1st post: just acquired XS400

[GuyS]

I haven’t got the point of startup yet. I had a discouraging set back last week. I put on a new OEM sprocket (back and front), a new chain. Then and went to torque up the axle nut to 75lbs…..and it stripped! I suspect it had not been torqued properly in the past. So now I’m waiting for a new axle to arrive (I wanted to have the wheel back on before I tried to start it), ……otherwise I would have run the engine before now. I replaced my pilot jets from a kit from MikeXS. They are tiny, tiny little holes and yet are responsible for so much up to about 20-30% throttle. I tore my carbs completely apart and ultrasonically cleaned them. But until I start the engine and run it down the road, I guess I won’t know if it’s going to run right or not. I certainly will be posting my results when the bikes done. I’ve replaced so much so far! Keep us posted on your success it’s so helpful to know what we’re up against and what solutions we’ve discovered along the way. I going to make a manometer in the next few days and I’ll post my build.

 

[Lemonysword]

Hope your startup went well.

I eventually found out that my issues were caused by low fuel when I finally sputtered and died on the side of the road. I had only gone about 65 or so miles on the bike since I had fueled it up, but I do remember that I had filled it up with the kickstand instead of the center stand so maybe I never had a full tank of gas. Given the 60MPG EPA rating of this bike, I was anticipating going at least 150 miles before worrying about out fuel.

I've been riding it daily, yesterday I went on a country highway and made it up to 70MPH which required almost wide open throttle at about 6000+ RPM. The bike has been running great save for three small issues that I have been living with rather than dealing with:

1: RPM spikes on startup with the choke on. It will go up to 2000, sometimes as high as 3000 RPM with the choke on, then slowly spool down. Without the choke on it idles fine. Guessing there is an air leak somewhere, but I haven't bothered to diagnose it.

2: Sometimes from neutral, the bike will not shift into gear. A couple times I was able to shift up into 2nd and go from there, but other times it will not move either direction. Thankfully if I blip the throttle it will allow me to shift. This does not occur when shifting into gear for the first time, it occurs after 5 mins or so of riding. Not sure what would cause this and I am not interested in fucking with the clutch so I will just deal with it

3: issues with the right turn signal turning on. I spent several days where I'd have to hit the switch multiple times before the signals illuminated and sometimes even then they wouldn't. On my ride yesterday I discovered that holding the switch to the right will reliably turn the right signals on. The left operate as normal. No longer a big deal since I can actuate the right side, but I am guessing maybe my turn signal switch itself is wearing out.

 

[GuyS]

I’m not claiming to be an expert but your point #1 sounds so much like it is running lean. A vacuum leak would cause that, as would a too lean idle jet screw setting. I’ve read even opening those two idle jet screws 1/2 a turn would make a big change in the idle to 30 mph range. The higher speed range where you say “almost wide open throttle” too, sounds like a lean condition. Changing the needle jet pin ring up a ring or two might help there. That would richen the main jet circuit. Failing that, upsizing the main jet size might help. Mine bike is a DOHC Maxim. There is a round rubber access hole (see photo) over the clutch that allows you to change when the clutch engages or disengages. The attached picture shows the black rubber cover just above the shifter on my bike. The SOHC engine might not have the adjustment access in the same spot, but there must be a similar way to adjust the clutch. I started my bike a couple of days ago. It fired up right away and idled at 500! I give it throttle and no hesitation. I next need to sync the carbs and road test it.