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Stumble @ 2500 rpm
- 55fbomb
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1974 CB750
1975 CB750
197? CB750 mutt
1977 KZ1000
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- TeK9iNe
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- What did you do!?!
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Turn them out 1 at a time. Listening for the engine start to stumble, then turn that screw back in just until the idle comes back up/smooths out. All the misture screws should stumble around the same number of turns out (give or take 1/4 turn or so). If not, then you most likely have air intrusion from somewhere.
Check to make sure you have really excellent spark, and a vacuum syncronization would help alot.
Also be sure to set your dwell with some good feeler guages, or a meter, and set your points/timing with a gun - static timing is crap at best.
Good luck.
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
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- 55fbomb
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1974 CB750
1975 CB750
197? CB750 mutt
1977 KZ1000
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- TeK9iNe
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Sometimes it helps alot to advance the initial timing a little (2-3 degrees) to restore some of your old girls bottom end power delivery.
Peace.
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
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- Patton
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Meanwhile, Boo on me for suggesting that the carb pilot circuits are still imperfect regardless of the reported cleaning.
Oem carb pilot circuit looks like this:
May adapt the following pilot circuit cleaning method (illustrated with side-located pilot screw) to use on carb with bottom-located pilot mixture screw:
Wear eye protection!
Good Fortune!
1973 Z1
KZ900 LTD
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- Motor Head
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- FIX UP YOUR BIKE RIGHT AND CHEAP
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What does it do if you put it up a clip/ shim it? There is so many "Pod" threads, I think everyone of them ends up with the needle raised at least 1 notch/ shim. Have you tried this?
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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- cavanaughracing
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55fbomb wrote: I have a 77 KZ1000 with 12,000 miles on it, the bike has k&n pods on it and a mac 4 into 1 with a short glasspack instead of the mac baffle and the stock non accelerator pump carbs. i have 120 mains, the needle in the stock setting and 20 pilots in it. when in traffic the bike seems to have a slight dead spot right off idle and just loafing along it sputters at about 2000 to 3000 rpms, somewhere in that area. if you rail it open, it runs great and if you generally run it hard its fine, just going to work in traffic it gets to be annoying. i have the pilot screws out about a turn and a quarter and have tried them everywhere from a turn and a half out to half out, and tried 22.5 pilots and the stock 17.5 pilots. the 22.5 and 20 had similar results, the 17.5 pilots it wouldnt even harldey run. the carbs are synced and there doesnt seem to be any air leaks and the floats are set to 1 inch. the carbs are very clean, i had them off again yesterday. Any thoughts would be appreciated, i dont ride this bike much due to this problem and its not gonna sit out there takin up space, thanks guys.
Put the #20 pilots back in and lift the needle up one clip position. That's one clip position more, down from the top of the needle from where you are now.
Eg... Currently 3rd groove. Move to 4th. Then do a really good carb synch. [That advice presupposes that your fuel levels, valve lash and ignition timing are correct]
You're at the transition point where it's just coming on the needle. Pilot circuit, slide cut away & clip position all influence that point. It's the trickiest spot to nail down silky smooth once you remove the air box and bolt on a pipe. It can be more so with 30 year old carbs with worn parts. Give it a whirl before you do anything else and see...
A lot of times what happens is guys will get it near cured by dumping in too much fuel via the fuel mixture screws [underneath front of carbs]. Then the plugs turn sooty and it idles poorly on hot days.
This stuff passing for gasoline these days has changed the game a bit. I'm finding more situations where I have to set a richer clip position than I used to run.
Larry C.
cavanaughracing.com
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- 55fbomb
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1974 CB750
1975 CB750
197? CB750 mutt
1977 KZ1000
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- 55fbomb
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1974 CB750
1975 CB750
197? CB750 mutt
1977 KZ1000
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- 55fbomb
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1974 CB750
1975 CB750
197? CB750 mutt
1977 KZ1000
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- Patton
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55fbomb wrote: Well, finally got out this weekend and put about 100 miles on er this weekend and ran perfect. . . . . . . until i got back into town and got stuck in traffic. Is anyone here running stock pilots with pods? i have the 20s in it still at about .75 turns out and it still fat and loading up at idle it seems. if i get stuck in traffic it sputters once i get moving and belches out a bit of grey smoke when i first crack it open, then it clears up and is fine until i get stuck in traffic again. should i go back to the stock 17.5 pilots?
have the 20s in it still at about .75 turns out --- perhaps pilot circuit is too rich. Side located pilot air screws should imo be set about 1.25~1.5 turns out from lightly seated.
If not already done, would also verify correct fuel level by performing the clear tube test.
A too high fuel level may result in an excessively rich mixture even in an otherwise perfect carb.
Reported issue can also result from overheating due to incorrect ignition timing or advancer function, or too tight valve clearances, or weak spark for whatever reason.
Good Fortune!
1973 Z1
KZ900 LTD
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- 55fbomb
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1974 CB750
1975 CB750
197? CB750 mutt
1977 KZ1000
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