Targa starting and running woes

Hi Guys, once again, i need your help and advice. My 750 Targa is running very rich (black sooty plugs but also wet with petrol) and is now a pig to start, back-firing and spitting its dummy out with more combustion taking place in the exhausts than in the cylinders. Over the winter, I replaced the original air filter which was a pain but this improved running but, still running rich and difficult to get a decent carb balance. In spite of my desire to retain originality, I am considering ditching the airbox which is a difficult fit to the carb intakes and so maybe causing an airleak on the intake rubber stubbs as a result, in favor of K&N’s. It may also be that the new air filter has none-the-less partially collapsed restricting air? This will improve access to everything else but also enable me to stick my fingers up the intakes to assess whether the slides are actually rising simultaneously. Now I know this question has arisen before but, what do I do with the big breather hose from the breather box where it goes into the airfilter box? I seem to remember I need a breather box from a T3 and modify it in some way? Any help and advice will be gratefully received.gogoguzzi2013-08-30 10:17:55

have you checked the float heights ?
also checked for worn seats on the valve surface just in case the flooding is caused be excess fuel being forced through
also have a look inside the carbs and see if lots of dirt is there. it coul dbe causing flooding
I would start by stripping and cleaning the carbs and inspecting the jets for wear
also are the accelerator pumps sticking open ?

If no petrol is leaking from the backs of the carbs I would initially suspect blocked air intake . Disconnect the rubber hoses between the carbs and the air filter and then see how it runs. Diagnose from there first then we can suggest next step.

Hi, there is no petrol coming out of the back of the carbs, though I will drop the float bowls to check the floats and operation of the valves. Excellent idea to disconnect the carbs from the air filter box though and will do that over the weekend. The last time I rode the bike was about a week ago and it was ok though not great and I gave it some stick which may have caused a partial collapse of the paper air filter element which is a known problem. Being a small block, it doesn’t have pumps on the carbs so I can rule that out. Will update soon and thanks for your help so far.

Are you sure the cold starting plungers are seating properly?

Update, I have put new plugs in and it starts and runs just fine. Checked the floats, fuel filter gauzes and float valves and all fine. My worry is that I put new plugs in a year ago and having only just finished a refurb of the whole bike, the new plugs have done less than a hundred miles although lots of starting and running on the main stand. The exhaust fumes smell rich to me so I wonder whether the mixture is over-rich? I didnt use choke to start and it fired on the button. I am still of a mind to change to K& N filters as I suspect the paper air filter which is also new but could be causing problems so, any help on what to do with the breather pipe that goes into the airfilter box would be appreciated i.e, can it just discharge to the amosphere being only crank case air and bearing in mind the oil return pipe can remain in situ from the collector box?gogoguzzi2013-08-30 17:26:15

hmmm, haven’t checked that the choke plungers are returning fully just that there is slack in the cables which isn’t the same - good point and would explain a lot, thanks.

Brian, you were right, the choke cable for the n/s carb was fowling the side panel lug - i rotated the carb on its axis by abut five degrees so that it cleared (carb at slightly weird angle now) and have had to reset the idle screw as a result so clearly this was causing it. Thank you

It’s often the simplest thing.