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I just put an after market 4 into 2 exhaust system on my 11E and research says I need to increase my mains to 140s. Seems I just read I need Large Round mains. What is the diff?
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Gunnery Sergeant, USMC (Retired), (A gung ho, lifer, Devil Dog) Semper Fidelis
XS1100E, 11.5" XV1100 shocks, "no name" 4 into 2 headers and turn out mufflers, stock air box, 140 mains, spade type fuse block, volt meter, LED conversion on running/turn/brake/tail lights, aux front driving and running light bar, 850 FD swap, Chrysler electronic VR. Ugly as a monkey's butt - runs like a scalded ape (WHEN IT RUNS
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The diameter of the head/screw pitch, and the orifice of the jet.1979 XS1100F
2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights. -
Only difference between large round and the small round main jets is the size of the head on the jet. For our stock carbs the main jets are of the large round type.
The threads and the jet orifice are the same for the same numbered jet.Nathan
KD9ARL
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1978 XS1100E
K&N Filter
#45 pilot Jet, #137.5 Main Jet
OEM Exhaust
ATK Fork Brace
LED Dash lights
Ammeter, Oil Pressure, Oil Temp, and Volt Meters
Green Monster Coils
SS Brake Lines
Vision 550 Auto Tensioner
In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.
Theodore RooseveltComment
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Hey Clyde,Originally posted by Clyde K. View Post
The jetting guide is just that, a guide, not written in stone. The earlier bikes were jetted a bit richer, and got leaner in the later years with the EPA standards. SO....stock your mains are 137.5. Before you go changing jets, put in some new plugs, and ride the bike for a while, see how it behaves in the TOP END rpm range, and then do a throttle chop technique to see what your plugs show. If you have a little color/light tan or such, and no sensation of running out of power in the top end, then you may not really need to rejet at all.
T.C.T. C. Gresham
81SH "Godzilla" . . .1179cc super-rat.
79SF "The Teacher" . . .basket case!
History shows again and again,
How nature points out the folly of men!Comment
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I've fitted several 4 into 1's and two 4 into 2's. In all cases, I never felt the need to re-jet. It's only advice and probably more of a disclaimer just in case there's a faint possibility of it affecting carburetion. Personally, I'd fit the system, ride the bike and see how it feels. If there is no noticeable deterioration in performance, I'd just run it! Maybe do the throttle chop and check the plugs but I wouldn't be unduly concerned re jetting if there is obviously nothing amiss.....IMO....XS1100F 1980 European model. Standard. Dyna coils. Iridium plugs. XS750 final drive (sometimes). Micron fork brace. Progressive front springs. Geezer regulator/rectifier. Stainless 4 into 2 exhaust. Auto CCT (Venturer 1300) SOLD. New project now on the go. 1980 European model.Comment
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Leave jetting as is for a baseline for plug readings BEFORE any re-jetting Clyde
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81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.Comment
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