CBR125RS6 - A bit fuelly

berzerker · Renault 5 Driver Joined: 27 Sep 2013 Karma :

My youngest son will be graduating from pedboi soon and in anticipation he has acquired a 2006 CBR125 for only £150 which has been standing for 4 years and not run for 2.
I have checked the oil/coolant levels which look OK, cleaned the plug, given it fresh fuel and a fully charged battery and it starts and runs for a few minutes but smells a bit rich.
To investigate I have removed the tank and top of the airbox and managed to get it running on what fuel was left in the bowl. It ticks over quite nicely but on increasing the throttle I get a horrible foamy petrol/oil mix blow back thorough what looks like the crankcase breather into the airbox. I have checked the oil level and the case also looks to be full of oily fuel.
What's wrong and is it beyond repair?
https://i1283.photobucket.com/albums/a549/1berzerker/th_20140521_111945_zpsade812bc.jpg

SQL · World Chat Champion Joined: 08 Aug 2012 Karma :

Check all the breathers, also don't just check the oil replace it.

Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

Is it blowing any smoke, and what colour?

How's the plug after running it?

How's the compression?
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berzerker · Renault 5 Driver Joined: 27 Sep 2013 Karma :

OK, I've drained the oil and replaced it, there was a good half a litre more fluid in there than should have been.
I have run it for a good half an hour, initially there was lots of smoke and smells but now the gas coming out seems reasonably clear. I have removed the plug a few times and cleaned it up and I can only describe it as 'sooty'. I have also backed off the mixture screw to make it a bit leaner but this doesn't appear to have affected anything. I can't check compression but I can get hold of a tester over the next few days.

berzerker · Renault 5 Driver Joined: 27 Sep 2013 Karma :

The compression is good.
I found the vacuum fuel valve was faulty. The diaphragm was knackered and fuel was permanently 'on' and also leaking fuel into the head via the vacuum pipe. This has been replaced, the oil changed, new plug and air filter and the flooding problems appear to be sorted.
The bike starts and runs OK other than the idle being too high. I have backed off the idle screw away from the throttle pulley and slackened the cable. If I push on the throttle pulley in the close direction the revs remain at an acceptable level and tickover is quite smooth. Would this indicate that the main jet/needle is not seating properly?