I friend gave me a 1983 Yamaha xs400r seca that had been sitting in his shed for about 10 years. After restoring it and cleaning the carbs, it starts up fine and runs well. The problem is when starting out you have to have the rpms above 5000 to get it to go into first gear and run. Anything lower than that and it immediately stalls. What parts do I need to be replacing?
I would recommend a compression check.
How many miles are on the bike?
Low compression will cause that symptom.
Does the bike rev cleanly when in neutral? Or does it sputter?
It wouldn’t surprise me at all if the carbs were still gummed up a bit. I would reinspect all your jets.
Is your air filter in nice clean condition? A clogged air filter can cause that as well.
Let me know what you find.
the bike has about 13,000 miles on it. It seems to rev fairly cleanly in neutral. I paid to have the carbs dissassembled and run through an ultrasonic cleaner so I would hope they arent still gummed up. The air filter is brand new stock replacement.
With the clutch lever pulled all the way in, shift into first. Does the bike immediately die? If you continue to hold in the lever and rev the bike will it want to move forward rather than just sit there?
in first with the clutch all the way it will sit there and rev. as soon as you let off the clutch it dies
With 13,000 miles your compression is probably fine – unless the bike has been beat on or run low on oil.
I’d bet it’s your carbs. If you haven’t personally inspected them then make no assumptions. Could be a clogged jet, a leaky float needle, incorrectly set float height, out of whack synchronization.
all I know for sure is that the friend who gave it to me laid it down the last day he rode it in 1999 then parked it in a shed until I took it last fall.
Take a second look at your carbs and let me know what you find. Pull out the jets and make sure you can see through them!