my bikes dying what could be wrong??

[Divy]

ok folks i got some issues with my yamaha yz125
i was riding for about an hour then stopped for a minute or two then started it back up to ride again but for some reason it just kept dying it starts then bogs down when i try to pull on the throttle
any ideas of what i can check to see what is wrong ??????????????
i cleaned out the carby incase it was blocked but that didnt help i checked to see if it had a good spark an it did an i dont think it could be the ring cause i just put in a new one

so any help would be great

 

[crazzy #1]

did it like lock up and stall? and then once u started her when she colled down she was fine untill she got warm?

 

[Delza125]

i had the same problem with my cr 125, it was the spark plug it kept oiling up check that its alright

 

[Divy]

crazzy#1 no the wheel didnt lock up an stall
delza125 i checked the plug there wasnt oil on it it sparks fine plus its a new plug

any other ideas guys?????????

 

[Dreadful]

Is your main jet clear ??

 

[sik-pj]

same thing happens to my rm125 wat is the prob

 

[Divy]

yeah i cleaned out the carby, sparky is working, an its got a new piston an rings so thats why im confused i dont know whats wrong
when i started it again it starts then when i rev it it revs up then dies i try to pull the throttle so it wont die but it doent work it just dies no matter what

 

[Divy]

well i got it going i put in a new plug an it started so i took it for a ride but....
got to this long straight i was in 5th an then the powerband kicked in an then the bike just decided to stop so i tried to gear down an let the bike while it was moving push start itself but nothing so i just got home an its got no compression so tomorrow ill pull the engine apart an see whats going on cause i think some thing fucked up internaly i hope its not the fuckin piston cause i just put a new one in
any ways ill let yas know what happened tomorrow

 

[crazzy #1]

i suspected it needed a rebuild before, but i didnt say anything... this must be the case! or the rings! if u say its recently been rebuilt did u run it in properly? u run it in easy ur did u go hard as you should

 

[Franky]

I no this sounds stupid but check that the air filter is seated properly and there isnt any gaps letting more air getting in.. it just sounds like your leaning out.. guy brought in his 05 yz125 to our shop, air filter wasnt seated properly and had a gap resulting in the engine leaning out and the piston dentonating and destroying the barrel..

 

[Divy]

i pulled the head off here are some pics it was a brand new piston an ring
WHAT HAPPENED???

 

[cranga]

was it stock bore size? also the piston?

 

[Divy]

yeah i dont think it did it cause of the new piston an ring some thing else happened the piston an head has all these chunks of metal dug out

 

[mad man]

dude take it to the shop and get them to re-jet it

 

[Divy]

so does that mean it was running too lean???
do i have to buy a new head??

 

[mad man]

so does that mean it was running too lean???
do i have to buy a new head??

my bad i didn't see those pics! shit did they do the rebuilt or did you? if they did it take the thing back to the shop and get them to fix it, genrally when it bogs down when you jolt the throttle quick there isn't enough fuel geting to the motor, or needs re jetting or there is a blockage. Check all your fuel lines then and then go back to the shop and show them, kind of weird situation ey

geting my rm125 02 model in 4 days.. YAY

 

[Divy]

i rebuilt it myself i didnt take it to a shop but dont think this happened cause i didnt know what i was doing cause i do an yeah i think i will just take the bike to the shop cause even if i rebuild it again its just going to do the same thing cause the mixtures are wrong an i want a pro to do my carby an i was gonna take it to the shop anyways cause i blew the fork seals lol i give my bikes hell

so just so im clear this happened cause of the carby running to lean is that correct??
an im corrious just cause its running lean how does it mannage take chunks of metal out of the head an piston??
some one please answer these questions

 

[tfmartin]

something came loose inside and bounced around on top of the piston, take the cylinder off, what does it look like, is the ring still there intact, what about the circlips. As far as jetting what color is the ceramic insulator on the spark plug ? did you take off the reed block when you were doing the rebuild ?

 

[tfmartin]

A good running bike shouldn't all of a sudden need jetting changes. On our two strokes the only jetting chnges we make are for elevation or temperature. I am guessing you might have had an intake leak that might have caused the bike to run lean, bog on acceleration or wot. It looks kind of like the ring might have busted and part if it bounced around on top of the piston.

 

[HardaFasta]

Franky may have something.Sounds like it`s starving,getting hot,then collapsing.CAREFULL