4-stroke engines quieter?

[Irish John]

WOW... these responses are fantastic! Thanks everyone for teaching the noob a thing or two about a thing or two!

Two things are important with engine longevity for both the 2-strokes & 4-strokes. Rear sprocket size and wheel size. I run a 70cc HT with a 44T sprocket on 700C wheels and it will sit at 21 mph for an hour without any strain or overheating because the engine is at about 75% peak revs. I have also found that the larger the sprocket size on the 50cc 4-stroke the more wear and tear on the motor because of the higher revs. With a smaller sprocket I can sit at 30 mph for 20 miles with the motor running nice and warm. The Hts won't last long at full throttle and peak revs.

 

[sparky]

Soo... if you're gonna run a motored bike all day long, it's best for you to use a 2-stroke?? Or it's best to use a 4-stroke so long as your gearing is optimized? Seems like the latter would be more correct to me, but I dunno...

If I understand this correctly... I'm moving from a 2-stroke to 4-stroke of nearly the same size, I would be best off reducing the gear ratio? Will I be able to run all day long now?

Also, about the 2-stroke -vs- 4-stroke noise issue... the TLE43 is supposed to be fairly quiet, right? How does it compare to the EH035 and GXH50? Anybody heard all three of them?

 

[duivendyk]

You mean the same displacement or the same power output?.2 strokes have about a 25% power advantage,but their torque falls off more rapidly at low rpm.If you run ANY engine continuously close to max power (rpm) and/or at wide open throttle,it's not likely to last.Those without forced cooling are esp.vulnerable due to possible overheating which compromises lubrication.The important thing is not to undersize the engine.The quality of construction (bearings, tolerances ) is more important than the type,4 strokes are inherently a lot more complex,so component quality is even more crucial.

 

[loquin]

The TLE43 is a quiet 2 stroke, but, it's still louder than the 4-strokes of equivalent size. Not by a lot, but louder. Plus, the sound is pitched higher. More piercing, more 'popping' in nature. Not only do you have twice as many power strokes per RPM as a 4-stroke, but, the 2-stroke exhaust port & exhaust tuning, versus exhaust valves in a 4-stroke influence the sound as well, I would think. Think about it. With a 4 stroke, the exhaust valves open when the cylinder as at the bottom of it's power stroke, and the then the gases are pushed out by the rising cylinder. With a 2-stroke, the gases escape through the exhaust post, in the very small time frame that the port is open. The result is a 'pop', rather than a 'hiss.'

 

[sparky]

You mean the same displacement or the same power output?

Same size... so displacement.

I'm just curious about Zev0's comments that you can't run a 4-stroke all day long, unlike a 2-stroke. I'd never heard that before, and figured that since 4-strokes were more reliable... they could be run longer & more often.

But you said. . .

"... reducing your gear ratio would reduce your rpm and speed some,depending on the torque characteristic of your engine of which I know nothing.But it does not fundamentaly change the situation,you are pushing the envelope as far as I'm concerned and I would limit my speed to 25 mph or lower, then it would take you close to 2 hrs,or else get a more capable (larger) engine."

So, what I'm hearing is that a 2-stroke can be run all day long at full throttle, but a 4-stroke can only be run 2 hours max wide open (if you're lucky)?? If you vary the throttle, and mostly cruise at 20~25... could a 4-stroke go longer?

Also, what components of the 4-stroke would start to stress the most at running WOT for a length of time?

 

[darwin]

If a chevy pickup is capable of going 120 mph what do you think would happen to the drive train if you ran it that speed for 24 hrs? The answer should be obvious.

 

[loquin]

I'm not sure about that, either. I know that I've pushed 4-stroke garden tractor/lawn mower engines all day long at full or near full throttle, with no problems.

 

[sparky]

If a chevy pickup is capable of going 120 mph what do you think would happen to the drive train if you ran it that speed for 24 hrs? The answer should be obvious.

It's not obvious when we're comparing 4-strokes to 2-strokes, and others say a 2-stroke *can* be run wide open the majority of the day with just one gear. Wouldn't a 2-stroke also burn up just as easily?

I guess I'm looking for specific examples of either a 2-stroke or 4-stroke on a bicycle getting (or NOT getting) "burnt up" from excessive wide open usage of the throttle. I'm just curious as to how many people would even ride it wide open and not vary the throttle whatsoever. Seems like the only time this could really be an issue is when we're talking about cross-country trips, and 4-strokes are recommended non-stop. But if this means you can only ride two hours WOT, take a 30 min break, and start again... then maybe 2-strokes are better.

Just trying to figure out how serious this accusation that 4-strokes can't be run WOT for too long is. And I'd like to know if there's a time limit to running 4-strokes if the throttle is 1/2 to 3/4 open. And does reducing the gearing of 4-strokes, leading to less RPMs, mean there's less wear on the engine while you've actually got an increase in speed?

 

[Irish John]

I wouldn't advocate running any small engine flat out all day cos it will shorten its life. The Honda 50 & China copy seem very happy to run long distances at near full throttle but I think it helps to check every so often by feeling how hot its getting. The HTs do not like long fast runs I think I can speak on this with experience because I live in the country and all my runs are pretty long on open roads with no traffic stops. After a short time things begin to go wrong - used to be HT's bearings but nowadays the rings seem to be going. My Huangsheng is running very hot since I changed the GB from grease to lube and I suspect that will shorten its life if I don't change back again to lithium grease. The difference in temperature is alarming. The HT's definitely like you to stop after 30 mins of fast riding to let them cool down.

 

[HoughMade]

If you have a governor, most any quality 2 or 4 stroke can be run at the maximum governed speed for a long time....but I'm of the opinion that governors are neither needed, nor preferred on these bikes. Witout it, I could blow any engine up in short order.

However, any engine will wear quicker the faster it is run. There are simply higher stresses on every moving part. This would have an effect over time, but not in the short term on a governed engine.