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Carburetor Problems
- NovaNewfie
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I got my parts today. I changed the oil and filter and put in a new air filter. I replaced all the O-rings, float valves and pilot jets in my carbs (VM 28s). I set my float levels to 4mm. The problem is it now runs worse than before. It won't idle smooth and back fires. The idle knob doesn't seem to have much effect.
The old float valves were 2.3's and the new ones are 2.0's would that cause a problem?
Any ideas?
Thanks
1979 KZ1000E-1 ST
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- NovaNewfie
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It runs rough and backfires at low rpm 1000-2000 seems to run fine up around 3-4000 rpm. After a minute or two of idleing it dies out.
At full choke it runs rough but with a lower idle 12-1500 if I ease the choke down to half it picks up rpm to around 3500.
1979 KZ1000E-1 ST
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- Patton
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1973 Z1
KZ900 LTD
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- NovaNewfie
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The only big change I made today (besides the new parts) was to set the float levels at about 4mm below the top of the bowl. The bowls were only about half full before I set them.
I believe I've got the air screws adjusted wrong. I've got them turned out one and an eight turn. This is a Canadian spec bike so no pilot screw just the air screw on the intake side of the carb and no accelerater pump.
I'm thinking its running rich at idle as its smoking some and doesn't take much/any choke to start. If its been running for a few minutes you have to open the throttle to get it to start.
Should I turn the air screws out more. When I took them apart the two outside carbs #1 & 4 were a turn and a quarter and the two inside carbs were a turn and a half.
1979 KZ1000E-1 ST
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- Patton
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Back fire through the carb may result from an imperfectly sealing intake valve, often due to insufficient valve clearance.NovaNewfie wrote: ...won't idle smooth and back fires....
Or might result from a timing advancer sticking in the advanced position.
Good Fortune!
1973 Z1
KZ900 LTD
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- NovaNewfie
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Patton wrote:
Back fire through the carb may result from an imperfectly sealing intake valve, often due to insufficient valve clearance.NovaNewfie wrote: ...won't idle smooth and back fires....
Or might result from a timing advancer sticking in the advanced position.
Good Fortune!
Thanks for the advice. The problem I have with your advice though is that it was idleing fine until I adjusted the float levels and put new valves and O-rings in the carbs today.
I looked at the timing advancer and it shows no signs of sticking or corrosion.
1979 KZ1000E-1 ST
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- Patton
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NovaNewfie wrote:
Patton wrote:
Back fire through the carb may result from an imperfectly sealing intake valve, often due to insufficient valve clearance.NovaNewfie wrote: ...won't idle smooth and back fires....
Or might result from a timing advancer sticking in the advanced position.
Good Fortune!
Thanks for the advice. The problem I have with your advice though is that it was idleing fine until I adjusted the float levels and put new valves and O-rings in the carbs today.
I looked at the timing advancer and it shows no signs of sticking or corrosion.
Given correct fuel levels, the new float valves and o'rings are imo unlikely to cause the degraded idle performance and/or back firing, and would suggest there being some other reason.
Good Fortune!
1973 Z1
KZ900 LTD
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- Patton
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Maybe the carbs aren't perfectly seated (for whatever reason) in the carb holders, and thereby allowing an air leak.
Good Fortune!
1973 Z1
KZ900 LTD
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- NovaNewfie
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Took carbs back off. For shits and giggles I pulled out my digital calipers and measured the new air screws in relation to the old ones. The new ones measured 2.99mm on the round shaft above the taper and 2.12mm at the end of the taper. The old ones measured 2.92mm on the shaft and 1.86mm at the end of the taper. I put the old ones back in. It seemed to run a bit better hardly noticed any backfiring.
Took the bike for a run. Came back after about 30 miles and the idle was high. I set at 1000 rpm approx, after the ride it was idleing up around 3200-3400rpm.
Its not idleing smooth but I have no idea how smooth or quiet these motors were to begin with.
1979 KZ1000E-1 ST
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- NovaNewfie
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Is it normal for the choke to make it run that high?
1979 KZ1000E-1 ST
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- 650ed
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1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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- NovaNewfie
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I know thats the way it should work. I set the idle the other day to idle at a thousand rpm and after a run of about thirty miles the bike was idleing at over three thousand. I lowered the idle down to around 1000 again.
The next day I started it with the choke and it revved to 4000 on full choke. I cut it back to just barely open on the choke and got it to idle at about 1500. When i took the choke off it was idleing so low it died.
I cann't seem to find a "set it and forget it" place on the idle adjustment.
It seems like between full choke and barely any choke there is a spot where it will pick up 2-3000 rpm around half choke. I don't think it should do this.
Most other engines i've had the choke would only raise the rpm 500-1000 rpm.
1979 KZ1000E-1 ST
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