Hi guys i've only just signed up here as im sure you can tell, But i would REALLY, REALLY appreciate it if some of you wise fellows could try and help!
I've been having some major grief with my bike recently.. I left her for a few days, and she wouldnt start after!
Full story:
I left her for two days as I had no money for fuel, i went out to start her when i had some money, and she point blank refused! Sounded as if she wasnt sparking, so I yanked the plug out, and it had an intermittant, but BLUE spark, albiet reasonably thin? Not a nice big chunky spark like my CG has!
Bought her a new (second hand) coil and brand new plug, and the intermittant problem dissapeared... but she still wont fire up and the spark is still small!
I've done a resistance test on the generator, pickup coil, ignition coil, ht lead, ht cap, neutral switch, engine cut out switch, ignition switch.. and everything seems fine. So i ruled out the electrics(minus CDI) and moved onto the carbie.
Whacked the carb off, no noticable blockages, float height was standard at 16mm... I gave her a nice blow through with the air compressor just to be sure, re-assembled, put it back on the bike and she still wouldnt start.
I left her for a few hours, went to start her and she did! Nothing had changed in the mean time.
BUT - When she started, she was burbley, and she had about a PINT of petrol in the downpipe! Which to me meant that it was flooding.. but the carb was fine? So i asumed it must be from where i've been kicking it over with no success
So i emptied the exhaust out, Put it back on and she ran for a while, but she was over-heating. I took her for a 10mile ride to a friends house (with tools, fortunately) as a test, and she felt REALLY strange and was overheating!
I went to go home at 10pm that day and guess what? she wouldn't start again!
I gave her an oil change, and the oil was FULL of petrol, so i gave her a nice new bottle of Castrol Magnatec 10w-40... So somewhere along the line, she must have been flooding, really badly! (Which i asume is the reason for my overheating, as the thermostat and coolant are fine)
I whipped the carb off again, re-adjusted the float to 15mm, put it all back together and she still would not run!
Whipped it off AGAIN, put it back to 16mm, still no luck. I left her for a few hours, went back out and started her! She ran, and she ran fine! She ticked over smoothly, reved fine and wasnt excessively smokey or anything (apart from being cold)
BUT - upon stopping her, she started peeing fuel out of the carb overflow! So i thought I can't ride home like that, Took the carb off again, put float to 15.5mm, and she stopped overflowing and wouldn't start AGAIN!
Eventually managed to get a friend to stick the bike in the back of a van and got her home so i had more tools & spares to work with.
I've had all the electrics apart again, all connector blocks are fine as far as i can see..
I'm really clueless now, i'm not sure if theres something wrong in the carb that i've managed to miss 6 times! i've had the choke mechanism off as well and it seems fine too.
I can't tell if its the electronics or the Carbie? Because the plug is still getting damp, but I have a THIN blue spark? Not sure if thats regular on DT's or not!
My only theory just now is that the CDI has died, and the voltage/timing within it have gone kerput!
I really hope i've given you guys enough information to work with, I'd rather give too much than too little.
Sorry this post has dragged on a bit.. thanks in advance, Sam
-- Edited by Dufferz on Sunday 30th of October 2011 01:05:32 PM
Now that was a 'hellofa' big read, I've seriously forgot what inside a mikuni carb looks like but you know the bit under the floats http://www.ebay.co.uk/itm/GS650-GS750-GS850-GS250-MIKUNI-CARBURETOR-FLOAT-VALVE-/290427499178?pt=Motorcycles_Parts_Accessories&hash=item439ed3f2aa (top right corner in that picture) Have you took that out and checked under there? Somehow on my GPZ I got a tiny piece of rubber hose under there and the bike just ran like crap, petrol out of the overflow aswell!!
I think if your getting a blue spark that's good enough for me (my GPZ has yellow sparks and still runs fine) I would go over the carb again, put floats back to standard (16mm+-2mm if I remember correctly) And then go from there..
I don't think there is any real way to test the CDI other then swapping it out with a "known working" one
The carb overflowing sounds like a worn needle valve, but it doesnt sound like that is the reason for it not starting.
I cant work out how you can get petrol in the gearbox oil unless someone has connected the gearbox breather to the carb overflow! Even a failed crankseal or crankcase joint wouldnt mean the gearbox would be full of petrol.
Intermittent starting does sound a bit CDI-ish, especially as that's the thing you havent changed. When you checked out the resistances of the other components with a meter, I assume you checked them against Yamaha's specification?
@gincat, yes im sure, all the carb has been fully cleaned and ran through an ultrasonic cleaner so im 100% there is no debris in there at all (its nice and shiny now too ;) )
Everything seems pristine! I cant figure how the fuel got into the gearbox either? i mean, a few months ago i replaced the crank seals, as they were blown.. and I can't imagine them having blown already
I've got my eye on anothe CDI as we speak, so im hoping thats what it is, otherwise im about to waste £100.
No luck on the bumping either, me and a few friends ran the poor things up and down the road as much as our backs could handle!
You push start your bikes with your back? I've read about petrol getting into the gearbox oil on another forum.. But that was on a 4 stroke bike with a vacuum operated carb! I didn't pay any real attention to be honest.. First port of call would be to scour the internet and find out why the petrol is going into the gearbox oil.
I thought I'd seen every 2 stroke problem under the sun but petrol in the gearbox oil and the header pipe is a head scratcher. The only way that much petrol gets into the downpipe is where the carb is flooding/overflowing into the engine and filling the crankcase which is not uncommon. But it would have been very difficult to kick over as the fuel would have been hydraulicing in the crankcase.
So along with the carb flooding into the engine, these are the only logical reasons for fuel in the gearbox:
1. Crank shaft oil seal worn on right hand side, blown out or incorrectly fitted.
2. Crankcase joint failed.
3. Crankcase cracked between the inlet manifold and the gearbox.
4. Carb overflow mistakenly connected to gearbox breather.
5. Someone has filled the gearbox with petrol through the gearbox oil filler.
There is always the chance that when trying to kick/bump start the bike with a crankcase full of petrol, the hydraulicing has cracked the crankcase through to the gearbox. This would make it very difficult to start as all crankcase compression would be lost.
It was a very thin light grey and dark grey mix, tasted like petrol! (one way to be sure, heh).
I'm just about to dump out the current oil and check the seal, as I have a spare; r/h crank seal was my very first thought, but when she ran she ran fine and didnt dump out excess smoke at all.
As silly as it sounds - she started at the roughly the same temperature and time when she ran the time before. So i think the expansion and contraction due to heat may have made the seal.. seal properly? I really don't know just now but i guess i will soon!
big thanks to everyone for your advice so far! .. and may the games... BEGIN!!
Thanks for the help guys! I just confirmed that it works, she runs, revs and ticks over smoother, with a nice rattle from the powervalve aha.. Also much more powerful!
Woohooooo!! Now just to get re-insured tomorrow and MOT before too long too.... then tax...... And a new front sprocket as mine has virtually no teeth on it.. And a sidelight bulb for MOT... but they are all easy :)
I'm so glad i got out-bid on that CDI i was looking at - it was £122!
