Too fat for a 4-stroke?

Discussion in '4-Stroke Engines' started by iwasgandhi, May 3, 2014.

  1. iwasgandhi

    iwasgandhi New Member

    Am I too fat for a 35cc 4-stroke engine on my bicycle? I weigh 240 lbs, and I'm afraid to admit the unthinkable. Could I actually need a 2-stroke instead of a 4-stroke?

    I'm considering the purchase of a new Staton-inc axle mounted kit with a new Tanaka PF4000 (40cc 2-stroke) on it, and I seek enlightened guidance on the issue.

    Background: in 2011 I bought a new Staton-inc axle mounted kit with a new 35cc Robin-Subaru 4-stroke engine on it (with a 60 tooth large sprocket on the rear wheel and a 12 tooth small sprocket on the gear reduction box,... later switching to an 11 tooth small sprocket for more torque going up hills). I installed it on my 26" wheel hard-tail mountain bike, and rode it with glee all 4 seasons in NH, changing the oil and filters regularly, and putting approximately 2000 miles on it. Then one day the engine started losing power. I figured I had probably lugged it to death by going up one too many long, steep hills, especially given my weight, and given that the engine only had 1.6 horsepower.

    But instead of troubleshooting and fixing the Robin-Surbaru, I decided to just replace it with a new Honda GX35 (35cc 4-stroke), which I also ordered from Staton. However, after only 4 months of use, the Honda started losing power, too. :veryangry: Oil started seeping out and dripping from the cooling fins, and gas started getting into the oil reservoir (which I noticed whenever I changed the oil -- the used oil emitted a strong gas odor, and it also had an unnatural color to it, like coffee with cream). Some people later guessed that this was likely a mechanical problem called "blow by" (a bad valve or whatnot--I'm not an engine mechanic), but that was just a guess on their part, as I never actually got it diagnosed and fixed.

    So I'm wondering -- can "blow by" (if it was, in fact, blow by) be caused by a 240 pounder riding a kit with 35cc 4-stoke on it? And/or can it be caused by using E10 gas (10% ethanol--sold everywhere in my neck of the woods) without adding ethanol fuel treatment? I never used ethanol treatment in the E10 gas. For whatever it's worth, Honda's official small engine website says that their engines can take E10 (but maybe it gradually destroys the engine over a long enough period of time that Honda considers it no big deal?)

    In any event, last summer I just got fed up :icon_cry: and sold my motorized bike: kit, frame, wheels, tires and all. With the money from that sale I bought a used touring/hybrid bike with 700c sized wheels, upgraded it a bit, bought some camping gear, and did some long distance touring & stealth-camping. I even lost some weight (but, alas, I regained it). Now, after several long months without any engine whatsoever on my bicycle, I find that I've lost enthusiasm for pedaling to get everywhere, and I really miss my motorized ride.

    So, to make a very long story short, I'm wondering if I'd be better served by a Tanaka PF4000 (40cc 2-stroke) instead of a 4-stroke. Whether or not I choose a 2-stroke or a 4-stoke, I plan to put my new kit on another 26" wheel mountain bike.

    Could it be that, given my weight, I lugged these poor lil' 4-strokes to their early deaths? God I hope I didn't do that them, those poor fellow creatures,...

    I don't like the idea of the added noise pollution from a 2-stroke, nor do I like the idea of added air pollution from burning 2-stroke oil, nor do I like the added cost of 2-stroke oil, nor do I like the inconvenience of having to mix oil with gas, but maybe it's the best I can do.

    Any ideas :idea: , suggestions, comments? Thanks.

  2. wheelbender6

    wheelbender6 Well-Known Member

    The 49cc Honda or Huasheng may work with your kit. The extra cubes may provide more durability.
  3. butre

    butre Well-Known Member

    I'd just go bigger displacement.
  4. professor

    professor Active Member

    I don't think with a centrifugal clutch you can lug the engine at all (lugging means full throttle at very low rpm).
    However, I think you need a lot more motor because you are probably beating the little ones to death- over working them.
    Maybe if your gearing was real low, it wouldn't be so bad, like a top speed of 20 mph wide open and NOT over-revving, the little nippers would live?

    I weigh 140 and my bikes weigh about the same, but one has a 212cc and the other, a 79cc. Both use a 3 speed hub on a jackshaft. Gears are great.

    What is the biggest motor you can put on?
  5. KCvale

    KCvale Motorized Bicycle Vendor

    You can build yourself a 'big boy' 4-stroke like this for under $600.

    [​IMG] 49cc 4-stroke with 4G belt transfer case on a 29" Macargi Fatal Love coaster brake bike.
  6. LR Jerry

    LR Jerry Well-Known Member

    I'm 6'2" and weigh 250 lbs. I'm currently using the RS 35. I can go up 30% grade hills. The thing is with these small engines large people on steep hills must have gears. So you'd need a shift kit. Staton makes a really good one. I suggest getting a White Industries Trails freewheel in the drive side. The SI shift kit will let you put 3 chain rings on it. It comes with a 28; add a 34 and a 42. Get stainless steel ones aluminum ones wear out to fast. For the rear freewheel run a 8 speed 34-13. I suggest getting the 18.75 gear box. GB to SK 15:44.

    Here is the best way to shift entering up hill at a slow speed, carrying an extra load or really steep hills 1(1,2,3,). Level ground 2(3,4,5,6). Down hill 3(6,7,8). This way the only time you shift the front chain rings is when you're in 3 or 6 in the rear.This will eliminate gear redundancy, cross chaining and chain droop. When coming to a stop on a hill be in 1(1) before stopping; then use that as a starting gear. For all other stops be in 2(3) before stopping; then use that as a starting gear.

    The RS 35 has its max HP at 7000 rpm. Get the tachometer/ hour counter. Then be in a gear where full throttle will hover around 7000 rpm.

    I now run a fully automatic 5 speed system. But when I ran the manual system level ground speeds were around 28 mph. I could climb 30% grade hills at 8 mph. Down hill speeds were 45+ mph.
    Last edited: May 4, 2014
  7. Racie35

    Racie35 Member

    Geared properly you'll be end will drop as you gear it deeper. Why not try a 79 HF? They're cheap too
  8. LR Jerry

    LR Jerry Well-Known Member

    A lot of what will determine what kind if build you need is how steep are the hills where you live and how fast do you want to go. KC has done some really nice internal geared hub builds so that too could be an option as well.

    Whatever you decide get the tachometer so you don't over rev your engine. Staton sells them or you can get one from Northern Tools. They cost around $50.
  9. powerstroke

    powerstroke Member

    Lose weight = lose worry my friend
  10. Bonefish

    Bonefish Member

    Are you planning on going with another staton axle mount? I'm not sure you can use a Honda gxh50 or a hausheung 142f with that kit. I'm only 180lbs, and I'm bumping up from a honda gx35 to a tanaka pf-4000
  11. IbedaYank

    IbedaYank Member

    or you can just pedal to help the motor out going up hills ....
  12. KCvale

    KCvale Motorized Bicycle Vendor

    The 79cc Pred engines are cheap and powerful (this bike rocked) but the transfer case isn't, this 79cc Prediator with a Q-matic was like $375 and that's just the engine and Xfer case.


    The 49cc kit with everything (gas tank, base mount, back sprocket, throttle, etc) is less than that delivered.

    I really like that 29" Macargi frame for fitting big engines in and I will be testing it's limits next week as I have one of these 86cc 4-stroke, 4-speed kick start motorcycle racing engines on it's way to try to cram in it.






    Single cylinder, 4-stroke, 2 valves

    Bore x Stroke: 47mmx49.5mm

    Measurements: 17" x 10 1/4" x 8 1/4"
    Displacement: 86cc
    Compression Ratio: 9.47:1
    Carburettor: racing carburetor
    Ignition: CDI, 12 volt, permanent magnetic stator
    Maximum Power: 6 hp@ 7,500 rpm
    Maximum Torque: 4.25@ 5,500 rpm
    Gears: 4-speed, semi-auto, 4 DOWN.
    Idle: 1,500 RPM
    Final Drive: 14 tooth #420 front sprocket included (we have other sprockets on sale too!!)
    Lubrication: 0.8 liters, 10W/30 4-stroke motorcycle oil, pressure and splash
    Fuel: Unleaded

    Package Contains:

    Buyer will receive 88CC Motor, 22MM Carburetor, Intake manifold, intake gaskets, Shifter, Kick Starter, Wiring Harness, CDI, Spark Plug and Ignition Coil.


    $289.95 delivered and already ordered :grin5:

    I already have everything new in the shop to build it out, most of it free because of all the jackshaft and other custom stuff I do and left over parts get saved, so it won't cost me a cent more than the $289.95 for a 4-stroke 4-speed shifter other than the bike cost which is another matter...

    I spent all morning surfing the net looking for an ideal bike with good brakes I could mount this engine in with a rag joint left sprocket and came up dry.

    That's OK, I can upgrade that 29" $230 Fatal Love with a new front shock and disc brake wheel, throw a C brake on the back to aid the coaster brake, and a seat post shock just for giggles and grins for about the same so I should end up with a kick ass quick and fast comfortable new personal 4-stroke 4-speed shifter ride for under $500.

    That would get you around ghandi but don't expect to buy or even build one anywhere near that cost, when I sell it the price will be around $1,400 and worth every penny.
  13. IbedaYank

    IbedaYank Member

    he transfer case receives power from the transmission and sends it to both the front and rear axles. This can be done with a set of gears, but the majority of transfer cases manufactured today are chain driven.[1] On some vehicles, such as four-wheel-drive trucks or vehicles intended for off-road use, this feature is controlled by the driver. The driver can put the transfer case into either "two-wheel-drive" or "four-wheel-drive" mode. This is sometimes accomplished by means of a shifter, similar to that in a manual transmission. On some vehicles this may be electronically operated by a switch instead. Some vehicles, such as all-wheel-drive sports cars, have transfer cases that are not selectable. Such a transfer case is permanently "locked" into all-wheel-drive mode.

    now a Qmatic is a belt drive unit that uses a depending on version a centrifical clutch on the jackshaft or a belt tenshioner to tighten the belt between two pulleys not anywhere related to a TRANSFER CASE thats is used to split power between two or more differentials
  14. KCvale

    KCvale Motorized Bicycle Vendor

    Call a 4G or Q-matic a firg'n transmission if you want, it's a frigg'n CASE that reduces output RPM and TRANSFERS it to a useable chain sprocket but has no gear changing ability so I don't call it a frigg'n transmission.

    Now this 86cc 6HP 4-stroke I got in yesterday has an actual 4-speed TRANSMISSION in it and I call it such.

    Here are a couple of pics comparing it to a 142F without the 4G TRANSFER CASE on it.



    It's a 100 pound beast with a kick start and it took a lot of looking to find this stretched 26" Electra it would drop in by caring around a cardboard mock-up of the size from store to store, and even that Electra will be tight, and it' wouldn't even fit in the 29" Macargi that 79cc pred is in.


    $270 just for the basic bike out the door and it's going to need another $270 for a front shock fork and disc brake plus an additional C brake to help the rear coaster brake and then of course a sprocket, gas tank and throttle but that's about it.
  15. IbedaYank

    IbedaYank Member

    You say you run a shop but yet you have no tax id nor do you have a legitimate place of business. Commercial can not be run out of residential zoned property so your nothing more then a guy who thinks he knows it all. I feel sorry for the people uninformed enough to buy your halfassed crap. Ever figure out how lipo batteries are rated yet? Watts or amp hours and you claim to be such an Ebike expert!!
  16. LR Jerry

    LR Jerry Well-Known Member

    KC its my opinion judging from advice given and the many builds you posted pictures of; you're an innovator not an inhibitor. Keep up the good work.
  17. Old Bob

    Old Bob Member

    Actually if your business is an extension of your hobby in a lot of states you can run out of your house.You also have the option of getting a variance.Its done all the time.
    Sorry but your the one with half assed crap in this case.
    butterbean likes this.
  18. Fabian

    Fabian Well-Known Member

    Even a person who weighs 180 lbs is too fat for an anemic 35cc 4-stroke.
  19. LR Jerry

    LR Jerry Well-Known Member

    I weigh 250 lbs and go up 30% grade hills with a 33 cc engine. Its all in the gearing. Granted I may only be doing 8 mph but I do get up them. My 5 speed setup range has reductions of 45.83-21.57:1.

    I will say I've got a Honda GXH 50 I plan to change out with the RS 35. The Honda has a much higher torque. The new reductions will be 37.5-17.65:1. I plan to make a gas electric with the RS 35.
    Last edited: May 22, 2014
  20. Fabian

    Fabian Well-Known Member

    Oh hush now LR. Of the 4 points that are listed above, i believe on 3 of them: 250 lbs [and...] 30% grade hills with a 33 cc engine.
    the 4th listing of 8 mph is ludicrously over optimistic for a 33cc engine