New Exhaust, Carb Adjustment Advise Needed

BamaBill

BamaBill

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I know this has probably been asked a jillion times, but with my limited research I didn't really find a lot. BTW, I'm more familier with Vtwins and have jetted a few from "package jet kits" such as cobra and dynojet.
What I have done is taken a saw to a perfectly fine tuned running completely stock 1982 XS400 Heratige Special. I just completely rebuilt these carbs and synchronized them to factory specs and the bike runs like a champ for the past 200 miles with the stock exhaust. Tonight I hacked the mufflers and installed a set of Emgo shorty mufflers onto the headers. Fired up the bike and she stumbles pretty bad, but once warmed up it smooths out over 3,000rpm, but it won't idle at all....... Give me some advice? Will simply adjusting the idle mixture screws clear this up? Or do I need larger pilot jets? Do you think I'm running lean or rich????????
 
I like the look and the sound is great. Not over bearing like straight pipes. Looks like they have good baffling in them, but high flow. I didn't use the reducer that came with them. I cut the stock mufflers as close to the factory weld as possible and grinded the welds that hold the short heat shield trim off. I had to grind smooth those welds and actually grinded around the pipe carefully to reduce the diameter about a mm. Then I used a 6" long piece of 1 3/4"ID exhaust pipe from the parts store and had to use a rubber hammer to force it over the header. Just temporarly I used an 1 7/8 clamp to secure the muffler onto the 1 3/4"ID pipe. I will be welding these in place before road testing it. This puts the muffler hanger bracket in place to bolt up right where the stock bracket bolted to. I'll try to post a picture soon.
 
Newbuilder, I'm planning on buying several size main jets, but what about the pilot jets? Do you think I should buy a couple of different sizes also? From the info I've found online, it looks like I just have to play with it till I'm satisfied. From looking at the diaphram and needle looks like the needle isn't adjustable. If I go up a size on the pilot, I'm not going to be able to drop the needle. Is there an aftermarket adjustable needle for our bikes? All the "package jet kits" I've ever used had adjustable needles that came with it to match up with the jets.
 
NewBuilder, check out the "garage" section, I reposted my original question there and added a picture of them mocked up on the bike. I just ordered several sizes up on the main jet and got a size bigger pilot jet.
 
Those look real nice..I'm looking at a set of Shorty'sfor like $60 for the pair trying to be as cheap as possible to fit my theme of car / bike builds....and looking into extending my exaist so they are bback by the rear tire and not under my feet

I once build a ratrod for $67
 
newbbuilder said:
Those look real nice..I'm looking at a set of Shorty'sfor like $60 for the pair trying to be as cheap as possible to fit my theme of car / bike builds....and looking into extending my exaist so they are bback by the rear tire and not under my feet

I once build a ratrod for $67
Click to expand...

Hey Newbuilder, I think you will be well pleased with the shorty's or cherrybombs. I love the sound, not too loud but has a mean growl to it. I ended up taking out the 6" pipe extension and just attaching straight to the header. I bolted the mounting strap to the lower footpeg mount bolt. The end of the pipe is right below the rear footpeg though. With the stock intake, minus the airboxes (stock filters are mounted to the stock plumbing though) I'm using stock needles, 45 pilot jets, 140 mains, screws adjusted 2.75 turns out. I'm probably a little rich but it runs great. I'm used to big cruisers, my other bike is a VTX1300 with Vance & Hines exhaust. I never thought this small 400 would sound like a beast, I just love the sound these twins make.:cool:
 
Kool mine just came in the mail..I'm gonna hang mine a little farther back so I gotta get a little bit of pipe but very excited to hear it..and mine have removable baffles..very interesting
 
My emgos look good..not welded up and still trying to find a new carb so I don't know the sound yet but I'm happy with the price and look..also has removable baffles which is nice
 

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