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Post by 139qmb on Apr 20, 2018 20:34:55 GMT -5
Received the 10 piece carb jet kit from part for scooters. Installed the 90 main jet and on the test drive I have lost about 400 RPM and about 5mph. I plan to install a UNI air filter tomorrow and test drive again. Stock exhaust pipe, timing advance, and currently stock air intake box with restrictions removed. If still have the loss in RPM and top speed after UNI install, I will go down one jet size at a time to slowly lean out the air fuel mixture.
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Post by KSR Moto on Apr 21, 2018 5:35:12 GMT -5
You need to increase air flow BOTH ways in and out of the engine when you increase main jet in order to acomodate for more fuel
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Post by kagetenshi on Apr 21, 2018 19:12:44 GMT -5
A new exhaust shouldn't be needed unless a large bbk is installed, I would think. Though many factory mufflers do sometimes become clogged.
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Post by 139qmb on Apr 21, 2018 20:50:41 GMT -5
Stock bore no big bore kit installed. I am considering the Tecnigas exhaust. I agree with the more air in and more air out theory. I have owned a few foxbody mustangs, all of which I installed an off road H-pipe on. Busy today, still havent installed UNI filter yet to see if it will make any difference. I did however make one quick test run with the UNI before changing to 90 jet and the scooter felt like it lost some power, too lean I am guessing.
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Post by KSR Moto on Apr 22, 2018 3:43:36 GMT -5
A new exhaust shouldn't be needed unless a large bbk is installed, I would think. Though many factory mufflers do sometimes become clogged. I disagree,on stock bore there is a performance improvement especially in the top speed, stock exhaust starts to create backpressure at high rpm
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Post by KSR Moto on Apr 22, 2018 3:56:31 GMT -5
There are a few of the stock exhaust types but usually they are very heavy and restrictive.., in my case I lost 3.5kg of weight and got improvement in top speed
I would say that it is optional for stock bore but if you have 47mm or above In my opinion I would go with performance exhaust
Sounds awesome too!
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Post by 139qmb on Apr 22, 2018 20:13:10 GMT -5
With UNI air filter and 90 jet I regained the 5mph and RPM is up to 7300.
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Post by dexameth on Apr 24, 2018 11:02:36 GMT -5
You were possibly running too rich with the stock airbox and that 90 jet. Adding the UNI filter let it breathe a little better, making the A/F mixture better. Try an 85 with the UNI and see what happens.
I was running a 95 main in a true 20mm with a 50mm bore, I think the 90 may be too large for your stock bore but every setup is different. Lemme ask, what's your elevation where you live?
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Post by 139qmb on Apr 24, 2018 12:17:16 GMT -5
Yes I plan to swap the 90 to an 85 and see if I gain any RPM or speed. I agree the UNI helped bring in more air and thus lean out the mixture. Still too rich with 90 though.
I am located directly beside the ocean in Cuba. Hot temps year around, coldest it ever gets even at night is mid 60s in Feb. Currently temps are low 70s night, upper 80s day.
Plan to order an exhaust pipe in the near future, should help with getting air in a nd out of the engine.
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Post by KSR Moto on Apr 24, 2018 12:30:29 GMT -5
I use 88 main jet, stock bore, pod filter, and perf exhaust
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Post by 139qmb on Apr 26, 2018 19:05:40 GMT -5
Finally got away from work at a more reasonable time. Changed to an 85 jet first and gained acceleration and the engine didn't sound like it was bogging at WOT. I then changed to an 80 jet and the engine seemed to sound even better and have slighty better throttle response. I am debating trying a 78 jet as my RPM is still at 7100-7500. I also plan to swap from 5g NCY rollers to 3.5 or 4g Dr pulley sliders to gain a few more RPM.
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Post by 139qmb on May 1, 2018 12:13:03 GMT -5
Ordered a Techigas exhaust pipe and 4g Dr Pulley sliders to replace my 5g NCY rollers. Leaving the 80 jet in for now until I get those parts installed. Then I will experiment with the contra spring. I currently get good acceleration until about 30MPH, then it's a slow climb up to 40 or slightly higher. Hills are the killers, large hills are costing 5MPH. Smaller longer grades cost 2 or 3MPH. Currently running a white malossi contra spring.
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Post by 139qmb on Jun 8, 2018 15:15:18 GMT -5
Installed the 4g Dr Pulley and the Technigas exhaust and now I am 8100-8300 at WOT. Acceleration is pretty good now to 35mph. I still have the 80 jet, but am thinking I should go up to the 85 and do a test drive to see if I can squeeze a little more out of this stock 39mm.
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Post by KSR Moto on Jun 8, 2018 15:22:51 GMT -5
Installed the 4g Dr Pulley and the Technigas exhaust and now I am 8100-8300 at WOT. Acceleration is pretty good now to 35mph. I still have the 80 jet, but am thinking I should go up to the 85 and do a test drive to see if I can squeeze a little more out of this stock 39mm. Well, the smaller the bore the more fine tuning you need to do in order to get some decent top speed, I suggest that you install a 44mm kit, it wont ruin your engine and it will give you a decent amount of power, no crazy tuning required, installed mine last week runs great, I higly recommend doing this
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Post by 139qmb on Jun 10, 2018 19:59:31 GMT -5
The 85 slowed acceleration dispite still allowing 8300 RPM. I then changed to a 78 (was running an 80) and acceleration is as good if not a bit better than the 80 jet. I will run the 78 this week to work and decide if I want to try next lower jet, which I think is a 75 in my 10 piece kit.
Now the remaining question is do I want to try changing this white malossi contra for a NCY 1500 or 2000? My RPM stays the same at WOT on hills so I assume the current spring is working correctly. I wonder would a 1500 or 2000 spring with increased pressure rating create an lower gear ratio when climbing hills?
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