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Post by scooterman21 on Jul 9, 2014 20:36:50 GMT -5
Hey everyone, I have a Tao Tao 50cc scooter with a 139QMB motor, very common. Ok well this scooter has always run very slow on take off and top end could be better. Most of the scooter is stock except/ Hot Fire Spark Coil  , 4.5g sliders and racing cdi (took off because made no difference). It has no restrictors on it. Well I have went through everything any cant find anything until today. I had herd about scooter makers putting smaller jets in the carb so it wont go to fast. So I pulled my carb off today and found that it only has a 61 Main Jet. What size should I get for it? I just ordered a new Gates belt for it because it has 2400miles with the original chinese belt, but the scooter has always had bad throttle response/ take off. I got the lighter weight sliders thinking it would make the take off better, but no difference. If anyone can help please do. Thank You |
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Post by birdman on Jul 10, 2014 1:17:47 GMT -5
Leave the jet alone for now. If anything just clean it and put it back. Its about time for a valve adjustment, and clean/ replace the air filter. And at 2400 miles, that torque spring is probably done, with your set up, I would go with a 1k or 1.5k tops..
As for a quicker start, try some tighter clutch springs, with your setup as it stands I would go with 1.5k or maybe 2k if your a lighter rider.
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Post by dude on Jul 11, 2014 0:15:22 GMT -5
That seems to be a small jet. Check the Inside Diameter of the jet. Carb size? Compression test?
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rexxk
Scoot Member
Posts: 65 
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Post by rexxk on Jul 11, 2014 0:47:55 GMT -5
if you want to make it go faster, you have to switch out the air filter. and 61 is small. should be like 75 or something? stock.
and if you change air filters, youhave to change jets. if you get a uni filter, then get a 90 main jet. and i used 5 gram sliders in my variator. they worked for me. if your revving too high and not got much top speed you mihgt need to put more weight in your variator. heavier, weights.
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Post by 90GTVert on Jul 11, 2014 15:46:05 GMT -5
78-80 main jets are what seem to be coming in recent TaoTaos.
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Post by usmcdoc on Jul 26, 2014 19:32:05 GMT -5
78-80 main jets are what seem to be coming in recent TaoTaos. Brent...I had one blow my mind today!! It was a 2014 Thunder and I have been seeing them come with mid to upper 70's size jets in them. Well....today I opened a guys sealed Carb so later we could up jet as needed. After slotting and removing the shear screws I found the jet to be a #84...stamped even! Odd cause some are not stamped so you have to use a wire gauge and 'gesti-mate' the size.. It was stamped #84 and a #85 Jet Drill fit it perfect. So ok..#84 to #85 is REALLY splitting hairs and in reality the same thing I suppose. BUT..what confuses me is that when I do an 80cc BBK and remove the low to mid 70's size Jet...I typically upjet to about a #85...sometimes #88.. Not torn the engine apart yet...but makes me wonder if it a 'secret 63'?.. cause I thought they stopped making them.  The Carb measured out to 19mm and everything was identical to the common 19mm replacement and stock Carbs. So I wonder why such a huge Jet for a stock 50cc? It runs fine..not rich...plug chop looks right on the money even. 'Restrictor' tube inside the airbox was in place..and oddly the exhaust pipe tip is so small that even my tiny pinky finger barely fits it. Stock as it is..it tops out GPS at 39-40mph(Only after I removed the airbox restrictor tube however) So now I am confused in that if stock likes a #84..then the 80cc BBK is probably want a #90-#95..  Not sure..but so far this has been interesting...and I think is gonna become more interesting to tune with the 80cc BBK. Oh one more thing..after pulling the A/F plug...I found that 'slot' type screw is an oddball 'D' shaped one. Never seen this and hope there is a screwdriver bit to adjust these...  |
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Post by 90GTVert on Jul 27, 2014 14:22:55 GMT -5
There is a single D type driver for those mix screws. I bought one off of eBay or Amazon for about $15. I've heard of others cutting a lot into it so a small screwdriver can be used or making their own tool out of old sockets or melting a pen cap to fit around it.
Doing 40MPH GPS it could indeed be a 63cc. Could be something different with the airbox or airflow path elsewhere. You did say you had to remove the airbox tube for it to run 40MPH though, so maybe it was richer than you thought with it in place?
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Post by usmcdoc on Jul 27, 2014 17:18:36 GMT -5
There is a single D type driver for those mix screws. I bought one off of eBay or Amazon for about $15. I've heard of others cutting a lot into it so a small screwdriver can be used or making their own tool out of old sockets or melting a pen cap to fit around it. Doing 40MPH GPS it could indeed be a 63cc. Could be something different with the airbox or airflow path elsewhere. You did say you had to remove the airbox tube for it to run 40MPH though, so maybe it was richer than you thought with it in place? Can't seem to find the screwdriver tip on Ebay or amazon..hmm. It did seem a tad rich with a sputter with the airbox restrictor tube in place...so just for the hell of it I pulled it out. It ran smoother and that is when we noticed it went from a max of 34-35 up to 40 even on the flats. Didn't time it but..acceleration seemed faster. Can't wait to tear into the engine..but I am sure it can't be a 'secret 63' since the EPA has been really hard on all Chinese import Scoots since 2012. Hence why only companies are still importing 2 T's while the rest gave up trying to get them into the states. Even in the 4 T world it appears we can only get Znen..TaoTao and Peace Sports..which I find sad because I am very partial to Jonway. I find a website called Jonway USA but cannot seem to locate anyone that carries the Jonway lineup. Would love to find the new version of their 'Sunny' that now has 12" wheels vice the 10" they used to have...  |
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Post by niz76 on Jul 27, 2014 17:30:50 GMT -5
I've been running an 85 main jet with 3 extra 1/2" holes drilled into stock air box. Stock 49cc. Expansion chamber exhaust. Plug looks pretty good now that I'm learning better how to read them. Sea level. Possibly even below sea level lol.
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Post by 90GTVert on Jul 27, 2014 18:03:35 GMT -5
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Post by usmcdoc on Jul 27, 2014 18:28:23 GMT -5
I've been running an 85 main jet with 3 extra 1/2" holes drilled into stock air box. Stock 49cc. Expansion chamber exhaust. Plug looks pretty good now that I'm learning better how to read them. Sea level. Possibly even below sea level lol. That equates to an 'Open' type or 'Free Flow' air filter..so in that case I can see where a #85 would be ok for a stock 49cc engine.  Even some of the hottest builds I have done..and a few here have ridden..I have always used a stock airbox. My thoughts on airflow have always been.. if it is a 50cc or 500cc engine..the most the engine can 'inhale' and 'exhale' IS whatever its displacement is.. It cannot intake more airflow than its combustion chamber volume..UNLESS it has forced induction like a Paxton Super Charger or Dyer Blower System. More air in does not mean more power...torque or quicker revving as a balanced stoichiometric air fuel ratio must be met for true output potential. Which by formula comes out to 14.7:1 depending on exact fuel composition and free air composition. So ya see more air does not mean more power. Which is why folks run into problems when they put a GY6 150 24mm Carb on a tiny GY6 50-80cc engine...and just can't get it to tune right. One day when it is 40 degrees outside..the engine runs good...but let the ambient temperature hit 70 degrees..and it just won't run right. That is seen less often on 'Stock for the engine' sized carbs. Trust me..Engineers put a LOT of work into designing and Engine/Carb setup.. They don't just 'grab n go'...  Not flaming anyone..please know this..I am just in a writing mood today..  So yes...even on a BBK..I use a stock carb. Oh but back in the day we used to bolt a Holley 750 Double Pumper 4 barrel Carb on our 350 engines thinking we'd get more power..and well...rarely did we..lol. Hell my '84 Mustang 5.0(last year the used Carbs).. I put an Edlebrock dual 4 barrel intake on it and bolted up 2 Holley 4 barrel 390cfm Carbs!! 8 barrel carb system sounded good..BUWAAAHHHH! Less power but it did sound bad ass...  Anyway..back to my post... I have never seen a #84 jet on a stock and fully restricted Scoot. Used to be they came with ones in the low to mid 70 range to meet emissions...so the new style PAIR system this one has must either really work..or most likely it just pumps more air into the exhaust inlet it goes to...thus diluting the true emissions.. Something tells me this build is gonna kick butt once the BBK is installed..cause it is already a lil sleeper...  Glenn |
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Post by niz76 on Jul 27, 2014 19:27:59 GMT -5
None flamin taken (?) haha. I was just addin my setup for some comparison as it seems everyones optimal setup is different. Mine sure seems to be at the high end for stock MJ wise, and my scoot seems to like the additional air and fuel. Just addin another setup for comparison/example! Happy Scootin!
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Post by usmcdoc on Jul 27, 2014 19:44:52 GMT -5
None flamin taken (?) haha. I was just addin my setup for some comparison as it seems everyones optimal setup is different. Mine sure seems to be at the high end for stock MJ wise, and my scoot seems to like the additional air and fuel. Just addin another setup for comparison/example! Happy Scootin! Thanks... Now toss a BBK on that..you will never go back or ride a stock Scoot again..  Just curious what Scoot ya have? Reason I ask is that because up till about 2012 MANY 63cc 44mm ones did 'slip through the system'...well..until they got caught and fined...which stopped that.. However a few more still did make it through.. |
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Post by Upgrayedd on Jul 27, 2014 19:50:21 GMT -5
Hey everyone, I have a Tao Tao 50cc scooter with a 139QMB motor, very common. Ok well this scooter has always run very slow on take off and top end could be better. Most of the scooter is stock except/ Hot Fire Spark Coil , 4.5g sliders and racing cdi (took off because made no difference). It has no restrictors on it. Well I have went through everything any cant find anything until today. I had herd about scooter makers putting smaller jets in the carb so it wont go to fast. So I pulled my carb off today and found that it only has a 61 Main Jet. What size should I get for it? I just ordered a new Gates belt for it because it has 2400miles with the original chinese belt, but the scooter has always had bad throttle response/ take off. I got the lighter weight sliders thinking it would make the take off better, but no difference. If anyone can help please do. Thank You r u sure it's not an 81 main jet? my '14 taotao came with an 81 main. |
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Post by Upgrayedd on Jul 27, 2014 20:07:14 GMT -5
a few ideas to help:
*a big bore kit. 47mm/72cc is said to be the most reliable big bore kit, larger bbks are hard on stock crank.
-tuning carb to right main jet, right fuel/air mix for max power
-tuning cvt to hug close to max power (max HP around 7500rpm)
-ensure not overfilled on oil or gear oil
-use synthetic oil and gear oil
-air your tires up all the way for less rolling resistance
-lighten your scooter (remove unnecessary things)
-aerodynamics / small windscreen may help a bit
-can try removing the snorkel inside your airbox cover, to see if it makes an improvement
-remove exhaust, check end that bolts to engine for globs of weld. if weld job was dirty, use a dremel or a file to clean that up.
-remember, if you run a pod filter, you will need a larger main jet than if you run an airbox. more air is not always better.
i dont think they would put smaller jets in them to control power output, as running lean can lead to engine damage.. i think most of their speed control is in the variator weights, which keeps the rpms low, and keeps the power output down
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, 4.5g sliders and racing cdi (took off because made no difference). It has no restrictors on it. Well I have went through everything any cant find anything until today. I had herd about scooter makers putting smaller jets in the carb so it wont go to fast. So I pulled my carb off today and found that it only has a 61 Main Jet. What size should I get for it? I just ordered a new Gates belt for it because it has 2400miles with the original chinese belt, but the scooter has always had bad throttle response/ take off. I got the lighter weight sliders thinking it would make the take off better, but no difference. If anyone can help please do. Thank You
Not flaming anyone..please know this..I am just in a writing mood today.. 
So yes...even on a BBK..I use a stock carb. Oh but back in the day we used to bolt a Holley 750 Double Pumper 4 barrel Carb on our 350 engines thinking we'd get more power..and well...rarely did we..lol. Hell my '84 Mustang 5.0(last year the used Carbs).. I put an Edlebrock dual 4 barrel intake on it and bolted up 2 Holley 4 barrel 390cfm Carbs!! 8 barrel carb system sounded good..BUWAAAHHHH! Less power but it did sound bad ass...
Just curious what Scoot ya have? Reason I ask is that because up till about 2012 MANY 63cc 44mm ones did 'slip through the system'...well..until they got caught and fined...which stopped that.. However a few more still did make it through.. 