Flash IV

[losthope]

Greetings:

I couldn't find the thermocouple/wire on the Westach site. Thanks for the kind offer. PM sent.

Westach site...products...accessories... CHT Thermocouples

[Wheelman-111]

Greetings:

Quite right you are, Bear. The sweetest-running carb I've had was the Arreche 17.5, but a bit small for Prodigious Polini, let alone mini-stroker 90. The VE24 CV carb ran pretty well too, thanks to the vacuum controlled secondary throttle. A PITA to set up the cable however.

I found the CHTs Hope, thanks. They all have 4' leads however. Mouse seems to think limiting the number of connections improves accuracy. I forget whether I need a J or a K?

Maybe I'll hit up Grainger and look around.

[bakaracer]

which motul oil are you using?

[Wheelman-111]

Greetings:

It's up there, I think. It's the 800 Ester stuff. VT-recommended, but I'd bought a quart before I talked to Steve.

[bakaracer]

the motul 800 has 3 different types. offroad, road and kart.

[Wheelman-111]

Greetings:

Mine's the Offroad stuff, and no I'm not draining it again unless there's a real good reason.

[bakaracer]

I'm using that one right now.I just was wondering which one your using. I might try the kart one next.

[Wheelman-111]

Greetings:

Phew! I was hoping you wouldn't say; "Dude, get that stuff outta there! I'll gum up your rings, seize your bearings, score your bore, and give you a nasty case of Scabies." If it's good enough for Baka-san, it's good enough for me.

Now if the stuff works, why oh, why would you want to Phoque Up a Good Thing? It's not like you can study the comparative outcome, unless you have two identical engines hooked up to Dynos and run for a few thousand miles.

The change from Honda-san's oil made sense for me. After two Deep-Fried Taiwanese bores, I lost Faith in HP-2. Then several Hawai'ian Scooter Cognisenti suggested the switch to Motul. However the Kart stuff is probably designed for liquid-cooled Shifter Karts.

[bakaracer]

they have aircooled kt100 engines to and that oil is good for 23,000 rpm engines. most of the kart engines turn over 14,000 rpms up as there normal rpm range

[Wheelman-111]

Greetings:

Well the demands of the Kart world and mine won't be the same. I'm thinking 10K RPM is plenty for these Taiwanese bores, particularly with the (Slightly...) increased piston speed of the mini-stroker, and limited cooling power. By the way, is the Daytona red fan an asset or not?

Clearly the 158 Main is coming online a tad early with the needle at #5 position (full-rich) and I plan to lower it to #4 and/or install generous LostHope's 160.

[Wheelman-111]

Greetings:

Quoth The Bear: (long ago, in a galaxy far, far away...)

That slow to accelerate with throttle thrown wide open is a sign of "TOO MUCH" carburetor. To much carb hurts low end and midrange will slightly boosting top end. The only cures are, slow application of throttle, smaller carb, or the best choice is a couple of smaller carbs.

Interesting tid-bit: My 1983 XL600 thumper had a couple of carbs. The "primary" was tiny - not much if any bigger than a stock PA-series Spree-ish mixer. The secondary was a CV40 or 45 that opened in tandem with the primary, only at about 1/4 throttle and up. Somehow Honda-san sorted it all out; that was one of the cleanest carbureting bikes I'd owned.

My issue with Flash IV is the heavy load of rollers in the variator, along with the low-end No-Touch exhaust. It never gets its revs up high enough to begin to demand the supply the OKO 30 can provide. Hence, the BLEEAAAhhhh and no-go. Once I get some miles racked up, and perhaps the PG Long reinstalled, I can let it gin up some revs and use more of the 30. In the meantime, I'd love to source an affordable 24 or 26 to make it easier to dial in the low-end.

[Wheelman-111]

Greetings:

First a public Thank You to LostHope for sending me a K160 main jet, tagged with an HD. Yup, I think it's an Harley jet, which uses a CV40 Keihin carb. Without Hope, I'd still be waiting on mail. If you ever need a spare that I've got, it's yours, Dawg.

Installed and lowered needle to Clip #4, then did 6 miles of errand rides at speed under 40. Temp clung stubbornly to 250, except after a coast-down to a light, where it sat idling at 325 until throttle re-applied. Still blubbered, but only a little. Plug now a rich dark Ebony. At least a hint of brown where it was pure black before. I'll attempt the run to work manana, sticking to 35MPH surface streets.

F4.2Engine.jpg (40.58 KiB) Viewed 3821 times

OKO 28/30mm carb with Mower Manual fuel shutoff peeking out behind UNI. Oil Tank fuel acts as carb-replenishing reserve when low-vac conditions shut off main tank, while still able to shut off fuel flow. There may be other ways to plumb this, but I like mine. Low Oil lamp acts as Critically Low Fuel Warning, too.

BTW It was 98F here in Deepinnaharta today, same forecast tomorrow. I wonder when it gets colder if I need even bigger than 60/160 when break-in complete and I uncork to correct weights and PG Long? Sheesh, my 1200 only runs a 165!

[losthope]

no problem mr. wheelman. Your scooter is looking clean... best of luck keeping it together.

[elitedio]

Wheelman
I have been using Motul 800 (off road) in my Rumia. 2 oz/2 liter pop bottle of 87 octane fuel. No alcohol. Higher octane fuel is not available most places and if it is it is blended with ethanol. I have always shyed away from gasohol with 2 strokes.

Motul 800 doesn't mix that well with gasoline but seems to stay in suspension once mixed. It is a pretty viscus oil. Are you still using the oil pump?

I can't quite grasp how come you have had so much trouble.

[Wheelman-111]

Greetings:

Esteemed EliteDio Axted:

Motul 800 doesn't mix that well with gasoline but seems to stay in suspension once mixed. It is a pretty viscus oil. Are you still using the oil pump?

The pump bit the dust with Flash 4, the one that resulted in the big hole in the piston. In addition to HP-2 oil + pump issue and a too-short break-in period, several errors were committed:

1. Compression too ambitious. (135-150!)
2. #7 Spark plug in a very high-revving, high-output motor.
3. Iffy cooling shroud fitment and gaps therein.
4. Small-ish Pilot and Main jets in a 28/30 OKO carb.

F4's Detonation demise was associated with a prolonged closed-throttle coastdown after reaching 69 MPH. Both the cooling effect of the Main jet and the added pump oil are shut down when the throttle closes. Maybe that's the reason the Cognisenti wire the pumps full open if they use them at all. Perhaps my engine could have survived the lack of one or the other, but not both, especially with an ill-advised choice of pilot jet.

I can't quite grasp how come you have had so much trouble.

It is Wheelman, after all. I am hopeful that I've addressed all these issues with Flash 4.2.

1. Lowered compression to ~115 with 2.12mm thick copper head gasket. (2 x 1.06 uncrushed)
2. Have a gaggle of NGK BR9 HIX plugs.
3. Shaved fins, muffler-taped the gaps.
4. Now running 60/160. Thinking about a 24 or 26mm to replace the 28/30.
5. Axed the pump in favor of Motul @ 25:1 for a half-tank - still not enough jetting - then 32:1.