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Engine cutting out if take revs off. (SOLVED)


Husci
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You reckon cleaning carbs is good place to start? I seem to run ok for a few minutes but then every time stop at junction if I take revs off engine just dies. Earlier It was constantly cutting out. Eventually it just wouldn’t re start at all five minutes later I managed to get it going and take it home keeping revs high. So lucky escape. Any help is very much appreciated.

Edited by Husci
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Have you tried adjusting the idle screw? Most bike idle at around 1200RPM. Turn it in a few turns and see if that sorts it. If the idle screw doesn't sort it try putting the choke on a bit. Does it run better with the choke on? If it does it means the bike is running too lean and you probably have a blocked pilot jet. You would have to take the carb out and clean it.

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Have you tried adjusting the idle screw? Most bike idle at around 1200RPM. Turn it in a few turns and see if that sorts it. If the idle screw doesn't sort it try putting the choke on a bit. Does it run better with the choke on? If it does it means the bike is running too lean and you probably have a blocked pilot jet. You would have to take the carb out and clean it.

 

Hi no I’ve not adjusted the idle screw yet. The thing is if i just start the bike like say first thing tomorrow it will just sit there running fine. Then if I take it out and go round block it will be ok for so long I’ll stop at junctions and it’s sound sits there at about 1200. But then five minutes in it just starts to lose it. Can’t seem to stop with out cutting out unless hold revs

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Have you tried adjusting the idle screw? Most bike idle at around 1200RPM. Turn it in a few turns and see if that sorts it. If the idle screw doesn't sort it try putting the choke on a bit. Does it run better with the choke on? If it does it means the bike is running too lean and you probably have a blocked pilot jet. You would have to take the carb out and clean it.

 

Hi no I’ve not adjusted the idle screw yet. The thing is if i just start the bike like say first thing tomorrow it will just sit there running fine. Then if I take it out and go round block it will be ok for so long I’ll stop at junctions and it’s sound sits there at about 1200. But then five minutes in it just starts to lose it. Can’t seem to stop with out cutting out unless hold revs

 

You can probably rule out idle speed screw then. If that was the problem it would never idle right. Could be a lot of things. It could be losing spark on a cylinder or it could be fuel supply related. Like a kinked breather or a dodgy vacuum fuel tap. Do they have a vacuum cut off taps? If it does maybe it's faulty and not got enough vacuum to open properly at idle. That's just a guess though. Not sure what the setup is on the ER5

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You reckon cleaning carbs is good place to start? I seem to run ok for a few minutes but then every time stop at junction if I take revs off engine just dies. Earlier It was constantly cutting out. Eventually it just wouldn’t re start at all five minutes later I managed to get it going and take it home keeping revs high. So lucky escape. Any help is very much appreciated.

That's what I did on Saturday . A complete strip , inspected all jets , blew through all passages , checked and cleaned the float valves , inspected the diaphragms and needles . Wound in and wound out the pilot air screws to 2.5 turns , everything . Checked , cleaned and gapped the plugs and made sure the petrol tap opened and closed when a vacuum was applied . Here's what I suggest . Stick a load of rags or a little bowl under one carb at a time and undo the screw in the bottom( right hand is easy , left will need a long reach Allen Key or an Allen bit on an extension ) . With the tap on ON , let all the fuel drain out of one carb . Then turn the tap to PRI for just a second to see if more fuel comes out . If it does that's good so shut it off for now . Close the screw . If it dosen't come out , whack the carb with a bit of wood and a hammer until fuel flows and close the screw . Repeat this process with the other one and then with both screws closed , stick the tap on PRI for a minute and the turn it to ON . Fire her up and hopefully it should be fine . It sounds to me like a float valve is sticking but I made sure they were operating freely before I put the carbs back on . Let me know how you get on . The V5 has gone off to Swansea by the way .
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Have you tried adjusting the idle screw? Most bike idle at around 1200RPM. Turn it in a few turns and see if that sorts it. If the idle screw doesn't sort it try putting the choke on a bit. Does it run better with the choke on? If it does it means the bike is running too lean and you probably have a blocked pilot jet. You would have to take the carb out and clean it.

 

The idle was perfect at a rock steady 1500 rpm with the choke off on Sunday .

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What bike is it? might help someone diagnose it for you

 

I'll do everything I can to help , it was me that just sold it !

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There is another possibility , and that is that a float valve is stuck open and one carb is flooding momentarily when you are at idle and then when the throttle is held open the fuel is used op again . This is a common problem with the ER5 but I really thought I had cracked it by fitting PVC Fuel Pipe and a big inline filter . The process that I described above might actually cure this as well if there's a speck of dirt behind the float valve that's small enough to be flushed into the bowl and out of the drain hole .

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[mention]fastbob[/mention] Thats bad luck! I'm sure you will though, I'll leave you to it as you will certainly know that bike better than me!


If I had lived closer I was considering buying it off you too :D

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Thanks Guys and Bob no worries I’ll try all these things tomorrow or Saturday. Still managed to have good fly about on it just had oh shit moment when couldnt get it going at all for 5 or 10 minutes while I pushed it into Aldis car park For a bit haha

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  • 2 weeks later...
  • 2 weeks later...

Update solved solved!! Was a spec of dust in float valve stopping needle shutting properly. Running perfectly now.


I think this is what caused it to drop to one cylinder in first place. So when I thought I fixed it before all I had done is got it firing on both cylinders again. But flooded again so back off with carbs and saw the spec of dirt as described above.

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