Project 90 (Stock 89cc And Beyond)

[90GTVert]

I think the Koso is intended for LC stuff. 302 would be pretty damn hot in that app. For these purposes, all that really matters is that it's consistent really. I just want to see what changes certain things make in engine temps.


I'm not having much luck today. I installed and tuned the Arreche carb for the next test. While tuning, I got back from a run and the scooter wanted to fall over when I tried to get it on the center stand. I just repaired this after it cracked next to this crack. Luckily, I had a spare that I ordered when this broke the last time.





Later, I got geared up (50F at night makes for a chilly ride with no fairings to block any wind) and headed out for the test ride. It ran well until 15 miles away when I went to go WOT and I got a warble... sort of a wuhwuhwuhwuh sound. If you've spent too much time tuning, you already know it's running lean. I pulled over where I found some light and didn't see anything obvious. At that point, I suspected an intake leak or a main jet issue. By the time I rode back home, constantly playing with the throttle to determine exactly where it started leaning out, I had decided that the main jet must be clogged.

My fingers are cold and I just didn't feel like doing that much more to it, but I did at least remove the bowl to see that I was right. I'll clean the carb tomorrow and replace the fuel filter and get another test ride at some point.

[190mech]

Ive seen some carbs with a fine screen around the main jet area to keep that from happening..I think it was the German Bing carbs..

[90GTVert]

For soem reason I always have trouble with this Arreche and debris. When I first got it and used it on my first 90cc it always got something in the float needle seat and would overflow. When I used it on the Venus I had a problem with a bit of debris once. Now I get something in the main jet within 25 miles of testing and riding. Oh well, I got up early this morning and cleaned it and swapped to a new filter and lines and got a ride in without issue. I'll post up the results later.

I was using a typical small engine filter like mower would use when I had the first problems with this carb long ago. Now I use Visufilters. Either my fuel filters just suck or there's a lot of crap in the gas or something. This is not even the same gas tank I used to have, it's pretty new. Lines and filter were redone with the tank. 2100 miles or less on that stuff. I forget if I replaced it during the project or just before. Either way, it seems whenever I install the Arreche I get these problems.

[90GTVert]

Phase 3 : 19mm Arreche


First up in Phase 3 is the 19mm Arreche. I tested this carb in the first phase of the project as well, so click HERE to see all of the pics and details of the Arreche carburetor.


I started off by moving up to a 95 main jet, from the 90 used when tested in Phase 1. I thought that since the stock carburetor needed to be upjetted from 85 to 90 from then until now, the Arreche probably would need the same change. After testing various jets, I ended up with a 90 main jet once again. The needle was set in the center position. No other changes were made from Phase 1's test of this carburetor.


I went for a 34 mile ride, seeing merely 38.18MPG. I had a very similar result, roughly 1MPG more, the first time I tested this carburetor. The gas mileage is pretty disappointing to me. I rode the same way as in the test with the stock carbruetor to the best of my ability and the Arreche was roughly 19MPG more thirsty than the stocker.


Throttle response was still excellent. There seems to be more power at lesser throttle positions. That made leaving stops without much throttle a bit easier.


Cruising speeds at wide-open throttle remained the same, 48 to 52MPH sitting up. Maximum speed was 58MPH at just below 8,500RPM. That's 1MPH short of the baseline benchmark, but power at speed felt about the same. As I've said multiple times now, the faster you go, the harder it is to stay consistent. I had a slight crosswind, and that's probably all it took to knock off that last MPH.





The biggest improvement I noticed was a cylinder head temperature drop. Ambient temp was 45°F. Cruising along at 40MPH I was seeing temps from 225°F to 240°F. Cruising at WOT the CHT showed 285°F to 300°F. That's quite a large improvement over stock.


While I think a larger than stock carburetor is a smart move on these big minarelli engines, it's more about room for expansion and keeping the engine cool according to this test. There really seemed to be no power gain at this stage. The poor fuel economy is the most disappointing part of this information to me.

[jmkjr72]

well you are doing a bit better on the mpg then i did when i had a 19mm arrechee
but also i was turning 10000 rpm and hitting the same speeds
my zuma could benifit a lot from some up gears

[90GTVert]

I guess to some folks it's slow, but any time you can do about 60MPH you aren't too bad off IMO.

[jmkjr72]

yeah it is nice the plus if i add up gears i could get the same speed at lower revs and use less fuel and maybe get back above 50 mpg

[90GTVert]

OK, this thing has been ticking me off for the last few days. I tuned the Dellorto 19mm Sunday and went to ride it Sunday night. All went well until I tried to stretch it's legs for the max speed on the way home. It climbed to 57 pretty well, right around 8,400RPM which is right were it was for the others around that speed. Then it acts like all of the sudden it found a gear that's never been there before and RPM dropped off to about 7500 and it started slowing. I let off and hit it again and it revved higher and again dropped down. I tried this a few times with the same result. I wish I had this extra gear on a lot of my scoots, but thi sthing hasn't got the power to accelerate from that speed at 7500RPM.


My first thought was simply to clean the CVT and hope that got me a good result. I pulled everything apart and cleaned it up. I forgot to get a closeup pic, but there was a black ring right in the center of the rear pulley on one side where the belt had been slipping at speed. I scraped that off with a razor and sanded the surface with 220 grit. I sanded the front pulleys with 400 grit to assure they were clean. Greased the torque driver, polished the drive boss, cleaned the CVT cover and case, and everything in that area.




The cleaning seemed to smooth some things out just a tad, but really accomplished very little. The belt slip in the center of the rear pulley made me think of 2 things, the contra spring and the torque driver. I started with the contra spring. It was noticeably less stiff than it would be new. I replaced it and the problem seemed to lessen, but was still there.


Next I went back to something I saw when cleaning. The torque driver has worn worse in one area and now the paths are no longer smooth.







For some reason, this torque driver has grooves a little longer than my other stockers. It's pretty much on par with one that I've modified. I really didn't want to replace the torque driver for fear that it would change everything with the CVT and really throw off any future results for this phase of the project, but I needed to try something.


I swapped in a modded torque driver and RPM steadily rises as speed increases as it normally would. Then the issue became getting the RPM correct. How smoothly the replacement pulley works and the stiffer spring are throwing off the RPM. I've been swapping in all sorts of springs new and used hoping one would put me right where I need to be with the same weights and everything to keep results on par with no luck. It seems like everything either wants to rev higher or lower than before now. Seems to top out at 57 no matter what I do.


On top of that, I'm getting no gains other than better temps and improved low throttle acceleration. I've only tried 2 19mm carbs, but I'd think I'd see some sort of gain there if performance were going to improve. So now I'm trying to figure out if I want to restart Phase 3 with just a new CVT setup or perhaps a new CVT setup and a pipe. I'm really not sure. All I'm sure of right this minute is that I'm tired of screwing with it ATM.

[190mech]

These darn 2 stroke scooters can get real complicated,yet be soo simple!! :beatup:

[90GTVert]

2T + CVT is a double whammy. The hardest part for me is that I need to keep it consistent but parts seem to need to fail. The slightest little difference under that CVT cover can throw all sorts of stuff off.

[2strokd]

I was just gonna say that. Amazing what one lil ramp angle, length, (smoothness) will change.
lol, Ive heard of OveRRange kits.. You had an "OveRDrive" one

[90GTVert]

I've been out looking things over, trying to figure out why I've lost a couple MPH and my max speed RPM has increased when everything else is setup close to before the CVT issues. While I find it frustrating at times, at least I can say my desire to keep the project consistent and the results on the up and up has taught me something else I probably wouldn't have noticed otherwise.


I have 4 fixed halves of the rear pulley here, and I was swapping the modified torque driver onto each of them to see if there was a difference. I found that two of them would allow the pulley to open a little farther. They would open just far enough for the belt to reach as far as it can in the center of the pulley, for the best top speed gearing.


Initially, I thought the issue must be with placement of the receiver holes for the little pegs that the torque driver rides on. Perhaps some are drilled at a different height, I thought. I measured base to center and top to center and they all came out with pretty much the same measurements.





Then I noticed it appears some of the bases are recessed farther into the pulley face, which would create less clearance at full open. Again, I took some measurements. Two of the fixed halves have the base recessed in about 4.1mm. The other two are recessed only 3.6mm. That makes an additional 1/2 mm of clearance when the pulley is fully open, and it's just enough to allow the belt all the way to the center.





I also saw that both of the more desirable parts shared the same marking on the back of them, while the others had no markings.





Now it sounds like I've figured out how to get this back on track, but there's a problem. Both of the halves that I have, the original from P90 and the one I had around, have damaged threads. I've damaged 2 of these in my history with scooters, and I just had to pick the 2 that are the best performers. :doh: For some reason the nuts that go on these are very easy to start just a little bit crooked. If you are in a hurry or not paying complete attention and hit it with an impact gun, that's the end of the threads. I already knew this, but I suppose I needed to learn again when I was doing a bunch of spring swaps and getting frustrated over the last couple of days.





So I'm still left trying to decide what I'm doing here.

[2strokd]

Nice find!!! Ive gotta bunch of spares. Lemmi go see if i have a "Jog90" one and i will donate it to the project just for the knowledge of this. Thanks! See Mom! Sometimes it does pay to sit and stare at my parts

[stepthrutuner]

I wish I could offer some insight into your problem. The damage in the grooves surely must be the result of vibration or hammering. I suppose the guide pins must have been hanging in the irregularities of the grooves somehow to create the rpm 'hanging' situation? Could I see you biting the bullet and springing for an overrange in the not too distant future despite wanting to keep this demo project as stock as possible? At least the parts should be higher quality I would think.

[90GTVert]

That's basically my thought as well, that the trans got stuck just shy of where it should and when I really pushed it it woudl drop into the high gear and RPM plummeted below peak power too much. I see signs of the same wear on every TD I have here in a similar spot, this one is just more severe.


My lack of an OR is simply a lack of funds. I'd like to test it, but really I've wanted one for a long time on T1. Had I known before destroying a pile of belts, I coulda bought an OR.