I have a 1985 Suzuki GS450L and I recently replaced the air filter box with new pods and I know I need new jets but I don't know what size. Carbs are all rebuilt and cleaned and now I only need the right jets to get going. Anyone know what size jets to buy?
The best way know is to run the bike with a new set of plugs for several miles, take out the plugs, read them, and then decide how far up you need to go on your jet size.
If that's not possible then the next best go-to idea is to run the bike for a bit and see what it's doing, and where it's having problems. Is it the low idle circuit or the main circuit? Assuming everything else has been correctly assembled and is functioning the way it should, your best bet is to go up one standard size on either jet from what you have in there. (You'll first have to know what you already have in there of course.)
If at sea level I'd start at, or around, up to, or about 4~6 steps larger that stock on the main jet and tune from there.
Maybe someone will chime in that's actually done pods on one of those bikes.
As you can see, I'm just guessing.
Here's a reply I had when discussing pod filters, air flow and such.
Thought you might be interested in seeing it....
"It boils down to this.
There is a proven formula for determining the ideal intake tract tuned length at a given RPM keeping space considerations in mind.
The tuned length being the distance from the center of the inlet valve/s to the point at which the velocity stack, air horn. pipe or whatever is open at the end.
So you would want your 'tuned length' to match the RPM your engine puts out the most HP because you'll be at and around that RPM when racing or just out blasting.
I've been in one Yamaha (I believe a ~2014 Yamaha YZF-R6) that has a movable variable length motor driven velocity stack system that changes length according to changes in RPM.
Higher RPM, shorter tuned intake length. Lower RPM, longer.
Me saying pods are all wrong is really an overstatement. They will flow much more air than most stock air box systems of old but ideally should not be placed directly on the back of the carb.
Pods should be placed at the end of the 'tuned length' intake tract, ideally.
Most or some bikes come from the factory with a tube of sorts leading from the back of the carbs going to the air box that is probably close enough to be called tuned. Old Yamaha RD 350's come to mind.
A guy could just copy that tube length, making it slightly cone shaped, put a pod on it and likely be in the ball park.
On Some models it's possible to modify the air box in order to remove the air restriction and retain the stock air box, air filter and tuned tubes / runners going to the air box.
Many times you need to go about 6~7 steps larger on the main jet after doing so indicating a huge increase in air flow."