Kz750b tuning.

Stocky
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Kz750b tuning.

28 Aug 2017 22:10

Hi Everyone,
Can't get fine tuning correct.
I have a rebuilt 79KZ750B. 2into 1 Mac exhaust. Checked valve timing twice , ignition timing also. New carb kit , new diaphrams , carb stripped and cleaned twice . No air leaks. Checked float levels etc etc. continually fouls plugs - black sooty.
Have had running reasonably well - some intermittent missing, However I read a forum a while ago that suggested going to 50 pilot jet.. since then more fouling and more missing past idle. Also Adjusting pilot screw doesn't seem to make a lot of difference.
Can any one who has Mac 2 into 1 pipes tell me what jet changes are necessary.

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Tyler
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Re: Kz750b tuning.

29 Aug 2017 08:21 - 29 Aug 2017 08:34

#769938

Are you sure about your float levels, any time I have had similar fouling issues the float levels were high.

I would then double check your work in the carbs. The BS carbs used on the twins are kind of odd balls.

There is a great write up here you should read through....

750 Twin Carb Info

My only experience with a MAC exhaust was using the 34mm carbs with three jets. I had to increase the large pilot jet and that was it. The MAC will lean the bike out a bit but not too much. You may need to go back to 40 pilot jet. The bike should be lean with that exhaust and stock jets, a fouling issue indicates a problem somewhere.

If I knew what I was doing all the time life wouldn't be any fun.

'80 KZ650 E 700cc, dyna ignition and coils, frame up restoration, daily driver
'81 KZ1300 A3 full restoration, custom big bore pistons, 1400cc 6 cylinder super bike
"77 KZ650 B1 - Barn Find, work in progeress
"74 Yamaha DT 400 Enduro

Last edit: 29 Aug 2017 08:34 by Tyler.

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JWKZ750
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Re: Kz750b tuning.

29 Aug 2017 11:35

#769944

Stocky wrote: Hi Everyone,
Can't get fine tuning correct.
I have a rebuilt 79KZ750B. 2into 1 Mac exhaust. Checked valve timing twice , ignition timing also. New carb kit , new diaphrams , carb stripped and cleaned twice . No air leaks. Checked float levels etc etc. continually fouls plugs - black sooty.
Have had running reasonably well - some intermittent missing, However I read a forum a while ago that suggested going to 50 pilot jet.. since then more fouling and more missing past idle. Also Adjusting pilot screw doesn't seem to make a lot of difference.
Can any one who has Mac 2 into 1 pipes tell me what jet changes are necessary.

FWIW my 77 750B had a slow leak in the brass carb float. Till it was identified, I was going crazy trying to figure out what my issues were.

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Stocky
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Re: Kz750b tuning.

29 Aug 2017 23:45

#769977

Thanks Tyler , I suspected it was odd to have signs of rich when it should be lean. I'll pull the carbs off and take another look and check floats etc as you suggested.

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