xscafe
XS400 Member
I'm looking for a place to get new jets for my 78 xs400. I'm going to run pods, open exhaust, and advance the timing as much as I can. I need a place that has a jet calculator and has all the jets I need.
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Jets?
- Thread starter xscafe
- Start date
Wow. Okay, I'll waste a couple minutes replying even though these topics have been discussed many times here. The search function in the top left of the page works well.
- There is no such thing as a jet calculator. Only a guesstimate chart that might get the jets sized close enough to get the bike running. Proper tuning requires testing and tuning. There are no shortcuts.
- Open pipes will cost you power and cause poor running. That is a statement of fact.
- Pod filters will cause tuning and running problems unless the stock "H-Pipe" is kept or velocity stacks are fabricated. CV carbs are sensitive to proper airflow.
- How are you going to know how much you can advance the ignition timing before doing engine damage? Or do you just intend to adjust and ride without consideration?
Search YouTube for Ichiban Moto for further info.
- There is no such thing as a jet calculator. Only a guesstimate chart that might get the jets sized close enough to get the bike running. Proper tuning requires testing and tuning. There are no shortcuts.
- Open pipes will cost you power and cause poor running. That is a statement of fact.
- Pod filters will cause tuning and running problems unless the stock "H-Pipe" is kept or velocity stacks are fabricated. CV carbs are sensitive to proper airflow.
- How are you going to know how much you can advance the ignition timing before doing engine damage? Or do you just intend to adjust and ride without consideration?
Search YouTube for Ichiban Moto for further info.
xscafe
XS400 Member
I've spent the last few days wasting my time searching the forum for the answer I need but nothing really helps.
I know that a chart can only get you close. This is not my first rodeo. This is however my first time working with a Yamaha. I'm used to working on Vtwin Hondas. I have a website that has a very accurate 'calculator' that is spot on every time for my Hondas, but they don't offer mikuni jets.
By open exhaust I mean that I will have a free flowing muffler with a pretty short 2-1 exhaust.
The pods that I run come with stacks and the pods go over then end of the stack just to make sure I'm keeping big stuff out.
I don't know how much I can advance it. That's something I'm still trying to research. The only thing I can find is how to set base time. It's going to be tricky because it only has a base tuning mark.
I know that a chart can only get you close. This is not my first rodeo. This is however my first time working with a Yamaha. I'm used to working on Vtwin Hondas. I have a website that has a very accurate 'calculator' that is spot on every time for my Hondas, but they don't offer mikuni jets.
By open exhaust I mean that I will have a free flowing muffler with a pretty short 2-1 exhaust.
The pods that I run come with stacks and the pods go over then end of the stack just to make sure I'm keeping big stuff out.
I don't know how much I can advance it. That's something I'm still trying to research. The only thing I can find is how to set base time. It's going to be tricky because it only has a base tuning mark.
Hi xscafe,
Welcome to the site! I also don't know of a calculator for jetting for the XS400. I would pull your carbs apart and see what's in there and then buy the next size up pilots and the next couple of sizes for mains and go from there. I haven't jetted a bike in a while, but I seem to always go too big and then come back down. I always think I'm going to need more fuel than I actually do, so now I've learned to just go up a size or two and start there. If anyone comes up with a good jetting "baseline" chart that would be great. Or perhaps it's already out there and I just haven't looked?
As far a place to get jetting, there is always http://www.bikebandit.com and http://www.jetsrus.com
Good luck!
Welcome to the site! I also don't know of a calculator for jetting for the XS400. I would pull your carbs apart and see what's in there and then buy the next size up pilots and the next couple of sizes for mains and go from there. I haven't jetted a bike in a while, but I seem to always go too big and then come back down. I always think I'm going to need more fuel than I actually do, so now I've learned to just go up a size or two and start there. If anyone comes up with a good jetting "baseline" chart that would be great. Or perhaps it's already out there and I just haven't looked?
As far a place to get jetting, there is always http://www.bikebandit.com and http://www.jetsrus.com
Good luck!
xscafe
XS400 Member
I appreciate the helpful reply Travis. Right now I'm in a toss up. I'm either going to make a 2-1 intake and use a Honda carb, or ins with the duals. From what I read one cyl will run lean on single carb. If I can verify that then I will stick with the stock carbs. If I do that I will make a stainless version of the intake ducts so I can still have the H pipe but now have old cracked rubber.
A whole new can of worms there with a 2-1 intake and a Honda carb! Keep us posted on your progress!
xscafe
XS400 Member
Ya. Lol. The only reason I would do that it because I have a space one, and parts are really cheap and easy to get.
Single carb conversions have been done before. Those who've done them always fail to report on the long them results, past the first week or so...
180 degree twins do not work well with single carbs. If they did, the factory would have saved the expense of the "extra" carb. Pulse tuning and other things I don't fully understand are the reasons given.
180 degree twins do not work well with single carbs. If they did, the factory would have saved the expense of the "extra" carb. Pulse tuning and other things I don't fully understand are the reasons given.
xscafe
XS400 Member
That's pretty much the conclusion I came to. I'm just going to stick with duals. I'll make a new inlet pipe and put the filters over the valve cover.
Check out this album. I have made "stacks" to mount the filters to and have a bunch of pics. There was also a short thread on these. http://www.xs400.com/forum/showthread.php?t=12406
Might give you some ideas.
Might give you some ideas.
xscafe
XS400 Member
Ok, I pulled it apart. It has 170 mains and 42.5 pilots.
Where is a good place to get some jets? I cant find anything by model so I'm not 100% sure.
Thanks in advance.
Where is a good place to get some jets? I cant find anything by model so I'm not 100% sure.
Thanks in advance.
170 main jets sound very large to me. There are genuine Mikuni jets, and copies. The copies are obviously less expensive. MikesXS carries copies. Some shops and dealerships carry genuine jets. Large round Mikuni jets are used in many carbs/bikes and are not brand or model specific. I've never bought jets online, so I can't offer any other suggestions.
xscafe
XS400 Member
It sounded big to me too. I bought the bike from my sister who bought it from a friend when she lived in North Dakota. As far as I know she brought it here and never road it. Someone has been in them before but I don't know how they jetted them. I got it running before I did anything but it wouldn't idle on its own and backfired through the filters when you revved it. They were gummed up too. So I think before I do anything I'll run it as is and tune it based on how the current jets act. Should be fun!
The 78 had a 170 air jet that is the mouth of the carb. The main should be a 137.5 for a stock 78. That one is at the end of the needle jet inside the carb.http://www.xs400.com/threads/stupid-air-jet.13902/ This thread has the site where to get real mikuni jets. This is the site. http://www.pjmotorsports.com/mikuni-jets.html
MrStubb
XS400 Addict
I haven't gotten my kit yet but I've seen good reviews about 6sigma jet kits. You give them basic info about your application & they will select jets for you. Info such as Exhaust system Air filters and even the basic elevation where you are. Seems like voodoo to me .
MrStubb
XS400 Addict
CRAP!!!!!! Oh well it can't be any worse than I have now!! Wish I'd seen this early yesterday before I spent $45.00.
Wow! $45US would buy a broad range of jets and a nice storage box for them...
Just wanted to say I ordered through jetrus and had good service.
Great option for US buyers.
By the time the shipping, conversion, and the import fee were added up my wallet was feeling a little light. Might check other options next time but that shouldn't reflect poorly on JetsRUs.
Very quick email responses, quick to ship, well packed, and exactly what was ordered.
