Chrisraven
CB750 Enthusiast
I have a 1981 Honda 900F (I know it is not a 750 but this is a problem that will be common to both). For some reason when I am running my bike I get a miss (popping) through the exhaust which I can hear and also feel with my hand. It is starting to drive me a little nuts as I have tried multiple items to source it.
I have done the following: 1) New Plugs, 2) tested all the plug caps, 3) tested the plug wires, 4) tried replacement coils, 5) interchanged the two ignitors to see if the problem moves (nope), 6) Using premium fuel (Chevron 94), 7) Leak down test from 1 to 4...100/97, 100/95, 100/97, 100/99, 8) Sync carbs, 9) Stock aircleaner, 10) Checked the ground path.. clean and no resistance, 11) Valve clearances are all within specs, 12) Battery is good and fully charged. 13) Timing is perfect,
Did a compression test (bike was cold) From 1 to 4 readings are 120 psi across the board, added oil to each cylinder and it jumped to 145/150 across the the board. While I know this is low it is not low enough to give me a problem with the unit running. I managed to track down which cylinder is was through feeling the exhaust, and removing the plug caps. Number one is the bad guy. I actually had the bike running on 2-3-and4 cylinders while I had the plug out of number one. With the number one plug connected the spark was a deep blue and did not seem to miss a spark. I believe the low compression is due to glazing on the cylinder wall (only 50 kms on a complete rebuild), however this will not effect the missing on the one cylinder, since the other 3 were the same compression and were running fine.
The 50 clicks that are on the bike since the rebuild is a ride I took to start the breakin procedure. Interestingly enough I only got the miss when the bike was under load, taking off from a start and going through the gears about 4000 to 4500 rpm it would miss, but cruising down the freeway at 100 clicks at about 4000 rpm's it would run just fine. If I cracked the throttle the miss would come back. Almost sounded like a backfire, hard to describe what it actually sounds like. Don't know how to put a sound bite on here otherwise I would add the audio, it might help someone find a solution. (If you know how let me know)
Looking forward to your assistance with this pesky issue. Thanks Chris
I have done the following: 1) New Plugs, 2) tested all the plug caps, 3) tested the plug wires, 4) tried replacement coils, 5) interchanged the two ignitors to see if the problem moves (nope), 6) Using premium fuel (Chevron 94), 7) Leak down test from 1 to 4...100/97, 100/95, 100/97, 100/99, 8) Sync carbs, 9) Stock aircleaner, 10) Checked the ground path.. clean and no resistance, 11) Valve clearances are all within specs, 12) Battery is good and fully charged. 13) Timing is perfect,
Did a compression test (bike was cold) From 1 to 4 readings are 120 psi across the board, added oil to each cylinder and it jumped to 145/150 across the the board. While I know this is low it is not low enough to give me a problem with the unit running. I managed to track down which cylinder is was through feeling the exhaust, and removing the plug caps. Number one is the bad guy. I actually had the bike running on 2-3-and4 cylinders while I had the plug out of number one. With the number one plug connected the spark was a deep blue and did not seem to miss a spark. I believe the low compression is due to glazing on the cylinder wall (only 50 kms on a complete rebuild), however this will not effect the missing on the one cylinder, since the other 3 were the same compression and were running fine.
The 50 clicks that are on the bike since the rebuild is a ride I took to start the breakin procedure. Interestingly enough I only got the miss when the bike was under load, taking off from a start and going through the gears about 4000 to 4500 rpm it would miss, but cruising down the freeway at 100 clicks at about 4000 rpm's it would run just fine. If I cracked the throttle the miss would come back. Almost sounded like a backfire, hard to describe what it actually sounds like. Don't know how to put a sound bite on here otherwise I would add the audio, it might help someone find a solution. (If you know how let me know)
Looking forward to your assistance with this pesky issue. Thanks Chris
That sounds incredible! Please, make a video!, I will stand back here and watch!
I'm next door in Langley actually.
