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Post by 90GTVert on Sept 10, 2010 21:15:16 GMT -5
This thing has been a major pain trying to tune it the last couple of days. It started out running really well, tune wise, when I was testing differnet cylinders and even on the first runs of this cylinder. Then, the other day I went to install a new plug and do a test pass for jetting. I go down the road a bit and then turn around. I go WOT turning around and in roughly 1/8 mile it falls on it's face while still WOT and the throttle won't respond till I coast for a bit. I checked the plug and it was dark. I went down on jets. Same thing. With smaller jets it would tend to fade a little more than just dropping off. I was thinking maybe it was a float issue and the bowl was getting drained, so I adjusted the float a few times and still couldn't get the issue resloved. After going all the way from a 70 main (sputters and won't run when you give it gas) to a 120 main (chugs and dies when you hit the gas), and adjusting the float multiple times, I inspected the float and set it back to a normal setting. I have my suspsicions about the float needle and/or seat. Anyway, all set back to normal specs and with a jet that worked well at first I tried and failed again.
Finally, at about 9 tonight after inspecting fuel lines and the filter, I decided to just put the Arreche on and see what happens. I made it 1/4 mile before it stalled and died and wouldn't restart. I pushed it home and realized the fuel hose and came off and drained all the gas out. I had noticed that the line was a little short but thought it was OK for a quick pass. Oops. After cutting a new hose to fit properly, I took another pass. I went down the road and ran WOT for about 1 mile and never stalled out and I even had throttle response when I let off. I guess there really is soemthing up with the other carb, so I'll just tune the Arreche for now. It was getting near 10PM and I was tired of messing with it, so that's all the progress I have to report.
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Post by 2strokd on Sept 11, 2010 1:42:43 GMT -5
At least it wasnt a total loss tune day  . Kinda weird that it ran the best with the carb you like the least :spin: |
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Post by 190mech on Sept 11, 2010 5:05:21 GMT -5
I was thinking plugged fuel cap vent at first,or maybe clogged petcock starving the carb at WOT,but the carb swap cured it,, wierd!!
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Post by 90GTVert on Sept 11, 2010 6:54:08 GMT -5
Well, even though I checked the fuel system, the lines and filter were full when I looked so I didn't really think it was a pre-carb fuel supply issue. Oh BTW, if you ever want to look like a real jerk on your scoot... set the float high. When it was way high it bogged and I got down to maybe 15MPH by the time it would let me touch the gas again. Then it started bucking. It would pull hard for a second, then die, then backfire, then pull, then die, then backfire. lol I know my neighbors had to think I was trying to show off or something.
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Post by 90GTVert on Sept 11, 2010 9:38:19 GMT -5
I 've been out annoying my neighbors this morning. ;D It seems that the Arreche like an 85 main jet. It's reunning pretty well with just a couple of little issues after messing with the needle and idle settings. I can open the throttle fast and it is fine, but if I snap it as fast as I can it hesitates for a split second. If I can get that out and fine tune the idle a little more, I think it'll be in pretty good shape.
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Post by 90GTVert on Sept 11, 2010 12:45:22 GMT -5
I richened the needle setting and the hesitation got better. After a little more tweaking, I took it on a 15 mile trip to see if I could make it home. It ran well. I am disappointed that it doesn't like to pick the wheel up on ashpalt unless I'm leaving a stop or going very slow. It seems to need a little slip to get going. I also noticed that it doesn't sound like it's revving all that hard and needs to "downshift" a little better. When I got back, I hooked up a tach and went for another spin. It was cruising at 40-45MPH at 7000-7500RPM. 57MPH showed my max revs of 8300. I know T2 would rev to 10,000RPM at times, and would always hit 9,500RPM with any decent setup. This Venus is supposed to be deep geared.... I remember one setup on T2 was doing 57MPH @ 9800RPM, and I'm doing that speed at 8300. Since I have a 50cc contra spring in there, I think I'll try the 90cc or maybe the 1000RPM contra next time I'm out there. Hopefully the lower revs aren't just a function of the smaller carb. I don't think so though. IIRC I pulled at least 9500 with the same carb on T2 at one point.
Another note... I think I need a longer or stiffer shock if I'm gonna use the Leo Vince and fairings. I haven't tried yet, but I'm almost certain. This one is 9.5" eye to eye, so I'm thinking 10.5ish eye to eye might be good. It might be fine with a smaller rider, but not with me.
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Post by 90GTVert on Sept 11, 2010 16:36:21 GMT -5
I swapped to a 1000RPM contra and the revs went up about 300 to 8600RPM max at just over 57MPH. Acceleration improved, top speed stayed about the same. Then I swapped to 8g sliders, from 8.75g. The speed dropped to about 53MPH and it sounded like it was on a rev limiter at 8600RPM. I'm guessing either I need more carb or more exhaust duration to get more revs. It runs so strong though, that I think I might leave it and consider my exhaust options for this RPM. I mean.. the fastes 1/8 mile scoot I've ever had and 57+ top speed sitting up... it's kinda hard to think of it as lacking performance. The lower revs wouldn't be bad for keeping it a bit mroe relaible either. Not sure. So...
Should I buy a new shock and pay about $250-300 shipped for a Leo Vince ZX like the one on it, which is intended for 9600RPM according to the specs I saw when I got it (although it seems to be working rather well as is)?
Should I get the Phongeerish exhaust for $145 shipped, and hopefully no shock?
Or should I get another Leo Vince and figure out why I am missing 1,000RPM?
Hmmm.
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Post by 190mech on Sept 11, 2010 17:10:01 GMT -5
Interesting!Since I installed my "nickel tach" my max rpms level off at 8600,maybe there is a rev limiter in our CDI boxes??
I think I'd try the Phonegeer style pipe as the LV calculates out kinda wierd by the dimensions you gave me..
What about a shock extension if you need to jack it up?
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Post by 90GTVert on Sept 11, 2010 18:09:24 GMT -5
With the same CDI (and whole ign system for that matter), I did 9,200 revs with the 70cc. I did read someone say they installed a Posh CDI on a Venus to riase the rev limiter, but some people just bolt thing son and swear it worked so who knows. We have pretty much the same exhaust and transfer durations. You have a larger carb IIRC. That would make me think it could be the port setup. I forget the exact figures now, but I beleive I had a similar figure on the exhaust, but the transfers were around 120 instead of 130.
Forgot all about extensions for the shock. I'll have to see what shocks are out there though. I wouldn't mind a stiffer shock.
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Post by 190mech on Sept 11, 2010 19:35:02 GMT -5
I never tach checked my Autotech 70cc cylinder,but it seemed like it would rev much higher..That cyl had nearly the same port durations we have,,what are we missing here?
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Post by 90GTVert on Sept 11, 2010 19:53:16 GMT -5
I stuck another CDI in there and it revved to about 8670. It did sound different and feel a little snappier... then again it's 10 degrees cooler and it's pitch black. It always feels faster when you can only see in your headlight. I did notice my CDI is marked with CPI on the back and it's bigger than the replacement and the Vento CDIs I have. I'll have to do a test run with each in the daytime, but regardless... I didn't rev to 10,000.
Obviously the bigger bore and stroke paly a part in the revs... but then that deosn't explain why T2 would run so hard in comparison.
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Post by 190mech on Sept 12, 2010 6:47:05 GMT -5
I'm quite happy with the power,much more "mellow" than the 70cc set up,quick takeoff,hills are easy,cruise over the speed limit,guess I ought to be dang happy with what I have,but always looking for just a little more...
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Post by 90GTVert on Sept 12, 2010 15:38:59 GMT -5
Yeah, it's mostly curiousity at this point. I just tested both CDIs and there is no difference that I can tell. I tucked down for a max of 8700 RPM @ 54MPH (really need to swap back to the heavier sliders). Same takeoff etc... I think we can rule that out. Not that our previous experience iwth revving higher on 70s shouldn't have, but it made me curious that we were both hitting the same RPM especially after seeing CPI stamped on my CDI too. Just had to be sure.  |
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Post by 190mech on Sept 13, 2010 9:16:46 GMT -5
Thanks for the CDI tests,guess thats not it..I noticed that from about 3/4 to full throttle there is no RPM change,now I wonder if there is something restricting the intake system,etc....
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Post by 90GTVert on Sept 13, 2010 10:39:14 GMT -5
Mine does feel like it could benefit from a larger carb/intake. T2 revved higher with the same carb/intake. This sounds kinda wierd, but could the longer port durations be having a negative effect with smaller carbs and/or intakes? That's all I can really think of that's different off the top of my head. I never modded the ports on T2 till after I had a 25mm carb/intake. The only other thing different is that I always used an open filter on T2 while this and yours both are stock airboxes. Perhaps that could play a role in the lower revs with the larger motors?
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