jack667
Scoot Enthusiast
Posts: 190
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Post by jack667 on Nov 28, 2018 21:35:07 GMT -5
I think it would be good to have a thread on this and I'm sorry if one exists - please point me to it and I can delete this one.
I imagine that there are a lot of 2t 70cc sport builds out there, and still being built. For those that want to cruise at high speeds and therefore maybe WOT for extended time/miles with that build, are there some strategies that should be used?
Here are some more questions and discussion topics I have:
- get gearing right. If emphasis is on max speed for sport build, what is best gearing? 11:1? Higher gearing? This could be expensive and/or difficult (DIY) for the sport build crowd so maybe the least desirable item?
- over-range variator? Would it be better to have a large variator and not worry so much about a large rear pulley? This might not be worth it for people with functional electric start. In that case, maybe just the best non-overrange variator for high speeds (MultiVar?)
- cooling ideas? Fan cover hacks? CVT venting?
- better tuning and matching of components for high speed, high RPM, and not so much about fast take-off. Variator weights, air box, carb, jets, intake, reeds, exhaust? This seems like a worthwhile discussion - particularly for people going from stock to mod. Buy right the first time.
- install tach and CHT gauges for this scenario, to monitor that WOT (or near WOT) driving over extended periods
What did I miss? What tips do you all have for the items above?
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Post by 90GTVert on Nov 28, 2018 23:00:53 GMT -5
- get gearing right. If emphasis is on max speed for sport build, what is best gearing? 11:1? Higher gearing? This could be expensive and/or difficult (DIY) for the sport build crowd so maybe the least desirable item? Will vary by power and RPM level, tire size and a bit by rider preference. With 130/70-12 out back, I think 10:1 - 11:1 works pretty well for most. I typically run stuff that revs 8,500-10,000RPM. That allows for 50-60MPH cruising as long as the power is there. Smaller tire diameters may require a little numerically lower gearing. - over-range variator? Would it be better to have a large variator and not worry so much about a large rear pulley? This might not be worth it for people with functional electric start. In that case, maybe just the best non-overrange variator for high speeds (MultiVar?) IMO, buy a whole OR kit and be done with it. Maybe a little late now that Black Friday just passed, but the things are under $300 on sale for the entire CVT system. That is a lot of money in a way and they aren't bulletproof (watch my vids and you'll see), but they have been more reliable for me with hard riding than the non-OR stuff I was using and great at keeping RPM where the power is whenever needed. - cooling ideas? Fan cover hacks? CVT venting? Yes and yes. I do both. I use scoops on the fan cover that I tested and found did lower CHT. I also vent all of my covers. The only way I wouldn't vent a cover would be if I were going through lots of water or doing crazy stuff like mudding. - better tuning and matching of components for high speed, high RPM, and not so much about fast take-off. Variator weights, air box, carb, jets, intake, reeds, exhaust? This seems like a worthwhile discussion - particularly for people going from stock to mod. Buy right the first time. Stuff like the OR kit makes choosing hard takeoffs or top speed nearly unnecessary. That's not to say there is no compromise, because there almost always is. A little more weight or a little less spacing or whatever can dial something in for certain tasks, but in general I can get hard takeoffs and good speed all day. Watch something like my latest car show vid and you can see that I will take off red light after red light for hours on end in town. Before that, 2 hours of heavy throttle riding usually. After that, 2 more hours to get home. Jetting is one place that is good to consider the fact that you want to cruise fast. Make sure it stays safe (on the rich side) so you can enjoy prolonged periods of high throttle opening. Sometimes spark plug heat range may need to be colder than what you use if you just want to putt around town and idle a lot. |
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Post by Lucass2T on Nov 29, 2018 3:11:54 GMT -5
I can comfortably cruise at 50mph at around 9500rpm without any problems. Over here in Holland we don't have that many remote places or really long stretches of road (where scooters are allowed) where i can cruise for longer periods of time. Normally i can keep @50 for a max of a few minutes before i have to let off for a turn or junction or whatever. Let's say i can easily and comfortably keep up with cars on common Dutch 80kph roads. The most important thing is getting the carb's needle clip position right. Cruising is done at part throttle where the main jet's influence isn't big and fuel metering is mainly by needle (shape and clip position). When it's lean on the needle you'll seize it eventhough you're just cruising and not really putting high loads on the engine. this my setup: 49ccscoot.proboards.com/thread/11245/lucass-70mph-yamaha-axisBtw i weigh around 160lbs |
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Post by kkzxxx on Nov 29, 2018 7:07:57 GMT -5
My setup has a top speed of 55mph @ 9600 rpm, final gearing is about 10:1 but since my rear wheel is 14" that comes to about 9:1 gearing if compared to 12" wheel.
Takeoff is still enough to beat 125cc 4t.
Ive sometimes ridden WOT for about 60 miles straight, never had a problem after I converted to LC, hard to imagine doing this with AC but I guess it should be possible with a rich a/f ratio.
Minarelli engines have an excellent cvt fan compared to some other scooter engines, making some cut outs near the fan and clutch you will make it draw/push air very efficiently.
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jack667
Scoot Enthusiast
Posts: 190
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Post by jack667 on Nov 29, 2018 7:14:17 GMT -5
Awesome info Brent, Lucas, and KKZ. I'm still taking it all in. Quick question - has anyone done testing to see if CVT venting (alone) improves CHT? Or are those two totally separate?
I can see the vents helping with the transmission, and helping for belt slip.
And - carb tuning plus fan mods helping CHT.
Just curious is CVT temp and CHT have much relation...
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Post by ryan_ott on Nov 29, 2018 10:42:32 GMT -5
As long as your carb is tuned correctly there should be no reason you can’t run at high speeds for miles on end. CHT gauge plays an important role here. Also as mentioned part throttle is the killer as not many people realize how little throttle it takes to maintain speed once your moving. Tuning so all throttle positions have close to the same temps take time but that is what makes for a reliable motor. I can maintain 50-55 at part throttle with temps right about 300 +/- without issues.
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jack667
Scoot Enthusiast
Posts: 190
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Post by jack667 on Nov 29, 2018 12:52:38 GMT -5
I hope I can get there with a 17.5 carb...
I have a full main jet kit, but I'd like to avoid buying a new carb if possible.
I'll work on CVT venting, fan hacks, and carb tuning, and see how far I can get with that. I'm also thinking of an OR kit for my Zuma that is kickstart only.
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Post by 90GTVert on Nov 29, 2018 13:38:37 GMT -5
Quick question - has anyone done testing to see if CVT venting (alone) improves CHT? Or are those two totally separate? Maybe the mixture would get heated a degree or two less because of heat soak. I don't really think it would do much for the engine. Sure won't hurt. Mostly it's about CVT component life. Also, kickstart only is not as big of a deal as it seems at first. I hated the idea for a while, but now I would think it was weird to electric start one of my 2Ts. Only time it sucks is if a kickstart breaks, since you'll have no easy backup plan, or when the engine is being a pain to get fired up for some reason. |
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