after market exhaust

MAGNUM SRT8

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I am replacing the original exhaust on my '73. I bought original headpipes and brit style mufflers. I can't figure out whether or not I need a gasket where the mufflers slip on to the headpipes. If so what do they look like? If not should I use something to seal the connection? Thanks, Tim
 

Gordon

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I'm not sure of the stock O.D. of the pipe's, but Travis' post is dead on. If those are the Brit style pipe's you have, they slip fit onto 1 1/2" pipe's. If the one's you got are smaller, the reducing bushing's work very well. No gasket needed where the muffler & pipe go together. Gasket's are needed at the head where the pipe bolt's on to the engine, & only on the crossover pipe on total stock exhaust. If you have original Yamaha pipe's, there are hole's in the top & bottom of them. The stock pipe's are double wall, & the outer pipe is away from direct exhaust gas, to avoid discoloring. So, you would have to block up the hole's for a good running bike, too much air get's into the exhaust & popping is the result, esp. on decelleration.
 

dlabkeeg

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Has anyone seen these pipes at Mikesxs? Says there is a 10hp+ improvment. XS650's put out about 50hp right? A 20% power increase from headers, seems like B.S. to me.
 

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Travis

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Well they posted the dyno chart.

Looks like it's actually decreasing HP throughout most of the usable rpm range and giving a 9hp peak increase at 7,700 rpm where the stock peaked at 7,000. Anything below 3k and between 4.2-6.3k you're losing hp with that system. I'd take the stock exhaust over that if that’s the only mod you did. I'd be curious to see what it would do with a more free-flowing intake. The little note on the chart explains a lot.

I’ve always though of it like this: If just an exhaust upgrade over stock will give you 5hp and just an intake upgrade over stock will give you 5hp, doing both will usually give you more than 10. These things all work together and sometimes one component will be your limiting factor. You can’t assign hp ratings to each piece because they all have to work together. That’s why I don’t pay too much attention to manufacturer's claimed HP ratings for aftermarket parts. Plus there are a lot of things that they usually don’t tell you when they claim a certain increase. Also a lot of times you might not care about peak HP and that's usually what they rave about. You might want to increase your low or mid-range HP depending on the machine and the type of riding (driving) you do.

So thumbs up to MikesXS for actually posting a chart and giving a little bit of info on what was done. It's better than just having the 10hp claim and nothing to back it up or any other information on what was done.
 

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inxs

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- inlet valve angle and exhaust port design seem to be the main problems...manifold inserts seem to have a beneficial effect...i dont have a set but talking to those that do is interesting
 

MAGNUM SRT8

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Thank you fella's. My next question will be regarding rejetting. I'm told to run it a couple hundred miles then check the plugs. Any chance I won't have to play with the carb's?
 

Travis

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You shouldn't be too far off depending how free-flowing those brit style mufflers are. You might just have to play with the mixture screws a little and raise the needles a notch.
 

Gordon

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DLAB, I got that set-up on my '80 G model. They work great. I am also using the taper tip muffler. The only 'problem' I had was that when all bolted up, the pipe's were up really close to the brake pedal. Solution was to 'bend' the pipe downward with a flat bar. Like a carpenter uses, the flat bar did not damage the pipe's like a round one would. Real easy install,too. About 30 minute's. I used a piece of mild steel for the muffler bracket, as the chrome one was way too brittle. Snapped right off after about 50 mile's. The mild steel one has been on for about 3500 mile's now. The first set of pipe's I got were the Ascot style, with the taper tip muff's. I like the 2-1 style much better, no more dragging when cornering.And they sound nice, not too loud, but loud enough for the cage driver's to hear ya. The sound is alot different than with the 2-2 pipe set-up. I'll post up some pic's when the camera is back.
As far as your carb's go, you might have to go down on the needle setting, & maybe 1 size up on the main. The pilot jet should be fine. Of course, every engine is different, but after a little riding, if you get problem's, post them here. You might run into some 'hesitation' or misfire just off idle up to about 2500-3000 rpm. If you do, that's when to start moving the needle setting. The middle of the needle is the stock setting. Moving the e clip down rich-en's the mix off idle. So moving the e clip up leans it. Riding is the only way to determine any problems, of course, but my BS34 carbs are real close to stock. If I remember correctly, 42.5 on the pilot,135 on the main's, & XS John's needles. He is on another site, but his needle's are worth there weight in gold. Not sure if he make's them for your carbs. Anyway, try this stuff first, then if you still got problem's , let us know. Happy Riding!!! Gordo
 
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Travis

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As far as your carb's go, you might have to go down on the needle setting, & maybe 1 size up on the main.

You're saying move the clip down one to raise the needle aren't you? I always refer to moving the needle since some don't have clips and you can only raise the needle by adding shims (washers) under the clips. So if you tell someone with those style of needles to "go down on the needle setting" they won't know that you mean raise the needle. If you refer the needle position and not the clip position, raising the needle or increasing a jet size both mean richer and it's easier to think about. Then again when someone pulls an adjustable needle out and isn't thinking (and someone on the internet told them to raise the needle) they might raise the clip and effectively lower the needle. Oh well, I guess it's just best to try to be as clear as possible.
 

Los D

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DLAB, I got that set-up on my '80 G model. They work great. I am also using the taper tip muffler. The only 'problem' I had was that when all bolted up, the pipe's were up really close to the brake pedal. Solution was to 'bend' the pipe downward with a flat bar. Like a carpenter uses, the flat bar did not damage the pipe's like a round one would. Real easy install,too. About 30 minute's. I used a piece of mild steel for the muffler bracket, as the chrome one was way too brittle. Snapped right off after about 50 mile's. The mild steel one has been on for about 3500 mile's now. The first set of pipe's I got were the Ascot style, with the taper tip muff's. I like the 2-1 style much better, no more dragging when cornering.And they sound nice, not too loud, but loud enough for the cage driver's to hear ya. The sound is alot different than with the 2-2 pipe set-up. I'll post up some pic's when the camera is back.
As far as your carb's go, you might have to go down on the needle setting, & maybe 1 size up on the main. The pilot jet should be fine. Of course, every engine is different, but after a little riding, if you get problem's, post them here. You might run into some 'hesitation' or misfire just off idle up to about 2500-3000 rpm. If you do, that's when to start moving the needle setting. The middle of the needle is the stock setting. Moving the e clip down rich-en's the mix off idle. So moving the e clip up leans it. Riding is the only way to determine any problems, of course, but my BS34 carbs are real close to stock. If I remember correctly, 42.5 on the pilot,135 on the main's, & XS John's needles. He is on another site, but his needle's are worth there weight in gold. Not sure if he make's them for your carbs. Anyway, try this stuff first, then if you still got problem's , let us know. Happy Riding!!! Gordo

Hey man, last night we were putting on dual taper tip mufflers and ran into the problem of the right mounting right under the brake pedal. The left side is fine, but I'm trying to come up with a solution to apply to both sides, so they don't look all wonky. If the headpipes were 3" longer they would sit perfect! Thought about putting on some kind of extension, but that will look cheesy as hell. Suggestions?
 

pamcopete

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If your stock headers are double walled, the functional pipe is inside the outer pipe, so if you are going to use the stock headers with an after market muffler, you need an adapter that will connect the muffler to the smaller inner pipe. And, yes...the outer pipes do have drain holes in them, so if you just clamp the muffler to the outer pipe, the exhaust will leak out of the drain holes.

Here is a pic of the inner pipe:

inner.jpg


The outer pipe may also leak at the head flange as well. The outer pipes were not designed to flow any exhaust, so there is no guarantee that they are gas tight from end to end.


I used this adapter on my '81/H:

adapter.jpg


This is a 1 1/2 X 1 3/8" adapter available at most auto supply stores, #548520. The small end will fit tightly around the outside of the inner pipe. Clamp the muffler around the large end. There is no way to clamp the small end around the inner pipe, but it fits real tight, so you can either wait for the carbon buildup to seal it or apply some Permatex muffler sealer.

The small end is completely hidden inside the header, the big end is completely hidden inside the muffler.

muffler2.jpg


This is what it looks like when installed.

muffler.jpg
 
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Los D

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I could swear that my headpipe is single walled, I was actually a little confused when looking at it because I expected a double wall. I will have to go look at it again tonight to see if maybe the inner pipe is just recessed a bit. Your solution is ideal though, thanks.
 
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