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Bad gas mileage.
- Schmeck
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1979 kz750 twin -Soon to be roadworthy
1988 El250 engine in custom hard tail frame - collecting dust
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- bountyhunter
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Might have found the gas mileage answer.... :laugh:Schmeck wrote: Thanks I'll check for the spring in the pilot mixture screws. That might solve that problem. As far as jetting. Because I haven't gotten bigger jets I moved the needle clip to the bottom position with a small washer underneath the clip. If I get bigger jets , I can move the clip position back up and won't have to open the throttle as much which means lower rpm and better gas mileage. Am I getting that right? Lol
I don't know what exactly is the best setup. But you can't compensate for a lean condition with clip alone.
have you checked plug color after running on the freeway a while?
1979 KZ-750 Twin
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60-65mph at 5,000 rpm on the highway. Won't go any faster than 80 and that's wide open.
In general, you check main jet with wide open throttle. If it pulls strong, you're good. If it is weak (sounds like yours is just running out of gas) it's probably lean but checking plug color after a freeway run is the way to know.
Once you get the main jet size right, tune the pilots and needles.
Fine tuning needles is basically to get a good off throttle response when cruising along at about 30 - 35 mph and you roll on the gas. If it balks, raise the needle but too much and it will bog down from being too rich.
1979 KZ-750 Twin
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1979 KZ-750 Twin
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- Patton
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Schmeck wrote: ... 79 750 twin... uni pod filters with open exhaust headers. It has a baffle in it for back pressure because the bike will not run at all without it... 14 front and 32 rear sprockets. 60-65mph at 5,000 rpm... Won't go any faster than 80 and that's wide open... does open exhaust and pods really make mileage this horrible? I think my pickup truck gets better mileage....
Schmeck wrote: ... Because I haven't gotten bigger jets I moved the needle clip to the bottom position with a small washer underneath the clip. If I get bigger jets , I can move the clip position back up and won't have to open the throttle as much which means lower rpm and better gas mileage. Am I getting that right? Lol
Tuning CV carbs with pods is already problematic enough, even with mufflers. Absence of mufflers worsens the problem, despite adding baffles inside open headers.
If stock sprockets are 16-38, would expect lower than 5,000 rpm at 60-65 mph.
Perhaps a better approach toward resolving the current issues would be to first return the carb settings (jets and clip position) to stock conditions, fit stock size sprockets, and add a muffler.
The following link includes a free manual download:
kz750twins.com/?p=15
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1973 Z1
KZ900 LTD
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- kaw-a-holic
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bountyhunter wrote: From your post:
60-65mph at 5,000 rpm on the highway. Won't go any faster than 80 and that's wide open.
In general, you check main jet with wide open throttle. If it pulls strong, you're good. If it is weak (sounds like yours is just running out of gas) it's probably lean but checking plug color after a freeway run is the way to know.
Once you get the main jet size right, tune the pilots and needles.
Fine tuning needles is basically to get a good off throttle response when cruising along at about 30 - 35 mph and you roll on the gas. If it balks, raise the needle but too much and it will bog down from being too rich.
When adjusting the needle a guy taught me to use flat washers to get a half clip adjustment. Slide the needle through the washer and put it back in the bucket and bingo. Make sure you mic the washers for thickness though, you want them the same on all carbs.
Jon
1977 KZ1000a1
Mesa, AZ
Phoenix Fighter Project
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1979 KZ-750 Twin
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Good Fortune!
1973 Z1
KZ900 LTD
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- Schmeck
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1979 kz750 twin -Soon to be roadworthy
1988 El250 engine in custom hard tail frame - collecting dust
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- Schmeck
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1979 kz750 twin -Soon to be roadworthy
1988 El250 engine in custom hard tail frame - collecting dust
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- Schmeck
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On another note I rode around a few miles with the choke on and it seemed to ride ok other than the high idle. Can I put a colder plug in to fight the lean condition ? It would probably be a good idea to prevent possible engine overheating .
Also, for those with pod filters is there anything u can put on them for restriction ? I bought pods because of my modified hardtail and am wondering if putting cloth or something over them would help to block airflow maybe???
This jetting is taking awhile .
1979 kz750 twin -Soon to be roadworthy
1988 El250 engine in custom hard tail frame - collecting dust
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1979 kz750 twin -Soon to be roadworthy
1988 El250 engine in custom hard tail frame - collecting dust
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