A second friend has almost the exact same setup, with the only difference being the pipe. His quad was dyno'd at 42 hp, with jetting being real close. I do believe he runs the lid on, however. Not sure about the jets. He may be running the 146/148 mains (Dynojet), along with the Dynojet needles.

We were expecting quite a bit more HP, obviously.

If several of you would post what your running for jetting on stock carbs (I've noticed some of you have...), it would certainly be appreciated. This would give us a better feel for where we should be as well. Of course, it really be helpful if the jetting posts pertained to modified 686cc instead of stock.

Regards,


Rog

 

RC350,

There are still going to be some discrepencies, due to the difference of each 686 build (cam, port, compression, intake and exhaust valve size, etc), exhaust used, airbox modifications and elevation. So I would only recommend you use this information as a learning tool, not for dial in.

On my old 686 I used 165/170 Mikuni mains, 22.5 (stock) pilots, and DJ needles, combined with just a slip-on exhaust and running an open lid airbox. I am at 500-700' above sea level and a average humidity in the summer of 80-95%. Air fuel mixture is a whole nother animal!

 

If your friend is using the webcam 80-421 cam (race profile) it is possible to lose some bottom end due to the extended duration the cam provides and some of the aftermarket exhausts (as exhaust gases can reenter the cylinder when the valves are open longer), this cam works best at high rpms, I have both the 80-421 and 80-411 cams (we have 2 686s now) and the difference is very noticable on the low end
on the jetting I also got rid of my dynojet kit, and went back to stock needle and 178/182 mains (at ~7000' altitude), the dynojet kit is a stage II kit, and a 686 motor is typically a stage IV modification that works better with the mikuni needle and much bigger jets

 

Thanks for the responses. I appreciate it.

Swytak, I had only planned to use any information posted here as reference material for the very same reasons you mentioned. I just wanted to get a better "feel" for what others are running with similar setups.

Thanks, Vraptor. The cam is indeed supposed to be the 80-421.


Regards,

Rog