2T Tuning Thread
I'm starting this thread to get some of the more relevant technical info out of JM and into a wrenchin' forum. Anyone with 2-smoke experience is welcome to chime in.
I'm in the process of acquiring a 2003 Stella with 115 miles on it, and 5 miles on a new kit.
The kit is a Pinasco 177, 24/24G carb, and SIP expansion chamber. Not sure which main jet he's settled on at the moment--110 maybe, though this kit usually calls for a 118-124.
When I get it home, I have the option of putting the stock parts back on, or breaking in the new kit. This will be the first air-cooled 2T motor I've worked on-- my RZ350 was pretty bulletproof.
Anyway, I'll probably be bouncing back and forth between the Stellaspeed forum and this one. There are a few experienced tuners there, but since there's such a huge pool of know-how here and there's a few 2T scoot owners in our midst, I thought I'd get this posted to get the ball rolling.
Any wisdom on how to do this sort of thing? I know I'll be doing some plug reading, but is there any routine to this that takes some of the guesswork out?
Hey Photog, it's me again! :wave
If I were you, I'd get myself all the gaskets to put that thing back to stock for a little while. You're not running a hack on it, so you don't necessarily need the power right away. It's a new bike you're just going to be getting comfortable with, so why not get everything back to the way it started just to feel it out for a little while and gain some understanding of how the thing works?
Just my .02.
Thanks. I think that's probably wisest--everything I've read so far says that the Stella changes quite a bit during break-in, and since I don't have a buttometer benchmark to go by, that would be good to just get it rolling and then go from there--stock it's got enough chutzpah to get me to the post office just fine.
At that point I'll rename the thread "am I doing this right" and ask questions about gaskets.
:bow You are the voice of reason
Screw what Fitzy sez! Go whole hog!! MORE POWER Scotty!
Can you do wheelies on a Stella?
In my experience, 2 strokes are basically indestructible as long as they have plenty of fuel and oil. They make more power as they get leaner, but you should work your way up to that as you gain expertise... but as long as you've got plenty of oil getting into the thing, what harm can you do?
I'm curious for how y'all jet those things... typically, desert 2 strokes get jetted 2-3 mains larger than the same bike in the same conditions run on a motocross track, since the MX bike doesn't spend as much time tapped out. Seems like getting on the freeway and leaving the thing WFO for 10 minutes is a pretty good approximation of desert racing to me... :dunno
Interesting thought about the desert racing. :nod
I'm not sure how I'll be running this one since it's a 4-speed, and not knowing how much gumption it has to begin with, I don't know if it'll need to be flogged. The last stock one I rode was remarkably luggable. It was perfectly content to just plod around town in 3rd gear.
I spent about 2 minutes on the Stella this afternoon due to other constraints and will start the process of dialing it in next week. What I found tonight was pretty much what the owner said--it'll start and idle, but fouls immediately if you give it any gas and bogs. He said that 3rd and 4th gear were scary-fast....not sure how he got to that point to find out.
The Pinasco is known as a "touring kit", not an all-out speed kit, but even so, folks say it's pretty speedy.
He also mentioned that the bike wasn't set up at the stock 20 degree timing.
So...my first step will be to reset the timing (I hope this is something I can do), then maybe take the main jet down a bit after I've done a bit of reading on the carb--it's supposed the carb setup for the T5 engine.
He's using oil injection but also adding 1% to the gas.
One thing's for sure...that SIP pipe makes it sound like a big-bore Maico. :eek1
Back when I was roadracing my Saab (V4 with Weber downdraught) I used to keep a little Bayer asprin tin full of jets and just rejetted whenever I felt the need. Will this 2-stroke require the same sort of mood-jetting?
I'll go out on a limb and say "that depends". :lol3
Here's my guess: If the carb is smallish relative to the motor, it will be much more tolerant of jetting, as it will have good intake velocity and allow the carb to work pretty well in most situations. If the carb is biggish relative to the motor, it will require jet changes much more often.
At least, that's my experience with off-road bikes. The new KTM's have a 36mm carb (they used to have 38's) and this thing runs great almost no matter what, where the old bikes used to require rejetting for every different condition.
Thank you, Doctor Science. :D
Thanks for the help!
I'll dive into it when it cools down a bit and orient myself to what's under the cowl, maybe see which main jet he's got in there now. I've been spoiled by so many turnkey motorcycles in the past 20 years that it's a bit new to go back to actually being hands-on with regard to the most basic tuning issues. :lol3
I got all the sales receipts--lit's a 177 kit, not a 166 like I thought. I've also got a bag full of tools he threw in with the deal. They look like gynecology tools for a giraffe--must be a flywheel puller by the looks of it.
Here's a thread from the original owner, documenting his work on the carb.
Here's the key info:
Just from my old tuning days. first I would get the timing relatively close to stock or the recomended setting for the "kit" if it came with instructions.
Then if it is loading up just off idle, most likely the "needle" in the carb is set too high and should be "lowered" by changing the position of the "clip" to a higher groove on the needle. This effectively changes the fuel delivery in the mid-range or transition from idle circuit to main jet.
Good renchin !
From the original owners post I would guess he was honking it in 3rd and 4th but not in 1st and 2nd. That means (I'm making some big assumptions here) he was in the lower speed circuits of the carb. As Mike points out the needle and idle screw control those circuits. If they are rich it would make it foul like the PO said (black plugs). However, once spun up it was on the relative lean (according to how others have jetted) main jet. Lean is mean and it probably would go like stink.
Your task it to hook up with someone on the other board who is running the same kit. Set the carb up like they have it for a starting point. Then tweak from there. Or better yet, ask the person who sells these kits for what they recommend "out of the box".
Good luck! That's way too sweet a lookin scooter to not run like it looks :nod
When I was taught how to 'tune' a carb there were 4 quadrants These quadrants relate to how open the throttle is, ie 2nd quadrant is 1/2 open throttle. Of course there is overlap.
idle - is the idle circuit
1st - is the jet needle (which one, ie length, diameter and degree of taper)
2nd - is the position of the jet needle and the selection above
3rd - is the selection of the needle jet
4th - is the main jet
I might have the relationship reversed between the jet needle and the needle jet (#'s 1 - 2 - 3) but I think I have it right.
The distinction between these 4 quadrants gets blury of course especially the 1st thru 3rd. The selection of the 'correct' needle jet and jet needle heavily influences the 1st thru 3rd quadrants and there is a strong interaction between the 3rd and 4th (the size of the main jet).
Of course some carbs don't use these parts exactly or they use different means of adjusting the fuel air ratio at different throttle openings... There is a way of changing the mixture, it's just a matter of if you have the range of parts to dial it all in.
And yes I agree it would be wise to keep the mixture rich until the rings break in... Then gradually lean it out till you find the 'sweet spot'.
It's 4:48am...I woke up, stumbled downstairs, and I'm ready to start wrenchin' on it. Of course, since I don't have a garage, I'm waiting for it to get light outside. :lol3
I like what Mike was saying and will start there. Since I've got the stock carb here in my hands, I can do a dry run of the operation and plunder around with it to familiarize myself with the critter.
There's a high school parking lot across the street--gonna push the bike up there to work on it, since it's a bit loud with the SIP pipe and the neighbors are not exactly supportive of gearheads. So I'll be doing the work with a few tools and a bottle of gatorade handy. Sorta like being on the side of the road somewhere. :lol3
I found this site which has a pretty decent explanation of jetting (it's a Lammy page but the idea is the same). My carb has an atomizer instead of the needle/clip arrangement, so I may be stuck having to order a few different types.
VespaFitz was right. These things will run regardless of what you do to them, assuming the plug isn't drowned in oil.
So I took the scoot across the street to the HS parking lot and fired it up the first night. It bogged and died when I gave it gas. The next hours were spent feverishly looking up every bit of jetting info I could find. I awoke at 3am on Saturday, anxious for another shot at it.
Saturday afternoon I threw in a new plug, grabbed a lid "just in case" and pushed it over to the high school. Threw on the choke, fired it up, and it idled. I gave it some gas and it coughed and sputtered but didn't die. I revved it again, and it sounded like it was loading up, but was still running. What the hell--I'll jump on it and ride it for 10 feet before it dies.
I eased out the clutch and it kept going. I motored up the hill in 1st, 2nd, then third, and it felt pretty good. Kept doing laps. Ventured out onto the road. Got it into 4th. Not only was it running, it was running strong.
REALLY strong. As I posted in JM, it's a much faster bike than I expected, very much like a short-wheelbase, small-wheeled kitted RZ350.
I put a total of about 40 miles on it yesterday, varying the speed. Did a few short wide-open runs through 3rd but only briefly. At a long stoplight it would load up the plug a bit, but cleared itself as I went through the intersection.
The transmission is buttery-smooth. Big difference from the demo bikes I had been on. I had a few 1-3 and 2-4 upshifts but I'm getting used to it :lol3 There's no notchiness, really, just a slight divot that lets you know it's in gear. The clutch is light, smooth, progressive. Easy to handle on a hill.
The brakes are hypersensitive, especially the rear, if you are not used to them. The scoot stops really quickly. I haven't locked anything up, but I'll need to think about being a bit less ham-handed and heavy-footed.
So how did this go from being a non-running art project to a nice little bike? I'm not sure. The PO said that he hadn't had a chance to really run it fast, so I think that being limited to his 25mph urban neighborhood meant that he fouled plugs and couldn't clear them well. The bike still needs to be dialed in but at this point it feels pretty reliable--though I wouldn't want to put it in a lot of stop-and-go traffic that includes long waits.
I haven't done any plug chopping. I suspect I'm way on the rich side, but the bike runs VERY smoothly in all rev ranges. No lurching, no sputtering, nothing weird.
The sound from the SIP pipe is marvelous. :thumb Nice and throaty, not buzzy.
The rollon power between 50 and 60 is incredible. Zing--you're there. It pulls hard down low and will lug really well--it almost feels like a 4 stroke in terms of being able to pull at the low end of the rev range. Overall performance between 30-55 is outstanding--perfectly suited for zipping in and out of holes in traffic with just a nudge on the throttle. You couldn't ask for a better-sorted bike for traffic. By the time you've gone through the gears lazily you're at 55.
I don't know what the top end is yet. Probably 65-70, since it's mostly gear-limited at this point and I've got the stock Stella gearing in it. There's an upgear and 5-speed kit available for it. I don't need them right now.
I'll post any updates--there are a few new Stella owners who are considering the various Malossi, Pinasco, DR, etc. kits.
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