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kz305 bogs high rpm wot
- Janz3n
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cleaned carbs and replaced diaphragms last year.
adjusted idle screw to 1.5 turns out this year.
adjusted static timing as close as i could get it. left side is perfect, right is a little off.
new gas.
float level is perfect.
new plugs. they look like a good colour when i pull them, havent done a plug chop though.
new carb boots.
pretty sure the baffles in the mufflers are shot
new oem air filter.
feels like less power than before i rebuilt the top end.
bogging starts at about 7k rpm in every gear.
runs great otherwise. just getting annoyed by the lack of power at high rpm.
any ideas? jet sizing?
81 kz305 ltd
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- Tyrell Corp
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I'd look at it running with a strobe, and ensure it is advancing and retarding. If your pipes are nearly shot the motor might sense a difference in backpressure and it may need upjetting.
A WOT plug chop and check timing would be a good start.
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces
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- Janz3n
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81 kz305 ltd
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- Janz3n
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Guess I need bigger main jets?
It's weird though. Last year before I rebuilt the head I was running the same mufflers and only a peice of foam glued to the air box that the PO put in and this never happened.
81 kz305 ltd
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- 650ed
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I would install a fuel filter and very carefully clean the carbs before fiddling with anything else at all. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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- Janz3n
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The bike had a filter on when I bought it but it was too restrictive and the engine would stall after 20 minutes because the gas couldn't keep up so I removed it and it ran about half the summer plus 500kms this year like that.
When I cleaned the carbs the first time I never removed the jets and cleaned them proper. I guess I can start by doing that.
81 kz305 ltd
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- Janz3n
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Have to put the choke on half to get any power past 7k rpm.
Noticed the one main jet said 82. Forgot to look at the other one. There was nothing blocking the holes at all.
81 kz305 ltd
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- Patton
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Test-run with fuel tank cap ajar (not snapped down)?
Good Fortune!
1973 Z1
KZ900 LTD
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- Janz3n
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will try the gas cap unlatched. i have noticed a sucking sound once and a while from the cap after a ride. figured it was normal?
81 kz305 ltd
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- Patton
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Janz3n wrote: just to clarify, it feels more like a hesitation than a bog, almost like its not getting fuel.
Janz3n wrote: . . . noticed a sucking sound once and a while from the cap after a ride. figured it was normal?
Inadequate fuel tank venting, as could happen with a clogged stock vent, may cause a vacuum inside the tank, which impedes fuel flow from the tank, resulting in "fuel starvation."
Perhaps such vacuum is being evidenced by the sucking sound as outside air is pulled into the tank.
Test-running with the fuel cap ajar aids diagnosis by providing more than adequate tank venting.
If the issue disappears with the cap ajar, it will be be time to correct whatever is obstructing the stock tank venting system.
If the issue persists with the cap ajar, there are other possible causes for fuel starvation that may then be addressed.
Good Fortune!
1973 Z1
KZ900 LTD
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- Janz3n
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There a small flat spot around 8k but its not bad. Stumped.
81 kz305 ltd
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