Hi I've got a tuned 3TJ that I took on track last week but I had a bit of carb trouble, It was bogging at about 9000 rpm up to 11000 then pulled real hard to the red line (15000) does anyone have the jet, needle sizes for a tuned bike with open bell mouths and for a BDK air box as I've got one sat about that I want to fit , mainly for the filter.
Dobbs.

Fit up the airbox and ask BDK - they might even have it on the website

Dependent on state of tune but open carbs start with 122.5-127 mains.. with kit yamaha a/box i ran 132's with 76bhp....Must use larger airjet for bellys/airbox
Bdk should have (BASE)settings

mmm.... my original "tuned" carbs had only #100's in them and ran well until they gummed up over winter, the spare set I had used #116's in them with different needles etc but had a massive flat spot at 9000rpm.
The plugs always looked just right so I'm not sure what's going on here
Who knows what size jet's the standard SP should have?
Me thinks dyno time is coming! ££££££

dobbslc wrote:mmm.... my original "tuned" carbs had only #100's in them and ran well until they gummed up over winter, the spare set I had used #116's in them with different needles etc but had a massive flat spot at 9000rpm.
The plugs always looked just right so I'm not sure what's going on here
Who knows what size jet's the standard SP should have?
Me thinks dyno time is coming! ££££££

Std import 3tj sp's vary on jet sizes 100-110 but base setting in kit manual suggests 127's..std
Best go dyno and wouldn't read into plugs when on unleaded fuel unless running motec 4 det counter as benzine in unleaded so will give false readings..

Thanks mate, I think I have a copy of the kit manual carb settings somwhere I'll go and see if the other jets match up as well. Does anyone know of a good dyno operator in the north London/ Herts area? I used to go to Road & Track in Aylesbury but think he's gone now.

What about BDK ... I think they have a dyno

Dont waste time guessing jet sizes and needle settings just find a good local dyno and get a price for set up before turning up. Had my #1 bike on the dyno yesterday and it certainly prooved that every engine is different and there is no such thing as base settings! It finished with smaller mains than my 73bhp engine and some huge bhp.

I'll agree with that as the bike is bloody quick, it's just a fine tune for the mid-range that's needed.
I don't know anyone I can trust around here now that will do a good job and not just tune it for big bhp at huge cost.

You cant really tune an engine for midrange over bhp or bhp over midrange with carbs, its all about getting the fuel/air mixture correct through the rev range, any dyno centre will be able to do that for you, aim for about £30 an hour and expect a couple of hours work, tops £100.