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Nighthawk 650


ShawnR
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I did clean them up with a rag, they all had a LOT of carbon build up on them. Like crumbs of crunchy stuff.

With a pair of vice grips on the crank, I can feel it move just a hair when I bump the starter, and the 2&3 pistons also move (just a hair).

Not so with either of the outside pistons, Having my fingers on them, there is nothing moving at all.

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Now I'm wondering if some of the carbon crap might have flaked off and lodged between the piston and cylinder wall.  Or possibly worked it's way between the inside ring groove and inner face of the piston ring.

Just guessing here.  Diagnosing mechanical problems over the internet is like sticking your hand into a burlap bag and guessing what kind of snake is in it.

Edited by Wandering Soul
Not enough coffee this a.m.
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It's normal to see carbon on piston crowns like that.

 

Your cyl walls would be dull and lumpy if you seized a piston. 

 

Pull the cyl off. It's easy to get back on, just gotta know the trick.

 

My bet is that you either have a seized crank bearing or something in the clutch/trans exploded....Or the primary drive chain broke and wrapped itself around the crank....Or a dozen other bottom end issues. Make sure all the bolts and stuff are out and pull the barrels off. Remove the clutch side cover, ignition pickup cover or maybe stator cover (I'd have to look at motor to figure out the best place) and put a breaker bar and socket on it. 

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Did you try nighthawk-forums.com and maybe put up a request for an engine ?

It's been some time now but I met a guy on the east side of Cleveland who something like  20  700s and 650s in varying states. I'm sure someone has an engine if it comes to that.

Unfortunately I had his info on an older version of the forum, and that and a ton of other information was lost.

Edited by mike884
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On 1/3/2017 at 11:36 AM, CrazySkullCrusher said:

Pull the cyl off. It's easy to get back on, just gotta know the trick.

My bet is that you either have a seized crank bearing or something in the clutch/trans exploded...

Pulled cylinders off with no issues at all.

pistons.jpg

#3 piston wouldn't move on the crankshaft at all, all others looked good. I could access the rod bolts from underneath and pulled rods 2&3.

Here are the bearings from #3 as they came off the crank (fused together). Crankshaft is toast there too.

bearings.jpg

Since you can't get replacement bearings for this anymore, repairing really isn't an option. Donor crankshaft with bearings is available (used), but I would really rather find a decent engine and just do a swap. Or else part it out. Not willing to rebuild with used parts and cross my fingers that nothing else was damaged. Quite a bit of copper in the oil pan from the destroyed bearings.

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Ouch!  Before you rebuild(if you choose to)find out why those bearings look like that.  Is oil flow obstructed, or a bad oil pump?  I'm curious what all the bearings look like.

Last thing you'd want to do is put all that time and $$$ into installing a good used crank & bearings, only to have it seize up again.

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Likely someone ran it out of oil, but there would be evidence of that on the cams, the lobes would be swedged out sideways.

 

You can mic the new used crank bearings and journals to determine if they're in spec.

 

You can access the oil passages with the crank out, and you can replace the oil pump pretty cheaply for peace of mind. 

 

Good luck, I have a great trick for getting the cyl back on over the rings. I will type it out if you request. 

 

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I have found another good engine up in Toledo and will probably run up there to get it Monday (MLK day) since I am off work so it should be a fairly easy swap and have it up and running again. It will probably be for sale again in the spring, but I'm pulling it off the market for now.

Thanks all for the advice & suggestions.

 

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  • 1 month later...
18 hours ago, max power said:

So did you get the new engine in?

It is mounted, carbs are cleaned and mounted and exhaust is on. I am a bitch of a time cleaning up the old valve cover gasket, I SHOULD have done it before I mounted it up and has it on its side. Now I am having to be careful with all of the little pieces of gasket crap falling in beside the cams. I am probably going to lay the bike on its side and flush everything out with kerosene to make sure all of the pieces are out. I'm still not positive it will even run yet.

I"ll have around $750 in it after new air filter and 2 oil changes and plugs. Hoping to sell it in the $1300 to $1400 range once it gets warm and is all pretty.

 

 

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On 3/19/2017 at 8:29 PM, ShawnR said:

It is mounted, carbs are cleaned and mounted and exhaust is on. I am a bitch of a time cleaning up the old valve cover gasket, I SHOULD have done it before I mounted it up and has it on its side. Now I am having to be careful with all of the little pieces of gasket crap falling in beside the cams. I am probably going to lay the bike on its side and flush everything out with kerosene to make sure all of the pieces are out. I'm still not positive it will even run yet.

I"ll have around $750 in it after new air filter and 2 oil changes and plugs. Hoping to sell it in the $1300 to $1400 range once it gets warm and is all pretty.

 

 

Let me know if you get it running good. I've been looking for one of those for quite a while.Let me know if you get it running good. I've been looking for one of those for quite a while.

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  • 3 weeks later...
On 3/21/2017 at 0:41 PM, max power said:

Let me know if you get it running good. I've been looking for one of those for quite a while.Let me know if you get it running good. I've been looking for one of those for quite a while.

All back together and running. Carbs are synced and the new air & oil filters are supposed to show up today. I haven't actually ridden it yet, but will probably go for a run this weekend. I'll pull tags off of something else for the test rundown. Shoot me a note if you want to come up and give it a look, Sunday looks to be beautiful.

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On April 7, 2017 at 11:56 AM, max power said:

Didn't realize I had a double Joel post. Man I just bought An enduro last week. I do know a guy who will probably be very interested.  PM me pics and details.                           Don't be stealing my bike I had one like that

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Just posted on CL this morning. Asking $1600 knowing that someone will offer $1500. It's a nice bike. I expect my kid will try to talk me into keeping it for him.

https://columbus.craigslist.org/mcy/6087980226.html

 

Edited by ShawnR
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 So did you sell it or keep it for your kid? Sent it to a buddy of mine and went to look at the ad today and it's gone. Probably a good thing because my finger was itching to pull the trigger on that thing. Might've got me divorced   

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12 minutes ago, max power said:

 So did you sell it or keep it for your kid? Sent it to a buddy of mine and went to look at the ad today and it's gone. Probably a good thing because my finger was itching to pull the trigger on that thing. Might've got me divorced   

Neither.,I just pulled the ad. Mainly because I am in a VMware training class all week, but I also noticed a fork seal leaking. New seals come tomorrow and I'll change them out Friday after I get home. Back up on CL after the forks are back together. They aren't too bad to do since the bike has a center stand to support it while the forks are off.

 

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