07 motovert expert - start/difficulties

[Hammer]

Hi there - im hamish.
I just purchased a used 07 motovert expert with a 140cc engine last week.
Being my first pit bike.

Well can some one help me out.

When cold the bike starts usually on the second kick (with out no choke).
When the bike is warmed up it has a tendency to stall when slowing down for a intersection - carbie closed engine braking ect.

The bike seems impossible to then restart when warm - im getting sick of pushing it home.

Ive:
- changed plugs
- removed carbie / cleaned it (the idle air bleed screw is set at 2.5 turns from bottoming out), needle is on the 2nd lower c - clip setting (i.e. 2nd richest).
- running a uni filter (i noticed that this is relatively dry and non restrictive)

I have added about 1/2 tank of regular unleadded (my spare boat fuel - about 2months old) to the premium allready in the bike upon purschase.

I did manage to take the bike for a decent drive here on bribie island in the sand - once going she had plenty of stick in all 4 gears - i hardly got into 4th in the soft and tricky sand. What i did notice was when i was in say 3 gear under acceleration and then i back off (throttle closed) engine braking it tended to back fire and pop - IS THAT NORMAL??

At the same time with throttle closed and usually coming to a intersection in the bush tracks - the engine was stalling each time - and i couldnt keep it going with a squirt of the throttle??? - so i guessed that the bike may be a little lean down low so i screwed in (clockwise) the air blead screw for idle (on the intake port side of carbie).

That appeared to reduce the enging breaking back firing and the stalling of the motor also.

I kept driving trying to get better at the bike and it started to feel as if it was runniing rougher (not very good down low/ bogging down so to speak) - erradic acceleration.

Is this a function of the bike getting hot? I was riding in various soft sand tracks - i used about a total of 1/2 tank of fuel in continious driving??

Any way the bike kept stalling often where id least wish it did and luckly the time at which it would not strat again was only a block from home.

The next day when it was stone cold, no choke - she fired up as usual on the 2nd kick.
And then say with in 2 min idle/warm up and a quick blat up and down my street - she stalls (say when you decelerate clutch in about to drive over the kerb) and just wont start again???

My only comment is that the bike is feeling easier (once warm - moreso) to kick over.

Hence im a little worried.

Any help would be greatly appreicated.

PS i was told that the motor had a bit of a cam in it.

 

[roost666]

well its an 07 model and its second had so its probably due for the valve clearances to be adjusted, maybe a new set of piston and rings even

 

[Hammer]

thanks mate - i drained the tank and carbie and put freash premium in it 2day - and she started today and idled well - after 8 min and warm i tried tuning in the idle mix screw once warm as per the mikuni instructions i found on the web site here - but i didnt get a chance to ride it.

So here is my next que - if i am to consider a upgrade rather than new rings n piston such as a big bore kit - how do i determine what sort of engine do i have?
is my motor a LIFAN,JAILING,YX ... ?

I have seen many parts on line with reference to the above manufactures including TAKEGAWA and they all look simalar- Are they intrchangable.

I guess id like to do a big bore n cam & carbi kit (say a 160cc).

My current motor is 138~140cc running a 22mm non Mikuni carbi.

Your help is most appreicated
Hamish

 

[headsmess]

didnt mention smoke...so i think the rings mite be ok... still be nice to change em though...

though if it was a brushcutter with a chrome plated cylinder, id say the chromes worn. thats what they do when it goes...fine cold but die when hot, but, i dont think you have a chrome plated bore, so forget that....

just as an idea...tried a diff cdi module? or coil? could be the problem...fine when cold, but starts failing when it gets warm.... is known to happen.

cant tell you shit on wether you got a yx or lifan though

 

[Hammer]

once again thank you

No there is no smoke - I like the idea of a daggy coil or cdi - i did notice that the spark was very weak looking when i tested it on numerous occasions-That was going to be my next cab off the rank.

Its so weird it either goes well when cool or fresh - if hot and tired and i stall her well - im better of walking.

Last night i saw cdi modules and coils on ebay - any brands worth chasing there?

Alternatively can you suggest a reputable dealer here in AUS?if i am to source rings, coils or cdi's

Cheers
hjd
Bribie Island
QLD

 

[roost666]

post up a pic mate then we will be able to identify your motor

 

[bulldog93]

if you don't know how to go into picture posting for dummes, couldn't find the link.

 

[motorman]

Mate it's your valves plain and simple. Have you tried roll starting it (with a decent amount of speed) after it stalls out? My bet is that it will start then which indicated the valves. Get the clearences fixed first then worry about the other stuff.

Pretty sure the 07's came with a YX engine but don't quote me on that!! Post a pic and someone can tell you in 2 secs.

 

[Hammer]

will post a pic - however that will have to wait untill the week end as im in brisy now and the bike is at Bribie Is.

Thankyou all anyway

Cheers

 

[Hammer]

here is a pic of my motor

i think it is a YX motor - read it on the kick start lever?

it has a 22mm carbi

It came with a 95 main jet (ive since put in a 105 and 110 as a a test - but either one causes the bike to misfire/break down only at full throttle and worse so on the largest jet) - so im gonna put the 95 back in and place the needle where it was when i got it on the 2nd richest set point.

I did check the valve clearances and they were quite loose arround 10 - 12 thou - i thought they would have been tighter. I set them to 4 & 6 thou for inlet/exh respectively.

can any one please advice me on their jet settings with such a motor assuming it is stock?

Hamish

 

[Hammer]

well now im a little confused - i threw in the original jet back in (it is a 92 - i previously called up a 95 in my earlier thread) and placed the needle on the 2nd richest point where it was when i got the bike.

Anyhow

i started her up, warmed it up, putted arround the place it was really good down low and i then took it for a quick blat - and this time it realy sounded crook at full throttle /or it didnt really get there (i.e. It misfired earlier in the preak rpm rev range than when i was running the richer 105 main jet with the needle lowered 1 space). Basically what im now saying is that the misfiring now happens earlier in the rpm range running the 92 main jet.

Are these bikes fitted with revlimiters? - thats kinda what the weird rough sound is at full throttle that i am speaking of - for example can you open the throttle up 100% in neutral and should the motor not hit a rev limiter/valve bounce? I did this and just marginly closed the throttle and the engine all of a suddern came on sounding sweet and clean and strong....then wind the throttle back to full (only a tiny bit to get there) and that misfiring occours again ????

I was advised that the bike should run a 105 or if i can get hold of it a 107.5 by a mechanic at Nerang on the Gold coast.

Hence the larger jets that i just tried.
Any help is appreicated

Hamish

 

[headsmess]

im still of the opinion you have an electrical problem.... it sounds so damned intermittent...even just a dirty terminal somewhere?wriglle the plugs a few times with some wd40 in there for good luck?

i think if you could borrow another cdi unit and coil.... shame to buy them if it ISNT the problem.... and...cams? did it have the hi lift cams in it? maybe...just maybe..... i had a problem sort of like this....

would idle...badly...and just backfire/cough/pop when i revved it.... originally thought it was the cams indexing with the sprocket not being right... swapped them, and it was fine...THEN!!!! the new ones that were fine started doing it after i adjusted the valves cause i set them really loose at first..like a mm gap...

closer inspection revealed that on the camshaft there is an oil slinger? not sure... that has a one way clutch inside it... it was interfering with my exhaust rocker.... only by a few mm, but that was enough

pressed off the end bearing, removed the part, and then...no problems...

easiest way to check is take the cover off the head... the one with the 4 head bolts...

BUT! it had nothing to do with bad running when warm, so i find it very unlikely this is your problem.

just throwing it out there...

start with the cdi

 

[Hammer]

Cheers mate

yes intermittant it is.

cdi n coil will be next.

i havent taken it for a long drive again to see if when hot it wont start again- i think i shall reinstall the 105 main and along with a new coil n cdi try adjusting the needle n seat for chrisp mid range - i simply droped it 1 notch when i upped the main to 105 from 92.

It wont hurt to carry a spare coin n cdi in my tool pouch as i like to do long rides and im usually alone.

well at least i am becoming familure with my bike now.
im thinking of raising my fuel tank a little to allow easy needle adjustment

hamish

 

[Hammer]

FIXED AT LAST
What a mission but im now glad i fully understand the bike now.

I decided to get a new CDI and well when i weas there i also got a coil, another new plug and here is the KEY!!! an complete new Carbi Mikiuni.

I dropped into my local bike shope in caboolture and to cut a long story short the mechanic asked me what carbi am i running? i replied a Mikuni copy with a butterfly choke...he replied 'look this pile of used carbies and tell me which one' - if found one and he said THERE IS YOUR PROBLEM !!!! at first i thought he was trying to make another sale.

So i arrived home with the following:
-new 22 Mikuni plunger type choke carbi
-new fancy blue racing CDI
-new STD coil
-new plug

I installed everythingat once - i know i shouldnt have but anyway...
the CDI was a head ache (blue - white pick up, red - black charge magneto, yellow to yellow on coil, green to all earths being coil & kill switch, black - blackn grey kill switch) (order being CDI wires - Bike wires).

the bike didnt start - Fkit

i then changed to my old carbi - no luck
i then put the old coil on - no luck

Bummer - i checked if i had spark - it looked like i did.

still wouldnt go.

So i unsoldered the CDI and took it off and installed the old one.

BINGO - she firedup (and the bike was back to how it was because all teh olds parts were on it again) -ie start, run and crap breaking down at full throttle.

so i then proceeded to put the new mikuni carbi on(note it has a 95 main jet - needle on the richest setting) and this carbi seems to need the plunger choke pulled on when cold and she easliy fired up and then after say 30 sec i turned the choke off.

I took it for a test ride and SHE IS AS GOOD AS yehaaaaaaaaaa espically at top end nice and crisp and no misfiring. Im yet to play arround with the needle and get her running even better.

The moral of the story is that the Kelin or whatever it is being a copy of the Mikuni carbi is good for SFA.

All the best - i hope i have maybe helped another.

Spewing the blue rectangular finned aluminium racing CDI didnt work - but teh stock one works fine.

Hamish

 

[shockerinc]

I just bought an 07 140 and My bike came with a Lifan motor, My valves are set at .003 and .004 (intake and exhaust). Try doing that first, and if that doesnt work start ur bike let it warm up a bit.. hold the throttle wide open and kill it while its running w.o.t. then take out ur plug...what colour is it? if its a white colour you are running to lean, if its a dark carbony colour you are running to rich and if its a tan sandy colour its running perfect. The adj. screw on the intake manifold side of the carb is you fuel mixture, turning it in allows less fuel to pass through for 0-1/4 throttle (idle). If you are noticing an erradic acceleration as you say that kinda sounds like its running to lean. but many things can make the bike run lean other than just the carburator. try some of those out and let me know how it goes.