what jet size to use with 70cc big bore kit/open cone filter

[matlock]

right now im using a 90 main jet when i goto 95 it full throttle on the stand i heard almost like a flame sound in muffler guessing this is back fire so went down to 90 and it seems perfect will this setup be ok 90 main jet open pod filter?

[repherence2]

Aug 12, 2019 18:56:06 GMT -5 matlock said:

right now im using a 90 main jet when i goto 95 it full throttle on the stand i heard almost like a flame sound in muffler guessing this is back fire so went down to 90 and it seems perfect will this setup be ok 90 main jet open pod filter?

you are asking for trouble...

big bore with open cone filter...it would be helpful if you told us what kind of bore (economy, sport, mid race, racing),what kind of exhaust, the size of your carb, premix or oil injection. the size and type of carb affects jetting.

sounds like this is your first attempt at modification/tuning.

first recommendation, put the air box back on.

if you insist on running that cone filter then you should invest in some things.

you should get yourself a Main Jet kit and a pilot jet kit. I recommend you get a main jet kit that goes in increments of 2. you should also invest in a cylinder head temperature gage.

if this is your first attempt at tuning a carb, you're in for a big headache and possibly soft seizing your bore. why are you planning on using a cone filter anyways? for more "power"?

[matlock]

i am using this ebay performance exhaust for 65 its ok from 0 -33 then 33 and up it really moves quick its 1pe40qmb stock pilot jet 90 main jet with malossi 72cc big bore kit spport kit or maybe its 68cc i hear but itt said 72 on ebay with 6.5g rollers i can go 40 up a hill and 43 on flat i can even let off the throttle and maintain 43 then i give it more gas it makes revs up but doesnt go anymore would lightenkng my rollers help 0-30 and keep my top speed ? input appreciated.. i use the orifignal oil injection system and add about 2 shot glasses to the tank when ever i put gas i keeep it well oiled so it wont sieze or overheat

[matlock]

i am using this ebay performance exhaust for 65 its ok from 0 -33 then 33 and up it really moves quick its 1pe40qmb stock pilot jet 90 main jet with malossi 72cc big bore kit spport kit or maybe its 68cc i hear but itt said 72 on ebay with 6.5g rollers i can go 40 up a hill and 43 on flat i can even let off the throttle and maintain 43 then i give it more gas it makes revs up but doesnt go anymore would lightenkng my rollers help 0-30 and keep my top speed ? input appreciated.. i use the orifignal oil injection system and add about 2 shot glasses to the tank when ever i put gas i keeep it well oiled so it wont sieze or overheat

[repherence2]

Aug 13, 2019 10:11:48 GMT -5 matlock said:

i am using this ebay performance exhaust for 65 its ok from 0 -33 then 33 and up it really moves quick its 1pe40qmb stock pilot jet 90 main jet with malossi 72cc big bore kit spport kit or maybe its 68cc i hear but itt said 72 on ebay with 6.5g rollers i can go 40 up a hill and 43 on flat i can even let off the throttle and maintain 43 then i give it more gas it makes revs up but doesnt go anymore would lightenkng my rollers help 0-30 and keep my top speed ? input appreciated.. i use the orifignal oil injection system and add about 2 shot glasses to the tank when ever i put gas i keeep it well oiled so it wont sieze or overheat

ok, thanks for the info.

I ran a Malossi Sport 70 on my Chinarelli
a while ago. I ran mine with the stock air box, but I opened up the inlet port to the air box.

as far as rollers, 6.5g seems a bit heavy. but then again, it also depends on your Contra spring. I like to run the yellow (medium) contra spring. I also ran a red
(stiff) contra spring. the red is good if you cclimb a lot of hills, it tends to want to stay in a lower gear. good for climbing hills and accelerating out of turns, but the transmission would get really hot, rollers would flat spot, and belts wear a lot faster too.

contra spring and rollers will dictate your rate of shifting as far as the CVT. clutch springs can have a slight affect too.

so, im assuming that you are using stock contra spring and stock clutch springs. if that is the case, you probably need roller that are 5g or less. ever since I went to big bore kits, I have always ran rollers less than 5g. however, I don't run stock springs.

I still think you should invest in a Main Jet kit, increments of 2 so that you can fine tune the jetting. get a Cylinder Head Temperature gage to make main jet tuning easier. that way, you can monitor temps as you make WOT pulls while tuning the main jet. just stay below 350°F and you'll be fine. don't want to see you seize the Malossi bore.

[matlock]

perfect thank you guys ill let you know i make out

[ThaiGyro]

I have said it many times, along with others...change one thing at a time and test.
Dump that, what, sexy pod filter? Use an air box and your life will improve. I have jets in many sizes and carbs in quite a few, as they all work differently, but no pod filter will help you tune. You will naturally need more fuel/bigger jets to make the same power.

I would further suggest you dump the oil injection and just premix your fuel. You cannot know your fuel/oil ratio with a pump. They mostly suck. Over time, they suck more.

DO NOT add oil to your fuel tank if you are running an injection pump. You are making matters worse and tuning near impossible.

Resist tuning your CVT until your engine is crisp and kicking ass. Then find the drive to better use that power.

Before I forget...ensure that your ignition is working well. OEM curves with no rev limiter. I do this first, even before carb tuning.

[matlock]

now i cant figure out my throttle when irev it up slowly its fine but if i gun it it hesistates like its sucking in air firstn thebn revs and when at max throttle if i let off then hit it full again it hesitates a few seconds like silence then starts revving since i switch the open pod filter for the stock air box some reason the open cone filter stopped working so well it wouldnt goto full throttle without bogging when the day before it worked fine thats why i put stock box back on but im puzzled

[ThaiGyro]

Tough call...air leak or ignition intermittently shorting. Inspect everything you can.