Gasohol to propane - should have done this a lot sooner!

Discussion in '4-Stroke Engines' started by fleebell, Jul 2, 2012.

  1. fleebell

    fleebell Member

    I've got one of the little HF 2.5 engines on my tadpole trike and have had nothing but trouble with the local gasohol around here. I was having to stop every few blocks to drain the water out of the carb to keep it running. That got really annoying so I have now switched it over to a propane only system.

    I finally got everything installed today. I need to add an elbow between the tank and regulator so it doesn't stick up so high behind the trike's seat but it's running.

    It took me a few minutes to figure out where the choke needed to be to get the engine to run correctly but once that was done it starts right up and doesn't shut off on me now like it was doing with the local crappy gasohol.

    I ran around my neighborhood for about a half an hour and everything works fine. It idles properly and had no problems giving me full power if I want it. I wish I had done this last summer!

    Here is a few pics of the new installation. It also shows the new larger pulley I used to change the gear ratio lower. The engine to rear wheel ratio is now 15.8 / 1 with a top speed of 20 mph and yep, it's got plenty of trailer towing ability too.

    Lee B




  2. srdavo

    srdavo Active Member

    Once again, sir..... Amazing stuff !!
  3. bigoilbob

    bigoilbob Member

    Looks interesting, but how long does that little tank last? I get less than 3 hours in my Coleman camp oven. Also, does it keep up without icing up on cool days? I suppose worst case is you could plumb up two in parallel.....
  4. fleebell

    fleebell Member

    So far I'm getting about 15 miles from the little 1lb tanks. They are refilled from a #20 grill tank. The trike has a very low gear ratio of about 1/15 on the engine to keep the top speed at 4400 engine rpm down to 20 mph. It could get better if it was geared higher.

    I'm getting about 63-65 mpg on propane as far as I can tell. That's about right as I was getting about 85 on real gasoline. and about 75-80 on gasohol. It runs so much better now though I don't mind the lower mpg at all. :)

    I really don't know about the cold days yet... We haven't had a day below 90 degrees since I switched it over. It should be ok though as it uses the tank mount and bike frame as a heat sink or heat source too. I won't really know though until next winter.

    If I do have a problem then I'll just wrap a few coils of copper tubing around the muffler and a few around the tanks connect them with a couple of small hoses and use hot water to keep them warm by circulating warm water around them. With an ice cold tank and hot muffler below it; it should circulate just fine.

    Last edited: Jul 13, 2012

    TREEWK Member


    Congratulations, you are the first that I`ve heard of with a motorbike. Have been checking out systems and DIY options for my House Boat generator.

    Am curious about your details if you care to share more.

    For my generator, located a on demand regulator that mounts close to engine and controls fuel supply acording to throttle position and engine vaccum. If engine stops, propane is shut off because of lack of intake vaccum.

    The setup that appeals to me is: The gasolene system is left intack/stock, just shut tank petcock so no regular gas flows to carb.

    The propane is sent into the air cleaner or a spacer that goes between carb and air cleaner.
    If the propane runs out the petcock can be opened and finish ride on alcohol free gas.

    "Thanks for sharing with us".

    Have been having carb problems from the enthanal gas myself, gets old/tiresome after awhile.

    The vaccum controlled propane regulator is a safty item needed for a generator, about $35 + sh.

    Ron PS, after I posted this I clicked on your picture links and got a better view! Looks like you have a secondary on demand propane regulator.
    Last edited: Jul 14, 2012
  6. fleebell

    fleebell Member

    I used the modified carb setup. Mine wown't run on both gas and propane anymore, just the propane. I would love to know where you can get a vacuum controlled regulator for $35. (also called an on demand valve) I have a couple other engines I would like to switch over. That kit I got cost me $169 but it had the piece that went into the carb too. I don't need that as I can make that part now that I've seen what it actually looks like. My HF 2.5hp engine doesn't really pull enough vacuum for the setup that mounts on the outside of the carb before the air filter. I made an adapter and tried that first before I modified the carb on it.