'80 XS1100SG Yoshimura 4-1 (?) vs Stock 4-2

[coasttocoast]

Hey there - great site guys!

Found this lovely '80 XS1100 SG on Craigslist, http://s820.photobucket.com/albums/z...ven%20Special/pulled the trigger and am thus far very happy.

I'd like to go back to stock 4-2 exhaust in-place of the high heat-painted 4-1 at current. I picked up a great set on ebay recently and am saving the job for a winter project.

My question - will I have to re-set anything re; carbs, jets, engine with the change back to stock? Also, can anyone please give me a basic plus/minus in the conversion? Any obvious diff's with speed/sound/performance/rpm's etc, etc.

Thanks for your time!
XS Newbie on Paradise Island, British Columbia

[Rasputin]

If that is indeed a Yoshi pipe the you want to talk to T99ford. He bought my old yoshi pipe and had to rejet up a few notches I believe. There are a few similarities to my old pipes but they look a bit different for some reason. Maybe I am just getting blind in my old age too. Anyways I would PM him and ask what he has found out about the Yoshi's before I did anything else. I never ran them myself so I am not knowledgeable in that area.

[TopCatGr58]

Hey there Coast,

What pipes did you recently get...the actual OEM 4-2's with the OEM crossover....OR...did you pick up a set of generic 4-2's, like MAC or Jardine??

IF TRUE OEM, then IF the PO jetted for the pipes....put larger in, then you possibly would need to rejet back closer to stock. Unless you have a set of those bastardized crossover early 80's carbs, then your stock jetting should be 42.5 pilots and 110 mains.

The later model XS11's were jetted more lean to meet EPA standards. I have an 81, and in stock configuration...OEM Airbox....I added some cheap RC Engineering(JW Whitney) at the time shortly after I got the bike....to "try" to provide more performance....thinking that the OEM's would be too restrictive.

I did NOT rejet larger....didn't know anywhere near what I know now....but it ran fine, never burned any holes in pistons, etc.! But when I went with my topend rebuild...Indy filters and my same 4-1 pipes, I upped my jets to 117.5 mains....my later dyno run showed that I could possibly go up another size. I stayed with the 42.5 pilots...due to problems removing old ones , and just turn the screws out a few more turns. Works fine, great plug color, power to redline, etc..

Depending on what kind of performance you want from the bike will also depend on whether you may want to keep the Yoshi's, vs. the 4-2's....depending on if they are true OEM, or aftermarket! The Yoshi's and most 4-1 pipes will move the power band a bit higher in the rpm range, but they don't provide as much back pressure, so the can cause the low rpm response to be a bit less.

The OEM's were engineered very well to provide the most from both low end, midrange, and to a lesser extent the upper rpms, since most regular riders tended to run the lower/mid ranges much more than the upper ranges...YMMV!

SO...if you want good low rpm response, good roll on power in mid range, then the 4-2's are probably going to be the better choice, but if you like to ring out the power with the WOT throttle type runs, then you may want to keep the Yoshi's!?

The jetting guide is in the MISC forum. With stock intake/airbox, you may not need more than stock jetting....so you'll need to find out what you have in the carbs now....and also which pipes you really want to use.

HTH!?
T.C.

[DGXSER]

Just to be certain, since your a new owner, check your petcocks for which direction is off. You want to turn them off and not to prime when you get off the bike. Either, you were turning them to prime, or someone swapped the petcocks from right to left on you. No big deal really, just as long as you keep it all straight.

[coasttocoast]

thanks Rasputin - you might be right, the pipes could be something else and I in my limited experience am limited to a google search.

I guess the key would be; suppose I do the switch back to stock 4-2, what/if any mod's/changes should I expect?

[coasttocoast]

ok, lots to assimilate, here goes; I did purchase the OEM 4-2's with the OEM crossover.

As I am a "casual" rider with nice days in mind and not Bonneville record-setting performances with the throttle - I appreciate your knowledge fellas - as a "jack of all, master of none" - please go slow so I can somewhat translate to my mechanic!

Re; Petcocks - you are correct, they have been altered to "on and off" directions.

Great feedback - thanks!

[Rasputin]

Just a pic to show you the Yoshi marking on their pipes. Maybe this will help or confuse I am not sure, but here it is anyways.

[coasttocoast]

thanks for that Rasputin - mine doesn't have that marking. Maybe a heat paint on Jardines?

Any damage inflicted with change back to stock WITHOUT rejetting or just not-optimal performance?

Thanks again all for your feedback.

[T99Ford]

Yoshi Pipe

Rasputin is right that if it is a Yoshimura, you will be be jetted way up. I had to go up two full sizes from my Mac 4-1. Also, I would not give up this exhaust for anything. This pipe makes more useable power than any other setup I have used, including stock. I have yet to run it on the dyno for the final tune, but the power curve is much smoother through the midrange, than the 4-1, and the top end is much better. The sound is close to a sport bike howl. Here is a better shot of the Yoshi 4-1 on my bike:





Thanks Rasputin!

For an indicator, I am now at 125 mains at an altitude of 5000' and may be able to reach for more if I stay more in the top end. Stock is 115 across. Fuel mileage suffers, I am told