RM125 mid range bog / blubbering

[honda_power]

out of nowhere my rm125 has decided to start bogging severely from about 1/4 throttle until almost tapped out. the best way to describe it would be a 'blubbering' sound - the revs go up and down very quickly, until almost full throttle where it starts screaming as usual.

i dont know what has caused this, its prob got 5 hours max on new top end and main bearings. i fixed it, had it running sweet, and gave it to my sister to ride, now its doing this (she didnt even notice :blink:).

iv pulled the carb apart thinking its a blocked jet or something, cleaned it, still no better. However i dont have a compressor, so i didnt blow it out with an air gun, i may do that soon. I havnt changed the plug as it was new when i fixed the thing, and they run a bloody expensive plug.

Any ideas?

[scott411]

check your reeds,

[Crasherfromwayback]

and the plug, as you sis may've oiled the thing up!

[noobi]

Check all the electrical connections are solid and not dirty, a dodgy connection somewhere gives the same symptoms you describe

[cheese]

is it hard to start also? my old one was a bit like that and it had a shot HT lead..

[krad_nz]

Water in fuel?

Been wet lately.

[honda_power]

thanks for suggestions have checked over everything

reeds good
plug looks fine and has a healthy spark
there was a bit of shit in one electrical connection, pretty sure its clean now
bike starts fine
no water in fuel

i pulled the pv cover off to check if arm was moving properly, the pv arm and the part it connects to had surface rust on them... hopefully this was binding the pv and making it come on late? or would this be unrelated?

i cleaned them up fine with steel wool, but i dont know how that much moisture got in there to rust them?

[morg_nz]

thanks for suggestions have checked over everything

reeds good
plug looks fine and has a healthy spark
there was a bit of shit in one electrical connection, pretty sure its clean now
bike starts fine
no water in fuel

i pulled the pv cover off to check if arm was moving properly, the pv arm and the part it connects to had surface rust on them... hopefully this was binding the pv and making it come on late? or would this be unrelated?

i cleaned them up fine with steel wool, but i dont know how that much moisture got in there to rust them?

well if moisture got into the powervalve assy (im assuming its like my cr, where the powervalve is in the same area as the bottom end, and oil does have a pathway to flow between them. maybe its possible you have a leak in your water pump and coolant/water is getting into the bottom end?