"Can I ask what will the bike run like with the jets off tune?? Does the exhaust play a part? I'm planning on getting a 4-2-1 any thoughts on these ?? Also back to what I was saying... How does the bike run if pods are bad? ? Or not right? How do you know how to adjust higher or lower on jets and main?? Not looking for in depth time taking in this answer unless you have time.. but what will the results be?? Will rain effect the pods? If they get wet? Thanks."
Well, it runs like crap.
You get a wicked stumble off idle and missing/hesitation at midthrottle , overly rich mixture at idle and lean mixture at full throttle with a mishmash in between on needle metering.
Yes the exhaust plays a part. For exhaust changes only, rejetting is usually just taking the main up a step, but can mean a needle height change too.
Do all the mods you want and rejet: you don't want to do it over and over as you add an exhaust, big-bore kit, hot cam, etc...
You adjust with plug chops or use a brake dyno with an exhaust gas oxygen analyzer. With an EGA you have to keep the idle mixture pretty rich - with no accelerator pump the engine will die when given throttle off idle, the idle mix is set rich to reduce this effect. With chops, there are instructions in this forum somewhere. Find out how the carb circuits overlap... you get the main jet right then proceed to the needle height and pilot jet. Usually pods require a pilot jet one size smaller than stock and probably a main jet one or two steps larger. The needle is the difficult adjustment since the stock taper just doesn't work: I reshape the needles using metal polish in a drill. This requires a lot of plug chops, if you're downtown in a big city this will be a problem since you need a longish deserted road without police interference to do a good plug chop. Also, of course, you will be removing and reinstalling the carb stack many many many times. You will need an assortment of main jets.
Seriously, tuning for pods so they work is a major hassle. I have tried with a 550 and never got it really right: maybe changing the slide cutout is required but I have never done that. I have set up a 400 with pods, exhaust, plus overbore and cam and a few 750s with pods and exhaust ... with good success. I can't say if they would be better or worse with the stock airbox. The 750s were choppers with no chance of an airbox, the 400 is mine and I just liked pods (and didn't know better I suppose).
Personally I haven't had problems with rain on the 400. Very rarely at highway speed in a strong crosswind there is some weird surging but opening my legs clears that up. If I had the time and inclination I would try some airbox ideas I've been thinking about but... right now I have neither. The bike is working really well as is and I don't much enjoy pulling and replacing the carb stack.
