*UPDATED REPAIR COMPLETE* Repair advice needed for 84 nighthawk 650

[patheticpuma]

First Post.  

Hi Everyone,
I just got my first bike recently, a 1984 Nighthawk cb650sc. The problem is there are 2 holes in the top of the crankcase. I uploaded a pic of the bike that I drew on to mark where the holes are, I will try and get a picture up close of the damage. The engine runs, it just spews oil profusely.
The following are what I have been considering:
-Buying a new engine (expensive, and im poor)
-Purchasing Haynes manual and a crankcase and changing myself (unsure about this, I don't know if it would be simple as swapping them out, or if there is tuning that would be necessary. i give myself a 4/10 for mechanical ability)
-Taking the motor to have it preheated and welded (not much cheaper than the engine)

Also, I had a coworker suggest using a cutout of window screen and jb weld to fill the hole, but I have no confidence in that goop holding up to the heat and pressure.

I guess my question is how would you go about getting this bike on the road again.

Thanks in Advance,
Troy

[NightHawked]

I've seen it done on a small engine not a motorcycle with I believe MarineX. But I tend to agree with you about it. As far as your other options you might be able to pick up a used engine for around $300., might be money well spent. I wish ya luck it's a good lookin bike.

[JB1290]

You could always try the JB weld idea first and if it doesn't work, move on to the next idea, It's not like you will hurt the engine any more than it aleady is, right?

[Option13]

, You could try this stuff, just turn off the sound as soon as you get the gist of what the speaker is saying. That voice is infuriating.



JB Weld's website, with all it's testimonials, claims that one guy fixed a truck engine block with JB Weld and some coins as filler material.

[fortyhourdays]

Hey Troy,
Welcome aboard.  Where do you call home? 
I agree that you should try some JB weld or similar first.  I have an extra crankcase I'd give you, but unfortunately one of it's motor mounts is broken and if I was going to the trouble of replacing a crankcase I'd want it to be in great shape.  If you want to see how much work would go into replacing a crankcase, take a look at my thread here.
http://nighthawk-forums.com/index.php/topic,9091.0.html

[NightHawked]

FWIW the small engine I saw fixed was tore down to get at it from inside. But that Alumaloy stuff looks interesting, hmm?

[biometrics]

I think JB weld could work, the problem is that the surfaces would have to be REALLY CLEAN AND OIL FREE.  

If the exterior surface is flat, you could try a fender type flat washer held in place on the outside with a moly type wall anchor (the sprint loaded kind you push through the hole) using a soft rubber gasket (or JB Weld) under the washer... make sure the wall anchor doesn't touch anything inside the crankcase...  Let us know how you solve this problem.  The bike definitely look worth saving... it is a 1 year younger sister of my bike!

[patheticpuma]

Ok so I sat down and scrubbed my engine with degreaser I got from work, got it cleaner than the day it assembled. tried a couple different ways to get the jb weld to hold, but it seemed like no matter how i went about it the jb weld was going to drip into the engine. SOOO I scrubbed again and have it shining again, looks like I will be trying alumiloy. Seems easier than soldering, and I'm quite proficient at that. Wish me luck everyone. I will keep you posted once I have an update.

[NightHawked]

FWIW I don't know if you could JB weld around the hole and put like a coin etc. on top of that JB, just a thought if you still have some.

[muttstang]

depending on the hole, you could maybe drill/tap it and put a short screw in there

[patheticpuma]

I already ordered the Alumaloy, or I would try the coin. The Alumaloy seems like the better way to go and I'm really sick of scraping that goo off the engine haha.

[NightHawked]

I hear ya. That's nifty how it doesn't "fall" into the hole. Good luck keep us posted.

[skramer360]

I used JB Weld on the top of my 700s engine 8000 miles ago. I ride it every day and ride it up to redline occasionally and haven't had any problems. I also used it on a Subaru Legacy transmission with a piece of screen and it worked fine. Just my $.02 BTW  to a great forum.

[patheticpuma]

I used JB Weld on the top of my 700s engine 8000 miles ago. I ride it every day and ride it up to redline occasionally and haven't had any problems. I also used it on a Subaru Legacy transmission with a piece of screen and it worked fine. Just my $.02 BTW  to a great forum.

how exactly did you go about it on the top of your engine without drops falling in?

[skramer360]

You can let it set up slightly before you put it on what you are trying to fix. That way it is not so runny and can be molded.

[patheticpuma]

You can let it set up slightly before you put it on what you are trying to fix. That way it is not so runny and can be molded.

That thought crossed my mind, but was told by a friend that once it starts to harden it loses adhesion. apparently he was wrong though if it worked for you. Im gonna try and have my roommate take a pic with his camera tomorrow of the holes in the crankcase so everyone can see what I'm trying to repair.

[Soupskin]

JB Weld makes a putty too.  Scuff it up real good first though.

[Option13]

If you're going to be using anything that requires that much heat you might be better off splitting the cases than hoping it doesn't drip onto something important. Sure, it might not drip in their videos, but they were hardly building up a thick base.

[patheticpuma]

If you're going to be using anything that requires that much heat you might be better off splitting the cases than hoping it doesn't drip onto something important. Sure, it might not drip in their videos, but they were hardly building up a thick base.

I thought about this as well, and came to the conclusion of busting some holes in some chunks of aluminum i have laying around that is very close to the same thickness. I am planning on suspending the scrap to practice and ensure it doesn't drip. One thing I have going on my side for this is the holes aren't a |  | shape but form more of a \  /  .

It is my hope that the v shape will provide me with an easier repair process. The rod should be here around Tuesday since mail wont be running this Monday. I will keep everyone updated.

[patheticpuma]

Okay so I finally got some pics of the damage up for you all, plus I now have a full plan on a repair strategy.

Top view of the holes. Yes I know I have some more cleaning to do before I take a torch to it.


I intend to file off the paint near the holes as well as file off a little of the walls of the holes to ensure a clean, rough surface.


Finally this is how I plan to repair the holes. My roommate and I had this aluminum sheeting sitting here for xbox 360 repairs. So with the trusty, ever so useful dremel I will cut out some pieces to fit over the holes. Once cut and shaped I will clean and tin the pieces with the alumaloy and put them in place on the case. From there I will heat and fill the remainder of the holes.


Any and all suggestions are welcome.

[Option13]

Filing a hole into an engine that you will run after this would make me nervous, as would the torch. If you're not going to tear the engine apart, I think it would be better to just remove the paint around the area with a paint remover, clean, and use the alumaloy.

[patheticpuma]

Filing a hole into an engine that you will run after this would make me nervous, as would the torch. If you're not going to tear the engine apart, I think it would be better to just remove the paint around the area with a paint remover, clean, and use the alumaloy.

Fair point I hadn't thought of. The only reason I am not looking to tear down the engine and splitting the cases is that I do not trust myself, manual or no. Also I am too broke to pay anyone to do it for me(I change oil for a living, far from well paying). Do you have any recommendation on a paint remover?

[patheticpuma]

Okay, so first off, MY BIKE IS ALIVE AGAIN!!!    

And this is what I ended up doing.
I ended up improvising a little bit. I plugged the holes and filed the raised portion between the holes smooth. Then using some thicker aluminum supplied to me by my roommate, I shaped, bent and ground a shim that fit snug against the case covering both holes. Using the Alumaloy, I built up little mounds on the ends and ground them down to fit inside the holes. because angling a torch to use the Alumaloy to "weld" my shim in place was near impossible i resorted to using JB Weld. I scuffed up both the crank case and the shim and ran a thin coating along the case between the holes and around the edges of the holes, and also a thin layer on the bottom of the shim. Pressed the shim into place and and ran more JB Weld around the seams and across the top. Let it cure for a couple days, put on a new filter and filled her up with oil and VOILA!! My bike runs again. I have put several operating hours on the bike since the repair and it seems to be holding strong. It may not look to pretty up close, but function is what is most important to me. I would have taken pics throughout the process but unfortunately was lacking the required equipment.

Only thing left is to get my hands on a new speedo drive, mine is shot

[fortyhourdays]

   Good to hear she's back on the road

[patheticpuma]

  Good to hear she's back on the road

Same goes to you sir. I'm sure it feels great to see how well all your hard work paid off.