New Jersey on the road

Discussion in 'Rides, Swap Meets & Other Events' started by Deoodles, Aug 17, 2019.

  1. Deoodles

    Deoodles Well-Known Member

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    I met up with Pat and we rode today it was NJ but he would have to say where. Beautiful area roads and trails. We geared 15/33 for the fairly steep hills and needed that setup a couple of times. Both are 124 builds and it was interesting to see the subtle differences. Pats was quicker off the line and both did hills well but mine was slightly better on steep hills. possibly my main jet one size smaller helped. I ran 5 degrees Celsius hotter and that could be his has a 10 row oil cooler and finned cam cover to my 5 row cooler. We held our own on all roads and managed to get in a top speed run. Both bikes flew and stayed together. Pats speedo registered 68 mph and mine displayed 64 both bikes were 10+ rpms on our tachs. We did over 30 miles mostly blacktop and had a blast.
    B881D49E-BA2A-48A2-A2BA-C5F4039C85A2.jpeg 2E2FFD61-95B8-4DE9-92B1-A440942AF0AB.jpeg 38DE0459-B04F-40C6-8AF2-1538396FCE89.jpeg
     
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  3. cjpayne

    cjpayne Well-Known Member

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    Awesome.
    Wow. 68 is haulin' on one of those.lol
    NJ must have been quite a drive for you Ray.
     
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  4. OLD CT

    OLD CT Well-Known Member

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    I had a blast, but we both agreed and came to conclusion that the 16-33 gearing is a better choice to tone down the revs a bit at 35-45mph semi flat road average speed.;) Maybe even 2 to 3 mph increase in top speed.
     
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  5. Deoodles

    Deoodles Well-Known Member

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    If you look close he gets it on one wheel on the way back. Actually watched him ride one wheel on some blacktop a good 50 feet but I was behind him and couldn’t get it on video. Nice riding OC

     
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  6. cjpayne

    cjpayne Well-Known Member

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    That bike is pretty quick!!! Thanks for posting the vid.
     
  7. racerx

    racerx Administrator
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    Either way, 64 or 68mph, is quite respectable top end from 124cc displacement. By-the-numbers, these tunes should be capable of pulling ~6.8-7.0mph/1000rpm...slightly taller gearing than 16/33. Over-gearing will hurt performance; once you reach the end of the torque, then exceed that with taller gearing, you'll hate the results. There are two schools of thought: one, get to within 3% of what the torque will allow; two, use 4th gear as an "overdrive/cruising" gear and 3rd to deal with grades. If you go for the tallest possible gearing, be prepared to accept whatever speed the bike can maintain in 3rd and downshifting, instead of being able to "surf the torque" in 4th. Regardless, the deal-breaker imho is how the bike performs from a dead stop; if you have to feather the clutch, consider it overgeared.

    The question is how much sprocket combo testing you're willing to do. If the bike sees only few hundred miles annually, chasing that last couple of tenths of an mph/1000rpm might not matter. OTOH, if you enjoy covering some real distance, over the road, reducing cruise rpm by 200-400 can make a big difference, at the end of the day...literally.
     
  8. Deoodles

    Deoodles Well-Known Member

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    Yes, it is personal preference. I ran 17/33 and was happy. Pat said try 16/33 and it’s my favorite now. I’m not that interested in top speed. It allows 4th to pull into mid 50’s where I ride. The 15/33 was more an experiment and has its place. It would be a great choice for the Blue Ridge but not back home in SC. IMO there isn’t a one and done it depends.
     
  9. OLD CT

    OLD CT Well-Known Member

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    The 15-33 has it's place, like trails and big hills. We still had to down shift to third on the big, steep hill in the neighborhood. The 15 may be the go to gear for the mini bike drags next year.:LOL: 16 is going back on soon.
     
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  10. racerx

    racerx Administrator
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    Drag racing is another story altogether... all about 0-10mph, the first 60 feet, probably less. I'd compare that to gearing for swap meet riding, where top speeds are nowhere near what the motor can pull and being able to all but drop the clutch from a dead dig translates into huge pulling power/rapid acceleration out of the hole.

    Road riding over longer distances, like 100+ miles in an afternoon, is the other end of the spectrum. That takes some saddle time and testing to truly dial-in the gearing. If you never ride more than, say, 30 miles at a stretch/50 miles in a day, it really doesn't matter that much. Go out for 3,4,5 hours over the road and you'll not only notice things for the first time, some otherwise minor things may become downright annoying. For example, every single has a "sweet spot" in the revband...as well as a rough spot, usually only a few hundred rpm wide. If it happens to fall just at the speed where you tend to cruise along, being unable to see clear images in the mirrors, plus the "buzziness", may grate on your nerves after a time. It's amazing just how much difference a slight change in cruising rpm can make. It also depends upon how discriminating a rider is in their mechanical preferences. In case it's not crystal clear, already, I border on obsessive when it comes to carburetion & gearing; IMHO, those are like "free horsepower"...or, more accurately, horsepower you needlessly give away when those parameters are less than optimal.

    I disagree, partially, about the "one and done" gearing solution. The explanation is kinda longwinded. For the sake of brevity (and sanity) I'll start with the extreme...the absolute limit of how tall you can go, before it becomes impractical. It is possible, with some tunes in this displacement range, to gear tall enough that a bike can pull its maximum speed on grades, in 3rd gear. That'd deliver maximum "snap" at, say, 50-55mph. The reason it will almost certainly be impractical is that the clutch would have to be feathered, from a dead stop; from experience, 4th gear would almost certainly be too tall, as well. the ratio spread of these transmissions are surprisingly well matched to the engine, almost regardless of displacement. This is more theory than practical instruction but, as with carb jetting & sizing, knowing the theory can save a lot of time. All of these engines, from 49cc stockers to the 125cc strokers (the largest displacement that is still practical with 49cc cases) are horsepower tunes (more hp than torque). Thus, they usually work better when slightly under-geared...and perform weakly (in top gear) when slightly over-geared. At the other extreme, cruising-through-top end, it comes down to a choice between gearing biased toward minimum rpm/mph and pulling power...whether to use 3rd for steep grades because 4th is too tall, or gear low enough that 4th can be used...and having the motor spin more revs per mile than it has to, everywhere else.

    Okay, all that windage having been committed to text, here's a bit of applied fine-tuning, learned the hard way...lots of years and miles. Terrain varies greatly, by locale and it does affect optimal gearing but, not by as much as you might expect. Generally speaking, 3rd gear can take you to within ~15mph of top speed,(engine redlined in 3rd), but with far greater pulling power. And 4th gear has an overall range that's ~40mph wide. That's a lot of overlap. And it's this overlap range that gets overlooked, too often. A 65mph bike that can pull 50mph up a <relatively speaking> steep grade is probably going to be able to do that in 3rd or 4th...a choice between higher revs (using 3rd) and more throttle (using 4th). If the grade + wind conditions drag speeds below that point, a downshift will be required, regardless...and it's basically impossible to over-gear to a point where 3rd exceeds available torque. Within these conditions, there's nothing quantifiable to be gained by under-gearing. This is where the process gets interesting...gearing to allow "surfing the horsepower".

    There are some conditions...combined effects of grade, wind, ambient air temp...where the bike may only reach its speed potential if the rpm can be maintained in 4th gear. IOW, slow down too much and you won't be able to downshift/rev-out/upshift your way back, until you're riding over more level terrain. I think of it as being like "crack the whip"...going into a grade at a high enough speed and the bike will maintain it, maybe even gain a few mph along the way, which it couldn't do any other way. The same applies to top speed runs. I've at least matched the my peak speed numbers while ascending slight grades; the key element was reaching a certain entry speed...then the motor just kept adding mph all way the uphill. This is where finding the torque limit really pays a dividend. Find the balance point and general -over-the-road performance will be acceptably strong and at minimum revs-per-mile. What makes this tricky is the fact that every engines power curve has small peaks & dips all the way to redline. Only way to figure this out, if one lacks access to a chassis dyno, is the seat-of-the-pants dyno. It takes time to accurately assess power output, in real time and in real world riding.

    Anyway, apologies for the lengthy dissertation. I figure that you've come this far with build & its tuning, you may as well have an overview of gearing. With these little machines, another 2-3 mph can't hurt, for sure. More than that, however, is the overall feel while at the controls and that's even harder to describe.
     
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  11. OLD CT

    OLD CT Well-Known Member

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    IMG_0079.jpg Managed to put on the front 120/90/10 K61 and new front linings today in this humid weather we are having. Thanks Ray! It is supposed to be a perfect weekend weather wise, much cooler and less humid. Will do the r&r on the back tire this weekend.
     
    #10 OLD CT, Aug 22, 2019
    Last edited: Aug 22, 2019
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  12. racerx

    racerx Administrator
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    You're going to enjoy those tires, especially exercising the bike through the twisties. Be prepared for the speedo input error and effectively taller (roughly equivalent to +1t at the wheel & -1t at the C/S) gearing, both will be noticeable. Since you said you were wanting to go with taller gearing, this might be just the ticket. Unfortunately, there's no way to correct the speedo drive ratio.
     
  13. OLD CT

    OLD CT Well-Known Member

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    I have done a little testing and found with my new taller tires the bike went 67 gps verified with 15-33. Changed out to the 16-33 and only hit 62. It really depends on the riding area as 50 mph seems to roll along effortless with the 16.

    Lots of highway speed, 16 is the ticket. Performance feels nice with the 15-33 for cruising around my current location, as I have a lot of 25mph roads. It really depends where I am riding. I like them both!
     
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  14. cjpayne

    cjpayne Well-Known Member

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    What psi are you running in the tires and are they softer or harder than the traditional bridgestones?
     
  15. OLD CT

    OLD CT Well-Known Member

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    I had Continental Zippy 3 tires that are about a 1 inch and a half shorter. With the new K61 tires, they are taller than a trailwing. I have trailwings on the red K1. These are far better for my needs than trailwings. As long as you are not planning to ride a lot of dirt and trails. This is the ticket. 30psi C.J. ...

    So I just got back from a run with a newly installed 150 main and cooler air temps. 65 mph this time.
     
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  16. cjpayne

    cjpayne Well-Known Member

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    Awesome. 65 must feel like your flying on that thing.lol
     
  17. racerx

    racerx Administrator
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    If you're sufficiently motivated, it might be worth trying 15/32, or 16/34. Not saying that either will be the "silver bullet" but...one of those might be the next best thing.

    Seriously, there's 6% difference between the 2 combos you've tested. As little as 3% can be the difference between more revs-per-mile than are necessary (too short) and exceeding engine torque (too tall). That happened to me when I switched to road tires; a single tooth added at the wheel made all the difference. The tire size increase and gearing change were each 3%.
     
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  18. Deoodles

    Deoodles Well-Known Member

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    It’s about all that’s left to try. The 16/34 would be easier on the chain. Unfortunately that’s going to have to come from Thailand. Slow and expensive shipping. 36 on the other hand would be easier to source. Would 17/36 be the same or are there fractions that come into play and the 3% changes?
     
    #17 Deoodles, Sep 1, 2019
    Last edited: Sep 1, 2019
  19. racerx

    racerx Administrator
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    Been too long since I did the math on your combo to trust memory. It's still close enough to assume 1t at the wheel is about 3%. Not ultimate precision but workable.

    There are ways of sourcing sprockets domestically. Dratv usually stocks oddball sizes. They can be ordered as custom-made. JT used to list some but I've no idea who retails JT sprockets as of this late date. I'd be willing to do a group purchase, if one of my sources still has them...and they can be added to another order. Otherwise the shipping is ridiculous. The other issue is lack of demand. Who in their right mind is going to stock items that are likely to only gather dust...for years?

    FYI...trying every possible combo is the only way the optimize gearing for a specific combo. Once that's been done, so too us the testing. Add the combo to the overall database...for next time and the next person who wants to build a similar tune.
     
  20. OLD CT

    OLD CT Well-Known Member

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    Webikes has the 32 rear sprockets, I'm just not dumping 50 bucks down for it. I do have a 31, I might try 16-31 next as it is already in stock.
    It will be slightly taller than 16-33. Just for testing purposes. IMG_0084.jpg Pic with BOTH new tires!;)
     
    #19 OLD CT, Sep 1, 2019
    Last edited: Sep 2, 2019
  21. Deoodles

    Deoodles Well-Known Member

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    Bout time you did the rear tire. :) I did some testing. I ran the 15/33 combo and used GPS as my confirmed speed. 64 mph; my tach was at 11k. I know there’s more there it’s under geared right now. I happen to have a 32t so will work my way to 16/32. It’s close and I don’t want to shoot past so I’ll need to make small changes and tests. Btw. The digital speedometer is fast by 3 mph. My trick for that will be swap out the 120 for a 130 front tire for now.
     
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