Author Topic: My Project - It Runs!  (Read 968 times)

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Offline JBCB500

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My Project - It Runs!
« on: February 16, 2017, 07:40:50 AM »
I finally got my bag of bolts running - and it feels great! (see video attached)

It definitely needs a bit of fine tuning, and the exhaust headers sound a tad leaky, but I'm pleased for today.

« Last Edit: February 16, 2017, 07:43:12 AM by JBCB500 »

Offline flybox1

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Re: My Project - It Runs!
« Reply #1 on: February 16, 2017, 07:57:51 AM »
Good job so far!  8)
Carry on. . .
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
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Offline evinrude7

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Re: My Project - It Runs!
« Reply #2 on: February 16, 2017, 07:14:53 PM »
awesome.  it's encouraging to see others making headway. 
« Last Edit: February 16, 2017, 07:16:33 PM by evinrude7 »
cb750 k6 - ugly

Offline Don R

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Re: My Project - It Runs!
« Reply #3 on: February 16, 2017, 10:32:05 PM »
 Where's the like button?
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Offline Deltarider

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Re: My Project - It Runs!
« Reply #4 on: February 17, 2017, 11:50:14 AM »
Your engine seems to run at a very, very low rpm. Are all four working? Sounds like a two cylinder engine to me. Anyway, increase to 1000 rpm at least to have enough oil working. Then there's some ticking. Are the valves adjusted correctly? Could also be a leaking or missing exhaust gasket.   
« Last Edit: February 17, 2017, 11:53:43 AM by Deltarider »
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Offline JBCB500

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Re: My Project - It Runs!
« Reply #5 on: February 22, 2017, 09:31:00 AM »
Thanks all!  Thanks Delta - you were right about several things!

I knew about the exhaust tick but I agree it also sounded like it wasn't running on all 4.  In fact exhaust headers for 3 and 4 were stone cold.  I checked spark and it was there.  I also took off the carbs and confirmed float heights as I had some leaking.  I shrink sleeved all four carb bowl needles as they all showed cracks.  Finally, I installed the rev counter cable as this was previously missing.

I also re-sync'ed carbs and adjusted idle RPM up quite a bit.

Now it idles much better, and all four pipes are hot.  I still have quite a bit of a drip from at least two of the carb overflow hoses though...

Finally, the idle did race a couple of times - this may have been a choke issue???

Offline PeWe

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Re: My Project - It Runs!
« Reply #6 on: February 22, 2017, 10:42:56 AM »
If you have had the engine apart completely I understand your feelings. It feels great when it starts and know that the engine has been in pieces, I have put it together and it works.

My last build was like I have had the bike running well for long time, stopped for a coffea and start it again. It ran perfect direct, ignition on all 4 after 2 sec electric starter. A little bit tooo good!

I heard leaking exhaust from 1 cyl. Might be more when all will run.

I agree on too low idle. Avoid that, oil pressure to cam is more important than low idle. My bike like 1200 rpm to ensure pressure. I have seen flickering oil lamp at 1000 or maybe just under when warm last summer
« Last Edit: February 22, 2017, 10:45:49 AM by PeWe »
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 JBCB500

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Re: My Project - It Runs!
« Reply #7 on: February 23, 2017, 08:33:23 AM »
Thanks PeWe, indeed I am feeling very satisfied as this bike came to me as a bundle of parts at the end of November.  It hadn't run in over 12 years so I've been into every nut and bolt on it.  Glad to have brought it back from the dead.