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Offline slaphead

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advance spark
« on: March 27, 2020, 12:03:33 PM »
Hi all
Im having real trouble setting the timing on my CB750k 1977, everything seems to be 180deg out, I bought this bike as a box of bits so unsure on the advance spark is the correct one.
Anyone help?

Cheers Kev
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Offline robvangulik

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Re: advance spark
« Reply #1 on: March 27, 2020, 12:14:49 PM »
Possibly the cam is put the wrong way round on the advancer, pull it up and put it on again a half turn further. You'll have to pull the weights out a bit.
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Offline slaphead

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Re: advance spark
« Reply #2 on: March 27, 2020, 12:56:15 PM »
Thanks Rob will give it a try, i just watched hackaweek no:19 were he refers to the advance unit and it looks like mine is pre 73  ??? not sure if uk bikes are the same but that would explain the 180deg out.
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Offline scottly

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Re: advance spark
« Reply #3 on: March 27, 2020, 01:08:17 PM »
There should be a mark on the end of the cam. The Hitachi unit like you have is interchangeable with the TEC units, not 180* out.
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Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline PeWe

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Re: advance spark
« Reply #4 on: March 27, 2020, 01:22:57 PM »
Cam is 180* wrong when engine runs with yellow and blue wire swapped where connected with main harness.
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline fxef79

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Re: advance spark
« Reply #5 on: March 29, 2020, 02:38:06 PM »
On the Hitachi advancer (which is what you have), the little "dimple" on the cam should be aligned with the Hitachi logo on the base plate (the "double circle").
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Offline fxef79

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Re: advance spark
« Reply #6 on: March 29, 2020, 02:39:07 PM »
And it is ONE of the multiple possible "correct" advancers... see here:
http://forums.sohc4.net/index.php/topic,178464.msg2071376.html#msg2071376

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