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Post by tygertung on Apr 25, 2012 2:02:06 GMT -5
How can I modify my variator to get a higher top speed? I have a high speed variator, but even so it still doesn't really want to go above 60 kph (40 mph for you Americans or British)
It just is pulling too many revs once you get up to top speed. Is there a face I can machine down, or some slots in the back pulley that I can lengthen to get more top speed? I need to get the revs down! It would easily go a lot faster, except it is pulling too many revs.
The belt doesn't go all the way to the outside on the front, do I need a slightly longer belt?
I was thinking that I might be able to machine the inside edge of the pulley with the roller ramps on so that the pressed steel can go further in, although that probably won't actually help. Maybe I can put a spacer in, to move the two pulleys in closer to each other?
I mean it has a lot more power than a Honda C50, but they are able to blitz me on the top speed on account of the higher gearing.
The bike is a 1994 Suzuki Sepia ZZ, same engine as an Address, but much nicer body. Is the high spec model with the disc brake front end and the factory expansion chamber exhaust.
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Post by skuttadawg on Apr 25, 2012 2:27:33 GMT -5
Lighter weights help most go faster but too light will hurt top end . Sliders perform better , last longer and do not rattle like rollers. Some 50s have a washer limiter in the variator to restrict speed . A larger size or 2 main jet and if you raise up the needle will deliver more gas to the engine . Exhaust on a 2T plays a more important role in how it performs than on a 4T . Most stock pipes even with expansion like my Magnum has are only good for 8,500 rpms . A sport can go around 11,000 and racing 14,500 but require rejetting and stock engine does not have the porting like a racing engine . Most run 4 gram rollers or sliders . I put on an unlimited cdi and it made no difference at grr . I did see it could rev up to 10,000 for a milisecond but still limits at 8,000 , can hit 8,500 at times and 9,000 downhill and restriction in exhaust becomes a buzzkill . Only a 5 mph gain downhill shows much restricted . I had 6 gram rollers , 4 grams it sounded like the clutch was slipping , better uphill but slower on top end since it hit the rev cap sooner then the 6 grams . I mixed them up to equal 5 and its ok for now . A larger diameter variator with steeper ramps can have more top end . Make sure you have a Gates Powerlink or other premium belt instead of generic factory one . Use premium gas and synthetic 2T not weed eater junk that smokes so bad . A NGK iridium spark plug will fire better , make starts easier , less likely to foul out from oil deposits and help it run at its best Go here 49ccscoot.proboards.com/index.cgi?board=2help&action=display&thread=3885 and scroll down to watch the videos to learn about CVT functions . 2Ts lack torque of a 4T but have the HP edge with ability to turn higher rpms . If you want more power then I suggest looking into a 47.6mm or 72cc BBK , upjetting and a better pipe . A stronger clutch with higher speed springs can help take offs like a stall converter on a car with an auto transmission . I think ( please correct if not ) a stock 2T crank can hit 10,500 max rpms but never been ridden with rpms that high . With only a small window of usable rpms like mine for example the clutch engages at 3,000 and fizzles at 8,000 with a 19mm carb and 75 jet but stock exhaust and airbox . I think DR Pulley has the largest diameter variator and their clutches have many tune options with springs and weights included |
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Post by tygertung on Apr 25, 2012 6:19:01 GMT -5
Thanks skuttadawg.
I saw some info in the technical repositories regarding modifying the variator to get a better top speed. I am not having any issues regarding power, as I have two of these scooters, one is remaining fairly factory, but one is getting the full treatment.
I ported out the exhaust a little with a rebore and barrel and piston, set the squish to 0.5mm and checked all the other clearances. She is getting very good acceleration, but the top speed is being limited by the variator.
I saw on some other technical articles how I can modify the rear pulley slots to allow more movement, and I can add spacers and modify ramps etc on the front pulley to get more movement out of that too, so I'll be able to get a bit more out of it.
The other engine I am building now should go quite good. I have a 46mm Parmakit big bore kit for it, which will go out to 63cc, an expansion chamber for it, and I have ordered a 19mm flatslide carburettor as well. I am getting the crank and casing machined up to take an extra bearing for a bit more reliability and I will balance the crank as well to reduce the vibration which will no doubt be influenced by the heavier piston. I am unsure of what balance factor I will go for. It's usually 50-60% on a single cylinder, so I guess I'll go for 55%, a nice middle of the road number. I'll just have to port out the inlet manifold a little and make up an adaptor to suit the carburettor and we should be laughing.
My workmate went back to Japan last year to visit his family, so I got him to pick me up a Kitaco variator and belt and some stiffer clutch springs so that should nicely finish off that package. Will put the whole thing together mabye next week after I machine the original head's squish band to suit the new piston and take it around to my mate to dyno tune it.
Cheers,
Sam
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Post by 90GTVert on Apr 25, 2012 7:45:09 GMT -5
 tygertung. Unless I've missed it, I haven't heard you mention heavier roller weights. That would be the first thing I'd try in your situation. I know sometimes no matter what you do the setup with any roller weights just won't go faster. Since you said you aren't getting full travel on the variator face, you may be able to modify the variator for more belt travel. The trick is to get the pulleys to close tighter together. I've done this in a couple of ways with different setups. On some I've modified the roller paths to let the weights move farther out. You have to be careful there because if you do that by cutting the paths at the edge too far or on certain variator styles it may let the rollers fly out and then you'll be replacing parts. On others I've filed the drive faces in a way that lets them close tighter. I did that with such success on one of my scooters that it was snapping belts like crazy from the tension I believe, so I either needed a longer belt or just to give up some speed and leave the variator alone. I opted to switch variators after ordering a longer belt by specs that was actually shorter than what I had.  Could have got expensive ordering a bunch of belts to find one that would work and it was definitely getting expensive breaking belts every 5-30 miles. If the engine just screams at max speed no matter what, it might be time to find a whole different variator or perhaps upgears. I know one of my scooters with deep gears just would not work the way I wanted with a stock variator. I think it would have been fine with upgears, but I like the hard takeoff. I started using an aftermarket variator and it quit screaming at speed and seemed to handle the power better all around. Sorry I don't really know about your specific model so all my info is general. Below are some links to a little of my variator experimenting on different engines. One thing I have to say, don't mod it if you aren't willing to risk ruining it and replacing it. Sometimes the smallest change makes the biggest difference, and not always in the way you'd like. Increasing the roller travel (done on a GY6 50 aftermarket vari)... 49ccscoot.proboards.com/index.cgi?board=builds&action=display&thread=20&page=44Various mods and tuning (Jog 90 variator)... 49ccscoot.proboards.com/index.cgi?action=display&board=yamajog&thread=1712&page=1#25985Drive face mod near the bottom of the Project 90 : Phase 2 post (Hoca variator, Jog 90)... 49ccscoot.proboards.com/index.cgi?action=display&board=yamajog&thread=1712&page=3#35514Can't seem to find the pics of the variator I modded that broke belts like crazy. The whole experience with that is in the T1 thread in the builds section, but I don't see where I covered the details of the vari.  Here's my attempt on a homemade over range variator. It worked to some degree, but didn't last long at all... 49ccscoot.proboards.com/index.cgi?board=transtech&action=display&thread=1227 |
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Post by 2strokd on Apr 25, 2012 7:47:18 GMT -5
Sounds like a heck of a build!
Extra crank bearing you say? Im tuned in and looking forward to pics.
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Post by tygertung on Apr 26, 2012 17:15:23 GMT -5
I did try heavier roller weights, but it didn't seem to make much difference.
I think I'll try slotting the rear pulley slots a bit further (called the torque driver?) and maybe extend the ramps on the foward pulley a little. I'll have to put a bit of sharpie on the front pulley to check how far it can go out.
I have a feeling that there is a lip on the rear pulley towards the bottom which is stopping the belt from going down too low, which will definatly be limiting my performance. I'll have to see if I can grind off that lip to allow more range on the back pulley.
I have started taking some pictures of the project with the big motor. I am working on the frame at the moment, then I'll start on the engine next week maybe. I am just getting my motorcycle mechanic to do some special machining which I do not have the capabilities at home to carry out.
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