One last question, I bypassed the PAIR valves, on the 2 left cylinders the vacuum lines was tee'd and feed. I did take the tee out in reconfiguring the vacuum lines so now they are not joined, should these 2 be joined for some sortmof balancing effect?
Troubleshooting rough cold running and carb backfire
- Thread starter john.berg
- Start date
- Joined
- Mar 18, 2006
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- 2,854
- Age
- 70
- Location
- Ilkley, W Yorkshire, UK
- Bike
- 2013 ST1300 A9
- 2024 Miles
- 000679
- STOC #
- 2570
They are just plugged individually on UK bikes.
- Joined
- Feb 5, 2005
- Messages
- 8,538
- Age
- 77
- Location
- Kingman, Arizona
- Bike
- 2000 ST1100 ABS TCS
- STOC #
- 004
John, the 2 5/8 out is the start point. Quoting here:
5. Turn each pilot screw 1/2 turn out from the initial setting.
6. If the engine speed increases by 50 rpm or more, turn each pilot screw out by successive 1/2 turn increments until engine speed does not increase.
7. Adjust the idle speed with the throttle stop control knob.
8. Turn the No. 1 carburetor pilot screw in until the engine speed drops 50 rpm.
9. Turn the No. 1 carburetor pilot screw out 7/8 turn from the position obtained in step 8.
10. Adjust the idle speed with the throttle stop control knob.
11. Perform steps 8, 9, and 10 for the No. 2, 3 and 4 carburetor pilot screws.
For the high altitude adjustment (consistent riding above 6500 feet), turn each pilot screw CW (in) 1/2 turn.
Keep us poSTed.
5. Turn each pilot screw 1/2 turn out from the initial setting.
6. If the engine speed increases by 50 rpm or more, turn each pilot screw out by successive 1/2 turn increments until engine speed does not increase.
7. Adjust the idle speed with the throttle stop control knob.
8. Turn the No. 1 carburetor pilot screw in until the engine speed drops 50 rpm.
9. Turn the No. 1 carburetor pilot screw out 7/8 turn from the position obtained in step 8.
10. Adjust the idle speed with the throttle stop control knob.
11. Perform steps 8, 9, and 10 for the No. 2, 3 and 4 carburetor pilot screws.
For the high altitude adjustment (consistent riding above 6500 feet), turn each pilot screw CW (in) 1/2 turn.
Keep us poSTed.
- Joined
- Feb 5, 2005
- Messages
- 8,538
- Age
- 77
- Location
- Kingman, Arizona
- Bike
- 2000 ST1100 ABS TCS
- STOC #
- 004
I ran a 1/2 can of Techron thru lipSTick, with the enricheners ON, on the way to Xmas STOCing Friday. Still got 45 MPG, and no "rich" running. Not sure it made a difference.
Couldn't find Berryman's locally.
Couldn't find Berryman's locally.
Just trying to get a plan of attack before I pull the carbs again this week, what kind of problem would I be seeing if I had an Air Cut Off valve problem, vacuum leak, non metered fuel, etc..? Are there 4 valves or 2?
A carb problem is really suspect for me, I bought the carbs from an ebayer, they were supposed to be fully rebuilt and tested. The first bad indication I had was the fuel drain screws were fully rusted and leaking, the drains screws were not removed when they cleaned the carbs and the orings were cracked. I also had to readjust the enrichment linkage. I'm really wondering if they were not fully dis-assembled and something like the air cut off diaphragms were installed when a cleaning was done.
A carb problem is really suspect for me, I bought the carbs from an ebayer, they were supposed to be fully rebuilt and tested. The first bad indication I had was the fuel drain screws were fully rusted and leaking, the drains screws were not removed when they cleaned the carbs and the orings were cracked. I also had to readjust the enrichment linkage. I'm really wondering if they were not fully dis-assembled and something like the air cut off diaphragms were installed when a cleaning was done.
Thought I would provide an update, I have some promising results and wanted to post my experience on what made a difference and what did not.
1. Berrymans, maybe made a difference but nothing significant. Actually when the tank was down to 1/4 I refueled and it ran better. I think this was just the heavy dose of Berrymans in the tank
2. Float level, 2 were too low, fixed, no real change
3. Low speed mixture adjustment, seemed it was running rich thought this was a part of it. Turned the screws into 1.75 turns. No difference in fact worse, they still need to go back to 2.5 turns
3. Valve Adjustment, dealer found 2 exhaust and 1 intake too tight, initially thought this made no difference after picking the bike up but found yesterday the dealer knocked off one of the vacuum caps.
4. Vacuum leak, tied to above. Again looks like the dealer knocked off a vacuum cap and I also found another leak in the line to the evap control purge valve. Not a large leak but the line had a crack
5. Plug cap out of spec by about 1.5x
I fixed the vacuum leaks yesterday and replaced the plug cap and then re-sync because of the valve adjustment, it was running really well when I went back in the house last night. The real test, a dead cold start his morning, now zero carb backfiring/popping when cold, it starts right up and even without the choke after a few seconds it will hold a smooth 1k idle being dead cold, it creeped up to 1200 after just a minute. I am very happy, this is the best it has ran since I bought it!
So, in conclusion between a small vacuum leak, tight valves and an out of spec plug cap all three were culprits to some degree
What's left, well now I still need to fix the coolant leak, since I will have to pull the carbs again I will set the mixture screws to 2.5 turns and then recheck the sync, then there's the Race Tech Emulators that came in...
1. Berrymans, maybe made a difference but nothing significant. Actually when the tank was down to 1/4 I refueled and it ran better. I think this was just the heavy dose of Berrymans in the tank
2. Float level, 2 were too low, fixed, no real change
3. Low speed mixture adjustment, seemed it was running rich thought this was a part of it. Turned the screws into 1.75 turns. No difference in fact worse, they still need to go back to 2.5 turns
3. Valve Adjustment, dealer found 2 exhaust and 1 intake too tight, initially thought this made no difference after picking the bike up but found yesterday the dealer knocked off one of the vacuum caps.
4. Vacuum leak, tied to above. Again looks like the dealer knocked off a vacuum cap and I also found another leak in the line to the evap control purge valve. Not a large leak but the line had a crack
5. Plug cap out of spec by about 1.5x
I fixed the vacuum leaks yesterday and replaced the plug cap and then re-sync because of the valve adjustment, it was running really well when I went back in the house last night. The real test, a dead cold start his morning, now zero carb backfiring/popping when cold, it starts right up and even without the choke after a few seconds it will hold a smooth 1k idle being dead cold, it creeped up to 1200 after just a minute. I am very happy, this is the best it has ran since I bought it!
So, in conclusion between a small vacuum leak, tight valves and an out of spec plug cap all three were culprits to some degree
What's left, well now I still need to fix the coolant leak, since I will have to pull the carbs again I will set the mixture screws to 2.5 turns and then recheck the sync, then there's the Race Tech Emulators that came in...
So I assume all is well? Hope it is!
Just got finished doing a VERY thorough cleaning of my carbs, but still have the little pop-back on what appears to be the Right Rear carb. Looking into vacuum leaks, per your findings...
Just got finished doing a VERY thorough cleaning of my carbs, but still have the little pop-back on what appears to be the Right Rear carb. Looking into vacuum leaks, per your findings...
Last edited:
- Joined
- Feb 5, 2005
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- 8,538
- Age
- 77
- Location
- Kingman, Arizona
- Bike
- 2000 ST1100 ABS TCS
- STOC #
- 004
Sounds good, John.
I balanced carbs on lipSTick yeserday after replacing the fuel pump. All looks good there too. Run to Phoenix today will tell the tale.
Glad you have yours under control.
I balanced carbs on lipSTick yeserday after replacing the fuel pump. All looks good there too. Run to Phoenix today will tell the tale.
Glad you have yours under control.