New guy, new idea

greg123 · Post by **greg123** » Fri Jun 15, 2007 6:57 pm

Well perhaps not new idea!

Hi all, uk guy here, well versed in bikes and diesel, but not diesel bikes. I have seen a yanmar type alloy v-twin 800cc direct injection diesel that is only a bit heavier than the single cylinder 10hp ones and is 20hp with electric start/alternator etc. If I do a project I'm thinking along the enclosed aerodynamic semi recumbent idea, engine under passenger seat with a centrifugal clutch on the crank with a 2000rpm engage for goo pull off on a hill etc and good disengage when coming to a stop. CVT to the back wheel. Top geared speed 100mph at 3,600rpm.

Semi recumbent with probably half the drag of your average bike, 20hp in a sit up bike will do 80mph so I figure this should hit 100 or in other words cruise at 85mph. I figure 150mpg should be easy.

What do you think? Any comments on the choice of engine? I see a lot of diesel bikes using engines that get around 65mpg, which a superbike can do if you keep it down to 80mph or so. I see no point in building one unless serious mpg can be reached, I can get 71mpg at motorway speed in a citroen AX 1.4 diesel I had and my friend's Octavia 1.9tdi overall averages 55mpg, on a run 65mpg. A bike has to be seriously better than that to make sense to me.

Any issues with only using a CVT or will I need reduction gearing? Can an efficient CVT with permanant engagement be combined with a good centrifugal clutch? Also how about a system to keep it at 3k other than at full throttle when it would sit at 3.6k?

Greg.

Fiddler · Post by **Fiddler** » Fri Jun 15, 2007 7:54 pm

Hi Greg,

Nice to hear the Notts custom scene is still alive and kicking.
In my opinion thats a great choice of engine for what you want to achieve. But then i would say that because thats what Im using. I set my sights low and aimed to be able to hold a steady 60mph. All the folks I discussed my project with at the British Diesel Rally a few weeks ago seemed to think I should comfortably achieve this and then some with aroung 150mpg. I spent many weeks looking for an available cheapish engine for this project and thought this near ideal.
Check out the Punsun harley post and it will give you some idea of the size of CVT required.
I really like your semi recumbent idea which the harley will be as im having forward pegs made.
Only thoughts off the top of my head are length of machine due to the drive train as you will need secondary gearing utilising something like chain/sprockets,belt/pulleys or other after the cvt. Also handling with so much weight rear biased but then the new breed of big scooters overcome this and apparently handle sweetly.
I think you may be a bit optimistic with top speed estimates. Although probably achievable in theory you will give the belt on the cvt a real hard time with secondary gearing so tall.
A nice advantage of your idea is you may be able to shroud the engine nicely and damp the noise somewhat.

All the best, Mark

Post by **Byrdman** » Sat Jun 16, 2007 3:45 am

Greg, the Yanmar 2V78 is a 749CC indirect injected diesel v-twin and I personally think it would make a great engine choice.

It was never build in a horizontal shaft configuration but with a few slight oil routing changes it can be made to run on it's end.

The engine was detuned several times to make it more emissions friendly but I was witness to the very first, pre-production versions and the 20HP badge wasn't very accurate. They would blow all kinds of smoke and would smoke competitive 28 ~ 30 horse gasoline engines.

oldbmw · Post by **oldbmw** » Sat Jun 16, 2007 8:33 pm

Byrdman wrote:Greg, the Yanmar 2V78 is a 749CC indirect injected diesel v-twin and I personally think it would make a great engine choice.

It was never build in a horizontal shaft configuration but with a few slight oil routing changes it can be made to run on it's end.

The engine was detuned several times to make it more emissions friendly but I was witness to the very first, pre-production versions and the 20HP badge wasn't very accurate. They would blow all kinds of smoke and would smoke competitive 28 ~ 30 horse gasoline engines.

I beleive that latest incarnation of this motor can be had with horizontal shaft...

greg123 · Post by **greg123** » Sun Jun 17, 2007 12:05 am

Greetings guys! Thanks for the replies. There is always something going on in my garden/workshop in nottingham, either chavs stealing something or me making something! The engine type I'm looking at is not the idi as I would rather have a di due to less pumping and thermal losses, also it's just 8kg heavier than the 10hp diesel. See here for the type of thing - it's the v-twin diesel and it comes in horizontal shaft, cylinder seems to be identical to the 10hp versions.

http://www.portable-energy.co.uk/Engines.htm

As for more than 20hp, with a bit of tuning, advance optimising, ram air intake, gasflowing, ceramic coating, decent exhaust, if 30hp or even 25 would be great as with a streamlined body I'm sure motorway cruising could be achieved easily.

So I need a reduction, how about a belt drive from a transverse shaft directly behind the enine, belt drive to the wheel, with the other side a cvt from the crank to shaft?

Is this engine similar to the yanmar in any way or familiar to any of you? I'm not too concerned about it sounding like a diesel, I have always prefered a 'crackly' di sound over a idi and yes a recumbent type style should allow an engine encousure, a seperate exhaust should take care of that side of things so noise wouldn't be too bad I think.

thoughts appreciated, Greg.

Fiddler · Post by **Fiddler** » Sun Jun 17, 2007 9:45 am

Greg,

Is that engine familiar to any of us? Er yes mate, wake up and read your replys

Check out the thread called Punsen Harley in the technical section of this site. You will spot the very same engine purchased from the very same supplier only viewed from the crank side not the flywheel.
Belt drive ought to work well, lots of info about online on setting up the transverse shaft, most people seem to refer to them here as jackshafts.
You guessed correct the cylinder is the same as the 10hp yanmar clones so there should be some spares back up.
Its basically two 10hp engines on a common crank with some balancing, larger sump, cartridge oil filter and an oil cooler to help. Still shakes like a bastard at idle although it smooths out at 3600rpm. Oh yeah and its definatly noisy and definatly sounds like a diesel.
Hope this helps, Mark

greg123 · Post by **greg123** » Wed Jun 20, 2007 4:46 pm

I did, well I thought I did, byrdman was talking about a different engine and I didn't recognise from your pics

Interested what you said about the noise etc, can you confirm it's direct injection? By the way I mailed the guy for a price and didn't get a reply, mind letting me know how much it costs?

So reduction gearing will be needed and the limits of the cvt ratio may mean a lower top speed than possible to enable a good getaway. I think I can live with that. Anyone put a 2 speed box on or something for a 'town' and 'out of town' use of a cvt? While I'm thinking about it, anyone used 2 cvt's, one either side of the jack shaft (one from engine, one to wheel) to have a very wide ratio set?

Greg.

Fiddler wrote:Greg,

Is that engine familiar to any of us? Er yes mate, wake up and read your replys
Check out the thread called Punsen Harley in the technical section of this site. You will spot the very same engine purchased from the very same supplier only viewed from the crank side not the flywheel.
Belt drive ought to work well, lots of info about online on setting up the transverse shaft, most people seem to refer to them here as jackshafts.
You guessed correct the cylinder is the same as the 10hp yanmar clones so there should be some spares back up.
Its basically two 10hp engines on a common crank with some balancing, larger sump, cartridge oil filter and an oil cooler to help. Still shakes like a bastard at idle although it smooths out at 3600rpm. Oh yeah and its definatly noisy and definatly sounds like a diesel.
Hope this helps, Mark

Post by **Byrdman** » Wed Jun 20, 2007 6:35 pm

greg123 wrote:I did, well I thought I did, byrdman was talking about a different engine and I didn't recognise from your pics

My bad guys.

I was under the impressiont hat Yanmar was still the only manufacturer that made a V-Twin diesel.

The Punsen looks like a nice powerplant.

greg123 · Post by **greg123** » Wed Jun 20, 2007 9:37 pm

If the punsen can be tweaked like you say the Yanmar liked and has a better mpg from direct injection that sounds very promising! I have no idea how durable/well made they are but it looks nice doesn't it. I was also struck how heavy the 10hp diesels are and how this weighs little more for double the power. Can't be bad!

Byrdman wrote: My bad guys.

I was under the impressiont hat Yanmar was still the only manufacturer that made a V-Twin diesel.

The Punsen looks like a nice powerplant.

oilburner · Post by **oilburner** » Thu Jun 21, 2007 1:36 am

The semi recumbent sounds a lot like the FF (feet forward) machines such as Malcolm Newell's Quasar (1975 - 1981). The Quasar weighed 680 lbs, was fitted with a 40hp Reliant engine, max speed and cruise speed of 100 mph, and got 65 mpg. If you can somehow shave off a couple hundred pounds, it just might work. If it wasn't for the huge hassle and expense getting such a machine licensed and insured, I'd go that route in a heartbeat.

Picture of the Quasar here:
http://www.voidstar.com/bff/quasar.html

Avery

Fiddler · Post by **Fiddler** » Thu Jun 21, 2007 9:36 pm

I think the bloke was hoping to retail them for about £1500-£1600. I paid £700 for one he had for testing with 40 hours on it. I know he originally had 4 for testing and two us from this site got one, so might be worth finding out what happened to the other 2.
Yes its direct injection and sounds like it. You'd struggle to hold a conversation next to it at 3600rpm, mainly engine noise I think hence I reckon shrouding would make a far more civilised ride for the neighbours and a less tiring ride.
Seems reasonably well built for the money, remember yanmars equivalent retails for over double this. Most people who have run bikes with the 10hp yanmar clones seem to be reasonably happy with build and relaibility, so unless the crank is weak i cant see any problems. Except for the obvious most parts are interchangable with the 10 so spares shouldnt be an issue.

Cheers, Mark

gordon160 · Post by **gordon160** » Thu Jul 12, 2007 9:53 am

Hi have you considered a aixam engine its a parallel twin its got everything you need.
Its 500cc about 20bhp no gearbox belt drive check out the cars on ebay or search aixam on internet for more info I would be surprised if nobody had used one to make a motorbike yet
The engine its self is a kubota a good make

greg123 · Post by **greg123** » Thu Jul 12, 2007 4:30 pm

It's an old fashioned Indirect Injection design, as far as I'm aware considering it's size and CC doesn't do much to a gallon. Also it's liquid cooled adding to weight. Don't know what weight the engine is but the Kubota's I have seen are pretty 'industrial' however would have to see one of these in the flesh before commenting more!

gordon160 wrote:Hi have you considered a aixam engine its a parallel twin its got everything you need.
Its 500cc about 20bhp no gearbox belt drive check out the cars on ebay or search aixam on internet for more info I would be surprised if nobody had used one to make a motorbike yet
The engine its self is a kubota a good make