robbiecampbellsoup
XS400 Enthusiast
Hi everyone,
I've recently gotten into the world of owning a bike (in general, this is my first bike) and owning an XS400. A 1983 Maxim to be specific. She's a lovely color - note the bluing on the Mac 2-in-1 exhaust the PO put on - this means it's running lean?
So far this is what I've done;
1. Tried to ride the bike home, but it died on me, kept loosing spark, stay running below 2500 RPM, would stall out when I used any lights etc.
I ended up partially solving this by determining that the battery was old, and the charging circuit was not working at all. I ended up repairing the old stator (all the connections were corroded off underneath the stator cover) and re-doing the wiring harness - and voila, the charging system is back to life. There is still something RPM related happening below 2500 though.
2. I changed the oil. It was pretty clean, but a bit low. I've not determined if the oil is making it's way up to the cam area, I still need to do this. I'm a bit scared as the bike kind of sounds like a sewing machine, between my crotch, which is unnerving.
3. I tried adjusting the idle mix screw to help with the low power at <2500 RPM - I first turned the screw all the way in, then set it to 2 turns out. Bike didn't want to start well, and it felt the same. Then 3 Turns, bike still didn't want to start very well (I had to give it throttle while turning the engine over, without enrichment as it was already warm). I then ended up going for a 40km ride with a friend, and found out some other things.
a) The power below 2500 RPM is heinously bad. Trying to accelerate up a hill, I couldnt let the motor drop below 2500, else i had to downshift. It just bogs down completely.
b) When Idling, it sits around 1200 RPM, if I blip the throttle, it drops down to 800-1000 and almost sounds like it will die. My strategy for start/stop has been to pre-advance the throttle a bit before the light changes, rev up to ~3000rpm and let the clutch out slowly then.
c) Highway driving around 100km/h had the bike around 5-6k RPM, it had pretty poor power above 6K RPM. Entering on the on-ramp, it would pull nicely between 3000 RPM and 6000 RPM, and then taper off. I never had it above 8000 RPM.
d) Throttle position does not matter if the bike is below 2500 RPM - it always bogs down.
What I'm planning to do in the near future:
-Sync the carburetors
-Adjust/inspect the valve tappet clearance (this is shimming correct?)
-Do a throttle map thingy where I go up a hill at full throttle 3rd gear, stop and check plugs at the top, rinse and repeat at 3/4, 1/2, 1/4 and idling - I was told this will give me some indication as to whether the engine is running lean/rich at these throttle positions, which can then tell me if my jetting is off/on etc.
-Adjust the idle mixture screw - I don't know how to do this properly
Can anyone offer any advice on the order in which to do these? Or whether I'm even pointing in the right direction??
Thanks so much!
-Robbie
I've recently gotten into the world of owning a bike (in general, this is my first bike) and owning an XS400. A 1983 Maxim to be specific. She's a lovely color - note the bluing on the Mac 2-in-1 exhaust the PO put on - this means it's running lean?
So far this is what I've done;
1. Tried to ride the bike home, but it died on me, kept loosing spark, stay running below 2500 RPM, would stall out when I used any lights etc.
I ended up partially solving this by determining that the battery was old, and the charging circuit was not working at all. I ended up repairing the old stator (all the connections were corroded off underneath the stator cover) and re-doing the wiring harness - and voila, the charging system is back to life. There is still something RPM related happening below 2500 though.
2. I changed the oil. It was pretty clean, but a bit low. I've not determined if the oil is making it's way up to the cam area, I still need to do this. I'm a bit scared as the bike kind of sounds like a sewing machine, between my crotch, which is unnerving.
3. I tried adjusting the idle mix screw to help with the low power at <2500 RPM - I first turned the screw all the way in, then set it to 2 turns out. Bike didn't want to start well, and it felt the same. Then 3 Turns, bike still didn't want to start very well (I had to give it throttle while turning the engine over, without enrichment as it was already warm). I then ended up going for a 40km ride with a friend, and found out some other things.
a) The power below 2500 RPM is heinously bad. Trying to accelerate up a hill, I couldnt let the motor drop below 2500, else i had to downshift. It just bogs down completely.
b) When Idling, it sits around 1200 RPM, if I blip the throttle, it drops down to 800-1000 and almost sounds like it will die. My strategy for start/stop has been to pre-advance the throttle a bit before the light changes, rev up to ~3000rpm and let the clutch out slowly then.
c) Highway driving around 100km/h had the bike around 5-6k RPM, it had pretty poor power above 6K RPM. Entering on the on-ramp, it would pull nicely between 3000 RPM and 6000 RPM, and then taper off. I never had it above 8000 RPM.
d) Throttle position does not matter if the bike is below 2500 RPM - it always bogs down.
What I'm planning to do in the near future:
-Sync the carburetors
-Adjust/inspect the valve tappet clearance (this is shimming correct?)
-Do a throttle map thingy where I go up a hill at full throttle 3rd gear, stop and check plugs at the top, rinse and repeat at 3/4, 1/2, 1/4 and idling - I was told this will give me some indication as to whether the engine is running lean/rich at these throttle positions, which can then tell me if my jetting is off/on etc.
-Adjust the idle mixture screw - I don't know how to do this properly
Can anyone offer any advice on the order in which to do these? Or whether I'm even pointing in the right direction??
Thanks so much!
-Robbie
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