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Sputtering Under Hard Acceleration
- Motor Head
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- FIX UP YOUR BIKE RIGHT AND CHEAP
1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...
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- Topper
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Battery Voltage: 12.05v
At the Coil: 11.45v
Primary coil winding Ohms: 4 (spec is 3.2-4.
Secondary coil winding Ohms: 13.6 (spec is 10.4-15.6)
I am running with resistor plug caps (5k each) but not resistor plugs.
So other than the possibility of seeing if running without the resistor plug caps fixes this, I'm back to thinking this is a carburation issue.
Permanent and perpetual noob.
1979 KZ750 Twin
2009 Kawasaki Versys
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- Patton
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Topper wrote: Ok, re-checked timing and it looks good. Advances smoothly and stays there.
Battery Voltage: 12.05v
At the Coil: 11.45v
Primary coil winding Ohms: 4 (spec is 3.2-4.
Secondary coil winding Ohms: 13.6 (spec is 10.4-15.6)
I am running with resistor plug caps (5k each) but not resistor plugs.
So other than the possibility of seeing if running without the resistor plug caps fixes this, I'm back to thinking this is a carburation issue.
Ignition aspects look good.
If not already done, would also visually confirm a fat blue spark on plug tips.
As to carburetion, if not already done, would perform clear tube test to assure fuel levels are within specs, because the fuel level will impact the mixture.
Given correct fuel levels, would check condition and fitment of the throttle slide diaphragms. And that the slides move freely.
Yet to be determined is whether the mixture is too rich or too lean when under hard acceleration, and if so, what is causing the condition.
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1973 Z1
KZ900 LTD
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- Topper
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Slide diaphragms look good. The slides seem to move up and down normally. I do seem to have a nice spark at idle.
I moved the clip on the needle. It was at position 4 and I moved it to 3. If I understand the needle clip positions they work basically like this:
1 lean
2
3 <- I'm now here
4 <- I was here
5 rich
This seems to have made some difference though honestly it's a little hard to tell. The problem didn't go away, but its nature changed a little. The stutter and misfire under hard acceleration seemed a little more smooth, more like it was running on one cylinder.
I'm not sure if that means I made it better or worse. But I guess the next step is to move the clip up one more notch and see what happens.
Permanent and perpetual noob.
1979 KZ750 Twin
2009 Kawasaki Versys
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- Patton
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Is it for sure that gasoline flows freely through the petcock?
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1973 Z1
KZ900 LTD
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- KZB2 650
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Topper wrote: I have set the fuel level with the clear tube method. (I've also synced the carbs)
Slide diaphragms look good. The slides seem to move up and down normally. I do seem to have a nice spark at idle.
I moved the clip on the needle. It was at position 4 and I moved it to 3. If I understand the needle clip positions they work basically like this:
1 lean
2
3 <- I'm now here
4 <- I was here
5 rich
This seems to have made some difference though honestly it's a little hard to tell. The problem didn't go away, but its nature changed a little. The stutter and misfire under hard acceleration seemed a little more smooth, more like it was running on one cylinder.
I'm not sure if that means I made it better or worse. But I guess the next step is to move the clip up one more notch and see what happens.
Is the 4th clip the stock position ? Don't think you'd want to lean this out from stock. What do you guys think ?
1978 KZ650 b-2
700cc Wiseco kit 10 to 1.
1980 KZ750 cam, ape springs, stock clutch/ Barnett springs.
Vance and Hines Header w/ comp baffle and Ape pods, Dyna S and green coils, copper wires.
29MM smooth bores W/ 17.5 pilots, 0-6s and 117.5 main
16/42 gearing X ring chain and alum rear JT sprocket.
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- Topper
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I haven't tried position #2 yet but hope to later today.
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1979 KZ750 Twin
2009 Kawasaki Versys
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- KZB2 650
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I'm really sure the 2nd clip is going to be too lean for you so I don't think you should even try that. We need Bounty hunter and Steele to chime in on this as they really know the 750 twin.
Since you have the Mac pipe.... what cleaner do you have? Maybe you do need a little jetting help but these two guys are gonna help you most on that.
1978 KZ650 b-2
700cc Wiseco kit 10 to 1.
1980 KZ750 cam, ape springs, stock clutch/ Barnett springs.
Vance and Hines Header w/ comp baffle and Ape pods, Dyna S and green coils, copper wires.
29MM smooth bores W/ 17.5 pilots, 0-6s and 117.5 main
16/42 gearing X ring chain and alum rear JT sprocket.
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- Topper
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www.kzrider.com/forum/3-carburetor/44245...8-on-a-76-kz750-twin
Seems like trying one slot lean (#2) is worth a go.
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1979 KZ750 Twin
2009 Kawasaki Versys
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- Topper
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In the middle position (#3) it seemed to run on 1 cylinder under hard acceleration. In 2 & 4 it stutters and sputters under hard acceleration.
Could this be a main jet issue?
I've never had them out and have no idea if they're stock. I did some experimenting with pilot jets a while back. My memory is fuzzy on where they ended up. But I wouldn't think they'd be playing a roll in this.
What do you think, could this be a main jet issue or is it a fuel supply / petcock issue?
Permanent and perpetual noob.
1979 KZ750 Twin
2009 Kawasaki Versys
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- Motor Head
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It might be hard to have a look, but after this stumble, pull over and look at the Filter you have and see if it is still full of fuel.
With the change in pipes you made it could well be a main jet change is in order. If you use brand new plugs, you can do a plug read at that throttle where it occurs. But you may need a long stretch of road where there is no traffic, or cops. Read the plugs for a sign of rich, or lean. Or if you had some main jets you could swap and experiment. Best to go richer first, then see where that goes.
1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...
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- Matteson
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KZ 900-a4
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