Exhaust trouble.

[85goldwing]

My son and i have been working on this 1981 xs400. He wants louder pipes, I told him he has to ride behind me from now on. So we bought a pair of Shorty Megaphone Muffler 12". As he was taking the bike apart, we discovered that the mufflers were actually welded to the header pipe. So now we have a sizing issue to deal with. I am looking to not reinvent the wheel here, and think someone else has done this before us. So any feedback would be appreciated. He is off to the local car parts store to look for a adapter fitting to join the two pieces.

Thanks in advance

85goldwing

 

[xschris]

I would look for a set of headers off a pre-80 xs400. Those were non-welded slip on pipes. If your stock pipes are in great shape, even more reason to not cut them up. They are hard to find and perform very well as they where designed for the best over all performance for these bikes. A "louder" muffler will require jetting and tuning to run right and most often hurt performance at certain rpms.

 

[85goldwing]

Ok we got the exhaust issue taken care of. XSChris i appreciate your feedback about saving the stockers, but they were in pretty sorry shape after several scrapes. So we got the bike running and here is the present issue. Pod filters with 12' exhaust pipes after the headers got cut. Pipes are wrapped with heat cloth, son like s the look, I have ?s about this as the pipes are double wall to start with. Son went up 2 sizes on mains and are now at 115. pilot went to 45 and this is a single step up in size. I rode the bike and noticed that the fuel was starving in the line coming from the tank when on run, ok on pri. Bike had the carbs sinked at 1100 rpm, nice steady idle, seemingly slow throttle response when static. Riding the bike it feels like there is nothing there below 3k rpm. pops and sputters at various speeds and rpms when my lard ass is in the saddle. I know the float height is ok. Pilot get is set at 3 turns out. Open for feedback, but the fun of doing this with son is still a blast.

 

[Scorpio1963]

If its popping or back firing this usualy indicates a lean condition.Take the plugs out and show a pic of the color.They should look light tarnished colored.
I have the same bike similar exhaust setup cut off headers at the crossover pipe with a bit longer mufflers.
I believe my pilot is is 47.5

 

[85goldwing]

we did take out the plugs, they look darker then i would have thought. Not oily but for sure not a nice light color of ash, more brownish.

 

[85goldwing]

thought i would add some pics.

 

[Scorpio1963]

Search spark plug color on the forum it will show you pics and indications of problems related to the color.
BTW what kind of pod filters are you using?

 

[XSLeo]

The XS400 uses CV type carbs. These use a vacuum signal from the air flow through the carbs for slide lift.
From looking at your pics it looks like you have a K&N type tapered possibly oval pods, or a cheap knock off.
In my experence and the experence of others we have found thast type of pods create to much turbulance in the air flow through the carbs. This disrupts the vacuum signal for slide lift. This gives you poor of idle to mid range responce, flat spots.
Some of those type of pods also have a lip around the inside that prevents the pod from going on to far. This lip can block off the airvents in the bell of your carbs. These vents go to the float bowl and jets. Blocking the float bowl makes it hard for the engine to draw fuel out of the float bowl. Blocking the jet vents, the jets don't get the air they need to mix with the fuel that they deliver to the engine.
The shorter more tapered these pods the worse the effect. The longer straighter ones may be better.
Those of us that have discovered these issues use a straight foam filter. Thes provide smooth air flow in the carb, fixing the flat spots.
Leo

 

[xschris]

Main jets should be 135 as a stock size. You said they are now 115? How many turns out are you on your mix screws?

 

[85goldwing]

I looked at the main jet. it is from is a carb rebuild i bought from local yamaha shop. The main has 110 stamped into it. As for the turns out we are at 3 turns out. I also looked at the pod filters. we bought them from Mikes XS they are Part #15-0035. They do not look to be covering any air intake port on the throat of the carbs. nice clean install.

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[85goldwing]

SO tonight adventure takes us to a partial solution. Son took found the original parts from the carbs. As several of you have stated, the stock main jet is a 135. So we figured out that the parts we got from our local yamaha dealer were incorrect parts. We put the stocks mains back in, tested, bike ran way better, but still not all the way to correct. so I will order the correct jets this evening, and put them in this weekend.
Progress at last.

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