LPG bike conversion, possible..?

[goto10]

Just curious, has it ever been done? I'm guessing the LPG gas tank would be a challenge to fit but not a deal breaker.
I know bikes are high revving which might be a problem, but something like the NC700 (with a car-derived engine) would be a good base.
At 75p a litre it would quickly pay dividends for people who pound the miles.
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'12 NC700S & '12 CB600F Hornet [Stolen by some dickless twat] Suzuki GT500 shed

[stonesie]

LPG has a lot of benefits, aside from the lower cost it is better for the engine with a much cleaner burn and lower emmisions. It can also provide the same power as petrol with a bit of extra enrichment and advanced ignition timing (about 106 octain iirc)


BUT, the tank will need to be at least 20 litres to make it worth while (16L of gas capacity + expansion gap) and it will only do 80% of the mpg of petrol (50 mpg on Petrol = 40 mpg on gas) The vaporisor needs water heating as evaporating all that liquid gas needs heat to keep it from freezeing up. Then you need to choose between an old fashoned venturi system or a modern injection system, Nither need a pump because the gas tank fills at about 150Psi but both need a lambda sensor for the mixture to self adjust with the closed loop management.


In short your biggest problem is packageing the thing, the components are designed for cars so are big and bulky, the tanks are made from 5mm steel and only have a 5 year service life before they need re-certifying or replaceing.... Then you will have to have it certified... Then you will have to find someone who will insure a bike with a highly pressurised gas tank.

[nowhere.elysium]

[Howling TerrorOutOfOffice]

virus (BCF member) could adapt his beer-keg trailer. He won't.
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[kelvyn]

Seen it done on bikes with sidecars due to the tank.

[temeluchus]

I did see a kit to adapt 125s kicking around (I suppose the fuel economy means you can use a smaller tank).

Will have a poke around later and post what I find.
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[temeluchus]

https://www.gastechproducts.com/gasconverter.html
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[Teflon-Mike]

Spotted an LPG Scooter once....

Think the main 'thing' with an LPG bike would be range & fuel availability.

I have a 90L / 20 gallon LPG tank in the boot of the Rangie, and the original 90L / 20 gallon Petrol Tank.. Book says the Rangie does 13mpg, which gives about 250 miles range. on either fuel. But being a bit 'paranoid' about how much it costs to fill, and actually finding Gas, can get the mpg up to around 25, giving almost 500 miles.

Around and about; Finding LPG tends not to be a 'problem'; though my nearest LPG outlet is on the other side of town 3 miles away, and if their tank's dry, next is Motorway services; which means about a 16 mile 'trip' onto the M6 and loop between junctions, unless I am actually heading out on the M6 some-where.

Heading off on an excursion; can be harder to find, and there are some parts of the country where the stuff is incredibly thin on the ground. An LPG 'Map' and the LPG Retailers GPS list, are pretty essential, but not all that reliable.... turned up to outlets in the book, before now to find they haven't had LPG for over two years!

With 250-500 mile range, you have to keep your tank filled when you spot an 'Auto-Gas' sign, and be a bit weary of doing long journeys and anticipating finding gas to get you home.

BUT, having the original petrol tank; I can burn Full-Price-Fuel; and have similar range...

NOW: I have a boot-mounted LPG tank in the Rangie.... great for giving me lots of gas, but completely ruins the practicality of a 'large' estate car, sat accross the back seat, so the seats cant be folded down, and robbing so much space that the boot's hardly bigger than that in the Chavic.

My old Rangie has twin 45 'under-slung' tanks; doesn't rob me of any boot-space, but does rather reduce the ground-clearance for off-roading.

Ideal, I have never got round to sorting, is to remove the underslung tanks from the old Rangie, and instead of fitting them as they are on that under the sills; removing the petrol tank, and hanging them under the boot-floor where the petrol tank would live. Two round LPG cylinders still take up a bit more 'space' than a single square petrol tank, and will rob a tad of ground clerance, but not so much as under the sills.... BUT I then have NO petrol tank.

Conventional answer is to use a small 'auxilliary' petrol tank, mounted either in the side of the boot, where the filler pipe comes through, and where the Jack & Wheel-Brace are normally stowed; finding a new home for them inside the spare wheel; and/or under the bonnet on top of the inner wheel arch.

Those Auxilliary tanks can hold perhaps 14l/3gal each; and are 'enough' for cold-start on petrol, and provide a LITTLE bit of 'reserve' if you cant find gas... but 3 gal at 13mpg if you cant find an LPG outlet within 30 miles, you are going to be petrol station hopping all the way home to run on FPF!

Translating that to a motorbike.....

To meet regulations; you would have to have the thicker, heavier 'external' tank, so you would be looking at something like a Caravan propane bottle for a fuel tank; maybe 7.5-15l ish to be a reasonable size to fit on a bike.

You would then be looking to put a propper petrol tank over the top of that, to give you Duel-Fuel, and hide the LPG cylinder; probably only another 5l/gallon or so.....

3.5 gallons of LPG, on my 750, at 50mpg, would give a 'reasonable' 150mile range.... but a gallon of petrol, would be rather restrictive, especially if I was on an excursion and couldn't find gas.

A 7.5l LPG bottle would probably be more 'do-able'; but that's less than two gallons.

This rather defeats the objective for a cheap mile eater.... you wouldn't eat many miles if you were having to stop and tank up every 60-70 miles, with a small tank, and wouldn't be much better with 120-150 range tank, paranoid of draining it, worried about finding fuel.

THEN we get to the performance issues: LPG tanks are heavy. swing a 15l caravan gas bottle around, even empty its no small weight. This is going to compromise both the styling of the bike and the performance. You then have the evaporator to turn it into vapour, and the 'auxilliary' carburation system to meter it into the engine, and the 'switch-over' kit for 'Duel-Fuel'.

This all takes space, and adds weight; on a gas guzzling Range Rover,m with loads of room, as shown space is still a 'bit' tight, but you do have plenty to play with; you don't on a bike. And weight, on a two ton car isn't a big deal, it IS on a 400lb motorcycle.

Then there is 'cost'; talking to people with the idea of 'gassing' Range-Rovers or Land-Rovers; they are often rather optimistic about the ecconomics and the 'pay-back' time, figuring that at umpety miles, and half price fuel, it will only take ten or twenty thousand miles to get the cost of conversion back in fuel saving...

Doesn't really work so neatly in practice though; and you only save when running on gas; still need to sup the expensive stuff on start up, or when you dont have gas.

And the 'margin' for recouping conversion costs, depends on how low your mpg is to start with, and how many miles you do, to recoup the saving.

On a 13mpg vehicle covering average annual miles, around 12,ooo, that's, about 925 gallons/ 4000 odd litres, maybe £5K of fuel...

Saving aprox 40% on fuel price, depending on ratio of LPG to FPF you actually manage to use, you COULD save perhaps £2K in a year.... but that would only be the cost of a DIY conversion using second hand and low tech 'mixer' technology. Cost of a high end conversion on a Rangie, using new parts and more sophisticated 'closed loop' mixture valve on a mixer, and better tanks, you are looking around £4-6K, and for a sequential injection system, pro-fitted, five figures.... which you MIGHT get back on fuel savings in around five years.

Ecconomics make it 'Do-Able', but on a typical 'family' car worth around £6K, expected to last maybe three years, often not.

And that's a case where the margins are wide; low mpg - high miles.

On a bike? Where average mileages are typically around 3-6K, and the fuel consumption more often around 50mph or better? The margin to make it ecconomical is getting slim, and the 'recovery time' to make the cost of conversion worth while, very very long.

So the bottom line is; it's not really an ecconomic viability, for the savings that could be found. Let alone the inconvenience of finding scarce gas; and any impligations on the conversion of making the bike still look reasonably pretty and not loosing too much performance from it.
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[stinkwheel]

Mate did it to his BMW R80 outfit (calor bottle in sidecar).

It kept eating valve seats post-conversion. Not sure how much testing has been done on small capacity, air-cooled engines.
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[Teflon-Mike]

[stinkwheel]

[Teflon-Mike]

[Shaft]

[sickpup]

I've looked into this a lot and concluded it can only be done on single seat converted bikes and scooters.

There are special round tanks available for scooters and there are gubbins available for vehicles of less than 60bhp as well as bike specific parts and parts suitable for air cooled bikes.

For big bikes you would need to do a single seat conversion so you could fit a Keith Gold box like the black one in the picture on the main page on here and ideally a powerbronze fairing to hide everything under. Use a full toroidal tank, the smallest commercial one is about 33 litres so I estimate fully loaded will weigh 50 odd kilos. I would go for a custom made toroidal of about 20 litres, this would be lighter and take up less space. A full toroidal would fit nicely in the bottom of a Keith Gold box and you could pretend it was a very light pillion.

As Tef states the problem is the return on investment, it only really works if you do 20k+ a year and can move the bits onto another bike after 3 years and stay using it.

[stinkwheel]

You could build a bike using a large propane cylinder as a stressed member, weld a headstock and engine/subframe lugs to it, throw a saddle over and away you go.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[goto10]

The mileage is the thing that made me think about it, I commute 22k miles a year and every day I go past a BP that [allegedly] stocks LPG (whilst taunting me with the price of it)
From reading the above information, it pretty much rules it out as feasible - I suppose if it were easily do-able then people would be doing it.
Cheers for all the feedback though!
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'12 NC700S & '12 CB600F Hornet [Stolen by some dickless twat] Suzuki GT500 shed

[dtoma]

Hello,
My name is Toma I`m riding on aprilia lpg powered and I`m interested to share experience regarding LPG two wheeler conversion.
https://www.youtube.com/watch?v=wF5zViHtLy0
I`m owned a workshop in greece www.motocontrol.gr
Thanks

[colicabcadam]

better off buying somethig like a gilera nexus 250 - 65mpg in TOWN, 80 mpg on a run, they do 85 mph too

you'll strugle to compete against that on an lpg converted 600+

i know a car kit costs around £1,500 quid so i suppose it would be similar for a bike - £1,500 quid on an average bike will get you 15000 miles......
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[Kickstart]

[Vincent]

When LPG started to become commercial, a mate of mine's Dad had a company called "Travel Gas". He used to convert loads of different types of vehicles, (including a Fire Engine that we'd get to borrow ), but I don't believe he had ever converted a bike.
Just thinking about another post on here about a bikes frame being used for the oil tank, I presume you can't compress LPG too much? What's the max pressure of a car LPG tank?
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[hmmmnz]

we have an old mazda van that has over 500000km on it,
its always run lpg, leaks a bit of oil but never had a break down,
still runs like a dream too,
but its an old carb'd thing an hardly what you'd call a performance
vehicle
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Wiring Diagrams BIDNIP it bitches

[Itxi]

https://www.gizmag.com/meet-the-greenfly-the-worlds-first-lpg-motorcycle/10414/

Interesting design, never seen a bike with a single piston for suspension at the front before
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[Tarmacsurfer]

This is a ZZR1100, belongs to one of the guys on another forum I lurk on.

CLICKY

Worth watching the update linked in the description as well.
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[Rogerborg]

Sounds like "ace project but never get your money back" territory.

I looked into it for a ~20mpg / 15,000 mile per annum car about a decade ago. Even with the available subsidy and LPG stations on my regular commute, it just didn't make sense once you factored in the initial cost, the insurance raping, the "yeah, good luck with that" warranty issues and the question mark over whether it was raising or lowering the resale value.

In the end, I just chopped it in for a more efficient car. Bike-wise, I think you'd be looking at a 250 or the NC700S or G650GS for those purposes.

The sums might be different now, although I doubt that the downsides and risks have changed.
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[Matt B]