My Flying Horse is Flying

Dayuum my bike is running good.

This is the best I've ever gotten a china girl to run. Throttle response is excellent. 4 stroking is almost non existent. Low speed acceleration is clean, but the real powwa starts to hit about 4000 rpm @ 20 mph. After that it's like a stick of dynamite with a short fuse till over 8000 rpm (40 mph). I really don't like running it higher than 7000 though, which is 34 mph. Even that's too much for sustained cruising. The vibration level is comparable the best china girl motor I've had. Once I get the clutch out the acceleration feels like a little motorcycle. In other words there actually is some acceleration lol.

Through the whole tuning process the idle has been rock solid like a clock. It can idle all day without ever loading up. That seems to be more a feature of a speed carb than anything else.

One thing I'm still in the process of nailing down is gas mileage. I started out running rich with a 68 jet, and the needle in the leanest position. It was getting around 70 mpg maybe less, but I was running way fat oil ratio. Then I changed the jet to a 66, and I had to raise the needle one slot, because it stumbled if I snapped open the throttle. I dropped the oil ratio to 32:1. It ran well on the top end, and mid range, but 4 stroked at low throttle settings. Fuel mileage improved to 85 mpg. Today I dropped the jet to a 64. The needle clip is still in second to the top position. Oil ratio is now 40:1. This is the best yet. No 4 stroking now at any speed. I expect the fuel mileage to be around 100 mpg now, but we'll have to wait a little longer to find out. Low speed running is so smooth that running at ultra low speed might be closer to 120 mpg. As soom as I find out, you'll know.

I've done no port work, and compression is stock. Nothing at all has been done inside this motor. This is everything I've done to get it to run like this.

Flying Horse 80
MM shorty intake manifold
Speed carb
64 jet
Needle clip is second from top
High flow air filter
SBP pipe with 8" long header
40:1 Torco GP7 synthetic 2 stroke racing oil
NGK BP5HS 0.025 gap. Probably needs to a BP6HS soon
overall gearing is 4.9 mph per k rpm

2door said:

How many miles do you have on it, so far? If it's running this good and a new engine, just wait until you get 2 or 3 hundred miles on that puppy. You'll be amazed.

I'm glad it's performing for you. With warmer weather coming you're going to put some miles on it this summer; no doubt.
Congratulations. It's a great feeling when all your hard work pays off with a good running and reliable bike. Especially one that looks as good as Stunner.

Tom

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It's got 275 miles so far Tom.

It's twin motor in the Atomic BB took around 400 miles to break in. It's takes a little longer because I start running synthetic after the first gallon.

Both of these motors have turned out to be great ones. It's a tough life having to decide which great bike to ride each day. Oh, the humanity! How did we come to this?

biknut said:

Flying Horse 80
MM shorty intake manifold
Speed carb
64 jet
Needle clip is second from top
High flow air filter
SBP pipe with 8" long header
40:1 Torco GP7 synthetic 2 stroke racing oil
NGK BP5HS 0.025 gap. Probably needs to a BP6HS soon
overall gearing is 4.9 mph per k rpm

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Last night I went for a 8 mile blast in traffic. What I'm finding is, like it or not, this motor loves running between 7 and 8 thousand rpm. It's got good accleration in th 30 to 40 mph range, which is right where a motor bicycle can use it in traffic. With my new lower pedal gearing I've learned that I can combine hard pedal power with hard clutch, high rpm takeoffs to get off the line with respectable accleration for a single speed motorized bicycle. I sure can't complain about the mid range, and top end running.

A couple of times small cars wanted to race me LOL.

I'm still not that impressed with the off idle speeds though. Now that I've leaned out the oil to 40:1, it seems rich enough to slightly 4 stroke down there. Earlier yesterday I went on a 20 mile, ultra low speed ride on Carrollton bike trails. Putting along mostly just off idle at about 16 mph. At those speeds it was 4 stroking slightly, and didn't feel smooth. When I got back home and checked the gas mileage, I found it had sucked a lot more gas than I expected.

This will get worse too because soon I'll be running 50:1 ratio. These little motors are so sensitive to tuning. The slightest change can make a big difference.

Today I think I try going back to the top slot in the needle. It didn't like that with 35:1 oil, but now? I'm not going to be happy till I can say I'm getting at least 100 mpg.

Frogster said:

can you explain the concept of four stroking to me, and how i would actually identify it once I finish my build? I too have a flying horse btw. Like i get the idea of four stroking, but not really, so plz explain

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When your motor 4 strokes it sounds like it's studdering, and acceleration doesn't feel smooth. It's usually caused by running too rich.

Expect your new motor to 4 stroke at partial throttle because the factory jets them too rich. It doesn't hurt anything so don't worry too much about it till you get your motor broken in. It takes about 300 miles

Start out running about 28:1, not 16:1 like the manual says. After about 3 gallons of gas you can start running 32:1 with dino oil, or 40:1 with synthetic.

Then you can jet your bike leaner. Order a 68, 66, and 64 jet. You'll end up using one of those. Start with a 68. You can put that in out of the box if you want. Stock is about a 70. Each time you lean your oil ratio your bike will run a little richer.

By the time you get about 300 miles on your bike you have a pretty good idea about 4 stroking and what it feels like.