1985 Nighthawk cb700sc mild resto.

[wahvtec]

Got this gem on a craigslist deal. Mix-matched body parts, things missing, about 24k miles.
First on the list of course is a good old carb cleaning. Little bit of pine sol and elbow grease got those going, and first start up revealed a tick from a tappet (video) and a cracked oil pan. At this point I think I'm going to pull the engine since I have to remove the cam. I'll inspect the rings and cylinders. I don't want to make the same mistake I made with my cb350 (view thread in sig) by doing a patch job. Other than the tick the bike sounds great. Also used some aluminum foil and marvel mystery oil on the forks to get rid of some rust...works pretty well. Now to build a small workbench and find a friend to lift this beast of an engine. Don't think I can do it alone like the 350. And also a special thanks to dreadrock for helping me complete my body part collection for this project. Looks a lot better then the rusty red white and blue murica tank.


https://youtu.be/_ynrpsS4nEw
running video

 

[Maritime]

Valve tic can just be loose valves, did you check them or is this model new enough to be hydraulic and auto adjusting. You should be able to just pull the valve cover and check them with a feeler and if too loose, fix them and be done

 

[wahvtec]

This is the model with the hydraulic tappet adjusters. I found the honda bleeding tool and ordered it. Haha I wish it was a simple valve adjustment, I bought too new.

 

[Maritime]

Ha gotcha, I couldn't remember when they switched.

 

[DreadRock]

Very cool man glad I could help !

 

[VonYinzer]

I love these things. Let a red/white/blue one slip through my hands (only $400!!!!!) years ago.

 

[wahvtec]

Well, I am hopeful I found the issue causing the tick heard in the video above. My oil pan had a small crack leaking oil everywhere so I started removing the exhaust to get to it today. Upon removal the cylinder nearest the noise had some interesting work done on the studs. As you can see one didn't even have threads an inch or so away from the head. Hopefully that's the issue. Also there wasn't a single copper crush gasket present. I got extra lucky and removed the questionable stud by hand.

 

[dg1]

Subscribed.

 

[wahvtec]

Alright so I've done a good bit the past two days. Got the new oil pan on and a new drive shaft oil seal, so now my garage isnt being soiled. I put the exhaust back on with crush gaskets etc and cranked it up to get the same tick. I took off the valve cover and pulled the plugs and turned it over while watching, and everything seems to move as it should, and I cant hear the tick. I can only hear it once the bike is firing, not when the starter is turning the engine over. Anyone have any ideas or things to check while I'm at it? I don't want to start pulling cams if it ends up not even being a valve issue. Runs and revs great other than the tick.

 

[wahvtec]

Good news is I determined the source of the tick before removing the cams and messing with the tappets. Bad news is its the #2 rod...crap. Here's a video that showed me how to check this out with a screwdriver while I had the plugs out in case anyone else finds it useful.

https://youtu.be/EiNAtTFFM-Y

(not me in the video)

 

[wahvtec]

So since compression and the head both check out well the current plan is to give buddies beer to help me lift this engine out tomorrow, flip it over on the bench, and remove the side covers and bottom of the case. If removing the cylinder 2 bearing shows that the crank isnt scarred ill replace it. From the more experienced builders would you assume the other bearings will soon fail even though they dont demonstrate any feelable slop? Would you replace all rod and main bearings? (Around 200 bucks in parts vs 20 for just the one con rod.). The engine has 23,500 miles on it and i just cleaned out the oil pan screens etc. Thanks!

 

[brt651]

Hello wahvtec,
I like your bike it's coming along nicely. I'm not a Honda guru but I believe Honda crank bearings have a colour system to the bearings. The engine may have different colours throughout equating to different size journals. Maybe someone started the bike with no or low oil in the pan. As you mentioned that it had a leak. Maybe that could be the cause of any bearing failure. Just a thought. Good luck
Cheers
Brt651

 

[wahvtec]

Thanks! Yes, I recently found a source for the different coded bearings, and found the info in the honda manual. After some discussion at nighthawk forums and digging in the manual the plan is to open up the bottom, and use plastigauge to test all of the crank/rod bearing surfaces. Those that fall out of the tolerances will be replaced. Nice to have a test rather than just purchasing parts. Will also wipe clean and apply assembly grease to all of those bearings. Ill have the engine out as soon as a friend has some free time to lift. Though I didn't plan on removing the engine and all guess its an excuse to touch up all the polished side covers, and lower frame paint.

 

[wahvtec]

Progress...I guess this picture signifies the point at which the "mild" in the title no longer makes sense, and is just mocking me for assuming it just "needed the carbs cleaned".

 

[dg1]

Progress...I guess this picture signifies the point at which the "mild" in the title no longer makes sense, and is just mocking me for assuming it just "needed the carbs cleaned".

I have one at home that I'm assuming just needs the carbs cleaned...

 

[wahvtec]

Haha I'm sure you may have better luck than me. If not the good news is I'm not having much trouble sourcing parts. Out of curiosity are your gauge needles broken for the tach and speedo? It seems that most are. Turns out orange cocktail swords from the party store are nearly identical to the factory orange needles. I found that hilarious..

 

[dg1]

Haha I'm sure you may have better luck than me. If not the good news is I'm not having much trouble sourcing parts. Out of curiosity are your gauge needles broken for the tach and speedo? It seems that most are. Turns out orange cocktail swords from the party store are nearly identical to the factory orange needles. I found that hilarious..

Mine still work.

Other than replacing the carbs I haven't needed anything else yet. <fingers crossed>

 

[wahvtec]

Got the engine split and started assessing the damage. I have learned a lot about inspecting bearings and digging into the engine. Unfortunately I don't think new bearings are going to cut it. Bearings had spun/ were moving all around while I was disassembling the connecting rod, they actually were overlapping each other a lot. I'm fairly certain the connecting rod and crank are toast from the looks of it. If anyone more experienced could verify by looking at the pictures I would greatly appreciate it. D*** this nighthawk.

 

[DohcBikes]

To be honest it really doesn't look that bad, mostly bearing material. Measure the rod journals to see if they have lost or gained material. Measure the i.d. of the big end of the assembled rod to see if it has lost or gained material. If they are within spec, clean em up and get some plastigauge results to see if there is a bearing option that is the right size.

Or, it's a 700 nighthawk. Just burn it.

 

[wahvtec]

To be honest it really doesn't look that bad, mostly bearing material. Measure the rod journals to see if they have lost or gained material. Measure the i.d. of the big end of the assembled rod to see if it has lost or gained material. If they are within spec, clean em up and get some plastigauge results to see if there is a bearing option that is the right size.

Or, it's a 700 nighthawk. Just burn it.

Hmm, What is a good method to remove the bearing material? I didn't consider some of that could be left over from the bearings. Ill have to borrow some calipers from work I only have plastigauge at the moment...plus im drinking now...I am starting to understand the general hatred of nighthawks lol.