Flash IV

[bakaracer]

are you going to rebore to a larger size?

[Wheelman-111]

Greetings:

I'm going back with another Ruima 51 from Limp here. The price was attractive, it fits and it'll be a simple re-install. I figure until recently nobody else has done much documentation, and these kits deserve to be evaluated. Might as well be Sanjuro and me.

Limp says he "never even soft-seized", and I believe him, using 50:1 straight pre-mix. His install compression was not specified, as far as I can recall. While perhaps not as forgiving of over-ambitious abuse as the Nikasil and the Italian bores, I see no reason why the Ruima won't last - and provide very good performance through greater displacement - if installed with more-conservative compression and adequate jetting. I'll shoot for 120PSI or so, a 140 Main and 50 Pilot (I think - Tai jets aren't marked half the time!) and I guess we'll see.

Meanwhile I've resurrected Flash III in another thread. With the PG long it takes about 1/8 mile for it to run out of breath at 9400 - small boost port?

[losthope]

I dont think the boost port is to blame for running out of breath. Reason being there are a few polini corsas around with no boost port porting and they hit 70-75 mph(or so they say). i realize the boost port on the corsa is prolly different from your bore but still the stock port in the block has proven to make some power.

[evilone]

Since Wheelman-111 doesn't mind...

Where can them metal head gaskets be found other than Roselle Imports? My head is also the o-ring style. And...can you use any o-ring for the head?

[elitedio]

Wheelman I blinked and you holed your piston. Good news is that when your wheel locked up it didn't spit you onto the road ready to get run over.

Good luck on getting it running.

[Wheelman-111]

Greetings:

The word is a Viton ring is one of few materials up to Head Gasket duty. Teflon may be another option.

Thanks EliteDio. I was going straight at the time, and an off-power stumble preceded the lockup, hastening clutch disengagement. I am aware of the consequences of a seize in a curve. Happened to me on a Kawasaki in 1973: suddenly I was a Dirt Tracker, only on asphalt.

[Dakine]

Haha d*** wheelman your lucky.. I just siezed up on a 66cc not to long ago, just started the bike and did some high sampos/wheelie. Rear tire just locked up, then i just handled the front to the ground and smacked my face on the headset!! Haha

But d*** tha hole in your piston idk what to say

[Wheelman-111]

Greetings:

Ruima 51mm bore and Ministroker 44.1 crank now with a good bit of base gasket and two head gaskets. Anticipating the extra 12cc of displacement above the 78cc Flash III plus "insurance" for break-in, I retained the 55 Pilot but swapped the 138 for two sizes up to 142.

Bolted up, the starter engaged, paused a millisecond, and fired right up. Funny how the owner/tuner can tell the difference in sound when nobody else could. I did two heat cycles but quit just before 10PM to avoid neighbors' ire. Both times the starter needed a second try to get it turning. I hope the starter pause is the result of a brand-new tight bore and/or a bit of Bendix pinch behind the belt cover. Flash IV never did get over that compression-related struggle, and look how it turned out...


"Acceleration" is a generous description with the 6.3:1 gears and a timid throttle hand on this shiny new bore.

It's leisurely all right. Twice around the Complex and parked to cool. Tuning begins in earnest tonight.

[Fishman43]

Very nice! I always look forward to your tuning threads.

[sanjuro]

Looking forward to the tuning notes.

[aerorob]

Wow, cool rebirth of the build.
What speeds are you looking to achieve with that gearing?! Freeway ready?

[losthope]

Good luck to you Mr. Wheelman. ill be watching.

[bakaracer]

mighty small gears 6.3to1 . thats to much gear for that setup.full stroker setups use those gears.

[Wheelman-111]

Greetings:

As usual, Bakaracer is correct. The take-off from stops and traffic lights is barely-acceptable. Needs more throttle than I feel is safe to apply with this shiny-new Ruima 51mm bore. The 8.3s are going back in soon. I'll save these six-point-threes for Flash 5.

[Wheelman-111]

Greetings:

Even jetted up to 142, this thing was hot Hot HOT! Smoking from somewhere in fact, maybe burning off the anti-rust spray off the PG Long. The new BR9 plug offered no insight, a uniform charcoal gray. I installed the biggest Keihin hex I have - a Mystery-Brand 148 - and went for a timid ride. The temp gauge fluctuated wildly enough that I cannot trust its readings. Idled at 250, dropped to like 200 when the throttle first opened, then a steady climb to 350 and a stall.

Uh-0h.

Re-started and got a few miles down the road, light on throttle and watching gauge, which seemed to stay around 275-300, still conked out a couple of times but re-started immediately. Then idling at the complex gate it stalled again - a sort of abrupt stall, not a slow wind-down. I think it's still seizing every time it gets heat-soaked. I'm sick of wrenching for now, but I'll have to pull the shroud and check out the bore after a compression check. The next thing I'm doing is getting some 150-ish jets to try. re-installing the 8:1 gears, at least for break-in. I figure it's hard to break in gently if the scooter's always "climbing a steep hill".

Are these Ruima bore kits really that finicky, or do I just suck that bad at tuning? Polini Contessa 65cc ran like a dream. Malossi on Flash 2 the same. Nikasil? You can't kill! First Ruima fried real fast. This one's no more promising. Is it even possible I really need a 58/155, or am I sucking air someplace??