Bike stalls when pulling away

[eastanglianbiker]

and plugs with a nice healthy spark can start to break down once hot spend the few quid on a new plug see if that helps

[zedhead]

Hi after many unforseen and unavoidable distractions i am back!.

Still got the same problem

The bike from cold pulls away and runs fine.After a couple of minutes riding [maybe 5-10 min at times], the bike will run as if it is running out of petrol .Thing to note is that the bike will run for ever if just left to idle.This problem only appears when riding bike.

Things i have done.

1/ Cleaned carb and petrol tap several times.

2/ Replaced spark plug with a new one.nice healthy spark.

3/ Checked coil

4/ Checked clutch plates, all still have friction material on them within specs

5/ Adjusted clutch cable

6/ Adjusted valves.

7/ Checked rear wheel/brake for any binding.

Current thinking is could the cdi unit be cutting in and out as the bike warms up under load.?

I welcome any ideas.

I have the goat and chicken handy for ritual sacrifice if all else fails.

[eastanglianbiker]

looking at the list of whats been done have you checked the breather in the fuel cap to make sure its not blocked as when ticking over it will be fine but after a few minutes of running it would build up vaccuum in the tank causing bike to cut out for a minute or 2

[zedhead]

Should add that to the list fuel cap breather checked for blockages all aok.

[uk190]

could it be a choke issue? or even a problem on the high speed jetting; the slow speed seems to be ok.

[Bonniebird]

Its a long shot but I was searching for answers to problems with my bike recently and there was a thread about the ignitor unit under the seat getting crushed and causing poor running and occasional cutting out. Don't know if you have any electricals in a similarly vulnerable place on yours.

Incidently, my issue and was sorted by replacing the coil and HT leads although there was no obvious problem with them

[zedhead]

could it be a choke issue? or even a problem on the high speed jetting; the slow speed seems to be ok.

 

I keep coming back to the carb whenever i think about this problem. I don't know much about the inner workings.I can take one apart and put it back together,but as to what each bit does im a numpty.The idea that the high speed jetting could be the problem sounds feasable . I will look into it thanks.

 

Its a long shot but I was searching for answers to problems with my bike recently and there was a thread about the ignitor unit under the seat getting crushed and causing poor running and occasional cutting out. Don't know if you have any electricals in a similarly vulnerable place on yours.

 

There are some electrics under the seat might be worth a look.thanks for the idea.

[Stu]

has the bike got a vacuum operated fuel tap? if so check the vac line as it could have a split and not enough fuel getting through

[zedhead]

No it has a gravity feed tap, simple on- off- reserve,one pipe to the carb.

[Joeman]

No it has a gravity feed tap, simple on- off- reserve,one pipe to the carb.

There has to be a tank breather somewhere - as the fuel comes out, air needs to go in to replace it, else you form a vacuum.. could be the problem!

[zedhead]

Somone asked that a few posts ago . There is a breather pipe coming out of the fuel cap which has been checked and is clear.There appears to be no problem with fuel flow from the tank to the carb,and the bike will idle forever and rev freely -until someone gets on the bike and tries to pull away. And if starting from cold the bike will run fine whilst being ridden for a few minutes and then act as if there is no power until the bike will not even pull away from standstill.Weird is not the word for it!!

[uk190]

..until someone gets on the bike and tries to pull away. ..

 

is the handbrake sticking?

it does def sound like a fuel issue. i am leaning towards a choke problem. but first i would strip it and clean it.

remove the carbs, strip them down and check for split diaphrams and anything obvious like sticky plungers. then clean everything inside with a can of carb cleaner. blow through it all with compressed air. spray more carb clean and reasseble and try it.

[zedhead]

No the handbrake is definatley off it's my sons bike and i think his just ate too many pies

Good advice with the carb that is my next job. Iv'e done it three times already [ooh err] but you can never clean a carb too much. No known split diaghrams or sticky plungers.Knowing me i have probably missed something really obvious and stupid!!

[zedhead]

Quick update . Whipped the seat off and checked for any misbehaving electrics. Found a couple of wires that could have been shorting out under the weight of a rider,so i sorted them.Took the carb off to strip down and check over again and found that the pilot jet had come loose under vibration and disapeared along with it's spring and 'O' ring. Can only think it was whilst we were testing the bike out on the road,because it was there last time i looked. Will have to wait for a rebuild kit to arrive and then i can try again. Such fun

[Tango]

Bonniebirds bike was playing up recently and not ticking over correctly and also bogging down when trying to pull away.......changed the coil pack and now it's OK. So don't rule out spark problems even though there is a spark there it may not be sufficient under compression....

[eastanglianbiker]

surely it must be the main jet thats missing as it ticks over ok but wont rev so that to me says main jet not pilot jet?

[zedhead]

According to the manual the jet that is missing is the pilot jet it is on the bottom of the carb exiting out of the float bowl. Also i don't think this has anything to do with the initial problem it's just a problem that has occured whilst testing the bike after the last attempt to solve the issue. It could have come loose at the end of the test and fallen away.

[Mrbarry]

Or fallen into the engine and bent/stuck to a valve, or annihilated the crown of a the piston. Could explain a LOT where compression based power problems go!

[eastanglianbiker]

Or fallen into the engine and bent/stuck to a valve, or annihilated the crown of a the piston. Could explain a LOT where compression based power problems go!

impossible for a jet to make its way into the engine itself unless there is no needle or main jet holder fitted into the carb

[Mrbarry]

Depends who puts it on the engine.... I've seen some crazy stunts in my time!

[zedhead]

Hopefully this is the final update . Got the Carb rebuild kit, fitted the new jets 'O' rings springs and gaskets. Lo and behold the beast works and keeps on working .It seems it may have been a Carb problem all along,but at the very least the rest of the bike has been adjusted and checked within an inch of it's life !.

We only did a small journry today so tomorrow we will push it further [hopefully not literally!!]

I am pretty confident it is all good now . The bike starts idles and runs smoothly as long as it is necessary.

Many thanks for all the ideas tips and comments much appreciated.

zedhead

[oslin06]

Have you checked for air leaks in the carb rubber and hoses? I would still favour a carb fault or a bit of dirt in it somewhere, I read you have cleaned the carb but with respects did you do it properly?

Keith

[zedhead]

If you read the previous post you will see that the problem has been resolved. It was the carb afterall ,with a rebuild with new jets and gaskets.Yes i did clean the carb each time i took it apart,but the fault lay with the components being worn.