XS360 Pilot Jet!

[nbriles2000]

I can't for the life of me find the correct pilot jets for this bike! What is in there right now is a 17.5 and I need to go up. The catch is it's the pilot jet without the little holes in it. My bike is running super lean so I'm going to go up another size in the mains (already went up 1) and one size in the pilot

 

[Recreateme]

You may also try changing your needle jet position to supplement the idle circuit with more fuel? It may just be a work around though.

 

[nbriles2000]

I thought that had more of an effect on mid rpm crusing..
My problem is when the bike warms up, the idle shoots up to around 3k rpm and most people have told me its lean in the pilot circut

 

[xschris]

Check to see if your diaphragms don't have any holes or leaks. Then make sure your idle mix screws are not broken off in the carb bodies. If all that is good how many turns out do you have your idle mix screws? Another thing to look at are there any air leaks around the butterfly seals and intake manifold boots. And as always are the carbs clean There could be a few other issues causing your problem but I would start with these. I run a set of xs360 carbs on my 400 with a 2-1 free flow exhaust and k&n filters and run the stock 17.5 pilot jet with the mix screws set at 1.5 turns out and it runs fine.

 

[nbriles2000]

Check to see if your diaphragms don't have any holes or leaks. Then make sure your idle mix screws are not broken off in the carb bodies. If all that is good how many turns out do you have your idle mix screws? Another thing to look at are there any air leaks around the butterfly seals and intake manifold boots. And as always are the carbs clean There could be a few other issues causing your problem but I would start with these. I run a set of xs360 carbs on my 400 with a 2-1 free flow exhaust and k&n filters and run the stock 17.5 pilot jet with the mix screws set at 1.5 turns out and it runs fine.

Diaphragms are brand new, mix screws are fine, the intake manifold boots are brand new. not sure about the butterfly seals... I wanna scrap that boot that holds the filters and just attach the right pods to my carbs to eliminate any chance of a leak there. I'll probably go back through and do my carbs again soon. I have my mix screws backed about 3 turns out. It seems to run fine most of the time just the idle shooting up when warm is super annoying. As of 2 days ago its been getting hard to start with choke, too...

 

[Recreateme]

The high idle could be that your throttle stop is set wrong. It should be used to set teh idle after the bike has been warmed up, if you set it when its cold you will end up turning it in to much and then when it warms up your idle will be high.

 

[nbriles2000]

I adjust that damn idle stop on a near constant basis. When its warm, it doesn basically nothing and then I have to readjust to get it started the next day

 

[xschris]

Have you synced the carbs?

 

[xschris]

You said you have new diaphragms did you use xs400 ones or xs360 ones. The lip of the 360 is thinner and different than the 400 also the length of the skirt. I don't know of anyone that makes them aftermarket for the 360. Are they N.O.S? Is the vent hole facing the engine like it should be?

 

[xschris]

Some pics of a xs360 and (77-79) xs400 carb body. The 360 is on the left.

 

[nbriles2000]

http://jbmindustries.com/Yamaha650.html

These are the diaphragms I have. I was told in a previous thread that they were the best ones to replace the poem's..

 

[xschris]

Did you state you had xs360 carbs? The xs360 carbs are a bs34 but nothing like the later ones. There where so few made in the U.S. (about 1600) that most people don't realize they even exist. I love em on my 400. Diaphragms are almost impossible to find. The only other carbs that I know of that used them was the 76-77 xs750's

 

[nbriles2000]

So here is the thread where I was originally assisted in the whole diaphragm thing...
http://www.xs400.com/forum/showthread.php?t=8428

and about the carb sync thing... I tried. got the left so the needle was steady on the left side but nothing I could do would make the right side stop going crazy. I figured it was because i couldn't have the vacuum line connected to that carb from the tank and kinda gave up. Shame on me, I know =/

 

[xschris]

What did you use to sync your carbs? You need to hook both the vacuum barbs up to sync them. Search manometer and do it that way. Air gauges don't work well You need to put what bike you have in your signature or people will just assume you have an xs400

 

[nbriles2000]

What did you use to sync your carbs? You need to hook both the vacuum barbs up to sync them. Search manometer and do it that way. Air gauges don't work well You need to put what bike you have in your signature or people will just assume you have an xs400

I used vacuum gauges. Hooked em up to both vacuum barbs and set the petcock to prime. I guess it just doesn't make sense to me how the right will preform normally without the vacuum line coming from the tank

 

[xschris]

Make yourself a manometer and do it that way. The petcock has nothing to do with syncing, just gas for the carbs. http://www.xs400.com/forum/showthread.php?t=6050&highlight=manometer

 

[jonjkim12]

hey xschris,

trying to buy new carb holder/intake manifold/carb boots, i suspect a leak in mine, would an xs400 carb boot fit an xs360?

i can't seem to find anything about it, so i'm assuming yes.

 

[BBS360]

I'm sure I've seen it on here too, but they'll fit:
http://yamahaclub.com/forums/topic/7968-xs360-carb-joints/
http://yamahaclub.com/forums/topic/23424-1976-xs360-carb-intake-boots/
http://www.xs400.com/forum/showthread.php?t=9989

Now I'm tempted to buy a set myself. The exteriors of mine are covered in cracks but the inside still look perfectly smooth.

 

[jonjkim12]

Thanks BBS!,

ya these are annoying cause they're >$20, so i've been procrastinating, Figured i might as well though.