Unstable revs at idle...any ideas?

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Minimoto
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Unstable revs at idle...any ideas?

Post by Minimoto » Wed Jun 14, 2017 12:42 am

Hi. Any ideas why the revs should vary at idle? After a few minutes the revs will surge to 2000 or slightly more, then drop back to around 1300-1400. Then pick up again a while later...

I've just stripped and cleaned the carbs, but the bike used to do it before anyway. I'll try and get a video of it happening. But in the meantime I was wondering if anyone might know what could be causing this...?

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Johannes
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Re: Unstable revs at idle...any ideas?

Post by Johannes » Fri Nov 03, 2017 10:15 pm

Hi minimoto, no expert but on the 24 common problems are, blocked jets and perforated rubbers that connect the carbs to the blocks. Air gets drawn in by the vaccum caused when the engine runs, the revs raise and then more air gets sucked in etc etc.

Also check that the circlips on the rubbers are tight. I had one missing! hardly surprising my revs were all over the shop!

ligurt
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Re: Unstable revs at idle...any ideas?

Post by ligurt » Sun Nov 05, 2017 1:28 pm

Cracked intake manifold or more probably wrong carbs syncro. In any case something on the fuel intake side.

Neosophist
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Re: Unstable revs at idle...any ideas?

Post by Neosophist » Tue Nov 07, 2017 2:49 pm

Minimoto wrote:Hi. Any ideas why the revs should vary at idle? After a few minutes the revs will surge to 2000 or slightly more, then drop back to around 1300-1400. Then pick up again a while later...

I've just stripped and cleaned the carbs, but the bike used to do it before anyway. I'll try and get a video of it happening. But in the meantime I was wondering if anyone might know what could be causing this...?

Sent from my Nexus 6P using Tapatalk
as above... likely an airleak / craked old carb rubbers / bad fitting carbs.

occasionally carbs can be well out of balance but most likely air leak if all carbs are set right.
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...

cbr400rrn
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Re: Unstable revs at idle...any ideas?

Post by cbr400rrn » Tue Nov 07, 2017 10:02 pm

Thread resurrection from June 13th

ligurt
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Re: Unstable revs at idle...any ideas?

Post by ligurt » Mon Dec 04, 2017 9:43 pm

Useful for others!


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