850T3 jetting question

[tonyduc]

All

During the bikes restoration I put K&N filter pods on the bike and also a complete Mistral exhaust system that fits perfect. The bike will only run with the choke on, and as a result black smoke comes from both exhausts (I assume unburnt fuel). I have stock jets in carbs main 120 and idle 50. Guzziology recommends 10% increase in jet size for the filter change, but I see no mention to compensate for the aftermarket exhaust. Should require greater than 10%? Also, when rejetting do you change just the main and idle jets?
Thanks
Tony

[Two Checks]

I had pods and Bubs. 142/145 on the mains. 50 on the pilots. 265 atomizer. Foget the slide #. Needle on second notch.
Ran flawlessly.

[guzzisteve]

Most likely has an 80 for choke jet, I change it to a 60 so you get no black plugs.

[redrider90]

I am hardly a carb expert but it's obvious you are lean if it will not run without the choke. I'd have to dig everything out to remember if I changed the idle but everything else was changed when I added a high flow K&N filter in the stock Mille box and then went with Agostini SS exhaust. I called Moto International and they had a Euro kit for the Mille that worked perfect with my set up. Lots more torque and no doubt a few more ponies.... a lot faster and pulled much better. But I lost that wonderful 55-57 MPG engine and it dropped it to high 40's on the HWY and mid 40's hot rodding it.

[Moto]

All

During the bikes restoration I put K&N filter pods on the bike and also a complete Mistral exhaust system that fits perfect. The bike will only run with the choke on, and as a result black smoke comes from both exhausts (I assume unburnt fuel). I have stock jets in carbs main 120 and idle 50. Guzziology recommends 10% increase in jet size for the filter change, but I see no mention to compensate for the aftermarket exhaust. Should require greater than 10%? Also, when rejetting do you change just the main and idle jets?
Thanks
Tony

My T3 has a similar set up to yours: K&N pods and Valtek mufflers, electronic ignition, but otherwise stock.

The stock jetting is: 120 main jet; 50 pilot jet; V9 needle; 2nd notch position on needle; 40 slide cutaway.

I run a 130 main jet, and have milled off about 0.7 mm from the bottom of the slide to richen the mixture off-idle, for better initial acceleration. Before I milled the slide I had put the needle in the 3rd notch (fully raised), but this didn't cure the off-idle leanness. After milling the slide I put the needle back to the stock position, and have good off-idle acceleration.

I have a note in my log that a #55 pilot jet is too much -- it made maximum idle speed occur with the mixture screw all the way in.

I live at 900 feet above sea level.

You need to understand carburetors to tune them. You should download the Dellorto Carburetor Tuning guide, and study it, since there may be factors that make your tuning requirement different from others.

Good luck.

Moto

[tonyduc]

Thanks to all for the advice. I think I will increase the size of the main jet and leave the idle jet stock. See what happens!

[Chuck in Indiana]

How's your ignition?  Was it running normally before the changes?