Converting Lehr paropane 4 stroke to Gasoline

[Deleted Member 4613]

Propane tanks are not a problem because they come in all sizes, but it would be difficult to refill larger tanks. These have to be refilled by a propane supplier. So using propane for a motorized bicycle still looks very inconvenient for extended use.

 

[Silvaire]

does the adaptor to fill the 1 pounders from a big bottle include a spanner for the bleed valve? not quite the same as a tyre valve tool

A bleeder valve is not generally used in the home refilling process of small disposable bottles. You put the empty 1 lb. bottles in the freezer first before filling on order to get the needed pressure differential. You can find loads of info on the refilling process posted online. It is important not to overfill these small bottles - and the consequences of overfilling them is the same as with any other propane bottle. They should be filled by weight. You need to weigh the empty bottles and mark them with their empty weight first. You can then know when you have gotten them full. This is simple to do if you have a small digital scale.

These small bottle refillers are about a $15 item from Harbor Freight, or one can easily be made by joining a couple of specialized propane fittings that you may likely have laying around.

Edit:
Here is a nice writeup about refilling disposable propane bottles:
http://www.instructables.com/id/Refill-Disposable-Propane-Tank-from-a-Standard-BBQ/

Also, I don't know where to buy them, but there is a "legitimate" refillable 1 lb. bottle available:
http://www.mantank.com/green/refillable.htm

 

[Deleted Member 4613]

I'd rather put on a gasoline carb than constantly refilling small propane bottles. Yes, there are demos online of refilling these bottles but very few, maybe two, people who have used the Lehr propane engine on a MB. It just isn't practical.

 

[HeadSmess]

ok, requote your statement. "2 people that have posted anything on a forum board as far as i am are aware are using lehr propane"

until youve done it you cant say its practical or not.

it is a matter of personal opinion i guess, but ive found refilling is easy, so thats no problem.

i need to constantly refill a fuel tank with petrol anyway so whats the difference?

gas doesnt make a mess when it leaks unless someone sparks up

i get two hours run time on however much gas i squeeze in when i do refill (weigh...huh?)

at the price i get lpg for, theres nothing anywhere near as cheap.


the only reason im NOT running lpg or propane, whatever, is more because im lazy and got a HT and just didnt bother with mounting the lehr...properly, anyways. found it slightly too gutless for my um...area of intended useage, so shelved it til future times.

but, back to the original question, almost any walbro type carb will work with modifications, but one thing i didnt mention is that you need to be able to retain the existing airfilter. it contains the pcv/bypass valve that is part of the lubrication system, not just a breather valve or emissions thingy. its an oiltrap, and crankcase pressure is actually used as the "oil pump". the valve allows excess pressure to escape whilst retaining and returning oil to the sump.

you CANT bypass or remove it. or use the crankcase as a pulse for the carb.


makes it slightly trickier. finding the ideal carb is just that lil bit harder again.

 

[Deleted Member 4613]

Sure you can refill the small bottles by putting them in a frig, but imagine doing this every 2-3 days. Eventually, I would get tired of cooling bottles in the kitchen frig. With gasoline, I can just pour in more gas and I'm done. I think if propane was so attractive more people would use them for an MB. Did you know some large retail chains don't carry the Lehr trimmer anymore? One chain told me there just wasn't enough interest to carry them. I'm not against propane, just don't think this fuel will catch on with builders or with the public for yard use.

 

[Deleted Member 4613]

Here some additional information on the cost per gallon of propane. The cheapest price on propane I can find for refilling a bbq tank is $13.93. The tank holds 4.1 gallons, so the price per gallon is $3.40. At $19.00 refill, the price is $4.60 per gallon. The conclusion is propane is currently not cheaper than gasoline.

 

[HeadSmess]

how many kg is this bbq bottle?

auto lpg here in OZ is 70c a litre. not sure what that is in kg.

i can get 1 9kg bbq bottle filled for $15.

im getting at least 20 fills from 9kg.

whats with the fridge? run them til theyre empty and they seem to refill again... but id rather use the bleeder and fill them like any other sensible bottle is filled...decanting.

the biggest killer is the lack of backup/support. its an unfamiliar area, not many people even know about them, ie the lehr on propane. in australia...i must be the only person with one at all!

everyone who sees mine wants them though... novelty factor?


but anyways, back onto the petrol conversion.

with my last comment on keeping the stock air filter, yes. true.

but the carb type has been narrowed down to the type with a BARREL. mainly because the spacer block/ manifold on the lehr has the nifty lil fitting for the cable to suit one. operating the throttle was the biggest challenge i found with my conversion...

most newer model upper market (husqy, stihl, shindaiwa, etc) are fitted with the barrel types. most POS cheapies (ryobi, mtd etc) are fitted with standard butterfly carbs.

stating a specific carb other than the subaru one, cant be done...theres way to many numbers!

 

[Deleted Member 4613]

OK, Headsmess, you're paying quite a bit for your propane.A bbq tank is contains 4.1 gallons of propane or 17.425 lbs. At $14-19/ refill, that is 71-109 cents per pound. You are paying 1900/454 is 4.1 lbs or $15/4.1 or $3.65 per lb, way too much. To put it bluntly, you are getting scre. .

 

[HeadSmess]

where does the 1900/454 come from?

17.425 lb is pretty close to 9.0 kg. 8.5 if you get those lousy swapngo ones.... (its 7.9kg actually). we have 9kg bottles. probably 20#

i pay $15 for that much. (most people pay 30, ha ha ha)

thats around 80c a lb to me, give or take...

gallons...how many litre gallons are we talking? 3.75, 4.5 or 5L?

auto lpg is half the price again, or 70c-80c for 2 lb. we say litres, once again, what gallon are you using?

petrol, gasoline, benzine, is around 150 a litre here now. despite how better our dollar is currently... or $7.50 a (5L) gallon

so bottled lpg from my refiller is roughly the same as petrol, and auto lpg is half that price...

as for screwed...these bernzamatic 1lb bottles are $20 each... and noone has a refill service for them, even though they are refillable.

now thats getting ripped off!

 

[Deleted Member 4613]

I made the calculation on the info you gave, $15 for 1900 grams or, 4.18 lbs. But what you actually meant was $15 for one 9kg bbq tank - much different. Now if you say it's actually 7.9 kg or 7900 grams or 17.4 lbs, than your paying $0.86/lb 0r 86 cents per lb.
A normal price. It still comes out to $3.65 per gallon, since there are 4.1 gallons of propane in the tank. Not any cheaper than gasoline.