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Mikunis won't idle down
- Godfrey
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1981 650CSR frame
1980 KZ750E engine
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- JakeB
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You'll have to do some research on your carbs to properly distinguish vents from vacuum ports.
1978 Z1-R
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- testarossa
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JakeB wrote: Are all of the vacuum ports on the carbs/intake boots plugged? You said that it had a vacuum petcock but no vacuum line on it, if the corresponding port(s) on the carbs/boots weren't capped or plugged they would leak a lot of extra air into the cylinders.
You'll have to do some research on your carbs to properly distinguish vents from vacuum ports.
Good call Jake. I had this problem initially. My bike had a vacuum petcock originally. The vacuum was supplied by the #3 carburetor which needed to be plugged. It caused me all sorts of problems before I got it capped. The port looks just like the vent on #2 and #4 except that it draws a significant vacuum at idle which the vents on #2 and #4 do not.
1978 KZ1000 A2 Click--->Build Thread
2004 ZX-10R
2007 Harley Sportster 1200
2020 Harley Street Glide Special
Angola, IN
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- Godfrey
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1981 650CSR frame
1980 KZ750E engine
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- Motor Head
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- FIX UP YOUR BIKE RIGHT AND CHEAP
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Godfrey wrote: Hey MH the exhaust sprocket was slotted to get the cam degreed in correctly
So have you had a look to see if as you thought it is correct or off a tooth? Any chance the builder can come to you and re-check the degree/ lobe centers? Or do you have the tools Knowledge?
The mechanical out of the way, engine timing correct, then timing and as mentioned possibly still lean/ vacuum at carbs. Verify the Ignition with a good strobe light with advance feature so you can check total advance as well. There would be a chart in the service manual for stock timing curve. Maybe your builder has changed the curve some, changed the springs? Or even removed them for racing?
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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- Kidkawie
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I'm not familliar with your carbs, can you remove the caps (if it has them), operate to full throttle, then try to manually push down on the slides. If any of them move then you have some binding. Remove the idle adjuster completely and make sure all the slides fully seat in the carb body. Disconnect any throttle cables and operate the carbs manually.
1975 Z1 900
1994 KX250 Supermoto
2004 KX125
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- Godfrey
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1981 650CSR frame
1980 KZ750E engine
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- Motor Head
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You have already stated that you cannot find any "External" vacuum leaks. Are those slides reaching the bottom of the carb bore? They should be able to hit the floor of the bore if you have backed off the Idle speed knob and have slack in the cable. They should hit with a noise, solid on the bottom. And all 4 need to be set so that they have the same lift, starting with just cracking them open with the Idle knob, use a wire gauge drill or a paperclip to get them set. If the circuit is to lean then where are the mixtures screws set to? # of turns out from their seats?
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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- Godfrey
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1981 650CSR frame
1980 KZ750E engine
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- Motor Head
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- FIX UP YOUR BIKE RIGHT AND CHEAP
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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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- Kidkawie
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1975 Z1 900
1994 KX250 Supermoto
2004 KX125
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- six862m6
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My post might be of some interest to you; I've been working the kinks out of a set of these on my KZ1000. I think you may be on the right track with the pilot jets being too lean. I have 20s in mine and was told to START there, not at the factory 17.5s as these were way too lean and I think mine is too lean still at idle because I have the same issue as you, though not as drastic (I'm hovering at about 3K). I did a bench sync already and they are as spot on as you're going to get with the ball bearing method. My plugs tell the same tale of being lean at idle as well... If I only let it idle for a long time and pull a plug it looks to indicate a lean condition. No vacuum leaks on mine. And you're correct, these carbs are really made for gravity fed fuel bikes, though I'm sure you could use one of the vacuum ports that is on each of the throttle bodies to work a vacuum petcock.
After talking to a lot of people and looking at different setups, it just comes down to your individual bike with these carbs, regardless if someone has a similar setup or not. I've had a guy on my post tell me that he's running 125s on his 1000 and his is bored out to 11XXcc, whereas mine is only out to 1075... and that he thinks he needs 122.5s. He's probably correct for his bike, but after testing out the 145s and seeing the difference they made (and not at all "drowning" it out), I'm going to start with 132.5s in mine when they come in and go from there. Before all this, I started at the factory middle clip position on the needle and 120 mains in mine and my bike would fall flat on it's face after much of 1/2 throttle. Raised the needle up to the next position (richer) and it corrected A LOT of that issue, though still certainly not right. Tried the last position on the needle (Richer) and it got worse. Put it back to the 4th position, then swapped out my 120 mains for a set of 145s that I got the carbs with.... I figured I'd absolutely drown the bike out but to my suprise, while it's definitely too rich as indicated by stumbling, especially WOTing the bike at low RPMs and the plug condition after immediately riding the bike, the 145s overall make the bike run MUCH better than the 120s. I ordered a set of every size mains from 127.5s to 135s from Z1 Enterprises last night and plan on getting that straightened out. After that, I'm going to richen up my pilot jets to try and correct my high rev at idle issue. BTW, if you need jets for these carbs, those guys have the best prices I've seen so far; $1.72 a jet. All those sets of jets I bought with shipping only cost me about $32.....
Good Luck!
David
'79 1000LTD
1075 Kit
RS34s
Mild Port&Polish
Kerker Header
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