Scooter suffering Jet lag?...  By  carasdad (Read 2,811 times)

Agreed 2 strokes are not very fuel efficient. My Suzuki RM250 takes one full tank of gas just to run one heat. But it is revving well over10,000 rpm...designed for it and displaces 246cc. But this lil 70cc should do better than 40 mpg. Odd part is...the plug is not wet..it is not fouling out...and no excessive smoke from unburned fuel and the extra oil. As you mentioned the condition of the cylinder...that may be an issue as it had one good tight soft seize and slightly scored piston/cylinder. Bottle brush honed it with a new and good cross hatch pattern and compression is running right about 140psi. I am just so curious to see what jet size others run in their 70cc 2T BBK engines...

On my Zuma 14.5 carb Autotech355 BBK-VM11/22 # jet. Went to a 17.5 Dellorto carb. It has a Naraku 92 jet but the ID is .037.
The factory Dellorto #80 jet ID was .033 the Naraku #80 jet .0295 Not sure what jet is in my Vento It seem like a 87 MRP 48mm BBK (soon to be a 90cc)
When I changed the carb size on the Zuma it came to life.
I always check the ID of jets.
What RPMs do you run most of the time?

I have a 19mm TK carb with a 45 idle jet and today put in a 105 . I did use a 120 but it sucked gas . I misplaced the 110 I had . Note I have a Uni and MMG pipe . What weight of rollers do you use ? My scooter came with a 40 IJ and 68 MJ but I put in a 75 MJ as I prfer to run rich . I put on a Uni vent cover which is smaller than the big red Uni and it ran great with a MJ on the 49cc engine . I later put on the big red Uni with the same setup with stock exhaust , had a mild midrange bog but dang it I only went a 1/4 of a mile and it soft seized and melted the sparkplug . It was in the upper 90s in the summer time . My second MOD cycles 47mm BBK came with a 45 IJ , a starter jet and a 74 MJ where the first did not have the jets included . I use Mikuni VM11/22 from PowerBarn but my second set of jets I bought were labeled for Kehin but were the same size other than the orifice .

Since it is so dang loud I will try to see if the stock exhaust will fit . The MMG pipe would needed to be bent to fit the 49cc engine but was a perfect fit with the 70cc . I will also reinstall the airbox since I ride in the rain and I can not with a Uni . I will order a , 100 , 110 and 115 as a 120 was too much and a 130 sputtered . Stock which was limited to 8,000 RPMs with 6 gram rollers it was 75 to 100 miles on 4 liters of gas . Lighter 4 gram rollers it had less top end and seemed to over rev . I mixed them up to equal 5 grams as many use 4 or 5 grams and it was fine when 49cc but too light with a BBK as it could redline on level pavement and I could not go WOT downhill . I now have 8 gram Dr Pulley sliders , 1.5k clutch and torque springs by Hoca plus their bb torque spring base . Take off is less but it never was an out of the hole like my Honda but has awesome top end and better MPG . Top speed unknown only registers 50 MPH but hits that at 7,000 and tops at 10,500 sending the needle beyond what it will display . Will borrow a geek phone to GPS it . You may have the larger variator like I do which normaly comes on a 90cc engine . Since I ride on highways and have a lil on interstates I wanted to be able to go 50+ without it screaming . With the RPMs up high I hardly slow down when going up a steep hill

I run 7gr DP w/ Moalossi var.