changed belts - wont run

[Porsche Monkey]

If I let my 900 sit for a week it is an absolute mothermake the beast with two backser to start.  If I don't ride it for a month then it will require starting fluid.  My guess is its the wonderful ethanol fuel separating in the float bowls.  if I ride it a few times a week it fires on the first revolution.

[MongoReturns]

If I let my 900 sit for a week it is an absolute mothermake the beast with two backser to start.  If I don't ride it for a month then it will require starting fluid.  My guess is its the wonderful ethanol fuel separating in the float bowls.  if I ride it a few times a week it fires on the first revolution.

Same with my 750 - though after I get a hellacious backfire it starts right up.  I always figure it's clearing the clyinders 

[Porsche Monkey]

Same with my 750 - though after I get a hellacious backfire it starts right up.  I always figure it's clearing the clyinders 

Yup ill usually get a few flames out of each pipe a couple times while it clears its throat.

[billg69gmc]

Check for spark?
Dead coil?
Blown Fuse?
Voltage Regulator?
After repeated starting attempts, plugs should be wet with gas. Are they?

Just throwin spaghetti and seeing what sticks to the wall.

[DTR]

I changed the belts once in my ST4 and encountered the same problem. I pulled the plugs to observe the spark and it sparked as it should. Put them back in and nothing even close to running happened. I removed the belts and turned the engine through one revolution and re-installed the belts and it ran like a top.
  Think about it being a 4 stroke and the crank rotates 720 degrees for each combustion cycle. If the crank got rotated (360 degrees) during the valve adjust/belt replacement the spark could occur on the exhaust stroke vice the compression stroke. Remove the belts and rotate the crank one revolution ,replace the belts and it should work fine. At least that is how I rationalized what happened to my bike.......

[WTSDS]

Yes, but the crank is geared 2:1 to the layshaft which has the central/ lower pulley attached to its end, so if the mark on the lower pulley is positioned correctly the crank and the ignition timing will be correct - unless the motor has been pulled to pieces.

The two cam pulleys are the same size as the lower pulley so if the marks line up all is good.

[ute]

The thing is if he has spark and fuel

the only thing left is timing ...i know the marks line up but this has to be it


OP you have checked for spark and fuel correct ?


lets not overthink this ....it only needs 3 things to run spark-fuel-air

[mitt]

Any updates?   It might just be coincidence, but when my bike sits for extended periods, and the weather is a little cooler like now, it is a b!tch to get started.  Always has been.  Like today, I had to hold the throttle at 3/4 open while cranking for about 20 seconds before it fired.  Have you tried holding the throttle wide open while cranking?

mitt