Post by tootsmcscoots on May 30, 2011 17:12:17 GMT -5
I just got a new Johnway Raptor 50cc. It is awesome but tragically slow. I have been told the easiest way to get speed is to cut the governing wire in the CDI. Is this accurate and won't kill the scoot? Any other thoughts. I know there are many options to get more speed, i.e... bbk, exhaust, etc. I am just trying to get a bit more speed, what are the simpler/cheaper ways to achieve this? Any help is much appreciated!! Thanks!
There aren't many CDIs that can actually be derestricted by cutting a wire. You're better off to buy a new no-limit CDI for about $20.
If you have a rev limit, you probably also have a variator restrictor washer, so you'll want to get rid of that. Restrictive air paths can be an effective way to limit power, so going free-flow on the intake and exhaust will free the potential of your engine. Air flow mods will require you to retune your carburetor.
Do a search for "Derestricting a chinese scooter." You can get pictures and even videos for some of the items mentioned.
While you are doing that you can also make a small transmission adjustment that can greatly benefit acceleration and average cruising speed... a set of 5g or 6g sliders are a cheap and effective tune.
The BBK is the way to increase the true engine power, but it will be next to useless if other restrictions are in place so make sure you take care of derestricting first, then you can up the ante if you so desire.
Post by tootsmcscoots on May 30, 2011 17:57:08 GMT -5
Wow, thanks D. I appreciate you taking the time to give me some advice. I will first buy a new CDI then. What kind of % of speed upgrade can you expect from those alone generally? Where is the restrictor washer located, easy to take off? I'm not super mechanical, but learning, I would love to get out what I can from this scoot with simple upgrades/adjustments without messing anything up. Where are the sliders? What exactly do they do? Thanks so much!!
To explain the sliders I'd have to explain how the variator works (and why removing that washer is a good thing). The reader's digest version is that the weights sit behind the variator. As the engine spins faster, the weights are forced to the outside. The backing plate is a ramp as well as ramps being engineered in the back of the variator, so as the weights are forced out the variator is pushed away from the engine (toward the drive face), forcing the belt to ride further to the outside and changing the gear ratio. On the other pulley is the driven face and a spring loaded torque sheath. Together they affect what's called the rpm constant, or the speed the engine revs at while accelerating. Heavy weights makes the constant low, light weights makes the constant high.
On restricted bikes one of the common things to do is to put heavy weights in, like 8g or more, which makes the bike shift early at a low rpm, almost like it has 2 gears. With a restrictor washer this isn't the end of the world, it hits the gear limit, you lug a little, then you're up to your 25-30 mph cruising speed. Without the washer, you shift up hard and lug in that area between 10-20 mph so you struggle to accelerate and hills are a pain. By putting lighter weights in, you bring the constant up. Your target is around 7000 rpm*, +/- 500 or so. The point is to accelerate in your power band. With the right weights, you get up to your cruising speed in seconds, which will magically be around 35 mph or maybe a bit more.
The stock variator weights are cylindrical in shape and are called rollers. They do the job. The performance weights are called sliders. Sliders are larger and have a polygonal geometry (IOW they already have flat spots). Sliders tend to shift down easier so they have a -1g effect compared to rollers (a 6g slider = 5g roller) and since they already have lengthy flat faces they last about twice as long as the rollers. Their wear is more predictable and has less effect on performance as they age. Because of their larger geometry you might be able to edge out a slightly higher top speed with sliders. All around, sliders may cost twice as much but they are a worthy investment. Dr. Pulley is the most popular brand but the generics work just fine as well.
Most of the advertisers here can help with the parts. My favorites is Scrappydog, but Rapid Jim and Absolutely (above advertisers) both also have good reps here.
*The Jonway Raptor 50cc is a 2 stroke, which has an additional tuning point to it. The photos I see show it to already have a semi-performance exhaust (with expansion chamber, though smaller than an aftermarket performance exhaust), of course what you have may vary (and may be a trick). If you do, you want to find out what rpm you "hit the pipe" (it's audible, fairly obvious), this is the rpm where you have the most power and thus is the rpm you should target for a constant with the variator weights. With a tuned pipe, your power band is much narrower than with a typical 4 stroke, but if you can hit the pipe with your rpm constant, the exhaust back-pressure will have a similar compression boost effect as a turbo.
Once done removing all of a 2-stroke's restrictions, it is not unheard of for it to hit 50mph STOCK, but 40mph is probably a more reasonable target without a BBK.
Post by tootsmcscoots on May 31, 2011 13:39:26 GMT -5
Good Intel D, thanks again for your help. I had no idea this was a 2 stroke until I took it apart a bit today and saw the oil/gas mixing unit...hope I'm not being too technical there:) I will start with the CDI box and the washer. I will need to do some more research on the weights I guess. Thanks!!
Post by thedirtypickle on May 31, 2011 19:20:46 GMT -5
I'll trade you engines! I soooo badly want a 2-stroke 50cc. Make sure you fill that oil unit up no-one likes a blown over-heated engine. Keep with it, those 2-strokes make a lotta power if the variator is tuned where the rpms stay within the slim powerband of the engine.
wereed: HOw can I start a thread?
Jun 1, 2013 10:55:49 GMT -5
wereed: or respond to a thread I started three years ago...
Jun 1, 2013 10:56:07 GMT -5
marklorenzi: I just bought one of the Fleetwoods. They look like a clone of the Honda XRM's they sell overseas. It is in transit now and I should get it this week. I will try to post my experience here. Call me the guinea pig hahaha.
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flyangler: wereed, this forum is read only the new forum is on the banner above. Dan
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