4-stroke engines quieter?

sparky said:

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?

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I was really curious about this also.

Here is my understanding about these kit engines. The 4 strokes (both the Honda and HuaSheng) were designed for commercial use. Most commercial applications will run the engines at the rated power. The rated power for these engines occurs at about 6800-7000 RPM. This is not the maximum allowed RPM. Commercial use is usually for extended periods depending on the application. The HT 2 strokes (without forced cooling) are not rated for commercial use and I would think that running these engines at their maximum power (not necessarily max RPM) for long periods could bring up reliability issues. In other words the HT 2 strokes, I believe, are designed for varying loads as encountered in using a bike for occasional transportation and not at a maximum power load over extended periods of time. This is how I understand these engines from their original intended use by the manufacturers.

66

I'm guessing that Zev's issue with 4-strokes is based on his Subaru/Robin EH035. Perhaps the 48~50cc's are a good bit more reliable for running full throttle at long times.

Soo... I've gotta bring this back up again, since my EH035 should be here in the next week or so.

Has anybody had a specific problem with running either a 2-stroke or 4-stroke for too long?

Are there any "guidelines" anybody'd like to throw out for running 2-strokes & 4-strokes WOT, besides "don't do it going downhill"?? Something like... 'Don't run a 4-stroke wide open for more than 20 min at a time'? ... or 'Don't ever run a 4-stroke for longer than an hour, regardless of throttle position'? Or should we stick with the 'Just vary throttle & keep it at a reasonable speed (rpm)'?

Which brings back another question, are continuously high RPMs the sole factor affecting these 4-strokes? Will gear reduction allow one to ride longer with a WOT, or is there still as much strain?

Sparky treat your new motor just like you would your car engine. Running any motor WOT for any length of time isnt good for it. Some here stated that 80% for a length of time is about right and feels right in the sound of the motor. Indy cars are designed to run WOT and after 500 mi they are toast and used for spare parts. TREAT YOUR MOTOR LIKE YOU WOULD YOUR CAR ENGINE!

Sparky, your 2-stroke is different to the HTs we talk about here. Your's is a high precision made Japanese motor and it will perorm like the Honda and possibly better. That motor has been used to drive tandem bikes all day with two people on board for an entire cycling holiday around Tasmania. That doesn't mean they went gunning along at max throttle all the time because it's neither sensible nor possible. You'll use peak throttle quite often and then you'll coast down hills with motor just idling and slow down in places and probably stop occasionally for whatever reason. Whoever wtote that 2-strokes can go all day and 4-strokes can't etc seems to have got it the wrong way around and who drives flat out everywhere anyway?
If you were to go to Bonneville Salt Flats and spend a month blasting up and down the flats all day at WOT your engine might not last long but I wouldn't be surprised if it lasted longer than a Honda doing the same and it would cxertainly last a lot longer than those HTs.
Don't worry about it I think you'll know what is best for it when you start riding it. It's a strong motor with a great proven reputation for bicycle motoring. You can read about the tandem trip where they towed a trailer with the Robin motor for 750 km over tough mountain roads. It's towards the bottom of the page. Admittedly they had gears.
http://www.macleaycbd.com.au/cycles.html

Why shouldn't we run a 4-stroke over two hours ? I don't think that my 4-stroke knows the difference between the 1 1/2 hr mark verses the 2 hr mark of running time --- most engines (I would think) will be as warmed up or hot as they are going to get in an hour. When we get in our car - how long does it take to warm up ? We used a lot of these small engines at my old job -- used as power for portable water pumps, small power equipment, ect. -- many of these operators (if I may call them that) were VERY HARD ON THESE SMALL ENGINES !!! At many times they would run full throttle from a cold start --- running full throttle for 5 to 8 hrs at at time --- and yet, I never saw one blow up that had the proper oil mixture with 2 stroke -- or engine oil up to level - 4 stroke... Does this mean that I run my 4 stroke hard, fast all day long -- no - I give it a break every once in a while -- I only run at full throttle maybe 50 to 75% of the time.. I have always treated 2 strokes and 4 strokes the same.. Happy Riding from - Mountainman

No, it's a combination of factors, high inertial loads at high speeds,high combustion pressures,affecting pistons&rings,high internal temp.affecting piston lubrication,destructive vibration causing metal fatigue.Gear reduction per se has nothing to do with it,but high temp can make quite a difference in air-cooled engines.2 strokes are not inherently less reliable,but they are usually more thermally stressed,(higher power/weight ratio,esp.if not forced air cooled,and can suffer from lack of lubrication on long downhills, if engine braking is used.(don't do that).The durability of an engine has much more to do with it's provenance than the type of engine I would never run an engine continuously at max. power,unless I was in the racing business then your SOP is to routinely tear things down and replace highly stressed parts,that are likely to fail.

Then follow the new guideline, "Just don't ride it like you stole it"... and you should be alright.

I'm not worried about blowing the engine.

I run mine at half throttle or 3/4 throttle most of the time, but on long roads, I'll run it full throttle for long periods with no problems. I have a 6.5hp Lifan engine, and I'll run it past 3600+RPM continously sometimes when I want to go fast or make good speed on the highway bike/shoulder lanes about 40-45mph.

Many small engines are meant to run for long times at the full governed RPM limit for the whole time, like a lawnmower does. However on a bike, the MPG suffers more when wide open.

To save gas MPG, lately, I'll use just enough throttle to push me up the road without slipping the clutch, (20-25mph) and get great results and a cooler engine.