Carb intake mod

dannyTheBoat

XS400 Enthusiast
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Hey all,

I have a '82 xs400 that has been mine for about 4 months now. I am a new rider and new to wrenching and I have found a lot of good info on this forum. My bike is below. As you can see, it is a bit chopped up, but the PO did a good job with it and it runs very strong. Lately it has been dying at idle which I am pretty sure is just a dirty pilot jet given that it still runs just as strong as ever in every other condition. It's time for a carb clean I figure, and while they're off, why not do a little project.

My question starts here: I have read a lot about how the stock air box and the H-pipe are better for performance on these bikes for a number of reasons. While I'm not really willing to install an air box, I am interested in doing a custom H-pipe like the one suggested by 16VGTIDave here. The bike has the oval type pod filters and the carbs have been re-jetted and tuned to suit them. Again, the bike runs pretty damn strong already but I think a project to improve performance would be fun and rewarding.

My main question is this: will adding an H-pipe require me to re-balance and tune the carbs? I am trying to research what to expect so that I am prepared and don't cause problems.

If any of you have other recommendations that are in within the same scope I'm all ears. I'm eager to hear what all you XS experts have to add. The info on this site has already helped me a lot!

IMG_20190313_190448.jpg
 
I had those mufflers when I first got my bike going, theyre no good. They were ridiculously loud (which I liked) and the bike didnt run right. I do like your bike though :cool:

I currently use these and I like them https://www.ebay.com/i/303022118880...MIsaeP5P2P4wIVN__jBx3l1AY6EAQYByABEgKRq_D_BwE
XS360.jpg


They have a metal diverter inside that directs the exhaust into the baffle, so they do provide some back pressure. The best exhaust would be a stock one. You might be able to see that I used high temp sealant right there.

I know using the H pipe will change the look of your bike, look at my bike for reference. Im using the stock air boxes there. Currently, I am using K&N filters that were made for our bikes along with the H pipe. It cleaned up a bit but I like the air filters exposed like that. My leg is over that spot anyways.

Using the filters, I do need to get into some tuning. It starts to break up on hard throttle near redline. I dont race the bike I just take it easy mostly now so it doesnt really bother me. I will be checking the plugs after some more riding and see what that tells me.

I dont know the exact interval if there is one, but I check the balance on the carbs every time I check the valve lash. If the carbs are removed and worked on, it should be done after that as well. You can never go wrong with checking things over and over until you learn how to tell when something is not right by the way it feels and sounds, or you come to the interval.
 
Thanks @NewHavenMike that's all good info. I think I will give those slip on mufflers a shot since they aren't too pricey, and I have noticed the signs of poor performance from my current setup. How do those mufflers sound? I still want to be heard in traffic. Its good to know that I should expect to tune the carbs, which wouldn't hurt to learn anyways.

What year is you bike? I like the tank a lot and I have been thinking about changing my tank to get a slimmer profile.
 
Oh trust me, youll be alright with the tapered pipes if you want to be heard.. a nice snap of the throttle will send a tingle down down your spine lol

My bike wears original paint on the tank and fender. The color was available for model year 1976 as my bike was originally 360cc. Transmission blew in the 360 and I had to use my spare 400 block.
 
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