Going back to stock muffler. Need immediate re-jet?

[geekonabike]

I just bought a '98 a week ago.  It has a D&D exhaust which is quite loud for my tastes.  I'm not entirely sure the fellow who put that on--two owners ago--re-jetted the carbs afterwards.  I'm not at all an expert in these things, but my impression from what I've read is that if he did not, that would be a bad thing, as the engine would run hotter.  Am I right?

Anyhow I'm wanting to put original exhaust back on and seem to have found one.  If I do that, will I be safe in riding it for a while, that is without immediately re-re-jetting, assuming the present setup is for the muffler that's on it?  And am I wrong in thinking that an engine with a stock muffler but carbs re-jetted for the D&D will run cooler?  And that should be safe for riding for a while then, right?

I ask because I'll be doing a fair amount of out-of-town, non-motorcycle travelling soon, and will be gone about two months, and for now I have time (and $$$) to do some easy work on the bike, but rejetting I'd have a bona fide mech do and that would eat up the riding time I have before my trip.

Thanks,
Mike D.

[JLKasper]

It's probable the carbs were rejetted when the PO installed the can.  The only way to know for sure is to remove the carbs and inspect the jets.  If they're Mikuni jets, they'll have a three or four digit number on the screw portion from 122.5 (stock) to as high as 150.  If those numbers aren't on the main jet, a Dynojet aftermarket kit's been installed.  For your bike to run properly with the stock pipe, it's recommended to run a 125 or 127.5 main jet.  The stock pilot jet is a 37.5; a better replacement for any GS is a #40.

If the carb's been rejetted and you switch to the stock muffler,  your bike will run too rich.  While not doing as much damage to the engine as one that's too lean, it's still not advisable. You'll end up fouling spark plugs and leaving unburned fual deposits on your pistons and valves.

Removing the carbs and checking them yourself is not a terribly difficult task, provided you have a repair manual to guide you and a suitable place to work.  Even if you're not proficient working a motorcycle, you should be able to accomplish this in an afternoon.   If in doubt, taking it to a mechanic you trust might be well advised; especially if time is an issue.

[geekonabike]

Thanks JL.  That's exactly what I needed.  --Mike D.