The "BlowFly" Project

My X8 250ie has an air intake to the airbox that looks just like that, same size too I rekn.
I did notice a slight improvement in performance when I drilled a couple of 10mm holes in the airbox to help, but not all that much really, mainly just noise.
That sits on 120kph+ all day with that little tiny air tube. :huh

Modnrod, that is something Driller and I talked about. If I can find some black plastic plugs for the holes I may still do that. I want to be able to go back to stock if it doesn't work or is too much noise.
Also, I've used a magic marker to put marks on the variator where the belt rides to make sure the belt goes all the way to the top. After my next top end run I'll check that.
BTW, how long does it take for you to get from west Oz to east Oz with the throttle pinned on that X8?

Took the BlowFly out today but too windy for any meaningful testing. Just ran it WFO a bit so I could check my marks on the variator. Here's a pix, doesn't look to me like the belt is going as high as it should, ie, not going all the way into the highest ratio. Anyone know anything about these things? Still new enough for me that I don't know how high the belt should go.

I spose it depends on how big the coffee cup is that's keeping me going! The bike will probably take 3 LONG days (I'm assuming 1200-1500km each), but dunno whether I would have got off and said "F&@k it!" before that!

Normally the front variator would have about 2mm-3mm of untouched pulley sheave left on the top on a standard OEM set up.

Wake up everybody, I'm back and I finally have some positive results to report. Today was perfact weather for testing but it was also my wifes birthday so only got in two full tests.
With the main jet opened to about a 77-78, the bike ran 9.57 sec. but the top speed didn't improve at all, still only 56.5 MPH.
Second test with main at about an 80 I got 9.44 Sec. at the exact same top speed.
While on the phone to Driller I discovered I'ld forgot to plug in both the carb heater and the enrichener, bystart, as Piaggio calls it. Hooked up both and tested again, 9.39 Sec. Didn't do top speed.
So now we are a little over 1.1 Sec improvment in acceleration. Very positive gain especially considering no gain in top speed.
I'm to the point now where it's just not going to get any better unless I do something to increase air flow. Next step will be to remove the intake tube. This I'm sure will throw jetting way off again. No testing weather for about a week at least so everything is on hold for now.

Carb size of fly versus Vespa 200?

Also, gearing is probably taller on the 200 Vespa as well.

Not sure about carb size or gearing. Maybe Driller will check in for us and let us know. I do have the Fly service manual on disk and will look it up. Gearing should show on a parts list but tire size also is a factor in the gearing.

Just checked, carb size is 26.5MM. Rear tire is a 120/70-12, nothing on the trans ratios.

Too cold here to do much on the Fly except I have spend some time going over the shop manual. It's a bit hard to make sense of, something has been lost in the translation. However, I did find an answer to my question earlier about a "soft" rev limiter. At 9000 rpm's one spark out of 7 is dropped. That means one power stroke out of four does not fire. If the rev's continue higher to 9300 rpm's 2 out of 3 sparks are dropped.

Today UPS delivered a neat little self contained tach that I will try the next time I get out on the fly. Will be very interested to see just what kind of rpm's it is turning.

Also while studying the air filter assembly it came to me that I may have installed the filter incorrectly, resulting in a restriction to the incoming air. I'm hoping this is the case and that it will account for not gaining any top speed with all that has been done. We'll see as soon as we get better weather. Stay tuned.

Ha ha. What have you been doing to this poor bike!?

Hope you get it running proper!

If anyone here knows exactly how the air filter should be installed, let me know. I've looked all through the service manual but can't find anything about it. Yah, I know, how hard can it be to put the air filter in. Just want to know for sure how it goes. Thanks, Vic

Here's the parts fiches, maybe they will help.
http://www.2wheelpros.com/oem-parts/0000-piaggio-fly-150.html

Finally have some decent weather today so was able to do a little testing. I've spent many hours scratching my head trying to figure out why this thing just doesn't seem to run like I think it should. Finally decided that maybe I installed the air filter incorrectly. I place the new AF in the cover of the air box, like this.


Notice the little rectagular slots between the bends of the intake tube. There are actually 4 of them and as can be seen here, they are half covered by the AF. The incoming air must pass through these slots.


By putting the AF in the AF box instead of the cover, this is what you would get. Much improved air flow. That intake tube is bad enough with all those bends, then the incoming air must find it's was through those slots.

This is the way I believe the AF should be installed, in the box, not into the cover. Try as I might I could not find any instructions on the proper installation. This just seem much better to me.

So the last 7 test runs I've done were a big waste of time since my screw up with the AF caused the motor to run way too rich. The first test I did with the 200 top end installed netted a 9.77 sec time. This with the air filter installed incorrectly. Today, after fixing the AF and going back to the stock 82 main jet, I got a 9.45 sec test, a tad over 3/10's of a second improvement. Again, this was the same as the first test with the 200 top end except for the air filter installed correctly. Also, we are still stuck at 57.5 MPH for top speed. My little tach shows the motor at 7956 RPM's, just over the power peak for the stock motor.
Tomorrow should be good weather again so I've removed that intake tube and will see how that works out. I did go for a very short ride today to try it and it became clear the motor now is way lean. Will go 85, 88, 90, etc with the main jet untill it seems to peak out.

You know, looking at the airbox, I'm assuming the long bendy tube is a bit of intake tuning, not unlike the airboxes on Kawasaki EX500's that people discard when 'improving them' (usually with pod filters..) and then wonder what happened to their bikes ability to rev above 9k.

Is the intake tuned for a 125cc bike? It might be in your best interest to see what the airfilter box of a Piaggio 200 looks like, and maybe emulate it as close as possible? The only other issue I can think of is that your CDI box has a rather low max rpm limiter for this engine, seeing how it seems to rev no higher, and seems to hit a 'wall' at 8000 rpm.

Good input,YG.
The airbox is supposedly tuned for the 125-150 Leader engine. Changing to the 200 jug and piston and the PM pipe obviously has changed the breathing needs of the beast. The kit is a Piaggio cylinder and the piston shape delivers a slightly lower compression ratio. Same stroke, just a bigger bore. Could the larger, heavier piston be holding the revs down? I wonder if the valves on the 200 Liberty are the same size as the Fly 150. :huh
Wish I could run this against a Fly 150 kitted with the Malossi BBK. Especially considering by all accounts, notable performance gains with that kit come with only minor jetting and no fiddling with the air filter.
The times Vic has been getting are right about where I was expecting. As said before, if we can get that lost 3-5 mph on top back, I would call it a success.
Vic may have some new results today if the weather cooperates.

Well assuming it's the same stroke as the 125, the piston weight shouldn't normally a factor. When going up in bore diameter usually requires bigger valves and better intake and exhaust tuning because the burning gases have more area to work against, and more gas volume to move. Generally, if all things are rosy the engine wants to spin up much faster and you'll have an increase in torque and HP.

The EX500 I was talking about is a good example as they have a redline of what, nearly 11,000 rpm? It's a short stroke, four valve engine so it's analogous.

Did you weigh the new piston against the original, does it obviously vibrate more at speed? how about the exhaust, maybe needs some internal baffle removal? Does it have a catalyst? They can be restrictive.

What's the bore and stroke of a 125 cc Fly? ( OK I Googled it.. it's a 48.6mm stroke, so it's short stroke by most 125cc standards. My Honda clone engine is 54mm x 54mm, and it's a little tractor.

You should be able to spin the heck out of that engine, it's not going to have the nearly flat torque output my pitbike engine has, but it should spin like mad, all things being equal. How about variator weights, did you lighten them to let it run at a higher RPM level?

No noticeable thump. PM Tuning pipe seems pretty free flowing. Lighter roller weights are next. We are running 70.5 grams which is 10 over 60 stock. Tried 57 grams before the kit went on with no improvement in acceleration. The engine did seem to spin faster. Now we have a tach, we shall see.

After some research, I've found that the stock engines power peak is at 7750 RPM's. A "soft" rev limiter kicks in at 9000 RPM. Today on a long shallow downhill I ran the bike flat out to see what RPM's the motor would turn. Got up to 64MPH, (GPS), at 8365 RPM's. This is well past the motors power peak. Power drops off, sometimes very rapidly, after power peak. I don't think this motor has any more rev's in it. I'm disappointed that we just haven't been able to get 60 MPH out of it on level ground. Piaggio claims 61 MPH for this bike in stock form. This bike is at 15k miles but the piston and cylinder are new.
As for the exhaust, The PM tuning pipe was the second change make to the bike and has been in place for all the tests since.

Mike, when it gets warmer, I will be happy to bring the Malossi Fly up to run head to head with your machine. I think I have a race in VIR in April, are you up for something along those lines?

Jim