Fab Flash 7: Fabrizi 50mm Cylinder Kit (74.6MPH)

[Wheelman-111]

Greetings:

Rumors of my demise were greatly exaggerated. I live to post again. Alas, nothing useful to report (if EVER!) until the weekend.

[Wheelman-111]

Greetings:

I take responsibility for Scorpion "failure". Wheelman mechanical "skills" were the cause of sudden rattle. I have no explanation, but evidently I failed to tighten exhaust nuts, and they actually worked loose. Fingers to remove loose. The Fabrizi came with a recessed donut gasket which seems to have crushed down some, but the nuts were torqued down, just not rechecked. Anyway the Scorpion pipe is fine, but I still reinstalled the PG. Real good low end, but falls flat above 50; a gearing , jetting, or roller-heavy issue, methinks.

Three other annoyances:
1. The light in the tach is burnt out.
2. My Trail Tech TTO is suddenly dodgy at the sensor wire.
3. The Kege tach seems to read 2/3 of actual RPM.

PLAN: Install 8.44s first.

[Dio Dawg]

Run 2 oval shape exhaust gasket, i found it better than running the donut gasket imo. Falling flat above 50..sounds like a main jet problem.

[Wheelman-111]

Greetings:

Yes I did notice that the recessed gasket protrudes into the port just a hair, obstructing an already-seems-small exhaust diameter. Then again, perhaps Fabrizi has a reason for what appears to be an undersized exhaust port, and they supplied the gasket in question. I used the donut and (Perhaps ill-advisedly...) a paper VW gasket over top to increase the thickness. This sets the holes at the muffler hanger just perfect and without tension. Anyway, it hasn't leaked so far.

Judging by its low-end performance, this thing seems to have the power to pull the 7.58s to over 70, so I'm holding off on the messy job of swapping the gears to 8.44.

I also wondered why it won't take full throttle - stumbles, engine sound changes and loses power - as the speeds get to 50. The jet being too big would be the first suspicion. However RPMs weren't very high - 9500 - and that is a function of the variator/belt drive sort of Forcing the revs down. We know that the size of the main jet has to match demand, which is a function of displacement AND RPM. So, I'm thinking, maybe the jet would be just right if the engine were ginning up the RPM that God and Signore Fabrizi intended. So rather than drop the carb, I started with reducing the variator load from 30 to 27 grams. I'm using a +2000 Malossi spring, so not sure why the RPM is dropping so low with such a light load. Also my temp gauge has gotten wonky, and so I'm not too eager to drop another jet size. More testing to come.

[Dio Dawg]

Possible dead center spring?

[Wheelman-111]

Greetings:

Good thought DD. I checked by the Unscientific method of manually compressing the rear pulleys, which I can do one-handed with lesser +1200 or +1500s. This one takes all I have, so probably not the spring. My seasoned Daytona 5gs were getting some flat spots, so swapping in 3 new 4s should help.

[Wheelman-111]

Greetings:

The display alternated between engine temp and ---F. I got it to resume reading temp by wiggling the wire at the spark plug a couple times, so pretty sure that's the issue. Ordering a replacement thermocouple is $43 with shipping, but less work than pulling all the plastics again.

[Wheelman-111]

Greetings:

Little time to work/tune this afternoon. I finally got the Tach lamp to go on. Once again Wheelman "skills" made one bad crimp connection. Just call me The Prince of Darkness.

Curiously the TTO Temp Gauge worked the whole time today - never saw the ---F display. Still installing a new thermocouple, and selling my vintage VDO Analog gauge. It'd look good on an old R60 Bimmer or somesuch - it too needs only a thermocouple.

The higher RPMs made for more enthusiasm for full throttle - no lean surge, but still a bit softer on power than I think it has. When I get a few more hours on the block I'll consider dropping the main another size. Before that I may move the needle down a click and see how that feels.

Finally, I have to decide whether or not to replace the 7.58s for 8.44s. It's plenty quick taking off as it is, so stay tuned.

[ped]

Greetings:

Yes I did notice that the recessed gasket protrudes into the port just a hair, obstructing an already-seems-small exhaust diameter. Then again, perhaps Fabrizi has a reason for what appears to be an undersized exhaust port, and they supplied the gasket in question. I used the donut and (Perhaps ill-advisedly...) a paper VW gasket over top to increase the thickness. This sets the holes at the muffler hanger just perfect and without tension. Anyway, it hasn't leaked so far.

Judging by its low-end performance, this thing seems to have the power to pull the 7.58s to over 70, so I'm holding off on the messy job of swapping the gears to 8.44.

I also wondered why it won't take full throttle - stumbles, engine sound changes and loses power - as the speeds get to 50. The jet being too big would be the first suspicion. However RPMs weren't very high - 9500 - and that is a function of the variator/belt drive sort of Forcing the revs down. We know that the size of the main jet has to match demand, which is a function of displacement AND RPM. So, I'm thinking, maybe the jet would be just right if the engine were ginning up the RPM that God and Signore Fabrizi intended. So rather than drop the carb, I started with reducing the variator load from 30 to 27 grams. I'm using a +2000 Malossi spring, so not sure why the RPM is dropping so low with such a light load. Also my temp gauge has gotten wonky, and so I'm not too eager to drop another jet size. More testing to come.

Hi WM. no power over 50. sounds like main jet to small. give 55, 52 a try.

[paulpauly7]

that vari load sounds really light for a 2k rear .Sir wheel whats going on?

[bakaracer]

Squeezing the center spring to check if still ok is not a accurate way. The spring can be dead in mid belt transfer under heat. Put a new center spring to confirm that the old spring is really dead or not. Malossi springs are notorious of dying like that. Even if using a torsion controller or roller bearing spring saver. After swapping to a new center spring and adjusting rollers and cht temps look good at wot, then port timing on cylinder not ment for stock stroke crank if your only seeing about 9500-9800 max rpms.

[bakaracer]

Did you do a port map of the ports before install? Does anyone have port maps of the new kits?

[LMH]

Ya thats what I figured seeing the piston through the port window from the get go. Should never see either ring through the ex port.
With a bad center spring under stress (heat) it will often do a quick flare up then shift suddenly to a low rpm if your clutch and bell are in good shape. A too fast of a shift is a good sign it not holding pressure.

[Wheelman-111]

Greetings:

New spring is cheap, but how to get one quick?

Forgot to mention I wasn't holding WOT very long with 40 minutes Run time. Temps (if TTO is reliable...) around 250 during part-throttle rides suggests Rich, not Lean Pilot. Testing Main has to wait for more time and miles, but soft power is another reason for quick upshift. The driven pulleys cam down when power falls off.

LInk me up to a quality spring?

[LMH]

With soft power you shouldnt hold it long. No poking the bear. 250 part throttle isnt bad, whats the WOT max temps at is the key.
How soft of power are you talking? That cylinder should make pretty good power. Does anyone else have experience with this cylinder?