2-Cycle motorized bicycle Performance Tables/Charts / Data Compilation

Kioshk · Feb 20, 2013

Hi all,

Has anyone compiled or considered compiling performance data related to our 2-cycle kits? I'd be very interested in collecting members' data related to engine-size, carb-type (and related jetting/needle setting), load-weight, wheel-size, cruising-speed, and pre-mix numbers to start with. I think this type of empirical data, when collected and presented properly would be an invaluable resource, especially for new MBers. I'm less interested in theory than specific performance characteristics on our China Girl builds. If someone knows where this data is, please point me in the right direction; otherwise I propose we start collecting this data systematically. I have a background in web development and data management and could create a simple off-site form to accommodate this if the administrators agree.

young grease monkey · Feb 20, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

Sorry to burst your bubble, but these engines have such poor quality control and tolerances that every engine is different and you can't apply the same settings to every bike. All you can do is know the signs of problems so you can fix them on each individual bike.

Bikeguy Joe · Feb 20, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

...yes, and listen to them closely so as to know what they need.

Just like engines in the "old days".

Kioshk · Feb 20, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

I agree that it's important to familiarize yourself with the idiosyncracies of these engines, and that using your own senses to monitor and diagnose their behavior is absolutely essential to their survival. However, I think it's irresponsible to write off data collection as useless based on the assumption that these engines are so sloppily manufactured that they can not have their performance characteristics usefully classified. The tolerances of our cheap little engines are large, but I am confident that their performance-boundaries can be usefully defined for our use. One important parameter I neglected to include in my first post was sprocket-size; this is important since I, with a 320lbs have a 29" build on a 66cc with a 56T. That's after having the same kit on a 26"er which resulted in a large difference in carb settings.

crassius · Feb 20, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

I'd be more inclined to think that the angle the carb sat at on the two bikes made the diff in settings, or maybe just that one frame allowed more fuel foaming in the bowl on one of them.

Bikeguy Joe · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

Here's the thing.

The made-in-china two stroke "80cc" engine is so unpredictable right out of the box that one basically takes is out of the box, mounts it on the bike and goes from there.

There has been for years now a massive amount of info right here on the forums as to what to do after that.

Putting together a ''table of data" that say "my bike has an "80cc", nt carb, total weigh of 300 pounds gross with 40:1 fuel mix with Penzoil non synthetic oil, does 28 mph top end is going to do anything for anybody coming in to the hobby.

There is a thread right now that is similar, but it's just a bunch of "info" that is handy only for comparison of random bikes.

Two bikes, with identical specs right down to the elevation/fuel mix/ect are going to perform differently for several reasons.

16v4nrbrgr · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

Tiny details make a lot of difference in small engines.

By using a gearing calculation and the realistic crank hp (1 HP?) of a motor, you could crank though some physics to get a rough idea of your performance, and by adjusting for wind drag you could find out where the drag equals the force of the bike and you stop accelerating.

It's not worth it, too many variables.

Kioshk · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

I'm surprised by the volume of dissension; I proposed that we collect empirical data SYSTEMATICALLY. I agree that these builds are characteristically "all over the place", but as I said, I am confident that there are defined boundaries of their performance that would be useful to us. Errors of 5%? 10%? 25%? Who knows? Exactly, "who knows?". Not us. Even very fuzzy boundaries of system characteristics are useful if you know how to apply them to your situation.

Yes, there is TONS of information here regarding performance-characteristics, but that's the problem; it's not as useful as condensed and well-defined information.

Bikeguy Joe · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

Dissension? lol, I think it maybe just an over-complication of a simple thing. But if you feel the need, get back to us when you finish it.

Kioshk · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

*GROAN*

How is gathering and analyzing a few simple metrics from our China Girl members in a central location over-complicating things?

Bikeguy Joe · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

Well, I think the fact that this thread has no support and has gone on this long is evidence enough.

crassius · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

well, I for one can't tell most of these engines apart even when disassembled - I can see long barrels & short ones, balanced cranks & cast ones, long conn rods & short, high wrist pin holes & low, but no idea who makes them or who sells them

no idea what size an engine is between 66 & 68

no idea how much horsepower, what RPM I'm getting, or how fast I'm going

I have no tools or instruments to collect anything like this.

maurtis · Feb 21, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

I can certainly appreciate your approach, but the pushback here is that it is a wasted effort. Due to the low quality of the china girls right out of the box, if you take samples of the same manufacturer on the same bike and compare them back to back, they will likely all run differently.

Add to the equation different bikes and riders, different manufacturers using slightly different components, etc, you end up with a whole lot of data that really does not tell you anything other than some motors run better than others, for some reason. Is it the break-in method? Is it the type of oil? Is it just a good motor?

With enough data I am sure that eventually you might be able to draw some conclusions, but with a sample of a couple dozen? Most likely not...

For the record, my BGF RB80 running a couple tanks of Briggs 2-stroke oil at 32:1 and then Opti-2 at 100:1 blew the wrist pin bearing at 500 miles. It had a Speed Demon pipe and Puch 70cc hi hi head. Are RB80's bad? Dunno. Did the Opti-2 have anything to do with the wrist pin bearing going early? Dunno. Did the higher compression lead to the early demise? Dunno. Did I treat her like a dirty whore? Yes, yes I did...

So I think we can conclude from that data that the number one killer of china girls is... ME! Anybody want to let me test ride their build? laff

crassius · Feb 22, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

I break in at 16:1 and then run 32:1 forevermore - never had any wrist pin problems.

but then, who knows?

maurtis · Feb 22, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

crassius said:
I break in at 16:1 and then run 32:1 forevermore - never had any wrist pin problems.

but then, who knows?

But that is exactly why people are against this type of thing, since someone grabs onto a piece of info like that, starts posting that if you don't break in at 16:1 you will have wrist pin problems, then after enough time becomes "internet fact".

There are plenty on here who run Opti-2 at 100:1 with thousands of miles with no issue.

Bikeguy Joe · Feb 22, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

That's all I was saying.

You can do 1,000,001 things differently, and it may or may not make any difference and to compile a bunch of info will be a moot point.

16v4nrbrgr · Feb 22, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

Ok, I'll post my limited experience with a 66 engine. I don't think charting is worthwhile because of all of the variables including the rider himself. Anecdotal bits are strewn through the site on speed readings for their bikes, which has raised contention, in reality you won't have any idea what your performance will be until doing it, things like humidity and air temp and pressure can have big effects on the performance of one of these motors due to carb tuning affecting performance, and elevation levels hurting performance in the mountains.

Two strokes are all about the conditions being just right to promote spool up toward and through the powerband, things never really being just right on a HT. This is acceptable because of the low cost of the motor, but I have to say that it is the most unpredictable engine that I've ever encountered reading about in my life!

OCC stock 20" rear wheel and tire, PK66, NT, long poo pipe, Lucas @32:1 44t, 32 mph strung the heck out, and I could take off with a push and the clutch, no pedaling

The_Aleman · Feb 23, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

I've had 5 HT66s; 3 Dax and 2 GT5s. All were straightplug head and ran the chrome stock exhaust. I found taking em over 6K for extended periods was bad lol

I ran Valvoline 2-stroke at 20:1 for a few hundred miles, then Lucas 50:1 thereafter. Gear em to turn about 6K at 30 and I'd try to stay under it

Must be said, I'm a pedaler. Sometimes I'm pedaling hard and sometimes I'm not. This probably has an effect on engine lifespan.
After all, chinagirls really only oil themselves properly under load!

Only 2 of my 5 engines lived over 3K miles before needing a wrist pin and bearings. 1 Dax and 1 GT5. How many more variables wouuld you like on your chart?

biknut · Feb 23, 2013

Re: 2-Cycle MB Performance Tables/Charts / Data Compilation

I think the idea is basically sound, but the problem is there's no uniform definition of a china girl. Almost every motor brand is different in some way. Many times you can't even know what factory made your motor. From my own experience, I know there's a lot of difference between a Flying Horse motor, and a BGF motor. After buying 4 BGF motors, there were differences between all 4 of them.

Another big problem is the difference in skill level between the tuner owners. Not meaning to knock forum members, but data coming from all forum members will mean a great deal of said data is coming from low skill tuners that lack experience.

These variables would somehow need to be taken into account, and separated before much useful information could be glommed from the data. I think that's why the experienced tuners don't have much confidence in the concept of trying to mine the data.

In spite of all that I still think the idea is a good one, but the execution would be very difficult.

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2-Cycle motorized bicycle Performance Tables/Charts / Data Compilation

Kioshk

Active Member

young grease monkey

New Member

Bikeguy Joe

Godfather of Motorized Bicycles

Kioshk

Active Member

crassius

Well-Known Member

Bikeguy Joe

Godfather of Motorized Bicycles

16v4nrbrgr

Active Member

Kioshk

Active Member

Bikeguy Joe

Godfather of Motorized Bicycles

Kioshk

Active Member

Bikeguy Joe

Godfather of Motorized Bicycles

crassius

Well-Known Member

maurtis

New Member

crassius

Well-Known Member

maurtis

New Member

Bikeguy Joe

Godfather of Motorized Bicycles

16v4nrbrgr

Active Member

The_Aleman

Active Member

biknut

Well-Known Member