The big 1st price goes to Slowpoke!
I took the carbs off last week to clean them, found a plug on the engine casing, but didn´t think much of it then, thought it came from the tube sticking up in the mibble of the carbs and the mech had dropped it and put a new plug back. I´ve been thinking of that plug while at work, so today I took off the carbs again (25 min. work) and Voila´, there it was, a vacuum plug missing! Put the plug back on and reassembled the bike, and Hurray! smooth as silk!!! I´m so happy, and what a ****ty problem!

 

Did the same thing myself except i'd left all four vacuum plugs off, bloody relieved when i spotted what was making the bike run like a bag of hammers. Fair play on fixing the problem...

 

Do you need to remove the carbs toobserve that avacuum plugsis missing on yor bike? On my CBR1000 F -92 the plugs where inspectable when just the fuel tank was raised. Good though you have found the problemat lastand that the bike run fine.

 

Probably not, but since I didn´t know where to look, and I also was aiming at a more extensive cleaning (removing jets), I just took them off. The plugs are located under each intake, in the aluminium except no:1 which is on the left side of the intake and where the vacuum tube to the petcock vacuum valve attach, so no:1 don´t have a plug.
At least something good came out of this, I now know that it isn´t such a mystery to do some job myself on the bike. I spoke to the local bike shop, and the owner said that the plugs could slip off at a backfire. I asked my brother to start the engine during winter storage, and he said today that he had some trouble starting it then, including some backfiring.

 

Honda in their wisdom put the vacuum plugs under the carbs/intakes from the 1993 model on. Real pain tryingto get at the no.2 cylinder vacuum plug.

 

Yes it is easy to miss when they are located under the carbs. On the -92 they where located on the top and one of the first thingto see when the fuel tank was lifted. The vacuum plugs are also securely fixed with flexible clamps on the -92.

 

That is not too far from the Truth!