SuperMoto Junkie banner

1 - 20 of 21 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Hello all, my 400sm is stalling whenever i pull the clutch to coast, but only at above around 40 mph in 3rd, 4th, and 5th gear. The bike starts and idles perfectly, and has full power while accelerating.

Not sure where to begin with this issue. All theories welcomed.
Thanks in advance for any help!
 

·
Registered
Joined
·
5,212 Posts
Check ur vacuum/vent lines under the tank. Pull them off and blow them out. Does the bike do it all the time or random? Mods done to the bike? Does it sputter at all past 40?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #3 (Edited)
Check ur vacuum/vent lines under the tank. Pull them off and blow them out. Does the bike do it all the time or random? Mods done to the bike? Does it sputter at all past 40?
Yes it happens 90% of the time at least, bike runs perfectly other than this issue. I can chop the throttle and roll while its in any gear no problem but when i hold the clutch in it dies rather than return to idle. Does not sputter or hesitate while accelerating in any gear.

bike has mods including yoshi rs4 duals, airbox, jetting, not sure about internals.

I will check the vacuum lines, thanks alot!!
 

·
Registered
Joined
·
5,212 Posts
Could the jetting be off? My wife had a similar issue but it would happen while cruising steady. Had a wasp in the vent line that would get squished just right at random times causing vapor lock. Blam bike dies...stop...start. keep going. Lol had me scratchin my head for awhile
 

·
Registered
Joined
·
9 Posts
Discussion Starter #5
Could the jetting be off? My wife had a similar issue but it would happen while cruising steady. Had a wasp in the vent line that would get squished just right at random times causing vapor lock. Blam bike dies...stop...start. keep going. Lol had me scratchin my head for awhile
I would be more suspicious of the jetting if it wasn't running so well. Spark plug color is also good. Vaccum issue is the leading suspect as of now. I would think it pretty much has to be a fuel issue.

I dont mind working on my bikes when i already know what the problem is but trying to diagnose just gives me a headache:damn:
 

·
Registered
Joined
·
5,212 Posts
Lol to where i enjoy the guessing game...cept for electrical. Look forward to ur report of it. Also check ur gas cap...maybe clogged there.
 

·
Registered
Joined
·
3,053 Posts
possibly - it could be something to do with Clutch Safety switch -
 

·
Registered
Joined
·
583 Posts
Hello all, my 400sm is stalling whenever i pull the clutch to coast, but only at above around 40 mph in 3rd, 4th, and 5th gear. The bike starts and idles perfectly, and has full power while accelerating.

Not sure where to begin with this issue. All theories welcomed.
Thanks in advance for any help!
The bike starts and runs perfectly, plenty of power but stalls when you pull the clutch in above 40 mph in higher gears. I gotta ask, why are you pulling in the clutch to coast?:headscrat
 

·
Registered
Joined
·
9 Posts
Discussion Starter #10
The bike starts and runs perfectly, plenty of power but stalls when you pull the clutch in above 40 mph in higher gears. I gotta ask, why are you pulling in the clutch to coast?:headscrat

well when im about to turn off the highway and im in 4th or 5th gear, i pull in the clutch and start downshifting. i engine break as well but it stalls before i get the chance

there's one example

going downhill behind a car on their breaks

there's another
 

·
Registered
Joined
·
583 Posts
well when im about to turn off the highway and im in 4th or 5th gear, i pull in the clutch and start downshifting. i engine break as well but it stalls before i get the chance

there's one example

going downhill behind a car on their breaks

there's another
OK, I guess everybody has their own riding style.:cheers:
 

·
Registered
Joined
·
105 Posts
If there's a way to avoid ever having to pull in my clutch in 4th or 5th gear on the street im all ears.
Yeah, just don't do it, the bike will shift fine without a clutch at all, you should never be coasting with the clutch in, you should be in the right gear for your speed. You still have a problem that needs to be fixed. The vent line is a good call.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #19
Still have the stock vacuum petcock? Wonder if the vacuum goes funny and shuts off the fuel

Yeah stock petcock. vacuum issue makes perfect sense just cant figure why its only doing it in the higher gears at speed.

Ill probably tear into it tomorrow and report back, thanks!
 

·
Registered
Joined
·
344 Posts
Yeah stock petcock. vacuum issue makes perfect sense just cant figure why its only doing it in the higher gears at speed.

Ill probably tear into it tomorrow and report back, thanks!
I assume there has to be an accumulator of some sort in there, otherwise it would shut off at WOT. if the accumulator has a leak or there is a general leak in the system it may shut off if you pull the clutch in before letting off the throttle, even by a split second.
 
1 - 20 of 21 Posts
Top