Author Topic: slow crank after rebuild  (Read 971 times)

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Offline Fourme

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slow crank after rebuild
« on: June 27, 2020, 06:09:44 PM »
I recently completed the rebuild on my CB750 k2 engine.  I used the CycleExchange method (drill oil pump) to prime the oil pump.  Good pressure and oil to the head etc.  I then attempted to crank the engine with the battery from my BMW motorcycle (relatively new battery that started the BMW today).  Engine cranks very, very slowly, then stops.  I checked and the cleaned starer per the Hackaweek episode. Would it acceptable to use a car battery to get this to crank and check oil pressure when cranking (just want to ensure no issue before I take the steps on dropping this in the frame)?  Am I missing something?  When I watch the videos of other doing same test engine cranks away.  Thanks in advance for your assistance.

Offline spotty

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Re: slow crank after rebuild
« Reply #1 on: June 28, 2020, 02:40:04 AM »
Have you tried turning the engine by hand with a socket on the end of the crank ? Just to make sure it turns without undue resistance and no tight spots ? Plugs out of course

I'm sure you have as it's an obvious go to but thought I'd offer it up
i blame Terry

Offline Fourme

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Re: slow crank after rebuild
« Reply #2 on: June 28, 2020, 06:16:48 AM »
I did when lining up cam for tappet clearance etc, but thank you for the suggestion!

Offline PeWe

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Re: slow crank after rebuild
« Reply #3 on: June 28, 2020, 06:20:06 AM »
Or use kick starter. Turning crank by the 23mm nut on ignition side must be done with care if spark plugs are in. Clock wise.
Take out spark plugs and rotate crank. It should move very easy. Fresh bores with new rings has some extra friction.
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