Rejetting the mikuni 30mm carb on the Lifan 140.

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These engines dont have conrods mate

I was meant to say con rod bearing lol. What do you mean they dont have a conrod? What would they have? A few of my mates have blown out there bottom ends from just jumping on their bikes and thrashing it.
 
I was meant to say con rod bearing lol. What do you mean they dont have a conrod? What would they have? A few of my mates have blown out there bottom ends from just jumping on their bikes and thrashing it.

Ha Ha Ha ! All piston engines have conrods - it's short for connecting rod ! Yes the #105 main , needle clip in the middle is correct - a #95 main is f*#cking ridiculous on a 110 and up motor - they come with small jets as standard to pass crappy emissions requirements for Import reasons !

Honda SL/XL 100/125's always had a #105 main and #38 pilot and even when their carbies are used on XR75/80's , the #38 pilot and #105 main are still spot on - so there's no reason why a pit bike engine of the same or larger cc's shouldn't also require similar jet sizes ! Mikunis run a different pilot jet number than Keihins so you'll most likely find that a #15 pilot is equal to a #35 or #38 keihin pilot ! Hesitation or bogging indicates that a larger pilot jet is needed because it's caused by a delay in the fuel delivery due to a vacuum drop when the throttle is cracked open !
 
Another thing I've seen is that some knuckleheads saturate the sh*t out of the filter sponge with so much oil that no air can get thru it - Ha Ha Ha ! The best oils to use are thin oils - 2 stroke oil or you can even use vegetable oil . Use just enough to be able to squeeze it right thru the sponge to trap dirt WITHOUT blocking the pores ! You can test them by blowing thru the flange part with your mouth (vegie oil is non toxic) . Thin vegie or peanut oil is good because you can wash the filter super clean in the kitchen sink using dishwashing liguid and hot water without getting a smack in the ear off your mother !

Using petrol and getting it all over your hands and all over the place is not too bright from a health point of view because it soaks into your skin and you can't avoid breathing in the fumes - I woke up over 30 years ago and have been using the vegie oil ever since ! It's excellent , simple and cheap ! Washing out air filters is a much less messy pain in the ass and you tend to do it more promptly instead of putting it off 'til later. It also pays to have several clean filters spare - kept oiled and ready in sealed sandwich bags so that you can just swap them over as they get dirty , wet OR muddy (they're cheap enough) and then you can clean them whenever you feel like it without putting your maintenance off or your engine at risk .

When I pull my engines down for inspection they are perfect inside - clean filters equal longer engine life !
 
Hey Cactus Jack I have been using No-Toil for the past couple of years. I quit cleaning filters with petrol after my hands wouldn't stop pealing non stop hehehe.
 
yeah petrol is pretty bad for your hands.... trick is to wear rubber gloves... use them when you're oiling the filter too, makes it a LOT easier... surgical style disposable gloves are fine

petrol is great for cleaning a filter tho, really gets everything out of them and it drys faster than anything else...

i use belrays, motul, shell or what ever filter oil, its not expencive so just buy actual filter oil ;)
 
I just put my 140 on the dyno because of the same problems and it was dangerously lean with the stock jetting. First thing to do is throw away your standard air filter and put on a UNI. then port match the manifold. The inlet on the actual head and the manifold to the carby end on mine were way out. Gave it another dyno run and it was better but not perfect. Still lean so went five sizes bigger on the main jet to 102 and lifted the needle all the way up. Man the thing hammers now. No flat spot no matter how fast you wind it on. Super stoked with it now. Lucky i used to work at the dyno though. The time i spent would have cost a heap.
 
Cactus Jack,your right on the money with the jetting,every pitty carb i pull down is jetted for long term disaster.
The 105 main/15 pilot in Mikuni's just about suit's every 110 to 140 pitty (with a fiddle of course!).
Kaneo,great stuff!!!! I'm actually running a 105 main in my 140 Lif,and it's a much better bike........now if only i had the time to play with my KTM 450 hhmmmm.
 
Yeah mine was still a touch lean still with the 102 but thats all i could find. Fatten it up to a 105 would be spot on i reckon.:) Cactus Jack are you jack C s dad in adelaide?
 
Yeah mine was still a touch lean still with the 102 but thats all i could find. Fatten it up to a 105 would be spot on i reckon.:) Cactus Jack are you jack C s dad in adelaide?

No I'm in Maitland NSW ! The #105 with the needle clip in the centre allows you to go richer or leaner at will if the temperature changes ! I raced XR75's years ago and I went thru all the different bore sizes (72 to 96 cc) , porting , trying different sized carbs , different exhaust pipes etc and I found the #105 main to work best no matter what ! The jetting has more to do with the atmospheric pressure and the size of the carb venturi than anything else - NOT the engine bore size ! All engines run best on a certain fuel to air mixture ratio and it's the carby that controls that - NOT the engine . When a carb is set right - it will provide the right fuel to air ratio at all different air speeds above about one quarter throttle . Drag racer Bill Jenkins used to set his carb mixtures up on a flow bench (glorified vacuum cleaner) and look at the fuel droplet size thru a special viewing glass !
 
i paid i think it was 11.90 for shell air filter oil for my uni filter i clean it with turps
 
daniel40,jump on the phone and ring around a few bike shop's for the 105 main,some have em,some don't.
 
just take your current to a bike shop and ask them for a 105 in that size. if they dont have it, they should be able to drill it out to the right size....

i took a guess with my jetting and went with a 100 main, definately not big enough.... better than the 95, but still hits a brick wall revving it out in 3rd or 4th gear.... it will hit the rev limiter in 1st or 2nd but not 3rd or 4th, just gets to a point where it stops picking up revs.... 105 here i come ;)
 
Drill it out? are you kidding. Don't drill or try to enlarge your jets this is asking for trouble. If your ring around and ask for a LARGE ROUND MAIN JET 105 to suit a Mikuni and you should find one. I went into two shops and the best i could do was a 102.5 so i got it it and seems ok.
 
you've never heard of jet drills? as i said, if they dont have the right size or cant get it... they can make it
 
aiight guys so i think rejetting the carb on my 138 should fix the bogging wen i W.O.T ( wide open throttle ) the throttle.. just out of curiosity..how much dosh would i be looking at for The 105 main/15 pilot in my fake Mikuni carb..?

and do i just ask for a 105 main jet and 15 pilot jet to suit a mikuni carb?
 
anyone else? and where abouts are jets located in the carb?
 
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