So I decided to put a crossover tube on my rd350 and now I am wondering why.. Prior to the change I wasn't having any problems at all except I thought the midrange could use a little help. No bog off the line, idled just fine, and pulling fine all the way through the RPM range. Now it bogs like a SOB on the bottom end and doesn't want to idle down as it should, top end seems to pull fine. I'm thinking maybe bigger on the pilot since its bogging when you give it throttle? I didn't think adding a cross over tube would have this big of a change in tuning. Any suggestions would be appreciated.
Here is the current configuration
Y boot with K&N
Moto Carrera chambers
Dave F mod
Main 180
Pilot 35
Air screw 1 turn out
Clip position 4
Thanks
Ken
yup increase the pilot, or just plug the crossover holes. i machined 2 blanking plugs to use for the very reason of isolating an issue when tuning
Thanks Mark. I think I will block the holes and make sure everything is running correctly and then put the crossover back in and see what happens. I had the motor apart this winter to change out the bearings and seals so I need to go back and check the timing too. I didn't mess with the carbs but a dip in the sonic cleaner to make sure everything is nice and clean won't hurt.
I probably need to find a technical paper that out lines the theory of how the crossover tube works and how the carburetor tuning is changed.
Did you do a leakdown test after changing the intakes? A crossover should make almost no difference to how it runs. There is something else going on there, especially when you mention not ideling down.
wait i misread. set pilot to 30 (mistakenly read 25) . it absolutely will make a difference idling and low end w a crossover. also need to set slide screws lower as well.
I also thought about there being a vacuum leak and will check it out to be safe. That said when I pulled the plugs to check the timing I am definitely running rich somewhere, I am assuming on the bottom end. At this point since I have made a lot of changes I am going to plug off the manifolds and go back to a known tune and work from there. To many changes at one time just confuses things. Once I get it all lined out with out the crossover tube I'll start over and change the pilot to a 30 and up the main to 185 or 190 and see what happens. Thanks for the advice guys.