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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Sat Mar 03, 2018 9:45 pm

Pulled the plugs and checked for play in the pistons and there is definitely movement in cylinder two. I may just end up parting this out :(

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GeorgeSweety
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Re: New to forum, new to Nighthawks. Howdy...

Postby GeorgeSweety » Sun Mar 04, 2018 12:58 am

Are you able to do a compression test? I wouldn't write it off yet.

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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Sun Mar 04, 2018 10:08 am

Yes sir I can definitely do a compression test, What exactly am I looking for? I mean aside from good compression.... What are my options if I do have compression. Thanks, I really appreciate your help here.

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Folsoml
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Re: New to forum, new to Nighthawks. Howdy...

Postby Folsoml » Sun Mar 04, 2018 10:17 am

pdxkevy wrote:Looks like a run away washer


For what it's worth, the washer is one of the ones that fit over the cylinder head bolts.

All the rest of the junk in your picture is metallic?
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Sun Mar 04, 2018 10:41 am

Thanks George and Folsoml. Makes sense, the condition of the valve cover install was kind of appalling. RTV everywhere, loose hand tight bolts. After work today I will put the oil pan back on fill her with oil, and run a compression test. I already recharged the battery so we shall see what we get. It would be kind of heartbreaking to part this out. I kind of like it and it's from the year I graduated high school. I'm willing to put in the time and work (and research) in to getting her back on her feet. As long as it doesn't end up being too cost prohibitive.

Side note If admin feels this topic should be moved at this point, Have at it. Thanks for your leniency.

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Folsoml
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Re: New to forum, new to Nighthawks. Howdy...

Postby Folsoml » Sun Mar 04, 2018 7:47 pm

pdxkevy wrote:... and it's from the year I graduated high school.


We must be about the same age! :D
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Sun Mar 04, 2018 10:14 pm

So cold compression test from left to right facing front of bike. 135, 90, 125, 140.
The service limit spec for warm compression test is 156. The piston movement a noticed was on 3 the one that read 125.
What do you make of all that @Georgesweety?

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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Sun Mar 04, 2018 10:26 pm

Folsoml wrote:
pdxkevy wrote:Looks like a run away washer


For what it's worth, the washer is one of the ones that fit over the cylinder head bolts.

All the rest of the junk in your picture is metallic?

yes all the other material was picked up with a magnet....

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GeorgeSweety
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Re: New to forum, new to Nighthawks. Howdy...

Postby GeorgeSweety » Mon Mar 05, 2018 2:46 am

pdxkevy wrote:So cold compression test from left to right facing front of bike. 135, 90, 125, 140.
The service limit spec for warm compression test is 156. The piston movement a noticed was on 3 the one that read 125.
What do you make of all that @Georgesweety?


Hi pd, so it is cylinder number 2 that has the 90 psi? As you sit on the bike, the 2nd from the left? Did you do the test with all plugs removed and the throttle wide open? On the cylinder with the lowest compression put a teaspoon of oil in the cylinder through the plug hole and turn the engine over a couple of times to distribute it around the cylinder wall. Then do the compression test on that cylinder again, if the psi rises then the rings or bore is worn, if there is no change then the problem is with your valves.
With regards to piston movement please can you describe the movement? Is it a sideways or up and down movement? Have you actually had the head off?
These DOHC's have auto valve adjusters on them so I've heard and the PO made a hash of replacing the head? or just the valve gear? What is the mileage on the engine? My idea at the moment is something the PO messed up if it is a relatively low mileage engine.

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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Mon Mar 05, 2018 9:23 am

Thanks so much for your help George. After putting a bit of oil in the cylinder with poor compression, I did see a significant improvement. Almost 150 psi cold. As far as the piston movement, all I did was manually cycle through pistons and when they were a touch past tdc i put a wood dowel down the spark plug hole and gave a push. On hole 3 (left to right) the piston had probably a mm or 2 drop. The rest seemed solid. I did receive a video from the PO of what he claims to be the last time he started it which includes the noise he was trying to explain.
https://youtu.be/YaiJzTRWLto
I am interested in your take on this. I am also very interested in your thoughts on how I should proceed. I have the Clymer manual (for what it's worth) as well as the Cyclpedia online service manual which is pretty detailed. I'm pretty good mechanically and have or can get most necessary tools. However I have never split the case on a bike. I am also concerned about the monetary investment that it may take to get her back running well. If it was going to be $500 or less-ish over the maintenance period. I feel ,like I could live with that. But if it looks like it's going to go beyond that, I don't know if I can justify the expense. Thanks again as always for your help.

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GeorgeSweety
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Re: New to forum, new to Nighthawks. Howdy...

Postby GeorgeSweety » Mon Mar 05, 2018 9:51 am

After listening to the sound on the vid and the movement you describe I could only presume that the big end shell bearing has gone on that cylinder, which would mean splitting the cases. As for the cost of repairs I really wouldn't have a clue :roll: I have only worked on the Honda SOHC engines up to now but if the bike was mine, I would search out as many replacement parts that I would estimate I need, allowing for worst case scenario, compare that figure to getting a secondhand engine, then judge both figures against what the bike would be worth in running condition and what it would be worth if you parted it out. I know that isn't a very clear answer but what it boils down to is how much are you prepared to pay to put it right.
That is only a part of the problem though, the cylinder with the low compression seems to have either a ring or bore problem, again, if it were mine and I intended to keep it I would probably replace the barrels/jugs or have them re-bored, because if the big end shells have gone on number 3 then that won't have done any good to the piston or bore on that cylinder.
I'd keep it and fix it but that's just the way I am, I don't like to be beaten :lol:

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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Tue Mar 06, 2018 2:13 pm

Let me ask you a question.. Where would I find a source for engine swap compatibility? My mechanic has a low mile engine from a 92 CB750 nighthawk that he believes would swap right over. But, I want to double check to make sure. Any leads on such info...? thanks again

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Folsoml
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Re: New to forum, new to Nighthawks. Howdy...

Postby Folsoml » Tue Mar 06, 2018 7:28 pm

I've never heard of the two engines being bolt-on interchangeable, but if you know how to weld, you can make anything fit.
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

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GeorgeSweety
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Re: New to forum, new to Nighthawks. Howdy...

Postby GeorgeSweety » Wed Mar 07, 2018 2:28 am

I just searched both bike specs and these are the first results I came up with so if your mechanic is talking about a different 750 Nighthawk then I do apologize.
http://www.motorcyclespecs.co.za/model/ ... k%2083.htm

https://www.totalmotorcycle.com/motorcy ... 0Nighthawk

According to "these" specs, the 750 is a water cooled, chain final drive engine. I think we are all aware that the 84 DOHC is shaft driven. If your mechanic can get that 750 motor in that 650 chassis then all respect to the guy.
The easiest source for an engine swap would be from an 84 Nighthawk, plug and play.

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pdxkevy
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Re: New to forum, new to Nighthawks. Howdy...

Postby pdxkevy » Wed Mar 07, 2018 12:20 pm

You are correct sir. It became pretty obvious that he was mistaken when I got a chance to look at it. Pretty sure the whole oil delivery system is different as well. From what I've read, I may be able to use an 83 or an 85 in addition to the 84. But, i'm still researching. If i can find a proven runner of an engine for around $400 in the next month or so I might take a run at it. Otherwise, I may just post it as is, with full disclosure on Craig's, take what I can get for it and eat the loss. Lesson learned I suppose... Thanks again for all your help.


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