Bike will not run

ricr378 · Post by **ricr378** » Sat Dec 01, 2012 2:27 am

I was riding to work last week when I pulled up to a set of lights. My bike then started to idle rough and died. I pulled off the road and then it restarted but when I blipped the throttle it died again. It kept doing this so I called the trusty RACQ who sent out a guy who knew next to nothing about bikes. Anyway, he thought it was a fuel issue which was also what Alex thought when I gave him a call (cheers Alex). I ended up getting the bike towed home and I am now trying to diagnose the problem.
Having left the bike for two days it started first time and ran and revved no problem for about 3 minutes but then died again. I have pulled the tank off and tested the tap which is working fine. On PRI the fuel flows free and with the vacuum tube connected it feeds fuel when set to ON or RES. The vacuum pump seems to be pumping fuel through so I am now a bit lost as to what to check next. If I leave the bike for 30 minutes it will start and run for 10-15 seconds but then stop again. What should I check next?

ricr378 · Post by **ricr378** » Sat Dec 01, 2012 3:07 am

I just started the bike and it seems to run fine off idle. It will hold 3000 rpm and not die but if I leave it to idle its OK for a minute and then stops. So it would appear to be a carb problem then? If I am taking the carbs off what am I looking for?

alextrx850 · Post by **alextrx850** » Sat Dec 01, 2012 4:07 am

have you checked the small fuel filter insert that sits inside the T piece that fuels the carbs..its where the rubber fuel line goes to the carb...if that is blocked, it would give you limited fuel.

ricr378 · Post by **ricr378** » Sat Dec 01, 2012 4:46 am

The puzzle is that fuel is getting through and it will run on half throttle no problem. It seems to only have a problem when on idle. What would cause it to die after being on idle for about a minute?

ekoja · Post by **ekoja** » Sat Dec 01, 2012 5:35 am

Ric, this may well be the silliest suggestion you will get, but maybe you have water in your fuel.

ricr378 · Post by **ricr378** » Sat Dec 01, 2012 5:40 am

Not so silly as I did ride it on wednesday when it rained on the way home. Why would this only effect the idle though and not any other time?

bagmaker · Post by **bagmaker** » Sat Dec 01, 2012 6:47 am

1- vacuum leak between carbs and fuel tap
2- breather blockage on fuel tank

davamb · Post by **davamb** » Sat Dec 01, 2012 10:12 am

Ricr, I'd just like to tell you about a strange problem I had with much the same symptoms. Took me ages to track this down. Above and in front of the carbs is a shaft with a white nylon slider which the choke cable drives. This slider is worn on my bike and as a result would cock on the shaft leaving one pot still fully choked after the choke button was pushed back to off. Bike would start up from cold ok but then run like crap when warm and often wouldn't hot start at all. A little dab of grease applied via a long screwdriver has sorted the problem - nylon slider now returns smoothly to home position. Might be worth a look though I don't know if it's relevant to you as knowing where you live you may never use the choke.

ekoja · Post by **ekoja** » Sat Dec 01, 2012 5:14 pm

ekoja wrote:Ric, this may well be the silliest suggestion you will get, but maybe you have water in your fuel.

My thinking was that the polluted fuel would flow through at higher revs without to much effect, but at idle the water wouldn't get pushed through as quickly and she dies.
Actually... sounds like bullshit!

fung · Post by **fung** » Sat Dec 01, 2012 9:23 pm

fuel tap would do this, but you have checked it.
Air filter choked might do it too.
The air / dirt traps (little black things attached to the back of the carbs by tubes) may be clogged so not giving even atmospheric pressure.
Tight inlet clearances will make a bike run rough and be hard to start.
A sticking choke will also do this
Hmmm
Cheers
Fung

cal · Post by **cal** » Sat Dec 01, 2012 9:26 pm

Is it running crap on both cylinders? if its just one then it might be electrical, but seeing as you havn,t mentioned this I would presume it is running crap on both, which does point towards fuel, have you checked the fuel tap? if it is loose and going to fall out (a known trx problem) it ...might,... be drawing air through the joint from the tap and the tank, when its running slow it might not have enough vacuum to break what seal is there, but when you you give it some beans it creates a bigger vaccuum (negative) pressure, and pulls some air in, dont think this would be enough to make it cut out...

It a bit of an if and a maybe but should be fairly easy to eliminate from the list, there are a few threads on the leaky tap problem with the fix for it as well....search!...

Ahh you beat me to it Fung! ...but I is postin anyways!!!

adamcrofts · Post by **adamcrofts** » Sun Dec 02, 2012 9:40 pm

Water in the fuel usually lets it idle, but won't rev up. It sits in the bottom of the bowl and gets drawn up into the jets as the fuel flow increases at revs. You sound like you've got a blocked pilot jet. Could still be water but less likely i would have thought. Has the bike been over on its side lately? Fixed alot of bikes that were running fine before the bike got knocked over, and all the built up crap in the bottom of the bowls suddenly floats up into the jets.

Have you fuelled up recently? If you're running 98 octane fuel then you may have a partially foulled spark plug. Optimax is nototrious for this. Worth a look

fung · Post by **fung** » Sun Dec 02, 2012 11:07 pm

nulon make a cleaner/octane booster which works well.
i have heard recently, some bikes tend to run too rich on 98 as it is more dense than 95.
have you checked your TPS and the coil rsistances?
cheers
fung

ricr378 · Post by **ricr378** » Mon Dec 03, 2012 1:24 pm

Thanks for all the feedback. I have pulled all the pipes off and checked the fuel flow as much as I can. All the vacuum hoses seem to in good order and fuel is getting through to the carbs. Alex rang and told me to check the filter in the T piece at the carbs as this might be partially blocked and causing a problem when at low revs and therefore low vacuum. It would appear that mine has been removed and not replaced by an in line filter and this might be what has caused then problem. After a change of fuel and much starting/revving/idling the problem seems to have clear up. I am guessing that a blocked jet may have been the issue but somehow the blockage has cleared. If this was the problem then and in line filter may be in order to stop any crap from making its way into the carbs again. I have had it idling now for 10 minutes without a problem and taken it for a quick spin round the town. Fingers crossed it will get me to work tomorrow. Cheers guys.

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