Do i need to retune Carby ? 125 to 140cc

[lerroy]

Hi Guys

first off i wanna thank all the guys that helped me out with doing my engine swap cheers

its all running fine now went for a ride today, working reliable and no problems

Thing is though i wanted to do the swap for more power and its doesnt seem to be a whole lot different i also raced/compared my mates 125 Ducar and it was exactly the same (just to compare)

so im thinking my Carby was from my 125cc so its tuned for 125 right ? so its not using my new 140 to full extent ? or was i just being stupid thinking 15cc would make a differnce ?

If so do i need a new Carby ? or just a Tune i think its a 26mm on ProX but maybe not genuine Mikuni (does say made in japan on it though)

 

[jayde156]

mate ive done exactly same as u....make sure u put the spark lead that come with the 140 on instead of the shit one that came with the bike and then tune the carby....it will need a bigger main jet to get peak performance or u can use a 1mm drill bit to widen the hole...and then just move the needle inside the carby up or down and test it to see if it works better if not..move it the opposite way and test it

 

[Divy]

when i put the 140cc on my bike an fitted my 26mm mikuni with the stock 127cc settings it ran but it was flat, it rode ok but i felt it had more in it

once i tuned the carby an put a 100main jet in it ran alot better there is no flat spots an even if i pull the throttle hard it wont bog down
im going to put a 105 main jet in an see if i can get even more out of it

so yeah i reckon if you tune the carby correctly you will notice alot more
but like i said tune it correctly

 

[lerroy]

ok thanks guys

ill have to learn about carbys now

 

[Ruby]

+1 on retuning the carby. Usually any engine mods = change in fuel needs.

 

[lerroy]

Yeah i thought as much but im still new to this

anyone suggest online store selling Jets ?

 

[Ruby]

You could always ask Maylands Performance.

 

[Cactus Jack]

A # 105 main and the equivalent of a #38 Keihin pilot would be the absolute minimum since that's what Honda SL/XL 125's ran (stock) - I run a #105 in my modified XR75 engines which are 80 to 82 cc and they run crisp and clean . SL/XL100's ran a #110 main with a #38 pilot . So a bigger engine doesn't necessarily mean a bigger mainjet because there is more vacuum to pull more fuel from a smaller jet .

They put small jets in pit bikes to get the emissions down for import reasons so they're usually under jetted as supplied !

 

[lerroy]

hmmm
dam even more to think about then anyone else recommend me a size they are running in a 140cc ?

otherwise im gonna get a 105 and 110 and have a play

 

[Divy]

when i tuned my carby with a 100 main jet the bike ran sick i could pull the throttle as quick as i could an wouldnt die or bog down
but i put a 105 main jet in it today to play around an see if i could get more out of it but it didnt like the 105 jet full throttle an it dies so i put the 100 jet back in and its back to being relly responsive so im sticking with the 100 main jet an keeping all the other adjustments were they are

 

[Ruby]

Now that you've found the 100 main jet is better, try adjusting/changing the needle.

 

[Divy]

why?

i allready tuned the carby with 100 mainjet and it runs perfectly

when i say i tuned the carby i dont mean i just changed the main jet

i adjusted the air/fuel screw, adjusted the needle clip position, adjusted the idle screw an changed the main jet , the sparky is the right colour

 

[Ruby]

adjusted the needle clip position

Thats what I was referring to. No worries!

 

[Divy]

thats cool..............

 

[lerroy]

Thanks Divy ill have to get a 100 main jet then

so it now is quicker than th 127cc though right ?

Where did you get your jets from ?

 

[cass38a]

I am running a 102.5 and mine is going pretty good.

 

[lerroy]

hhhaha

Thanks Cass i actually was just reading over a few of your old post when divy was asking almost same thing and i got the part numbers you mentioned for main jet just called a shop hes gonna send me a N100/604 - 102.5 and a 105 so ill have a play

 

[cass38a]

Thats the way to do it. I dont know why all these guys stuff around trying to drill the suckers out. It is very easy to do it properly and buy a jet.

 

[Sidney]

Maylands performance is drilling mine out

 

[motoluver]

Guys the 100 main jet is still to lean. A 102.5 would be getting better but I imagine the 105 would be the go. I'm still waiting for my local bike shop to get the jets in... its been 3 weeks I think I'm going elsewhere if they haven't got it by this friday.