GX35 Running Costs?

Discussion in '4-Stroke Engines' started by Tressie, Aug 1, 2013.

  1. Tressie

    Tressie Member

    I just ran the numbers for my 48cc HT bike motor, de-tuned to 200W, and it seems it's cheaper to fuel my Honda Jazz. My 3-litres per 100km doubles in expense when 2-stroke oil is factored in, so it looks like I'm better off driving! :ack2:

    Okay, so how do 4-strokes go on fuel, and in particular the Honda GX35, when puttered-about at no more than 25-30 km/h?


  2. grinningremlin

    grinningremlin Active Member

    The HT/China girls (from what I've read) are all gas hogs, and if you factor in how much oil you use to run, highly inefficient.The GX35 will surprise the heck out of you with it's mileage, and how quiet it is.If you still want 2 stroke power/speed try a Tanaka PF4000, it uses a 50 to 1 oil mix, basically smokeless, and plenty of power.
    My EH035 is the equivalent of the GX35, VERY quiet, and I figure roughly 175-180 MPG, my PF4000 goes considerably faster/quicker and roughly 150 to 170 MPG.HT are disposable engines, Honda, Tanaka, Robin Subaru, will last and last, and if looked at properly are cheaper in the long run.How much is "no engine problems" worth?
    Good luck, GG.
  3. Tressie

    Tressie Member

    Hi GG,

    Ah, that was just the bit of news I had really been hoping for. I have a GX35 copy on order from China, and I'm quite frustrated at the difficulty I'm having in finding affordable drivetrain components (to Aus.) to finish the job. Once I got the HT running costs figured out, that was pretty much it for petrol engines for me. I subsequently cancelled my GX35 order, and started to look at completely unsuitable electric alternatives.

    Thankfully, you've managed to allay my concerns about changing to a 4-stroke engine, and the Honda copy motor acquisition and drivetrain component hunt are back on.

    Thanks for the very welcome dose of perspective, GG. Yes, a quiet engine, with good economy and reliability, will be just the ticket.

    T. :)
  4. bigoilbob

    bigoilbob Member

    Since the thread title is "GX35 running costs" I'll limit my comments to that. But maybe include stress as a cost.

    Low, low, low. I've got ~130 hours on mine, and NO problems. Changed oil 4 times, with less than 1/2 quart, and occasionally check the air cleaner/element. Truth is, I need to do that again, since I'm forgetting what it even looks like. The tiny engine IS kind of cold natured for the first 2-3 minutes, but just runs thereafter.

    I've got a Nuvinci kit that keeps the engine above 5500 r/m and I keep it below 8000 with a tach. But I spend lots of time at full throttle on warm days, with no hot engine power loss. I think forced air cooling not only helps performance, but longevity. I get ~125 m/g, but I'm on a heavy recumbent tandem, with losses thru the Staton drive and Nuvinci hub, and occasionally with a passenger, lawn chairs, refreshments and picnic supper (summer park concerts). Now, I've read about repair complexity/costs, but I'll just save up. After all, it's a Honda!! My buds constantly tweak their 250's and 450's without lower end mods or problems. Overbuilt = stress relief, both mechanical and psychological.

    Power is outside the scope here, but you can obviously stay legal and have 2-3* the power with a "49" cc 2 stroke. And they are getting more tractable and less smoky every year. But the GX35 is perfect for what I want, quiet (enough), and green as grass to boot.
  5. Tressie

    Tressie Member

    Hi BOB,

    That's my first experience hearing about the GX35, and it sounds very much like you're fairly pleased with yours, BOB. I read something about CVT transmissions with small 4-strokes, and that users try to keep the revs up quite high. Maybe 5500 RPM at a cruise, as opposed to something like 3500-4000 RPM for a HT 2-stroke (?). That seemed to worry me a little, but if you're getting 125 MPG at over 5500 RPM, then I'm sure that's what I'll be setting up for. I guess with only 1 power stroke in 2-revolutions, the 4-stroke has to spin nearly twice as fast as the same size 2-stroke to make similar power (?).

    I just Googled the Nuvinci transmission, and that's a new one to me also. I was looking at a belt drive CVT, but a suitably large sprocket to drive my 26" back wheel still eludes me. Even the small 10-tooth drive sprocket is a bit out of reach. There are 1 or 2 drive sprockets for #41 chain available on US websites, but the extra $50 shipping to land each one in Aus is making me look at other options first.

    Glad to hear you're having some fun with the recumbent, BOB, choofing off to concerts, etc. I'm planning some long distance rides up the WA coast as soon as the weather warms a little, which you can do here in West Aus with not much more than adequate water and a light sleeping bag. Can't wait!

    T. :)
  6. bigoilbob

    bigoilbob Member

    G'day, Tressie;

    One man's opinion, don't hook a GX35 to a Nuvinci 360 (what they are selling now) CVT. Not beefy enough. I have an older, heavier, 171 version, that I shift automatically with a power shifter. I don't think they sell them any more, probably because of problems getting enough power to the power shifter. I had to build a full 12 volt, 70 watt charging system to power the shifter. It was very satisfying to do it all "myself" (thanks again for the critical advice, Loquin), and having a high/low ratio of 3.6 instead of 2 (as with most belt drive CVT's) is nice, but it was lots of work.

    I set my trans to shift at 5500 r/m to stay safely within the fully engaged speed of my centrifugal clutch. I have a standard clutch and I believe it engages at ~4000 r/m. 5500 is also my peak torque speed.

    Belt drive CVT's do seem to work well for lots of forum participants, but I am not well versed at all. Do some forum searches - lots of good stuff available. Also, look at L.R Jerry's posts. He has successfully adapted a bike derailleur type auto trans to a bike with an engine having about the same power and torque range as a GX35, and one of his videos has it shifting up quite well under power.


    Bob D.
  7. Tressie

    Tressie Member

    Thanks, Bob D.

    Well, the Nuvinci is a bit steep for my budget, though a rugged version is quite appealing. I imagine it might help me to make the best use of the permissible 200W motor output, especially whilst adding pedal power. My fixed ratio HT won't go a lot faster pedalled, as opposed to when not pedalled, but I'm sure some sort of CVT would make all the difference to that situation (?).

    Ah, GX35 centrifugal clutch comes in strong at 4000 RPM. Hmm, I hadn't considered that as a factor in my gearing analysis. I'm guessing that peak torque occurs at the same RPM as optimum efficiency, so the 5500 RPM cruising rate is starting to sound more sensible.

    Oh, I think I might have seen one of the videos of a motorised bike using the standard gears and derailleur to change ratios. It looked a bit scary though, as the guy on it was doing motorcycle type speeds, and I'm not really that comfortable above 30 km/h myself (~20 MPH).

    Well, I've priced out a few different options, and I think it's going to have to be a side mounted setup, with one of those tiny 5:1 gearboxes, chain-driving a 44-tooth (hopefully LH freewheel clutch mounted) HT style sprocket. I just need to find a half-reasonable and affordable freewheel clutch with a left hand thread, and some 14mm, 6-spline drive sprockets to attach to the gearbox. Presently, I'm looking at about $200 in delivery costs alone for those 2 items, but everything else is cheap and close at hand.

    T. :)
  8. HeadSmess

    HeadSmess Well-Known Member

    i dont know if its any comparison but i go through about three metres of 3mm line for every tank of fuel i use as a line trimmer... so about ten line changes.

    i also like to change the oil that regularly myself. at least while its only a few tanks old ;) after a few more tanks ill start being a bit stingy on the changes. wooeee. 100ml of oil :jester:

    any fourstroke will blow your mind if all youve played with is 2poppers...
  9. 5-7HEAVEN

    5-7HEAVEN Active Member

    Sorry to burst your bubble, but the tiny 5:1 gearbox reverses engine rotation.
    In other words, you cannot drive the gearbox and connect it to the left side bicycle rear sprocket.