Tuning a ministroker?

[Lunytune]

I finally got my '99 SA50P rebuilt, with a 41.1mm mini-stroker and 45mm bbk, ending up with 70cc. Exhaust ring had already been removed or different exhaust (no drill marks) and changed 68 jet to 78. Variator plate not removed yet, waiting to install aftermarket variator. It seems to have a flat spot/bogging about 1/2 way through acceleration. Initial takeoff is stronger but after that, doesn't seem to be any more powerful than stock. It doesn't seem to wrap very tight. No tach, so not sure about that, just going by experience of other bbk's I've built.

Anybody had any experience on this type rebuild? What jet would you recommend? I'm thinking a 100 jet would do better.

[losthope]

The 78 is probably too small. Best bet would be to keep going up on the main until you loose power then go back a size or 2.

[elitedio]

Yeah the first thing to check is your mixture. You have about 40% more displacement and probably have more brisk porting. If you have the same intake/exhaust you are not in balance. I would also start opening it up with a more resonant expansion chamber (bigger head pipe and volume at least), bigger carb and reeds.

[bakaracer]

I finally got my '99 SA50P rebuilt, with a 41.1mm mini-stroker and 45mm bbk, ending up with 70cc. Exhaust ring had already been removed or different exhaust (no drill marks) and changed 68 jet to 78. Variator plate not removed yet, waiting to install aftermarket variator. It seems to have a flat spot/bogging about 1/2 way through acceleration. Initial takeoff is stronger but after that, doesn't seem to be any more powerful than stock. It doesn't seem to wrap very tight. No tach, so not sure about that, just going by experience of other bbk's I've built.

Anybody had any experience on this type rebuild? What jet would you recommend? I'm thinking a 100 jet would do better.

41.1mm is not a mini stroke crank. 41.4mm is stock

[evilone]

Nice catch bakaracer, Bravo!

[Wheelman-111]

Greetings:

Yeah, 41.4 and 44.1 can be very confusing. Presuming the latter crank is installed, 70.14cc is your new displacement. Why didn't go with a 47mm bore or greater? Do I find a fellow cheapskate on the Forum?

Speaking as someone who's tried to tune the stock carb to two different BBKs, I can tell you it's tough. Your only hope is to keep the airbox to have anything like acceptable low-end, mid-range and off-throttle jetting. As you know, the stock carb's Pilot can't be altered much, and some intake-side drag will help keep the Pilot circuit from becoming completely silly.

With stock airbox and pipe, my suggestion is to run a Main no smaller than 85, more likely 88-94, particularly now during break-in. You should also seriously consider putting the needle clip in the lowest position - richest - as long as you keep the stock carb.

If you can afford it, look into the Arreche-for-Honda 21mm carb at Scooter-Center.com. (It was under U$100 shipped last time I looked, and the Euro is sucking right now) It'll mount to the stock mani and the airbox will work if you wish to keep that, but with that carb and a bigger pilot you'd have the choice to go to an UNI pod.

But the elephant in the room is the variator restrictor plate. Why not remove that even if your Keli hasn't arrived? Quickest way to burn a bore is to run it WOT in 2nd gear.

[bakaracer]

hey wheelman there still is not a 44.1 mini stroke.its called 44.4 ministroke which is really a 43.2mm stroke.

[Lunytune]

Boy, can't nobody slip a typo by you guys. Yeah, it is 44.1, nor 41.1. Sorry bout that.

Why didn't go with a 47mm bore or greater? Do I find a fellow cheapskate on the Forum?

Wheelman, Not so much a cheapskate as just wanting to rebuild a crashed scooter, not build a zinger. It crashed on me in late fall, and I bought the bbk without tearing down, thinking I just had a ring problem. Then when I tore it down this Spring and discovered the bad rod journal I opted for the ministroker. So if you think opting for ministroker rather than Hondasan is cheapskate, yeah, I guess I'm a cheapskate. Besides, Obama said to spread the wealth, so I did... some to daywot, some to Limp1144.

hey wheelman there still is not a 44.1 mini stroke.its called 44.4 ministroke which is really a 43.2mm stroke.

I bought the kit from Sleepyscooters, a member, in the forum, (Limp1144). http://sleepyscooters.yolasite.com/ On his website, he describes it as a 44.1mm. What more can I say.

[Wheelman-111]

Greetings:

It's nice when your scooter's quick, but all the more satisfying when you didn't spring the Big Bucks for Italian Exotica. I saw a 44 or 45mm kit on eBay or someplace for $75, just wondered if the quality was acceptable. My first experience with RUIMA 51 was disappointing, but probably self-inflicted. The affordable Nikasil has exceeded durability expectations, despite my best efforts to underjet and kill it. My Ruima crank is from a Forum supplier, Economy mode as well.

BTW I put my caliper on the deck and measured (as close to precisely as the technique will allow) something very close to 44.1mm taking the piston from top to bottom. I'm sure there are other specs, but pretty sure mine's a true 44.1.

[Lunytune]

BTW I put my caliper on the deck and measured (as close to precisely as the technique will allow) something very close to 44.1mm taking the piston from top to bottom. I'm sure there are other specs, but pretty sure mine's a true 44.1.

Can I assume it's a Ruima? What bbk did you put on it? How did you tune it out?

Could be wrong but still think I should be able to tune out a 70cc without upgrading carb and exhaust. I put a 80cc bbk on my 2001 rat, stock stroke, without carb/exhaust upgrade. Plenty of power. So should be able to do the same with the 70cc, unless that 3mm stroke changes it that much.

[Wheelman-111]

Greetings:

Ministroker 44.1 is Ruima and Flash IV is its story.