Two Stroke versus Four Stroke

roughrider

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I do not wish to re-ignite the old debate…

Well, er, maybe I do.

The fact is, I decided to go with a 2 stroke for my first build, and that is despite my first impulse—a four stroke. So I'm a four stroke guy who's converted.

Here's why: 1, I just can't STAND the idea of how wide 4 stroke builds come out. I'm coming from a bicyclist's background, so width and weight are REALLY IMPORTANT! 2, contrary to the buzz, reliability is a function of the mechanic and the rider, not the engine. The deep study I have made of these Chinese 2 strokes has convinced me I can handle anything that goes wrong with them; more, I can make considerable improvements. I do not have that confidence with any of the 4 strokes. 3, the 2 stroke China Girls look really cool. The 4 strokes look… well, OK in the better builds, but only that. They don't just TOTALLY suck in the looks department. 4, CC for CC, two strokes just make more power with less weight. It's that simple. Facts talk, and BS walks.

But one selling point for the Chinese two strokes is that they are cheaper. That does not fly. By the time I was done ordering the mods and accessories, I'd spent just as much money as a basic four stroke kit.

But I ended up with a QUALITY 2 stroke kit rather than a cheapo 4 stroke build. First, I ordered a "Flaming Horse" from enginesonline.com. I wanted the kind that had the straight up and down spark plug, not the "slant." This accords with my understanding of the place the spark needs to be to get the proper fire. I got a 415 chain. I bought a spare muffler so I can experiment with an extension and various mods; plus, I've noticed that a lot of people have exhaust failures from engine vibrations. I also ordered a Jaguar CDI kit (which includes a hotter coil) and the NGK iridium plug. On top of that, I got a Sick Bike Parts engine hardware kit. The enginesonline stuff, with tax and shipping came out to just under $250.00. The Jag CDI kit was ~$75.00. Another ten (with shipping) for the plug, and fifteen for the SBP stuff brought the total up to $350.00. ALL that was with tax and shipping, of course. Real costs, not just advertised prices. Not cheap! Even so, I'm got the DELUXE 2 stroke kit (black, no less, with Allen head hardware, and quite a few spare parts) for the price of the CHEAPEST 4 stroke kit. But who knows what my additional costs will be?

I'm looking to do a Jaguar inspired series of tests for more bottom end torque. I don't really care about top speed. I need a torquey beast for pulling a trailer with camping gear in the mountains. Unladen, in the flats, I'd prefer a stoplight jumper. I'm gonna do intake and exhaust extensions for starters, starting with bone stock, followed by a series of cheap mods and tests. I won't even fire the engine up until I've broken it down and inspected every detail. (The enginesonline specs say that their motors already have good bearings and wrist pins. We'll see.)

So that's my first build design theory. This is all going onto a Schwinn bomber style frame, the only stock item being the frame. In another post, I'll put up the pix of the build. In the meantime I wait, impatiently.

With respect,
Rick
 
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I need a torquey beast for pulling a trailer with camping gear in the mountains.

Then you will need a Rock Solid Engines reed valve intake and a CR Machine Man twin spark plug cylinder head, not because it has twin spark plugs but because it has the biggest cooling surface area of any of the billet cylinder heads out there.

This is my heavy haul setup and it's set up to haul, though my next door neighbour gives me a hand on the mountain climbs:


 
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The deep study I have made of these Chinese 2 strokes has convinced me I can handle anything that goes wrong with them

Just about all of the Chinese 2-stroke Chinese bicycle engines come with the newer crowded roller big end connecting rod bearing, which has proven to be almost bullet proof for reliability and with the Jaguar CDI, you can expect to have excellent reliability and engine life.
The 4-stroke engines look like you've bolted some hideously ugly and ungainly large and clumbsy rototiller/rotary hoe engine on your bike - they look plain terrible and ugly as sin.

Mention must be made that it costs around $50 and takes 10 minutes to disassemble and reassemble a complete top end on a Chinese 2-stroke engine, and they are good for about 4,000 kilometers at high duty cycle.
 
Then you will need a Rock Solid Engines reed valve intake and a CR Machine Man twin spark plug cylinder head, not because it has twin spark plugs but because it has the biggest cooling surface area of any of the billet cylinder heads out there.

I have been wondering about the head, actually. I'll be installing a heat sensor. I won't be increasing the compression at first because I want to test and compare, doing mods bit by bit, carefully and patiently. A good part of the fun for me is the whole research process, and one thing I really like about these 2 strokes is that they lend themselves to tuning mods.

Great photo! Made me laugh.

(Also, I sent you a PM regarding your trailer recommendations, but it was bounced. The error given was that you had exceeded your storage limits. You might want to look into that?)

Cheers,
Rick
 
Yep

Tired, old debate. Whatever.....just keep it legal and you're okay.

I was being tongue in cheek. :giggle: I'm not really interested in the same old debate either! I have noticed that there is some real innovation happening in high tech two strokes in the world though. One suspects a comeback is under way.
 
Was that "tired and old debate" or "I'm too tired and old to debate"?Fabian, is that a pic of you?Nice set up, I thought the semis in Montana hauling three and four trailers were crazy.Personally I prefer 4 stroke, low end torque, ease of starting and low noise are the winners.
 
Apples and Oranges

I like both. I'd just hate to have to pick one over the other. It is not, to use a trendy aphorism, a "zero sum game." Picking a two stroke does not mean I won't use a four stroke.

Shoot, one of my other projects is an 82 Yamaha Virago 750. I'm doing a cafe racer with it. The monocoque frame and mono-shock were hidden by this lame-ass "chopper" look. Underneath, was a race bred, awesome machine with that bubbah-dah bubbah-dah super reliable V-Twin.

Seriously, anyone who does not like the sound of a big twin four stroke is, well, er, fracking insane. And while we are on the subject of sound, do not Harleys rule?

So yeah, man, I like the sound of four strokes. And I basically just hate the sound of two strokes. It is not the volume. It's the pitch. I'm not a fan of violins or lead guitars either. I like the bass, the bassoon, the trombone, and the cello. But that's just an aesthetic opinion; like any digestive exit orifice, opinions all stink.

Just being honest.

I had to get over that to even consider a two stroke build. However, a little research showed how to quiet down the screeching pitches. Sonic amplitude does NOT equal power.

All that being said, I guess what I'm getting at is that I'm super sensitive to sound. Part of my project is to get better bass and less treble out of my build. This forum has proven to be a grand resource for that. In this post, I avoid any technical details, but I think I got a handle on getting a good bass tone out of a two-stroke.

Regards,
Rick
 
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An easy way to quieten down a 2 stroke to almost silent exhaust levels is to attach 2.5 feet of high temperature soft silicone hose. The soft silicone absorbs noise tremendously well and under full throttle i can only hear intake noise.

Yes, we all like the sound of a 90 degree V-twin 4-stroke but unfortunately motorized bicycle engines are not made in a 100cc V-twin configuration that can be attached to a SickBikeparts shift kit.
If it was, i would have a small V-twin 4-stroke and SBP shift kit attached to my bike tomorrow, so long as it didn't look like a rortiller/rotary hoe engine.

I'd be equally happy with an 80cc boxer twin cylinder 2-stroke bicycle engine that could be attached to the SBP shift kit - It would be almost vibration free by design.
 
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