gs650E - exhaust question (airbox too)

[upb4dawn]

I've just started my second gs650 project. The first was an L that was actually my daughter's bike. It came w/ pods and a drilled exhaust, ran pretty awful, and I went down the rabbit hole of jetting challenges, much to do before getting it right (or even acceptable). But, I had so much fun w/ it, and riding it afterward, I decided to get something similar as a winter project and future "county line" rider.

This one's an '82 650E, in stock trim (except the air-box top is missing, and there's a Uni-style filter in it). It's got 12K miles, good compression across all 4, and seems to be a good base for a project. It starts and runs smoothly, and pulls very well (more later).

The exhaust is intact, not rusted through or drilled out or anything, but surely not pretty, and I'm considering a 4/1 system. I plan to keep the stock air-box/intake setup because I've become convinced that going the 'pod' way screws up too much of the engineering that went into developing this setup. The other option would be to have this one ceramic coated.

Is there wisdom out there about the relative merits of a 4/1 setup? I understand that some re-jetting will be called for, but hope/expect it to be simpler than the 'hide and seek' I went through on the first one. Frankly, the bike's fast enough for me as it is, and I'm not determined to make it louder, the aim would be more for appearance sake.
Thoughts and suggestions, please.

As for the 'more later' part - the bike pulls like crazy up until about 8K, and then falls flat. Would the missing air-box cover and foam filter be suspect in that regard? I'd rather not buy a whole air-box just for the lid.. & am wondering about fabbing one up if it's the answer. Pulling the choke at this point does not seem to change things.
Thoughts on this issue requested as well.

I'm not able to test-ride it lots and do plug chops for a while, as it has the original tires (very cracked) and I've got it apart to do tires & wheel bearings and refinish the wheels. This should keep me preoccupied for a while. I just wanted to start the info search so I can be considering my options while I work on it.

Thanks in advance,
Doug VP
Oregon USA

PS: I've got an airbox cover coming, and a K&N filter. Best to get it close to stock as a starting point.
Sill interested in knowing anyone's experience w/ a 4/1 exhaust (seems Mac is the only ones available now) & KN in stock airbox.
Thanks again.
DVP

 

[High Lord]

gidday, My GS650e came with a 4-1, locally made, I think off a gs550 but stretched out a little. It ran fine even without rejet, stock everything. T'was all good till 4 years of header wrap turned it into a pile of rust coloured flakes...

 

[tom203]

If you keep the stock airbox/ filter setup, a 4 in 1 probably wouldn't require much jetting fun.
the stuff about running well till 8000 might mean engine is gasping for air.... over oiled filter? one vacuum diaphragm not lifting?

 

[tkent02]

You can make a temporary test air box lid out of plastic or tape or something. See if it has any effect on how it runs. My guess would be it's too lean to run at all at that RPM, which means it's lean enough to damage the pistons and valves the rest of the time, but without doing any testing it's just a guess.

 

[Steve]

I'm going to agree with Tom (both of them) on this one. Suzuki did a pretty good job of designing the exhaust system, a 4-into-1 header isn't going to flow that much more, unless you are running open megaphone.

Easy enough to tape over the top of the airbox for a quick check. At worst, might have to bump up the mains a couple of sizes.

.

 

[Nessism]

That bike looks good in the photo. Keep it stone stock and you will never have to question whether or not the jetting is correct.

 

[upb4dawn]

Thanks, Ed, Steve, Tom et al.
FYI- I've got an airbox from a salvage yard coming in the mail, for the lid. Will use a K&N filter in the stock airbox, hope that doesn't mess things up. (thoughts? It didn't affect my other bikes - BMW, Guzzi - at all).
As for the exhaust, I'm pretty sure I'll keep the stock system unmolested, and may have it ceramic coated for looks if I get the urge.
It's a nice bike, only 12K miles. Was pretty crusty as it had lived near the coast, am cleaning it up and redoing brakes, lines, tires, bearings, etc. Tires are original and very cracked, new ones (Avons) coming. Charging system good, all electrics work except horn (switch I think). Once its on the road and running as it should, I'll dive into the cosmetics more. Winter project.
Doug

 

[Nessism]

You need the lid or you will have to rejet the carbs.

 

[upb4dawn]

Yep, one's on the way.
Thanks

 

[Steve]

Will use a K&N filter in the stock airbox, hope that doesn't mess things up. (thoughts? It didn't affect my other bikes - BMW, Guzzi - at all).

K&N in the stock airbox should be just fine. That is the setup I have in 3 of the 4 GSes here.

As for the exhaust, I'm pretty sure I'll keep the stock system unmolested, and may have it ceramic coated for looks if I get the urge.

If the pipes look as good as they appear in that picture, you might have a chat with your ceramic coater to see if they will just coat the header pipes and leave the shiny chrome on the mufflers. Cowboyup had his entire exhaust system ceramic coated. It looks a lot better than it used to (was a bit rusty and/or discolored), but lacks the 'pop' of nice shiny chrome on the mufflers. My son and I have 4-into-1 headers on our bikes (click links in sig to see), just the headers are coated, the mufflers are still chrome. I have a set of replacement pipes for my wifes bike. I have already talked to the coater, it will be no problem to do just the header pipes.

.

 

[upb4dawn]

Thanks, Steve.
Just the kind of info I need. The pictures are deceivingly unclear - the mufflers do have some shine but have several surface rust spots and lots of scratches. I've tried most of my basket of tricks to improve and have not succeeded. This won't be a show bike, but I'm counting on making it look rather sharp, and so am looking at the options.
Doug