125-200cc seizing problem

[webbski93]

hello my 2012 wre 125 keep seizing I have a full fmf pipe and the jets to suit I also pre mix 32/1. can someone tell me what has happened to this piston to course this marks thanks

 

[Johnnymannen]

Overheating problem. have you tried bigger jets/ raised needle? How do you ride? Lots of wide open throttle?

 

[webbski93]

I've had the the main jet and polite jet changed I also raised the needle and i Ride it I ride it slow ish but do ride it hard sometimes.

 

[Johnnymannen]

How does the plug look?

 

[webbski93]

Not sure what it was but it is black now it's all been fixed if that helps

 

[R-J van Hulst]

You have a WRE that's an engine with a auto lube or not? do you rely on the oil pump in the engine or do you mix yourself in the tank?

Robert-Jan

 

[webbski93]

I mix in the tank at 32/1 mate

 

[R-J van Hulst]

check your plug on different openings of the gas throttle
it could be that your bike is rich on open throttle but lean at half throttle.

the scratches on the piston is a typical issue of getting to hot by either to lean or to less lubrication
on auto lube systems I 've see n this quite a few time as the motors where tuned and the oil pump not adjusted for the engine change
but when you nix in you tank its a fuel supply issue or replacing the piston with a to big version

you have slightly different sizes for replacement pistons and when your cylinder is a A size and you stick a D size piston in there it is running OK for some time unless you heat it up while riding hard and the piston expansion is simply bigger then the barrel

Robert-Jan

 

[webbski93]

check your plug on different openings of the gas throttle
it could be that your bike is rich on open throttle but lean at half throttle.


the scratches on the piston is a typical issue of getting to hot by either to lean or to less lubrication
on auto lube systems I 've see n this quite a few time as the motors where tuned and the oil pump not adjusted for the engine change
but when you nix in you tank its a fuel supply issue or replacing the piston with a to big version

you have slightly different sizes for replacement pistons and when your cylinder is a A size and you stick a D size piston in there it is running OK for some time unless you heat it up while riding hard and the piston expansion is simply bigger then the barrel

Robert-Jan

Hi could you tell me how I would check if it is to lean at half throttle and rich at full throttle thanks for the info

 

[R-J van Hulst]

run the bike in that throttle position and hit the kill switch the you have to check the plug

check the bike on idle position but if you have a steady idle then that is normally OK then you check on 1/4 ope throttle this is the pilot jet area

check it on half and 3/4 position this is needle setting of different taper of the needle it self

full open throttle is the main jet area

keep in mind that temperature altitude and and humidity changes can have a big affect on the jetting and some of the carbs are more sensitive then others
the mikuni TMX is sensitive for that and can give you a great deal of work to get it right only to find out that 1 week later you can do the exercise again



Robert-Jan

 

[webbski93]

Ok thanks I will try that and btw them marks on the pistons in the picture is only on that one side if that makes any difference thanks

run the bike in that throttle position and hit the kill switch the you have to check the plug

check the bike on idle position but if you have a steady idle then that is normally OK then you check on 1/4 ope throttle this is the pilot jet area

check it on half and 3/4 position this is needle setting of different taper of the needle it self

full open throttle is the main jet area

keep in mind that temperature altitude and and humidity changes can have a big affect on the jetting and some of the carbs are more sensitive then others
the mikuni TMX is sensitive for that and can give you a great deal of work to get it right only to find out that 1 week later you can do the exercise again



Robert-Jan

Ok thanks I will try that and btw them marks on the pistons in the picture is only on that one side if that makes any difference thanks

 

[R-J van Hulst]

if that happens constantly on the same place/side then that is the hot spot you might want to measure your cylinder if it is perfectly round (you might have a flatter spot in the rounding then the pistons could seize on that side.
it could also that your cylinder is not completely straight in the horizontal line of the piston movement (this can occur if the gasket is not even or when you have the center rings that centers the cylinder with the engine housing is not 100 % aligned and/or some metal dirt is in the way and lift/tilt the cylinder on a corner)

Robert-Jan

 

[webbski93]

Ok thanks mate iv had it resleved to the New piston size I hope that helps me

 

[R-J van Hulst]

If it is re-sleeved then the cylinder rounding should be OK

it points more into either a mechanical assembly issue (tilted cylinder) or simply a jetting issue.

not much things more that i can come up with what it could be

Robert-Jan

 

[webbski93]

Thanks for the help guys

 

[webbski93]

if that happens constantly on the same place/side then that is the hot spot you might want to measure your cylinder if it is perfectly round (you might have a flatter spot in the rounding then the pistons could seize on that side.
it could also that your cylinder is not completely straight in the horizontal line of the piston movement (this can occur if the gasket is not even or when you have the center rings that centers the cylinder with the engine housing is not 100 % aligned and/or some metal dirt is in the way and lift/tilt the cylinder on a corner)

Robert-Jan

Hi what would course a flatter spot in the head??

 

[R-J van Hulst]

Its not a flat spot in the head but a flatter spot in the rounding of the barrel
this is in the micro mm territory but gets worse over time when you have it

its either a production mishap (very unlikely these days but not entirely ruled out) or if you run with a worn out bearings like crankshaft and piston bearings the free play of the piston would be to much in the barrel and it simply wears out more in the barrel on one or 2 specific points

boring the cylinder is the remedy if the plating it allows

Robert-Jan

 

[AUSKY]

Have you done a leak down to test for air leaks around the airboot/reed block/crankcases?
My 13 165 seized twice due to a warped airboot.