Couple "Stupid" Questions.. :)

[JustinBoots]

1) My understanding is that Apex quads are more "race ready" then DRR's when you buy them new.....what makes them so different? I know the transmission gear ratio is lower (12:36 compared to 11:31), but wouldn't that rob top-end? Other than that, what else could be different....maybe the crank?

2) When doing CVT tuning, is my understanding correct:
a) heavier roller weights, move to the outer variator ramp area slower than lighter weights
b) the heavier the weights in the variator, the sooner it will overcome the torque spring in the rear, thus shifting to higher gear at a lower RPM
c) ideally you want belt travel to the outer most edge of the front variator

Here's what I am looking at....I've got a 2010 DRR LC 50cc with ported stock case and cylinder with stock tranny gears. Carb is a 20mm with a 48/112 jetting. The front sprocket is a 19T and rear is a 34T. The exhaust is the G-force National pipe and air filter is a TwinAir. Currently my weights are 3.0/3.5 offset. He's running a 5.30 in the 200ft drag strip area I test in. I can hear it shift from 1st to second after about 100ft. I'm wondering if putting the Apex gears in it would rob from that time and give him a slower bottom-end, but ultimately place his shift point at a higher speed.

My spark plug is chocolate and it runs really well, just wondering what I can do to make it better for him.

Does any of that make sense?
:huh

[jerkyboy]

biggest diff between apex and drr is the size of the frame apex is a little bigger.
heavy weights make it shift faster and if your plug is chocolate brown you need to go smaller on the main jet.

[JustinBoots]

Makes sense....I haven't rejetted since we went from the mid 80's to triple digit temperatures so that would make me a little rich. thanks for the advice.

[JustinBoots]

Well....I dropped the jet size to a 108 and it actually slowed it down by .20 seconds, but that could be coincidence. Does anyone have opinions on how long the bike should be staying in 1st gear? Seems more like the bike is shifting to high towards the 150/175' mark now. Wish I could ride the bike so I could watch the tach, but that's not an option. Guess I can go up on the roller weights to get it to shift sooner, but that will more than likely hurt the 200' times. Maybe I'm looking at this all wrong though.

[EthansDad]

Does anyone have opinions on how long the bike should be staying in 1st gear?

you're not hearing gear changes. CVT, or Continuously Variable Transmission has no First, second, third gears as such. just constantly changing ratios. sometimes, folks (myself included) will talk about shifting from first-second, but no such hard change happens, or can be heard. its just a way to think about the changing of ratios.

what you are likely hearing is over shift, or over shoot...basically, the motor takes the CVT up to a higher rpm (say 11k), shifting is happening, but then the CVT system settles into a lower RPM (say 10k) for the remainder of the shifting. it sounds like a hard shift, but its not.

I've had that happen on a couple of bikes, not a big deal, you'll (most) always have a bit of that, would be nice to have it like 11.2 and settle to 11. that can sometimes be caused by an inbalance in weights/spring (too heavy weight VS too light spring - change 1), or can even be caused by a worn variator with grooves in it (belt hop). even still, the torque driver and the angle of the torque driver rail can also play a part, or can itself be worn such that it allows the bike to shift out quickly at first, then not so much later.

bottom line, that over-shift can be a pain in the @$$ to get rid of.

for your other Qs - there is only 1 ratio from the crank to the rear tire rotation. you add up all the systems to get it (CVT+tranny+final drive +tire height). if one of those is different, then I change the others to balance, and yes if the overall system is too tall, you lose bottom.

2a - incorrect. its all about spinning mass and rotational force in the variator. if I have Xgrams weight spinning at 5000rpms, it creates a force on the rear spring via the belt. if I have X+3more grams weight spinning at 5000rpms, it will be creating even more force on the spring at the same given rpm, thus shift you out sooner, and overall shift out at a higher rate - sometimes too high for your motor to handle.

2 b and c - you are correct.

If you want more theory and background on CVTs and spring rate, here is a cure for insomnia in these overlong threads...


http://www.exriders.com/vbb/showthread.php?s=&threadid=460092


http://www.exriders.com/vbb/showthread.php?s=&threadid=460100

-EA

[JustinBoots]

Thanks man! 2a makes more sense to me now.

[EthansDad]

no prob. I also see you're mixing 3.0 and 3.5. you know they make a 3.25? :-)

I've found that sometimes mixing to the 1/8 gram will make a difference because its 1/8 * 6 or almost a full gram difference. I found a rotational force calculator once, and at the rpms we turn, 1 full gram is a large amount of force difference.

-EA

[JustinBoots]

Yeah I've actually been stepping it down with the 3.25's, 3.5's, and 3.0's. Son says it felt faster running 3.25's and 3.0's staggered vs. the 3.0's he tested last night. Stop watch only showed .06 difference slower so doubt he could feel that. Going to make him think I switched it back and ask him his opinion again tonight. :)

Can I mix it even further than that or is it best to only have 2 different roller weights maximum with them staggered. For example, is there any harm in running 2 - 3.0's, 2 - 3.25's, and 2 - 3.5's? Assuming the combination doesn't come out the same weight as 3 staggered or 6 equal weight rollers. Does my question make senes? :ermm:

[EthansDad]

I know what you are saying with young riders, hard to get solid feedback sometimes.

no reason you couldn't multi-mix 3 of them. I never have, but doen't mean it wouldn't work. maybe you are on to some secret sauce of your own. just look at it as total spinning mass, so add up all 6 in any combo and that is your spinning mass. also of note in a rotational force calculation is the farther away the mass is from the center of rotation, the more force it creates. so when you shift out, the force of more weight is increased even more as the rollers move away from center. kind of like spinning a rock on a sting above your head. you let out more rope, and it pulls on you more.

[JustinBoots]

Thanks for all the help man!

[nitrofish]

Good day Mr. Ahlm! Congrats on Ethan's championship and to the family supporting cast. Why you are in your technical thiking kina mood, I got some added questions. Not trying to hijack your thread mr. Justinboots, I just know any info Eric gives out it's worth everyone's reading pleasure.

1)I tried an older vario I had laying around the garage that I had used on his stock set-up in the past. By just changing the vario, which looks to be a stock Yamisida, although it is different from our new Yamisida it really upped his rpm's by a couple grand or so. The older one is lighter in total weight, but not that much. We went from mid 12s to hitting high 16s? It sounded like a true 2 stroke, pulled decent out of the corners, but really poured it on 10 feet out. It was kinda amusing actually! Thoughts?

2)I am unable to attain our desired stall on our S/6 clutch anymore? I have tried new springs (red as always) and I am still only able to get 7500 out of it. No changes in CVT set-up. My thoughts are that the shoe holes (where the springs snap in) are grooved/wore not allowing me to achieve the rpm's we want. Could shoe wear cause this? I would think if the shoes were worn down that would increase the stall?

3) Are there 2 different types of rear pullys? I recently got a new one and I noticed the 2 little slots that the pins ride in are different. The new one has more of a curve to it, My old one has straight slots. What would the effect be? I have yet to test and compare myself. The old one seems to be working well and I am the" if it aint broke don't fix it kida guy", especially during race season.

Thank you for your time, Matt.

[EthansDad]

sure..here is my $.02

1) I've got a dozen or so different variators in my stockpile. here is my bottom line after talking with a bunch of Mechanical engineers around the globe working in CVT technologies...I don't really know, and sometimes I think they don't either.

I can tell you what each part is suppose to do, but relating that to the impact on the next part of the system remains a black box of sorts. I'd like to figure it out one day 100%, but until then trial and error it is. I won't mind talking about it more on this forum, but don't think I'd gain any more insight back than I've put in. I'm sure folks know, but aren't sharing. ok...off my soapbox now.


lighter var will spin up quicker. less steep sheave angles will shift out quicker, total sheave angle in relationship to belt groove angle will come into play, roller ramp angle (or hyperbolic) will factor in (steeper = slower shift, hyperbolic =quick at first, slower shift later), and so will the distance from the roller ramp to the center of the variator. and the friction between the belt and pulley sheave is also a factor, so different belt types respond, well different. got all that? build me out a chart with the different variators one day on how they respond with the same weight on the same bike. that would be helpful.

2. yup, the s/6 will fail, had that exact thing happen. get a new one, or switch to another brand clutch.

3. that specific part of the rear pulley is called the torque driver and is very critical, and most often overlooked. if there was no angle, but rather a straight up/down slot then the equations would be easier to figure out - variator pulls on rear torque spring, and it compresses due to the force put on it and we get shift. the angles on that torque driver now dissipate that energy over the curve, so now trigonometry comes into play (oh joy). basically, the angle (instead of straight groove) slows down (or speeds up) the back shift rate, and I *think* the shift out rate. sometimes, that torque driver is also a hyberbolic, or dogleg really, can get two from DRR oem, and they are both different. again, trail and error and you might find the best fit. the dog leg one is my fav, steep at first, then shallow. so it holds it in first longer (the var force is less effective on the spring compression), then later on shifts out quicker - well in theory.

[nitrofish]

Thank's for the insight! Matt.

[JustinBoots]

All I can say is :huh and then "Trial and Error" .... CHECK! LOL

[EthansDad]

Yea, you got that right Justin. I actually spend some time on physics forums, and no better answers there. I put a lot of content up here, but how to test is one area I keep to myself. I will say though, t&e still remains the best method. Knowing what stuff is suspose to do does help a bit.

On a Side note, if anyone has access to a machine shop and wants to foot the shop time, I have a handful of ideas I think are worth trying.

[JustinBoots]

My next-door neighbor manages a machine shop and he just turned the inner hub area of my clutch bell down. He doesn't charge me so ar. If you want me to try something and I've got the parts lying around I'd be glad to be a Guinea Pig. We can take it offline via email justin.folkers@gmail.com or on the phone 281-380-4132. Thanks again for your help, this is our first full season of racing and I'm learning the best I can. Wish I could offer you advice, but know what you mean about some types of people just don't share.

[JustinBoots]

Raced this weekend and things went much better....running a close second place. Thanks for all the help....but I've got a follow-up question. I brought it home and did the typical cleanup, removed torque spring and replaced, new rollers and this time I put in a new Yamasida variator kit. Running 2.5s and 2.75s staggered, same as during the race. During the race it seemed to need a little ramp-up time to come alive and now that I am running it on the stand, I can definitely here a change in RPM from the low range to the high range...is that normal? I was thinking that I should have a stall around 7k and then the bike should hold the optimal power range from there on out. Thinking I might go down in weight a little more to see if I can delay overcoming the rear torque spring until the RPMs are higher.

I might have jsut talked myself into my next move, but any advice is welcomed. :)

[nitrofish]

Have you looked at the cvt workings with the cover off? Sounds as though you are getting some pre-shift (belt dropping in the rear pulley before the rear wheels turn) essentially starting in a higher gear ratio. Start the quad, carefully remove the cvt cover ( beware the gasket may get eaten by the belt) slowly rev the engine and watch the belt at the rear pulley. If the belt drops into the sheaves you are getting that dreaded pre-shift. you may have to shim the vario. Also watch the belt travel on the vario, make sure you are getting decent travel to the top. If you are getting pre-shift, shim and play with your roller weights, you can again increase your roller weight to get your belt travel back on the vario. Remember don't rap out the quad with the cover off to hard, without the bearing support of the cover it can be hard on the rear pulley shaft. Matt.

[JustinBoots]

Great idea! I actually have a CVT cover that had drilled in the wrong spots for ventilation and I've been considering cutting it more so I could watch belt travel. You gave me some good points to watch for though. My belt travel currently is within an 1/8" of the outer lip of the variator so I've felt good about that, but my belt is tightwhen the quad is off so I could very well be getting pre-shift and need to do some shimming.

[nitrofish]

Sounds like your belt travel up front is ok, check for the pre-shift. I bet you will end up going heavier on the rollers once you shim and should see a bit more travel up front. Good luck. Matt.

[EthansDad]

Great idea! I actually have a CVT cover that had drilled in the wrong spots for ventilation and I've been considering cutting it more

That is exactly what I do. My kid has already named it the "peek-a-boo" cover. I used a door knob hole drill (big, 2 1/2"+) bit made for wood. it ripped right through the cover no prob. I did it on the top of the cover, both front and rear so you can see whats happening while you are on the bike.

As for what to look for, you and nitrofish on on the right path. just remember belt travel is belt travel. if its dropping in the rear, it MUST also be climbing in the front and visa versa.

goal would be for it to launch (clutch engage) while the belt is still full height on rear pulley.

[JustinBoots]

Thanks again for all the insight! Things are making more sense each day. :)

Only thing resonating in my head right now though is why I would have to go with larger weights if I add shims? Seems that would cause the pre-shift to worsen.

[EthansDad]

During the race it seemed to need a little ramp-up time to come alive and now that I am running it on the stand, I can definitely here a change in RPM from the low range to the high range

I don't know what that means. I get the slow to ramp up, that usually means its shifting out to quick (too high a gear) or your down on power down low (typical for 50s). as for the change in rpms, yea, you should hear that.

This is shift out goal IMO.


forget the mph on the graph, just look at rpms VS speed.

on this graph, the bike stalls at 5k rpms (when mph starts to move up). then from 5k-9k the bike stays in first gear (no shift). only at 9k, do you see the gear ratio change, but the rpms hold steady at 9k, which we could assume was peak HP of that motor. also no the first time the bike hits 9k, it overshoots a bit to say 9.5k, then settles back in. that is normal and I get that a lot. just want to make sure the overshoot is like 500rpms, not 1.5k rpms if you can.

[JustinBoots]

That's my understanding as well...as far as the RPM sound I am trying to describe is something like this: gun it --> weeeeee --> wheels start turning at about 7k --> waawhhh (maybe 1sec or 2secs) --> wheels turning fast --> Weeeee --> Wheels turning faster and sounds super fast. :D

I have a tach so can measure the RPMs tonight...just ran out of time last night. Your graphs are very PRETTY ;) and take up my entire monitor width! LOL...I'll study them more, but understand the point you are making.


Originally posted by EthansDad
I don't know what that means. I get the slow to ramp up, that usually means its shifting out to quick (too high a gear) or your down on power down low (typical for 50s). as for the change in rpms, yea, you should hear that.

This is shift out goal IMO.


forget the mph on the graph, just look at rpms VS speed.

on this graph, the bike stalls at 5k rpms (when mph starts to move up). then from 5k-9k the bike stays in first gear (no shift). only at 9k, do you see the gear ratio change, but the rpms hold steady at 9k, which we could assume was peak HP of that motor. also no the first time the bike hits 9k, it overshoots a bit to say 9.5k, then settles back in. that is normal and I get that a lot. just want to make sure the overshoot is like 500rpms, not 1.5k rpms if you can. :D :D

[EthansDad]

gun it --> weeeeee --> wheels start turning at about 7k --> waawhhh (maybe 1sec or 2secs) --> wheels turning fast --> Weeeee --> Wheels turning faster and sounds super fast.

you need to make a video of yourself making those sound effects and post it on youtube :-)

IMO - its 1 of two things

1) jetting / motor is spot on, but cvt is off - you are shifting out too soon (putting it in a higher gear before its time) and causing the rpm drop (waawhhh). -->slightly higher spring rate??

2) your CVT is fine, but your bike is low on power down low (like pilot circuit or needle) and it can't make the power it needs to pull the ratio - again causing your rpm drop. -->move pilot jet up/down a unit, and do same with needle clip.

3) a little bit of both??

from stall, there should be only a climb in rpms, no dip like that.

[JustinBoots]

LOL!!! I was thinking about YouTube when I was writing that! :)

Needle adjustment is my next item of business to understand and learn. I determine my pilot jet sizing by checking to see 1) if it dies when I screw the air/fuel screw in and 2) I know if I'm unable to hold constant low end throttle without it rising out of control I need to adjust. That's the full extent of my knowledge at this point. :) With time comes knowledge though :)

[EthansDad]

when in doubt, just change it and you'll see what happens. kind of like going to the eye doctor - better now, how about now?

just note the position you started in, can't really screw things up too bad, and you'll see how it effects things the first time you do it. pick one direction to go, say leaner (moving the clip up =leaner = dropping the needle = all the same). go one position, try it. better/worse? if better, try two position in that direction? better/worse? then flip direction to richer from your starting place. rinse and repeat until you find what works best.

-EA

[JustinBoots]

EthansDad - You're really an awesome guy! I really appreciate all the advice you've offered me and others that I've been able to review as well. Just wanted to say thanks.

[nitrofish]

Good stuff Eric!

[quadscrib]

Imagine somebody who has no idea what the discussion is reading this....a muffled gunshot would follow :huh

[JustinBoots]

:p LMAO! I guess there's a delay before the gunshot rings out for those of us that might have a slight idea of what is going on. :)

[JustinBoots]

Ok, got it on the stand and checked everything....

- Stall: 7500 RPMs
- Front belt travel within 1/8" of outer edge
- Rear Travel: No detectable pre-shift before tires move
- Max RPM on stand: 13,200

From all that I felt it had to be carburetion and then I heard a bobble in the acceleration off the line....AhhhHaaa! Reeds!!!! Sure enough my reeds were not seating completely. So I changed those out and it seems a lot better. I am concerned about the RPMs though...doesn't that seem quite excessive even for testing on the stand. I feel stupid for asking but how do you keep your RPMs lower? Thinking it's the torque spring, but also afraid that is my answer. Also, my RPMs are slow to drop after I let off the gas, but I think my pilot is just right because it barely starts to die when I screw in the screw all the way.

[EthansDad]

The on the stand rpms are pretty pointless. Need to have your tach on, and run the bike wot for 6-8 sec riding it. You will see the rpms settle in at one point. That is your shift rpm. My guess for you, likely 12.2-12.5, which is good. You can move that up/down with weight/spring combos, but your peak rpm (on stand) will stay the same with any cvt set up.

Oh yea, and since I'm guessing you weigh more than your kid, add 200 or so rpms to your numbers.

[JustinBoots]

Ok wasn't sure if my riding it would affect it that much so good to know to add 200 RPMs. I outweigh him by 150lbs. :)

[chunky0071]

Hey Eric I want to borrow that cover you have one week end. THink it could help Tanner understand about staying on the power.

[JustinBoots]

Ok with my heavy butt on it its showing 11,500 RPMs to 11,700 RPMs so it sounds like I am pretty dang close to the 12,200 that you were estimating.