Flash III PhaseII: Tuning MadDog's Worst (Again!) Setup

[scooterwerx]

i think what he means is to put a 4 barrel holley on it. ill make you a manifold adapter for it....

[Wheelman-111]

Greetings:

i think what he means is to put a 4 barrel holley on it. ill make you a manifold adapter for it....

Now that's something I'd like to see!

I have high hopes for the Mikuni and its reputation for smooth even mixtures from idle to WOT.

[Bear45-70]

Greetings:

The Bear axt:

Wheelieboy, You do know that in the high performance world of carburetion that,

"A lot of little holes are better than one big one."?

Yes, in fact that was my Dating Motto during much of my young adulthood. Not sure how it applies to the Variator issue at hand, but perhaps you mean the Mikuni?

Yes, I was remarking about the Mikuni. A too small of a carb is better than too big of a carb. Too big kills all bottom end and mid range while only improving top RPM power. Where as too small enhances bottom end, mid range and fuel economy while only delaying (Slow to reach max RPM) the top end power. There is a formula for determining what size (Cubic Feet per Minute) carb any given engine needs. Most carb manufacturers use CFM to rate their carbs.

[Wheelman-111]

Greetings:

I'll probably come around to The Bear's way of thinking, but I just have to try this one first. The stock carb exceeded 58 with my setup, AND was capable of feeding the engine up to 9600 RPM @ 350 degrees recently during a failed belt/variator issue. Realistically this engine/pipe combo may not be capable of much more, and the Mikuni probably can't change that.

But... There's the challenge of seeing if I can get it all to work. Mikuni's reputation for consistent carburetion may make the low-end palatable. The allure of increased top-end performance I enjoyed with my CV24 carb on Flash II, which really did perform better than it had with the Arreche 17.5. Also I'd like to see my shiny-chromey CT manifold installed somewhere again.

Mostly, it's because I like monkeying with stuff that ain't broke. Until I break it...

[Bear45-70]

Greetings:

I'll probably come around to The Bear's way of thinking, but I just have to try this one first. The stock carb exceeded 58 with my setup, AND was capable of feeding the engine up to 9600 RPM @ 350 degrees recently during a failed belt/variator issue. Realistically this engine/pipe combo may not be capable of much more, and the Mikuni probably can't change that.

But... There's the challenge of seeing if I can get it all to work. Mikuni's reputation for consistent carburetion may make the low-end palatable. The allure of increased top-end performance I enjoyed with my CV24 carb on Flash II, which really did perform better than it had with the Arreche 17.5. Also I'd like to see my shiny-chromey CT manifold installed somewhere again.

Mostly, it's because I like monkeying with stuff that ain't broke. Until I break it...

For your purpose a diaphragm carb would help keep the low and mid range will increasing the CFM on the big end. It would eliminate to big a carb low end stumble (which fools way too many in to thinking the low end response is better when it isn't. The ATV big single cylinder engines do this to keep the low end while allowing the top end power to still be there.

[808BMW]

My 24 carb has no hesitation on the bottom. While the stock carb did work (although only tested with goshi pipe) but with my aftermarket carb, being able to change the idle jets has made a HUGE difference. Especially if you try different exhausts as often as I do.

[Wheelman-111]

Greetings:

I agree with The Bear on this one, as usual. The VE24 Constant Velocity carb chronicled in Flash II had very clean low end due to the throttle "behind" the throttle. Ham-fisted grip twisting was modulated by the vacuum-controlled slide. However all that is necessary with a direct-connect round or flatslide is a little discretion when going to the whip. I'm still going for the Mikuni smoothbore, as I believe this engine's current limit is the stock intake and carb.

Back to my current ride: I went back to the stock belt but decided to leave the 1.2mm washer shimming the drive face boss. This, I figured, would drop the belt down in front, and leave it a bit closer to the rim out back. It really seems to help take-offs, and it was just as quick off the line as with the extra-long Polini .006. (see above) I magic-marked all the pulley faces this time to record the belt's travels.



As you can see (despite legendary Wheelman flash photo... ) the belt did indeed ride very near the boss down low, but - I believe due to that boss shim - was left a good 5/16 from the rim at WOT. This translated to a more-reasonable 9200 RPM peak engine speed, but still a disappointing 52.3 best on the GPS. Wind was flat zero.

So I took out the shim, and expect it to get back to the double-nickel or a bit more as the engine matures. Approaching 325 miles or so on the bore. Good news is the engine is running 325 mostly. Never exceeded 350 all evening.

I plan to re-try the long Polini belt once I score a larger Ruckus variator and perform the required surgery on the starter housing. Werx or anyone with a Ruck vario, can you guide me here?

[SpyderMike]

Greetings:
Werx or anyone with a Ruck vario, can you guide me here?

if you have a dremel just grind off about half of the starter housing boss about 1/2" deep

kinda should look like this when looking at it straight on

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i never was good at art but you get the idea

[Wheelman-111]

Greetings:

Thanks SpyderMike!
I have a high-powered Roto-Zip with lotsa rocks to chuck on. Next time you have your cover off I'd appreciate a pic.

[SpyderMike]

you got it... probly tomorrow-ish

[Wheelman-111]

Greetings:

So as I understend it, the ruckus variator is a couple mm bigger than the Aero/Elite's. This requires carving out some space in the crankcase starter housing.

I also know that some aftermarket variators for the Elite are a mm or two bigger than the stock ones. Does anyone know if the Aftermarket Ruckus variators are similarly oversized compared to the Stock Ruckus units? If so, is there still enough room to carve room for one of those, instead of installing a stock Ruck?

I'm splitting this thread off in Perf. Tech., but would appreciate any knowledge before buying a Polini or something that can't be made to fit in the Elite.

[SpyderMike]

i have heard that the preformance ruck vari's are to big to fit w/o extensive case cutting

[Wheelman-111]

Greetings:

Does anyone have the diameters? Elite, polini-for-Elite; Ruckus, Polini-for-Ruckus...

[maddog]

what r-u trying to build as the 2 pics you posted -r way off, P.M. me for the right way to cut cases & trans covers.

[Wheelman-111]

Greetings:

The Mikuni took 3 days from this eBay seller. Came with a full complement of jets 125-150.

Advantages: Nice quality and design. Fits the CT and the 1.75 UNI filter.

Downsides: The stock cable lacks an inch of free pull, and there's no oil port as I previously thouht. Instead there are 3 vent ports that I probably shouldn't obstruct.

I shortened the casing on a spare cable, and added a T fitting to the CT vac port. I would prefer to inject the pump oil closer to the venturi, but I don't see that option.

Very nice float system that's adjustable, along with replaceable low-speed jet. Sort of fussy throttle cable attachment.



The choke and the idle mixture screw are sort of on the wrong side, but reachable.


Anyone with Mik TM carb experience, or am I the first to adapt this carb?

Testing Monday.

Dog, why don't you share right here? It's not like we're protecting Nuke-You-Lar secrets from the middle east. It's scooters, fer cryin' out loud, really little ones at that. Let's help one another get the most out of them.