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one cylinder miss at low throttle
- fastidiots
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82 KZ1000 J
76 KZ750 B1
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- kaw-a-holic
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Jon
1977 KZ1000a1
Mesa, AZ
Phoenix Fighter Project
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- Patton
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Good Fortune!
1973 Z1
KZ900 LTD
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- fastidiots
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82 KZ1000 J
76 KZ750 B1
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- fastidiots
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It seems that the miss happens right about where the carb would be just going from the idle jet to the pilot jet but goes away with just a bit more throttle. I'm thinking I might just have a bit of something partially blocking the pilot jet on that carb. Will continue riding the bike as is for a while since I just don't have the time or the patience to tear into the carb AGAIN this soon and clean out the jets., and the miss happen only in such a small throttle range.
82 KZ1000 J
76 KZ750 B1
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- bountyhunter
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fastidiots wrote: My kz750twin has been running quite well for a few weeks since I got the crabs mostly dialed in, but about 2 days ago it began having a miss in the right cylinder at low throttle positions. It idles smoothly, and pulls great at higher throttle, but misses and sputters at very slow throttle position. Right where you hold it to say run through town at anywhere from 30 to 45 mph, it runs rough and misses a lot. ?
1) That is mostly the pilot jets range. Make sure they are clear and I would up size to 50 for the pilots, they run much better.
2) Do a physical sync on the bench: use a very small drill bit to accurately gauge the throttle plate's opening and sync the two together. That is probably good enough for sync, that's always worked for mine.
3) The hesitation you describe can also be caused by a vacuum leak, check the intake manifolds (mounts)
4) On mine, it had a hesitation at low throttle caused by air leaks in the diaphragms which caused them to not lift as quickly as they should. I missed the holes because they were fine slits that I couldn't see until I took them out and held them up to a strong light. The slits were hidden in the folds.
Just a bunch of possibilities. Good luck.
1979 KZ-750 Twin
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- bountyhunter
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That sounds like it could be the problem:fastidiots wrote: Tried re-syncing the carbs yesterday... they were within spec but I got them even closer. No difference
It seems that the miss happens right about where the carb would be just going from the idle jet to the pilot jet but goes away with just a bit more throttle. I'm thinking I might just have a bit of something partially blocking the pilot jet on that carb. Will continue riding the bike as is for a while since I just don't have the time or the patience to tear into the carb AGAIN this soon and clean out the jets., .
there may be an easy way to get it without teardown. Get some liquid carb cleaner and some carb spray cleaner.
Take the fuel lines loose at the top fitting to the carb. Take the drain plug out the bottom. Use carb spray to hose down from the top and clean it out. Then put the drain plug in and dump some liquid cleaner in the top and fill the carb bowls. Plug the tops and let it sit a day and then open the drains and hose it down from the top again.
That might clear it out without removal of carbs. The pilot jets and associated paths are located in the bowls on the BS-38 carbs so the cleaner will soak them.
1979 KZ-750 Twin
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- bountyhunter
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1979 KZ-750 Twin
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