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Post by deejae on May 12, 2018 1:02:32 GMT -5
Hi everybody. I'm new to gy6 cvt style engines/bikes. I recently purchased a Chinese 50cc Metro scooter from Baodiao (TaoTao ATM50-A1 clone). This scooter had several limits/restrictions put in place to prevent it from exceeding 30mph. I have removed or replaced all parts that I could imagine having any restrictions including the fuel valve, belt, variator, clutch, carburetor (100 port), intake and insulator gasket (was a strange restriction in stock insulator at 14.5mm opening now 19mm), removed emissions PAIR system, changed valve cover to non pair cover, upgraded engine to SMS Performance's 100cc big bore kit, performance A9 cam, rear gear 17t/49t, performance CDI, preformance spark cable, NGK spark plug, new unrestricted performance straight exhaust and new pipe and I even put new high performance Pirelli tires. Wow can I go over board or what? =) So why am I writing this post? I still can only go 30-35mph!!!  Ok here's my actual question; does upgrading to a BBK change the stock engines normal power band? I spoke to the manufacturer's rep and they could only tell me the stock engines peak power band should run between 6000-7000 rpm's. I have spoken to people with two different opinions on how to properly tune a gy6 engine. Non techie's response seems to always be add weight to go faster reduce weight to get more launch power. The other opinion (techie) is watch your rpms and increase weights until you cruise between 6000-7000 rpm's with a wot at about 7500. That statement can be found in multiple forum posts but non that seem to be referencing a bike with a 100cc BBK. I'm not sure what the BBK might do to the power band's peak range. I started at 5g = wot about 9000, went to 6.5g = wot 8300 and I'm now at 8g = wot 7480 cruising at 7000-7200. At this point I feel I'm actually getting slower. Should I still order 9g and 10g variator weights to try getting to a power band range of 6000-7000 rpm's or do I now have a higher power band threshold because of the BBK I installed? Why can't I exceed 35mph? |
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Post by pistonguy on May 12, 2018 8:27:10 GMT -5
Ok first lets clear up there no such thing as a 100cc kit for a 50. Scamming advertising a name rather than a actual displacement.
You can do the math,, .7854xborexborexstroke = displacement in cc's.. if itsa 50mm or 52mm bore your in the 80 some cc area..
Ok check you Belt Climb on the Vari.use a black marker to simply draw a line and see how hight the belt will actually ride.
The 17/49 gearing, is that stock? and if not what was stock?
And No not really the BBk will raise the rpm power band, the Cam Will, the A-9 is a top end Cam it makes most of its power on the top end of the rpm's and whatever you gain on the top you will lose on the bottom..
What are you running for Clutch and Main Spring?
And lastly put the Scoot on the center stand and make sure the rear brake is not dragging..
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Post by deejae on May 12, 2018 15:30:40 GMT -5
yes I am using a 50mm piston which mathematically is around 80cc. I called it a 100cc because that was what the manufacturer claimed. They gave me a story saying due to replacing the smaller stock rocker arms with theirs that they get a little extra cc boost. I am in no way agreeing with them (just fyi).
The marker was rubbed off in the middle of the pulley wall from about 25% -75% variator wall height. Marker remained on the bottom 1/4 and top 1/4 of the variator. I am using a Gate 669-18-30 belt I was looking for something like a 669-19(20)-30
belt but the 20 mm with doesn't seem to come in a 669mm length. How would I utilize more of my variator wall height?
I changed the rear gearing to 17t/49t at a local scooter shops suggestion. That was the only gears they stocked under the performance category for my bike. I do all my own work except the gears because they needed to be pressed in. The shop did the swap for me so I don't know the original teeth specs.
I put a racing clutch in with a 2000 rpm torque/clutch springs setup. I was still not getting the top end increase so I thought maybe the pulley wasn't opening enough so I reduced the torque spring down to 1500 so now I have 2000rpm clutch springs with a 1500 rpm torque spring. Was reducing the torque spring from 2000 to 1500 rpm a bad idea? I still have the 2000 rpm torque spring and I also have 1500 rpm clutch springs if you think those need to be changed to match the current torque spring's specs?
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Post by pistonguy on May 12, 2018 22:15:24 GMT -5
Elaborate more on the Rocker Arms you are now using in comparison to the OE you replaced. if you have a link to them would be great
and no anything you do with the rocker arms has any affect on displacement. Now that being said a different Rocker Arm ratio will affect the cam numbers as in More Cam or Less Cam.
Are you using a Stock Cylinder head ?
And what were the Original rear gear numbers? Im not as familiar with what most stock 50's come with as in rear gear..
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Post by deejae on May 13, 2018 5:02:23 GMT -5
The new rocker arms were part of the BBK kit I purchased from SMM my east coast Tao Tao dealer. This is what they listed on their site. ---- Performance Cylinder Kit Chinese Based Scooters Boost your 50cc from a 39mm Bore to a 50mm Bore, This is one of the biggest kits on the market 4 stroke 50mm cylinder set. Kit includes cylinder, Performance Head with Valve Set, Rocker arms, Piston, rings, Piston pin, cir clips, head gasket, and base gasket. Specification: Cylinder Bore: 50mm Wrist Pin Diameter: 13mm Total Piston Height: 34.8mm Compression Height: 18.3mm Valve Length: 64mm Rocker Arm: 64mm I replaced item 14 in this diagram with the 17/49. It was originally 51/15 I haven't changed item 12 yet. I believe it is 52/16. www.partsforscooters.com/scooter-parts-diagrams/50cc-4-stroke-QMB139-Gear-Box-Parts_2 |
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Post by pistonguy on May 13, 2018 7:27:14 GMT -5
Ok thanks for the good info, I'm needed the whole package to look at. Definitely going to have to work on the Belt Climb, its the key to getting the max mph from a stocker to a hot rd. The dot on the top of my Vari is the only thing left of the marker line I drew, I'm getting some 96-98% climb?  |
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Post by pistonguy on May 13, 2018 7:33:59 GMT -5
After looking at your gearing did you/they replace a "set" of gears or only the Gear Item #14?
I'm thinking your gearing is jacked
Scrolling down on that page to the Hoca gear sets they only offer a 16/42, 17/41 and a 18/46
I would research what they really sold as you can see on the 17/41 the 41 is a whole Ten teeth smaller compared to your 51 and Eight teeth smaller than what you have now.
Theres a whole bunch of mph right there..
Do you have your old gear set to count the teeth?
I do see that gixal sells a 17/49 set but they make no reference to stock gearing.
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Post by deejae on May 13, 2018 21:18:22 GMT -5
I received a 17/49 set I'm sure because they were in two pieces so I was disappointed and double checked the specs to make sure everything else was up to par. I had to go have them pressed together by a local machine shop. I counted the teeth again before I gave it to the mechanic. I have the old gears and they are 15/51. I haven't actually seen the #12 yet but according to the dealer it is stock at 52/16.
I haven't touched or discussed # 15 in the diagram with my dealer. Im not sure of the specs on the stock #15.
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Post by pistonguy on May 14, 2018 8:02:37 GMT -5
They are in two pieces and they are the Only gears that change your final drive gear Ratio. nothing else to buy.
You made a Ratio change but not that much, look at those Hoca sets they are a whole 8-10 teeth smaller. thats were your MPH is.
Skip all the packing that says "race" or "high performance" I saw some labeling that claimed 7-10mph gain. week that depends what it was to begin with.
If you search around or get the formula to do the math on the ratio you can compare what it is to what you have now or had.
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Post by deejae on May 14, 2018 23:24:42 GMT -5
Does any body know how to calculate the ratio of the three set of gears, I guess 12, 14 & 15 in the above diagram? I guess I should also ask if anybody knows a formula to translate the old and new ratio's to actual top speed potential?
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Post by pistonguy on May 15, 2018 9:10:07 GMT -5
No Bro item #14 is a Gear Set and thats the only thing in there to change and is available to change.
Your Gearing change made a small percentage of a change. The other gear sets are moving the small gear by two teeth and the larger by up to Ten, from some searching and technical information from these manufactures and retailers is horrible I found the 17/41 is moving the gearing by some 35%.
It sucks because you have to spend more money.
The A-9 cam is a top end cam and makes peak power right around 7,500 rpm, so get the correct gearing and tune the Vari to max out around 7,500 and a little over rev is ok, just a Little!
Good Luck
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Post by pistonguy on May 15, 2018 9:24:17 GMT -5
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Post by onewheeldrive on May 15, 2018 19:52:20 GMT -5
Yeah something is seriously not right here. I have a 72cc with no mods pretty much and I could beat you (at least in the long run, maybe not off the line) and I have nothing to brag about except a 72cc with pretty much stock everything else, lol.
Did you put all your mods on pretty much all at once, or gradually and still no change? With the 49/17 gears you should go over 35mph easily, especially since your engine has the balls to pull those gears. I’m not trying to be funny here, but unless you weigh 400lbs, you should be able to top 35mph. Is that GPS verified?
What performance head is in that package, do you have an actual link to the package you’ve bought? Honestly, this is the first I’ve read about different rockers used on these smaller Chinese engines.
Your’re running a 100 main jet, right?
I’m really curious as to what all restrictions were in place on this scooter. Do you mind telling us what all they were? Also, what performance CDI?
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Post by deejae on May 20, 2018 15:01:46 GMT -5
I did all my mods the sames weekend. In regards to specs for the bbk I only have the info that I posted above from the manufacturers website. Yes I am using a 100 main jet on my new carb.
Here is a cut and paste from the manufacturers website showing the specs on the bbk I installed
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Performance Cylinder Kit Chinese Based Scooters
Boost your 50cc from a 39mm Bore to a 50mm Bore,
This is one of the biggest kits on the market
4 stroke 50mm cylinder set. Kit includes cylinder, Performance Head with Valve Set, Rocker arms, Piston, rings, Piston pin, cir clips, A9 cam, head gasket, and base gasket.
Specification:
Cylinder Bore: 50mm
Wrist Pin Diameter: 13mm
Total Piston Height: 34.8mm
Compression Height: 18.3mm
Valve Length: 64mm
Rocker Arm: 64mm
In regards to limitations I removed so far;
I replace a carb with the screw heads cut off (prevented port access).
I replaced an intake insulator gasket which had a restricted ID of 14.5 mm and is now 19mm.
I removed a spacer/limiter from the variator. (Prevented stock variator from closing enough to push belt to end of pulley)
I replaced stock CDI with blue performance racing CDI.
I removed stock throttle grip which wouldn't allow full twist of stock throttle.
I removed air box and replace with exposed bug screen covered performance air filter.
I removed PAIR system.
I replace Chinese no name 100/60/10 tire with Pirelli 100/9 0 /10 tire.
I replaced stock restricted exhaust with wide open performance exhaust.
I replaced stock reduction gear from 51/15 to 47/17.
I replaced fuel valve and fuel filter (just incase - not sure there was any restrictions there)
BBK didn't have a port for PAIR so I replaced valve cover to a non PAIR cover.
I replaced the spark plug and cable.
I replaced the stock clutch assembly with a racing clutch with 2000 rpm clutch springs and 1500 rpm torque spring
I replaced the variator and weights.
I replaced the variator drive face gear... required changing the bendix and starter as well.
I replaced 4ma battery with 7.5ma battery.
I replaced the stock rotor with a performance rotor and pads from EBC (FYI - EBC part # FA-151 fits Chinese stock caliper.)
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Post by pistonguy on May 21, 2018 8:34:41 GMT -5
Have you put the Scooter on the center stand and removed the belt and pinned throttle? if so what happened.
Have you worked the Throttle valve with your hand to make sure it is opening all the way ?
You need to get a tach to tune for sure, she doesn't sound on the video she is running past 5,000rpm,
On the center stand make sure the rear brake is not dragging..many of the drum wheels are out of round and a user must adjust them up to were there dragging to have any working rear brake..
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