Thinking about the "pros and cons" of a four stroke build...

markjs

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I don't know that I would ever really be able to afford to build a 4 stroke bike, but I was thinking a lot about it and watching videos folks have done. It's something I'd like to do someday, but IDK if I ever will...

Many say the "reliability" factor favors four strokes, but to me, it seems the opposite. First, almost everyone who isn't connected to selling something has chain alignment issues, and issues getting the engines to mount solidly where they don't move. So throwing chains seems to be a problem. Then I hear tons of clutch issues, it seems to me the centrifugal clutch is more problematic than the manual clutch of a 2 stroke.

Further, then they have transmission issues, where a 2 stroke has no transmission to worry about. I can't imagine one of these holding up long riding trails, dirt roads or even bad bumpy roads. Then you have oil changes, which to me seems like more of a PITA than just mixing fuel oil and stabilizer.

Just seems to me, in the long run, that 2 strokes are easier to build, and get and keep running right, with less trouble?

I mean I suppose none of these Chinese engines and kits is going to be what one would call "reliable", but it truly does seem to me that the 4 stroke kits are not only more complicated, but more expensive and problematic in the long run.

I wonder if anyone with experience with both would agree?

(PS Not really talking about friction drive setups, but just center mount engine kits.)
 
I don't know that I would ever really be able to afford to build a 4 stroke bike, but I was thinking a lot about it and watching videos folks have done. It's something I'd like to do someday, but IDK if I ever will...

Many say the "reliability" factor favors four strokes, but to me, it seems the opposite. First, almost everyone who isn't connected to selling something has chain alignment issues, and issues getting the engines to mount solidly where they don't move. So throwing chains seems to be a problem. Then I hear tons of clutch issues, it seems to me the centrifugal clutch is more problematic than the manual clutch of a 2 stroke.

Further, then they have transmission issues, where a 2 stroke has no transmission to worry about. I can't imagine one of these holding up long riding trails, dirt roads or even bad bumpy roads. Then you have oil changes, which to me seems like more of a PITA than just mixing fuel oil and stabilizer.

Just seems to me, in the long run, that 2 strokes are easier to build, and get and keep running right, with less trouble?

I mean I suppose none of these Chinese engines and kits is going to be what one would call "reliable", but it truly does seem to me that the 4 stroke kits are not only more complicated, but more expensive and problematic in the long run.

I wonder if anyone with experience with both would agree?

(PS Not really talking about friction drive setups, but just center mount engine kits.)
Then someone like me comes along who has had the same 4 stroke setup for 14 years (engine, gearbox, clutch). My setup is now on its second bike with a manual shifting system instead of an automatic shifting system.

Oil changes are easy, simply use a tachometer/hour counter and a siphon pump. On my current bike the Sidewinder neither chain has ever came off. On the LandRider I'd have to replace the bicycle chain once every couple of years. The engine drive chain never came off though. My engine/gearbox has never moved around on me. Also not all rack mounts are friction drives. If you go to the early forum photos you'll see lots of rear rack chain/belt drive setups.

If you're referring to china-girl 2 strokes they do have an internal transmission/reduction gearbox.

Then again maybe a very few others and I on here are just the exceptions and not the general rule lol
 
I've built about 12 bikes in all, both 2 and 4 stroke. My preference is 4 stroke because of noise, vibration, mixing fuel, smoke, etc.. Yes the 4 strokes are a bit more tricky to set up right but they're so much nicer to ride.
 
YEP...I have zero smoke with the P-85 very little if any vibration even when I hit 51 MPH, noise is more than tolerable, and I would rather mix oil and gasoline than doing constant oil changes...lol.
I can probably change my oil every 25 hours of use (in less than 5 minutes) as you can mixing gas lol
 
The problems with the cheap four stroke kits are like you said, the mounting plate, poor alignment for the transmission, and making pedaling very difficult.

Those problems can be overcome by using mounting it to a rear rack. Not particularly easy or cheap. But not tuned expansion pipe hard. Not frame building hard.

We get guys coming in here asking why their 49cc four stroke cant climb hills. The issue is always insufficient reduction for the system weight and grade of incline.

If you, your bike and everything you got loaded up is 400lbs, you're not getting up a 25% grade with a 32 tooth sprocket.

Over-gearing is part of the clutch wear issues, but trying to start from a stand still is also very hard on the clutch. These engage around 3k rpm, peak torque isn't until 5.5k. Thats hard on the clutch. Go carts and minibikes are notorious for burning up clutches in the same way.

Assuming you get the gearing right, everything aligned, and are willing to pedal your bicycle, the four strokes seem to keep on keeping on.
 
The problems with the cheap four stroke kits are like you said, the mounting plate, poor alignment for the transmission, and making pedaling very difficult.

Those problems can be overcome by using mounting it to a rear rack. Not particularly easy or cheap. But not tuned expansion pipe hard. Not frame building hard.

We get guys coming in here asking why their 49cc four stroke cant climb hills. The issue is always insufficient reduction for the system weight and grade of incline.

If you, your bike and everything you got loaded up is 400lbs, you're not getting up a 25% grade with a 32 tooth sprocket.

Over-gearing is part of the clutch wear issues, but trying to start from a stand still is also very hard on the clutch. These engage around 3k rpm, peak torque isn't until 5.5k. Thats hard on the clutch. Go carts and minibikes are notorious for burning up clutches in the same way.

Assuming you get the gearing right, everything aligned, and are willing to pedal your bicycle, the four strokes seem to keep on keeping on.
So we're in agreement, if you're going to build a small cc 4 stroke and live in hill country, then build a shifter bike.
 
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