Bike wont idle when cold? but will when hot.

[M@rkay]

hi. i have a 2005 motovert 125cc. the problem is when i start it when its cold it wont keep running. but when it warms up it idles. we have tried to adjust it so it idles but we cant get. Does anybody know what the problem is. could you please help me. would be very appreciated.

 

[MITTZ]

ya gota warm it up for a bit!

 

[mini bike pride for life]

yeh mate you gotta let it warm up i let mine warm up with the choke on untill it starts too slow down in revs with the choke on then your motor will last longer too if you let it warm up same as a car with a carbi dude.

 

[Sidney]

it happens to basically every single combustion engine.

 

[Cactus Jack]

Check that your valve clearances are OK and if they are ...... your bike is OK ... They can be slightly tight when cold then the gap grows bigger as the engine warms up ....

 

[M@rkay]

yeah it revs fine when its warm and everything and probably idles a bit too high but when istart it when its hot its fine

 

[coolmodee01]

Check that your valve clearances are OK and if they are ...... your bike is OK ... They can be slightly tight when cold then the gap grows bigger as the engine warms up ....

what he said for sure
my 3valve 110 does the same thing

 

[M@rkay]

ok thanks guys. really appreciate all the info you have given me

 

[MasterSpoon]

Check that your valve clearances are OK and if they are ...... your bike is OK ... They can be slightly tight when cold then the gap grows bigger as the engine warms up ....

Doesn't the gap get smaller as the engine gets hot due to the valve stems and what not expanding with heat?

 

[coolmodee01]

not sure i thought the valves where heat stabelized and didn't expand as much as the head
especially alloy

 

[crog]

Yeh give the valves a bit of a check over. My mates 3 valve used to do that aswell.

 

[M@rkay]

how do i check the valves. are they in the carby or the motor. do i have to pull the engine apart or what

 

[crog]

Nah mate not in the carby lol If you look on the head of the motor there is 2 caps probably allen key bolts or 8ml spanner or something like there wil be 1 on the top and one on the bottem. http://media.bbrmotorsports.com/How_To/Windows/CRF50_ValveAdj_Win.wmv
This should show you how to adjust them

 

[Cactus Jack]

Doesn't the gap get smaller as the engine gets hot due to the valve stems and what not expanding with heat?

As coolmodee says .. the alloy head definitely expands more than the steel valve stems ....... BUT ... if the valves aren't seating properly , they build up heat and can expand at a greater rate than the head (mainly the exhaust valve) ..... The exhaust valve lives in pure flame when it opens and can get hot enough to glow so it passes its heat off thru the valve seat making clearances critical to engine life ..... an overheated stem can expand and fry the oil then seize up in the guide ..... usually at the full lift position .......

If you check on the BBR site , they show the valve adjustment procedure and the guy says that the lash clearances get bigger as the engine gets hotter ....

This link saves a lot of typing : (lol ..... crog just beat me to it .....)

http://media.bbrmotorsports.com/How_To/Windows/CRF50_ValveAdj_Win.wmv

 

[edzy]

i just love cactus

 

[M@rkay]

would anybody know the valve clearances for my motor. its a motovert 2005 125cc model.

 

[edzy]

you have already got a thread on that

cactus answered it

 

[edzy]

do not listen to that^^^^^^^^

it should be
inlet : .003 and exhaust : .004 or .005