My 1977 Rd.400 bogs at hi rpms. above 7000 in 5th gear.Have 27.5 pilot jet 200 mains.air screws 1.5 out.plugs a mediun brown.this when I open the throttle completely!If i back off a little it runs again. Is it rich on the main jets?Should I try the air screws at 1.75 or 2.0?Oh yea stock porting, compression Tomey y boot air cleaner. thank you all.
always err rich. stuff 220s in it see if it gets better. if it gets worse, go back down to 190s. If that doesn't do it...
i had the same issue on my hybrid, as soon as i clicked into 6th wot.. turned out the bowls were getting sucked dry, had to go to a bigger needle and seat. if you have 2.0 needle and seats, jump up to a 2.5 or a 3.0. & check the petcock flow. if you are runnign fuel filters, make sure they arent restrictive. the brass insert ones are choke points.