Too fat for a 4-stroke?

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iwasgandhi

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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. :mad: 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 :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 :unsure: , suggestions, comments? Thanks.
 
The 49cc Honda or Huasheng may work with your kit. The extra cubes may provide more durability.
 
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?
 
You can build yourself a 'big boy' 4-stroke like this for under $600.

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gasbike.net 49cc 4-stroke with 4G belt transfer case on a 29" Macargi Fatal Love coaster brake bike.
 
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.
 
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Geared properly you'll be OK...top end will drop as you gear it deeper. Why not try a 79 HF? They're cheap too
 
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.
 
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
 
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