Author Topic: Another 750 Four.  (Read 7337 times)

Offline barnabasantioch

  • Posts: 98
Re: Another 750 Four.
« Reply #40 on: Dec 02, 2017, 08:21:53 »
I had no intention on dragging this project out for nearly 2 years, but life happens.  We ended up moving, and our new garage is more of a storage shed, so it put me behind.  Thankfully, I was able to send it to a friend's house where we were able to get it to where she stands today.  Essentially complete, minus a few odds and ends to make it road legal.  Ran into an issue with a faulty R/R, but she runs beautifully.  Hoping to have her on the road within a couple of weeks, because I hear December is the best time to start riding  :o

Offline barnabasantioch

  • Posts: 98
Re: Another 750 Four.
« Reply #42 on: Dec 27, 2017, 08:51:54 »
Ok folks, I need your help with this one.  I was embarking on my maiden voyage (riding it home) when I began getting a distinct "flapping" from inside the engine.  By the time I was able to pull over, it was too far gone and had seized.  Now I'm in the process of trying to determine what may have caused the engine to dry up.  I had noticed the oil light at the same time the flapping began, so I am under the impression that the engine stopped getting oil.  I am using the oil can from cognitomoto, and I'm trying to determine if that may have been the fault.  When I opened the cap to ensure there was oil in the can, I noticed that the oil was smoking a bit.  I'm assuming that's not normal.

Any thoughts?
She ran great for about 10 miles. ::)

Offline Odontologist

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  • Umina Beach, Australia....Where does that part go?
Re: Another 750 Four.
« Reply #43 on: Dec 27, 2017, 09:20:30 »
No oil pressure? Clogged arteries!
Run out of zip ties? Dental floss is an excellent alternative.

1982 Honda CX500 Roadster build

Offline CrabsAndCylinders

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  • Careful With That Axe Eugene
Re: Another 750 Four.
« Reply #44 on: Dec 27, 2017, 17:14:03 »
Your bike looks great, sorry to hear about the engine.  Did you jet it to work with the velocity stacks? 
Lighter, Quicker, Faster.
ZX-14, 900F x 2, 1100F, R100, CBR600, SR500, GT500, RZ350, KZ1000 x 2, Moto Guzzi Lemans lll, CBX550, RD 350, 750 SOHC police special, RG250, TL1000R, GT750, KTM Super Duke 1290 R, Harris/Z-1, Norton 750 Commando, Green 77 KZ650

Offline irk miller

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Re: Another 750 Four.
« Reply #45 on: Dec 27, 2017, 18:09:22 »
First thing I would do is make for damn certain the thing is locked up.  Could be something as simple as clutch or gear or cam chain related.  If your oil bag was smoking, then I would think it was at least circulating through a hot motor.  You sure it was smoke and not steam?  Start at the top and work your way down.  It's a pretty bike and the motor looks fresh. 

Offline teazer

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Re: Another 750 Four.
« Reply #46 on: Dec 27, 2017, 20:06:38 »
First thing I would do is make for damn certain the thing is locked up.....

I would start by pulling the spark plugs and while they are out, how do they look. Then I'd remove the valve covers to see if the valves are all where they are supposed to be.

Next I would remove the points cover and see if the crank can be turned in either direction.  Normally a motor should not be rotated backwards, but as long as you are just determining IF it can rotate, no harm should be done.

If the crank will not rotate even a little, I'd pull the motor and strip and inspect it.  Loss of oil pressure suggests a spun bearing shell or an oil pump that failed to pump and that could be blocked oilways or a failed pump or pressure relief valve. It could be as simple as a blocked oil screen that caused the failure.

If pressure dropped and bike did seize, you are looking at a replacement crank if smaller shells are not available, plus replacement of any other internal damage.

In the thread you mentioned that the motor was going out to be rebuilt but no mention of what was done.  Was it just an external clean and paint or was it stripped and rebuilt?
« Last Edit: Dec 27, 2017, 20:10:42 by teazer »

Offline cxman

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Re: Another 750 Four.
« Reply #47 on: Dec 27, 2017, 22:47:52 »
when you reinstalled the motor did you "prime" the oil system by pulling the

plugs and cranking the motor a bit at a time till the oil light went out ?

or did you just start it?

how long did the motor sit dry before it was started
1978 CX650 Super Deluxe
1979 XS1100 Special
1974 xl350
1983 cx650 Custom
1973 cb750
1980 cb750
1981 cb650
1982 cb900 c
1974 kawasaki 350 bighorn
1983 GL1100 aspy full dress
1983 GL1100 Nekid
and a bunch of others

Offline WhyNot

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  • ~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Re: Another 750 Four.
« Reply #48 on: Dec 28, 2017, 10:17:00 »
Lots of questions, lots of instructions, bike looks great.

Hope it's something simple, good luck.
2006 Harley Davidson Heritage Softail
1975 Honda CB750K5 needs carb work
1974 Honda CB350F2 needs tins painted (being lazy)
1972 Honda CB175K2 roller no engine
1972 Honda CB/CL350 Engines need roller
1972 Honda SL350K2 Frame for above engine
1972 Honda CB100K2 needs kicker shaft
1990 Mitsubishi MM needs engine rebuild
1984 Dodge D50 Beater DD since 1997

Offline coyote13

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Re: Another 750 Four.
« Reply #49 on: Mar 01, 2018, 16:37:38 »
Did you ever get anything figured out with this?  When you said flapping I immediately thought cam chain.  Hope you got it sorted out, bike sure is pretty
Half the fun's in the get there...