K&N/MAC questions......

[Chris Daniel]

I have a 1983 GS650GD that came with what I believe to be a MAC exhaust (4-1 with megaphone and non packed baffle), and UNI foam pods.

The bike runs really well bar some petcock problems that I will be solving shortly. Anyway, I really do not like the look of the UNI filters and would rather run K&N's simply because I think they look better.

Going from UNI's to K&N's, will I have to rejet?
If so, will it be a simple rejet or something highly complicated (my funds are very limited and this is my daily work ride)?

Also, I would like the bike to a bit louder.....not to the point I need ear plugs, but louder and more powerful sounding than it is right now. I pulled the baffle out of the megaphone and it basically consists of 2 round discs, one smaller and one larger, at either end and 2 pieces of pipe overlapping each other between them (the incoming pipe is flattened almost in half at the point that it overlaps the outgoing pipe).

Is there a way to modify this baffle for a louder more powerful sound without screwing up the jetting?
Can I simply cut everything out except the larger disc that you see when looking at the mega from the rear...again without screwing up the jetting?
Can I drill holes, put larger pipe in place of the small pipe that is in the baffle now, basically is there anything I can do that will not adversly affect the jetting?

I really dont mind simple jetting changes as long as it is not something that I am going to have to spend alot of money and time jacking with.

I am not trying to get huge power gains or make a race bike out of it........just kind of trying to get it to the way I want it....now what I mean?

Anyway, any help would be very much appreciated.

Thank you.

[Mr. Jiggles]

Was your bike ever re-jetted after the addition of pods and exhaust?

[Chris Daniel]

I honestly do not know if it has been rejetted, however, whether it is stock jetting or not it is running very well.......

I base this on the fact that when I changed plugs they all looked perfect (light chocolate brown) except for the #1 which was fouled. The fouling of the plug I believe happened when the previous owner ran it with the choke on not knowing that it was on....he said it was running really rich but couldnt figure it out.

He bought it mechanically the same as it is now......all he did was a few cosmetic changes and never changed anything but the oil and filter.

Anyway, the point is.........seemingly it is jetted (stock or otherwise) very close, if not perfectly on, where it needs to be.

[Chris Daniel]

Anyone?

[Pete's GS]

Although K&N's are considered to be better than Uni's, if it's running fine with the Uni's and its present jetting it will probably run fine with the K&Ns. The K&Ns might flow more air but probably not enough more than the Uni's to make a difference. Anyway, you'll know when you get there.

[andyjohnson]

I switched from the stock set up to Uni pods like you, and didn't have to re-jet or adjust the carbs, which means that they flow about as well as the stock filter and airbox right? From what I hear though, the K&N pods will flow alot more air than the UNI's, and usually require bigger jets to one degree or another. I'm not trying to put you off of the K&N's, it's just that since the UNI's didn't require rejetting on mine, I would wager that you've still got stock jets, which will probably not be able to keep up with all the extra air from the K&N.

On another point, the previous owner of my bike made the exhaust louder by drilling 3, 1/4"(aprox) holes into the plate at the back of the baffles. It seems like this would not affect the escaping exhaust gas too much, and so you could probably do it without having to make changes to the carb. Try doing a search for threads in the forum about this procedure, it could be a cheap and easy way to give you a fuller sound.

Good Luck

[gspaul]

If you put K&N on you will have to rejet, if you free up the exaust flow to get more noise you will have to rejet.

[wayne cooper]

Just curious, is the bike too quiet with or without helmet? Had exact same pipe on the 11 and had to be careful late at night(Yoo Hoo,Officer,over here) If it is running good now you might want to leave it alone. At least consider your option-K&N, not cheap- jetting(jets, plugs,at least 2 sets) a trip to the shop to have the carbs dialed in $50-$125 depending on where you go. The real kicker is the only up side is more noise, granted if the bike is kinda out of whack all the re- tuning might get you a couple more hp. Just thought I'd show the other side of the coin as you mentioned "tight" funds.

[Anonymous]

Rejetting

with the pod filters is so freakin easy that taking it to the shop is a waste of money...........You can literally have the carbs out in change main jets and put them back in in about 40 minutes..............just a thought.........g

[Chris Daniel]

Thanks for the replys.

The guy that was going to buy my filters backed out on me, so I am just going to stick with the current set-up.

Down the road I will change them and tackle the jetting etc.

Thanks again.

[Anonymous]

Gary: I change my mains with the carbs in place. It was tricky with the philips screws in place but now that I've got Allen-Key bolts it is a lot easier to locate the screws by touch. If I was smart I would have gotten shorter than stock screws to speed things up even more! The only trick is to not push the brass pipes into the carb when threading the mains in. If you do you have to fish them out with a bolt of proper thread.

I don't know how much quicker this method is but it saves wear and tear on the boots/filters. If you've got an airbox like me it is way faster.

Cheers, Steve