Help Diagnose top speed issue

[steffen707]

Okay, like normal I don't post on this forum for 6 months, then get on a scooter kick and post on 5 different threads when i should just start my own.

So here is my setup corsa 72cc, oko24, pg long, 9:1 gears, 36grams of roller weight, ruckus variator, zx rear pulley and clutch. Yellow contra spring (no idea what stiffness it is), red grabber springs, ( i think they're 2000rpm more?)

I'm running a bando 654x18x30 belt that is basically brand new, with zx drive pulley, and ruckus 93-94mm variator. Its not a polini.

I have a trailtech gauge and right now when its pulling its right around 9600rpm through mid speeds, until the rpm start to climb (meaning the variator is maxed out right?) to about 10,800 max. It blipped to 11,200 once, but immediately went back to 10,800, so I think that was a fluke.

The setup rips, and I love its speed; however, wheelman and others reported a lot higher top speeds with basically the same setup. I'm not sure if its because they got to a higher rpm, I have smaller tires or what. I know 8.4:1 or 8:1 would give me more top end, but I'm wondering what's holding me back now.

Attached is a picture of sharpie marks on the drive face and variator. Looks like the belt got pretty high up, can anybody tell me if it's suppose to get higher?

I have to open up the carb to get my jetting numbers, because I can't remember them, and I'll get my tire size. I posted another thread about how to calculate mph based on tire circumference, rpm and gearing, but nobody posted if my formula is correct.

Thanks.

[Trafficjamz]

if you play around with different boss lengths, you can get those sharpie marker marks to disappear.

[Trafficjamz]

your 9:1 gears are holding your top speed back too.
i would use 8.4:1 gears or 8.0 if you want over 65mph with your setup.

[steffen707]

your 9:1 gears are holding your top speed back too.
i would use 8.4:1 gears or 8.0 if you want over 65mph with your setup.

I know my 9:1 gears will hold back top speed, but when I calculated the max mph with the gearing on this thread, posting.php?mode=quote&f=4&t=27530&p=239930 it appeared I should be able to get more out of the scooter even with 9:1 gears.

So during lunch I went home and found the oko variator, SEF ramp plate and stock clutch and belt. I threw that in there, and though it wasn't in the right powerband (7500-8500) rpm on acceleration it still got up to a top speed of 59.2 on my test road by my house. I marked that variator and there was hardly any mark left, so it had to be maxed out, leading me to believe that i'm not maxing out the variator on the zx trans.


The ZX certainly accelerates very well. I think I might need to do more case shaving by where the starter bendix went. With the 93mm ruckus variator it might be rubbing there and limiting maxing out the variator.

SO, i'm thinking what i need to do is play with the rollers and contra spring with the stock transmissing setup and see how fast I can get it, then once I know what its capable of, i can start screwing with the ZX trans setup and figure out why its slower.

[Wheelman-111]

Greetings:

The spreadsheet is an excellent theoretical guide to maximum potential, but belt, clutch and even tire slip subtract 5 or 10% from theoretical maximum. Stronger contra spring reduces but does not eliminate the belt slip. Soft grippy and wider back tire (90/90?) might help astern, but Jamz is correct; 9:1 is fine for stock bore but legs are too short for mighty Corsa.

[steffen707]

Greetings:

The spreadsheet is an excellent theoretical guide to maximum potential, but belt, clutch and even tire slip subtract 5 or 10% from theoretical maximum. Stronger contra spring reduces but does not eliminate the belt slip. Soft grippy and wider back tire (90/90?) might help astern, but Jamz is correct; 9:1 is fine for stock bore but legs are too short for mighty Corsa.

But it accelerates SO FAST.

[Trafficjamz]

A zx trans with a 669 belt and 8.4:1 gears will accelerate just as fast.

[steffen707]

Now I have some kinda high speed run problem. I think its ignition related because the motor didn't sieze up, runs fine after you slow down for 20 seconds or so. Below is a video of the issue. I can't see how its fuel related because the rpm stays right around 10,200 when it happens.

Right around 30 seconds or so the rpms start bouncing around and i left the throttle Wide open, you can just see my right hand in the video.

Can you guys watch it and give me your opinion?
http://youtu.be/uGvQ2rMB8wU

[patthesoundguy]

That thing rips hard is there some sort of rev limiter built into the cdi box maybe? Certainly sounds like it

Sent from my Nexus 7 using Tapatalk 2

[steffen707]

Well from what I read there is no rev limiter.

I also swapped in another cdi, same problem.

I swapped in another coil, same problem.

To see if it was a speed thing when it started happening I tried slamming on the brakes then back on the throttle and it stumbled again.

I think tomorrow i'll hook the wideband o2 back up for a high speed run and see what the AFR does when the rpms freak out.

I was really hoping it was an easy fix, never is though.

[steffen707]

I forgot to add, it was running fine at WOT from 20-30 seconds before the stumbling, and it was holding steady at 10,200 rpm. I didn't notice the engine temp spike at all, and it runs at about 300degrees so its not hot.

Maybe i'll pull the plug and check my jetting as well as the wideband test.

[Wheelman-111]

Greetings:

Temps staying cool-ish? Consider fuel starvation due to vacuum deficit at WOT. Happened to me with a paper inline filter on Flash 2. Loose vac line allowed vac to drop too low to keep the petcock open and flowing after 30 seconds at WOT.

[steffen707]

Very cool wheelman, I'll have to give that a check.

Can I hook a vacuum gauge with a T to the vacuum line to see if it decreases?

[steffen707]

Today was toasty testing day. We have a heat advisory for Wisconsin, 90 degrees and 50% humidity. Thank god my garage is air conditioned.

I hooked up a vacuum pump to the vacuum line connected to the petcock and applied vaccum, i capped the vacuum port on the intake and went for a run, still weird issue with long WOT runs, even though the petcock was getting a constant vaccum. I checked and the engine doesnt pull that much at WOT, so it was a good guess wheelman, but doesn't seem to be the culprit.

So i hooked up the wideband and with stock driven pulley, stock belt, 2k grabber springs and 1500rpm contra spring with 33g roller weight, 118main jet, and 50 pilot. At WOT it was starting at 12.8-13:1 AFR and it would hold that but once you hit about 55mph, and began holding that RPM at WOT the AFR started to creap up after about a 1/4 mile and at around 14:1 it started freaking out.

So I threw in a 120 main jet with same exact setup and tried it again, now at WOT it was at 12.5AFR, and then started to climb as well, this time, it took 0.8 miles before the AFR reached 14:1 and the rpms started freaking out. PROGRESS!!

I noticed during these two tests I at about 34-45mph and crusing at 8500 rpms I was getting AFR in the 14-15:1 range. and the temps were climbing up to 360-370. So I checked the needle, and the 6k8 I had in there from a year or so ago was one notch above middle. So I put it back into middle (raising needle) hoping that would increase fuel and it did. But i was still having some lean issues down low so I put a 52 pilot in.

Now with the ZX trans, ruckus variator, 33 grams of weight, 120 main 52 pilot, 6k8 in middle spot with 2k grabber springs and 1500rpm yellow contra spring, The scooter runs awesome 0-52 ish, where it gets all the way up to 55 or so, and if you hold it long enough, the AFR climbs from 12.5:1 to 14:1 and it runs crappy. During WOT i'm keeping temps around 325 now, and all around crusing 30-45mph temps are about 350. It appears the more throttle I give it the cooler it runs. I probably could go back to a 118 main for a tad more power, but I like it running cooler, and i'm less likely to lean it out at max MPH.

So if anybody read through all this, any new suggestions why the AFR is leaning out with steady speed, steady rpm around 55mph? And yes I still have the 9:1 gears in there, and if I want to go faster I should go with 8.4 or something else, but still.......Could I have a partially clogged petcock that can't keep up with the flow at those speeds, and I'm eventually draining the bowl of all fuel? How do I test this? How do you clean a petcock?

[steffen707]

So I marked the bottom and top of the trans as well as over by the starter bendix area.



And after full speed run with the zx trans and 654 belt and ruckus 93mm variator, i was only able to get 55.7mph on flat ground, 57mph on downhill. I did not rub off any of the black marks, so at least I know the belt isn't hitting something that's limiting my top speed.

With the stock trans, it did kinda suck at accelerating from 0-8, but then went pretty well, but i was able to get 59.4mph on flat ground, didn't try it down a hill.

I think i'm going to have to try wheelman's new 660 metropolitan belt idea and see if I can't get a bit more top end, max out my variator, and get that belt tight into the rear sheaves. I did try the 1000 contra spring, but that didn't seem to increase my top speed at all and acceleration felt better at 1500 contra spring.