790 Bonneville Carb Problem

Hi to all again further to my list of a few months ago regarding starting and running problems I have just removed the carbs and given everything a good cleaning, replaced them on the bike and have the same issue Bike starts missfiring on offside then it cuts in.

Will warm up on choke and Rev ok but when choke pushed in it runs rough again.

I have fitted Norman Hyde Togas and upped the main jet size but not touched the mixture screws since I changed the silencers and have found to be 2 turns out from fully closed. I am assuming that opening the screws up will richen the mixture to perhaps I need to open them up to 2.75 turns?

 

Hi Callumity thanks as ever for your post - I do have the Jenks tuning guide and just checked it - looks like the pilot jets should be 2 3/4 turns out so will try that and post again!

 

Ok so I get home tonight and go straight into the workshop and open up the idle jets another 3/4 turn so now 2 and 3/4 turns out as per Jenks guide.

Started her up and same old problem not firing on offside cylinder. After a bit of coaxing the offside cylinder starts firing so I leave the engine running but after a few moments the offside cylinder cuts out then backfiring starts cylinder cuts in and out and backfiring in between so it’s like the spark is coming and going on that side New plugs fitted so coil perhaps? Or plug leads breaking down? It’s odd as I tested the plugs and leads previously with a pair of those see through plug tester gadgets and the spark seemed good with no corresponding interruption of the spark during the misfire....

 

Good idea I will swap plug leads first but don’t think I can swap left to right on the coil as timing will be out?

 

Well chaps here's an update for you and a very strange thing indeed - I swapped over the two wires at the front of the coil and hey presto all is well.

Now this is a total mystery as I really cannot recall swapping hem around previously for any reason at all especially as they are quite fiddly to get to!

The red wire is now on the offside and the yellow one on the nearside.

I am very pleased but totally mystified

 

Ok that makes sense - the connectors were quite loose and at some point someone had smeared grease on them ..