride plate a bit flimsy and hanging down a bit so fitted some lightweight aluminum turnbuckles to fine tune the handling.
Title: Re: Jeff jet 1750
Post by: Jeff B on July 04, 2021, 15:40:04 PM
Not happy with the crappy heat wrapped exhaust, now that I now the concept actually works (there was a tiny amount of doubt)
So I started making proper jacketed exhaust, this shape has been designed to optimize power with a strong bottom end, punchy mid range and a screaming top end.... ;)
Title: Re: Jeff jet 1750
Post by: Warwick Marflitt on July 05, 2021, 08:18:20 AM
You'd win the NZ Sculptured art award with that creation Jeff!
Title: Re: Jeff jet 1750
Post by: Jeff B on July 05, 2021, 20:31:12 PM
Exhaust inner all welded up.
Just need to fit water jacket to it now.
Title: Re: Jeff jet 1750
Post by: Henry on July 06, 2021, 10:00:16 AM
niiice
Title: Re: Jeff jet 1750
Post by: Kakapo76 on July 06, 2021, 12:17:15 PM
How many hours in that pipe Jeff? Georgeous work mate.  b>
Title: Re: Jeff jet 1750
Post by: steelo on July 06, 2021, 14:58:06 PM
Didn?t something like that start the virus in China?
Title: Re: Jeff jet 1750
Post by: tyro on July 06, 2021, 15:21:49 PM
ribbed for pleasure
Title: Re: Jeff jet 1750
Post by: Jeff B on July 06, 2021, 20:18:16 PM
Exhaust looks like a lot of work, not too bad, I think about 6 hours to make inner.
Started making outer. 3mm gap for water jacket.
Title: Re: Jeff jet 1750
Post by: Warwick Marflitt on July 07, 2021, 10:28:12 AM
Jeff. Could you not measure cut and weld a flat shaped profile. Then hydroformed it making the outter chamber, then cutting and welded it over the inner? Time wise would it be quicker? It wouldn't look as fantastic.
Title: Re: Jeff jet 1750
Post by: Keltik on July 07, 2021, 12:17:42 PM
Time wise would it be quicker? It wouldn't look as fantastic.
Shhh....I wanna see nice things
Title: Re: Jeff jet 1750
Post by: Jeff B on July 07, 2021, 19:55:20 PM
I have hydro formed a couple of chambers, stainless works better, ali welds dont like it much. And it stretches the material, not as dimensionally accurate, especially if you want a jacket close to it.
Time wise probably not a lot of difference? Both pretty time consuming.
Got the jacket tacked on, just a little sleeve to fit then weld up.
Title: Re: Jeff jet 1750
Post by: Paul on July 07, 2021, 20:45:07 PM
Do you put spacers/ nuts/ washers between the skins, or is each skin able to 'float' relative to the other?
Title: Re: Jeff jet 1750
Post by: Jeff B on July 08, 2021, 07:51:44 AM
Paul this is not a back yard job, we dont use nuts and washers as packers... l-l
Packers will just fight against befitting it up and rattle.
They are 2x seperate chambers, quite rigid not sure if I will get much flex?
Don't think I would here it rattle with the little piston jumping up and down nearly 200 times per second...
Title: Re: Jeff jet 1750
Post by: orac12 on July 08, 2021, 10:47:07 AM
That's badass. Did you have the pie cuts profile cut?
Title: Re: Jeff jet 1750
Post by: Henry on July 08, 2021, 10:48:31 AM
My wee JS300 pipe just has a jacket for the first downwards 3" and baby water injection at the low point. Might be an idea when you go into production on motorbike powered jet boats
Title: Re: Jeff jet 1750
Post by: Jeff B on July 08, 2021, 11:06:47 AM
That's badass. Did you have the pie cuts profile cut?
Yes, I drew the cone sections on a basic 2 stroke exhaust development program and cut them on CNC router. Took about 12 minutes to cut one pipe (inner or outer)
Saves a lot of time and is very accurate
Title: Re: Jeff jet 1750
Post by: Jeff B on July 08, 2021, 11:15:00 AM
My wee JS300 pipe just has a jacket for the first downwards 3" and baby water injection at the low point. Might be an idea when you go into production on motorbike powered jet boats

Yes most all factory 2 stroke jetski exhausts are done that way.
The last and most powerful models had fully water jacketed chambers (dry pipe)
The water injection alters chamber volume, very complex to get it right. Some aftermarket ski pipes have needle valves sent different points along the chamber to fine tune. Some even have rpm activated window switch on water solenoid valves letting water in at low rpm then shutting it off up top.
Adding water is another variable I'm not quite ready to experiment with.....yet.....
On Mohawks 300 home made race pipe, we gained 200rpm by shutting water off to chamber.....then the exhaust rubber melted and we lost a heap of performance by sucking exhaust into carburetor (EGR) ..
.
Title: Re: Jeff jet 1750
Post by: Jeff B on July 10, 2021, 17:00:20 PM
All done, fits a lot better than the chopped up factory pipe and I dont get itchy fiberglass heat wrap on me when I reach into engine bay.
It better add at least 1hp or I'll be pissed.....
Title: Re: Jeff jet 1750
Post by: steelo on July 10, 2021, 17:05:29 PM
As they say in raiders of the lost ark
Title: Re: Jeff jet 1750
Post by: Matthewf/Norbert/TuiDog on July 10, 2021, 17:39:53 PM

Awesome

http://25.media.tumblr.com/tumblr_lhy1qtdS011qhtn5fo1_500.gif (http://25.media.tumblr.com/tumblr_lhy1qtdS011qhtn5fo1_500.gif)
Title: Re: Jeff jet 1750
Post by: Ross Goldsack - JBNZ Immediate Past President on July 11, 2021, 15:24:01 PM
How did testing go cou cou cou
Title: Re: Jeff jet 1750
Post by: Jeff B on July 11, 2021, 16:42:39 PM
Well the pipe works good....
Warmed it up then cruised off, pushed the power valve and gave it the berries, revved to the moon....and slowed down to a crawl....puttz.
Belt crapped out.
Title: Re: Jeff jet 1750
Post by: Jeff B on July 11, 2021, 16:45:58 PM
On closer inspection it appears my bottom engine mount bolt/tensioner rattled loose....engine moved and belt went floppy....puttz
Probably not the belts fault.
Title: Re: Jeff jet 1750
Post by: Ross Goldsack - JBNZ Immediate Past President on July 11, 2021, 22:41:04 PM
Put the boat back in the box and ask for a refund..... or just fix it and accept counciling from Mohawk
Title: Re: Jeff jet 1750
Post by: Jimmy Jet on July 12, 2021, 07:07:02 AM
Did you tie pantyhose around the pulleys to get you back to the ramp  ;D
Title: Re: Jeff jet 1750
Post by: Jeff B on July 12, 2021, 12:41:12 PM
I didn't have any pantyhose handy unfortunately.
I took the highly undignified route back to the ramp using paddle power.
Title: Re: Jeff jet 1750
Post by: Warwick Marflitt on July 13, 2021, 10:08:39 AM
I bet you'd gone upstream incase you had ta paddle home. Pantyhose tied in a figure 8 you'd have had reverse and could've backed back to the ramp cou . Are your paddle strokes longer  than the boat ;D At least you had some quiet time to reflect and plan your next   project?!
Title: Re: Jeff jet 1750
Post by: Jeff B on July 13, 2021, 18:01:09 PM
Swapped a new belt on, 1 down, 4 to go. These are pretty cheap, about $7 each.
Put a new engine mount bolt with nyloc nut and tightened the crap outa it.
Title: Re: Jeff jet 1750
Post by: steelo on July 13, 2021, 18:47:23 PM
Would the engine mount under spring tension or idler pulley save any grief.
Title: Re: Jeff jet 1750
Post by: Allen M on July 14, 2021, 08:53:11 AM
Swapped a new belt on, 1 down, 4 to go. These are pretty cheap, about $7 each.
Put a new engine mount bolt with nyloc nut and tightened the crap outa it.
Might pay to put those other 3 belts in the boat somewhere for next time. Might be adding unwanted weight but could save a long paddle back to the ramp.