Got the 21 back after having the main bearings replaced and the carbs sonic cleaned. All standard jetting running 128 mains and it seems to be running too rich. Removed the air filter and it ran a little better. Then done the wire splice and seemed to run better again. Does this seem right, i want to run it with the filter so should i start coming down on the mains or could it be something else. The rest of the bike is standard. Any help gratefully appreciated. Ive had the bugger since July last year and have yet to have it running right..

Have you opened the airbox lid up?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

If you mean modded it in any way Dave no. Its standard.

may have a air leak spray some carb cleaner or somthing like around the carb and inlets and if the revs change you have a air leak

Have a read of the tuning section, and then come back here with a damn good excuse why you shouldn't open up the airbox and let that engine breathe as it should!

Running without a filter is a bad idea on the street, as everything sucked in to the engine grinds its way round the crank of course.

I doubt you'll find anyone who agree with leaving the engine stifled when de-restricting it is free.

Once you've done that, then you'll need to re-jet accordingly.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Thanks Dave, is it usual for it to seem so rich on the standard set up to the point of it being un rideable above 6 rpm.. Any idea where i can get some mains from.. Once i get it running what i deem normal im going to take it to the dyno. By opening up the airbox i assume you mean drilling four 1 inch holes in the lid as i,ve read on here.

Sounds like it could be flooding if its definately rich. Check your floats for leaks, also check the height and the float needles for wear. Do the plugs look rich when you chop it?

Haven,t chopped it yet, went down to a 125 main and put the filter back in again. A t least its rideable now though still not there yet. Will drill the air box lid and see how that goes. Have a set of 122.5 mains but dont know about tryin them. Havent chopped it yet cos it of how poor it was running so now its gettin there, soon. By the way already replaced the float valves.

How many miles? Have you de-coked the pipes?

You need to do a plug shop and have a loog at the colour really.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

There,s 16000 odd kms on it hopefully. If i drill the lid and its still not right what do you think of trying the 122.5 mains. Dont know if im imagining it or not but when it starts to stumble up the revs it seems if i roll off slightly then accelerate again it seems a bit clearer. On the over run it sometimes feels like its hunting if you know what i mean. Dont remember when looking over the pipes that they looked particulary coked up.

Have u done a compression test ?
You shouldn`t need to go smaller than stock really

Just a side thought.... I presume you are confident that the ignition is as it should be? If you have serviced the bike recently with new fuel/air filters, checked float heights/condition and nothing is obstructing the inlet then it should pull standard jetting. Weak ignition at higher revs can seem like richness. I`d make sure your ignition was sound before I played with the fuelling....

MC 21 BRIAN wrote: what do you think of trying the 122.5 mains.

We'll have to go to the members only section to discuss jetting!
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball