Chad Taylor
XS400 New Member
Hi Everyone,
I'm new to this site (actually to the whole "forum" thing entirely!) but I've been having trouble with my bike and would gladly take all the help I can get!
So a little history: In a previous buy I got two yamaha xs400's (1977 and 1978 I think). The 77 had a title so I used that for a Cafe Racer build and robbed the carbs off the 78. Now I'm getting into a project where I'll need a power plant and that 78 engine was looking like the best candidate. But before I buy new carbs I want to know if the engine even works.
I cleaned it off and I just need to know if it'll run at all, I'm just looking for any sign of life in this engine. So the name of the game is to wire up a battery directly to the coils (points ignition bike), spray carb cleaner (only thing on hand, no specific starter fluid in arms reach) into the intake right up against the valves and kick it over. If I hear just a small cough, sputter, single ignition then I'm happy and know the engine can run. This is the same approach I had on the 77 bike and it worked well enough then, so I figured it should be fine now.
Of course it didn't work first kick, so I've run through and checked these things:
-points gap (right distance, but I'm seeing small sparking across the points is that okay?)
-timing (the mechanical advance is stuck in the no-advance position, but should be fine for just a kick over test. I wont be idling the bike. Also set the timing for each cylinder)
-spark (I'm getting spark on both plugs and they're consistent)
-compression (~115 and 125 psi on the cylinders)
-battery I'm using is at 12.40 volts so it should be okay
-valve lash is good on intake and exhaust
So it seems like I have everything I need, spark, compression, fuel, timing but not even one smallest puff of combustion yet! Is there something I'm missing?
I'm new to this site (actually to the whole "forum" thing entirely!) but I've been having trouble with my bike and would gladly take all the help I can get!
So a little history: In a previous buy I got two yamaha xs400's (1977 and 1978 I think). The 77 had a title so I used that for a Cafe Racer build and robbed the carbs off the 78. Now I'm getting into a project where I'll need a power plant and that 78 engine was looking like the best candidate. But before I buy new carbs I want to know if the engine even works.
I cleaned it off and I just need to know if it'll run at all, I'm just looking for any sign of life in this engine. So the name of the game is to wire up a battery directly to the coils (points ignition bike), spray carb cleaner (only thing on hand, no specific starter fluid in arms reach) into the intake right up against the valves and kick it over. If I hear just a small cough, sputter, single ignition then I'm happy and know the engine can run. This is the same approach I had on the 77 bike and it worked well enough then, so I figured it should be fine now.
Of course it didn't work first kick, so I've run through and checked these things:
-points gap (right distance, but I'm seeing small sparking across the points is that okay?)
-timing (the mechanical advance is stuck in the no-advance position, but should be fine for just a kick over test. I wont be idling the bike. Also set the timing for each cylinder)
-spark (I'm getting spark on both plugs and they're consistent)
-compression (~115 and 125 psi on the cylinders)
-battery I'm using is at 12.40 volts so it should be okay
-valve lash is good on intake and exhaust
So it seems like I have everything I need, spark, compression, fuel, timing but not even one smallest puff of combustion yet! Is there something I'm missing?