View Full Version : Hoverising a motorbike engine

tom loomes - n/a
25-Nov-07, 06:55 PM
Hello, im a tad new to all this so here goes...

basically thers a group of 6 of us trying to make a hovercraft more environmentally friendly by replacing the 2 stroke rotax 503 engine with a 4 stroke honda cb500 engine

i was wondering if anyone has had any experience in hoverising a motorbike engine and generally what is involved?

Also, i am aware that the 4 stroke engine will be a helluva lot heavier than the 2 stroke so im wondering where some weight can be lost. I know the gearbox isnt needed but is there anything else?

Any suggestions welcome


sixpackpert - n/a
26-Nov-07, 10:51 AM
Ooooooooooh, how much for the 503 engine, is it twin carb?? http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

tom loomes - n/a
26-Nov-07, 12:56 PM
ahh sorry its not for sale...um but yes it is twin carb hehe...and its a bit broken at the moment in that it lets rip some massive backfires out of the rear cylinders carb, and we're unsure as to what the problem is at the moment. We've checked the points, leads, plugs, timing and all thats spot on...furthur investigation required.

the hovercraft is for racing. Up to 500cc 4 stroke is the what the regulations suggest and on our budget a honda cb500 engine seems to be the best compronmise between performance, reliability and weight

thanks for the quick response....furthur suggestions welcome tho

profqwerty - n/a
26-Nov-07, 12:57 PM
I thought with 4 stroke you could have higher cc?

like 750cc 4 stroke ~ 500cc 2stroke?

sixpackpert - n/a
26-Nov-07, 01:03 PM
Depends which formula you want to race in.

Four stroke engines:

F3 Up to and including 500cc total engine capacity

F2 Over 500cc and under 750cc total engine capacity

F1 750cc and over total engine capacity

F35 4 stroke engines of total horse power of not more than 35HP, engine

revs not greater than 5500.

tom loomes - n/a
26-Nov-07, 01:06 PM
yeh thats it, we're going for formula 3...

Dave - n/a
26-Nov-07, 03:14 PM
Hi Loomesy! Always nice to see new racers esp enviromentally freindly ones!!! (Shame im not http://hovercraft.org.uk/images/icons/smiley_icons/icon_redface.gif ) Esp in F3!

I have raced a few craft mix of 2-stroke and 4-stroke, A while ago Bearwood purchised Tony Goldneys CB500, which was plesantly writen off! But the origial craft was a fine craft it was a rather heavy, but powerfull enough, wonderfull noise!!

Its is a good engine, Its a 4-stroke relable when set up right, the engine needs to stay pritty much as it is out of the bike, you need to keep the gearbox, as its a 4-stroke. So theres not much you can do to remove some weight...(from the engine)


tom loomes - n/a
26-Nov-07, 04:34 PM
ahh id better come clean i reckon...

its part of my team project at the university of hertfordshire.

theres a group of 6 of us working on it and eventually the plan is to have the hovercraft firstly running a 4 stroke, then convert it to fuel injection, then look into biofuels and then possibly hydrogen

we competed the hovercraft with the rotax 503 last year at magnolls farm and came 3rd and 1st twice before the backfire i mentioned previously started...and we still have this problem..were waiting for new condensers as i type

actually ive just thought if anyone can think of any possible sponsers who may be willing to lend us some monies of some sort we have a sponsorship pack we can send you

sorry about the shameless plug...

sixpackpert - n/a
26-Nov-07, 04:44 PM
actually ive just thought if anyone can think of any possible sponsers who may be willing to lend us some monies of some sort

We're all after sponsors so gerroff http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

Seriously though good luck with the project, though fitting that engine into a Storm could be a bit tight?! http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

jon_curtis - n/a
26-Nov-07, 05:15 PM
depends on the type of engine, many bike engines have a wet clutch and are very hard to remove the gear box from, others combine the crank and gearbox in the same oil! like a mini engine!

not sure on the details of a cb500, never had one to bits!

but just take a pto off the sprocket! as mentioned its important to have the engine set at a similar angle/orientation as that in the bike! this is to do with the oil distribution in the sump!