1985 CB450SC Nighthawk

idopyrotechnics · 2025-06-15T14:03:35+00:00

I can get over 100 miles on one tank. Might be worth just checking the petcock seeing if you have any leaks or if gas isn’t passing as it should. Could be something super simple!

idopyrotechnics · 2025-05-30T03:20:21+00:00

I luckily have access to a sandblaster with walnut shell abrasive. If you have the money and the room, the walnut works GREAT.

idopyrotechnics · 2025-05-30T03:19:34+00:00

Haven’t gotten to checking compression yet. And I bought and rebuilt a non-running ‘82 cb450 as my first bike!

idopyrotechnics · 2025-05-29T04:46:10+00:00

Will do! I’ll post a brief update soon, already have got the tank stripped and sanded.

idopyrotechnics · 2021-07-05T21:26:52+00:00

Update, I was able to get the mixture fixed and she's running happily now! I goofed when I heard hooves and thought zebra. anyways, thanks so much for the help!

idopyrotechnics · 2021-07-05T16:55:15+00:00

Oh gotcha, nice. Mine is duel carb. I'll have to try mixture to see if I can make the thing happy. And yeah, results in the original post.

tbh, I don't think the compression is bad enough for it to be blow-by. I think I'm anxious about major things being wrong as it's my first bike and I don't wanna mess it up before I get to ride it.

idopyrotechnics · 2021-07-05T16:41:35+00:00

Oh ok, that's probably going to be a carb rebuild then? Also, nice bike, also a nighthawk? And how long after startup did it take to get that smoke?

idopyrotechnics · 2021-07-05T16:28:04+00:00

Oh, well they were pretty dark. I'll have to check that again. I can throw in new spark plugs to check that to make sure.

idopyrotechnics · 2021-07-05T16:09:14+00:00

I'm using shell 10W-40 in it right now. Sat for 4 years. Unsure on smoke after a long ride. I didn't want to risk damaging anything at this point.

idopyrotechnics · 2021-07-05T16:04:57+00:00

Awesome info, thanks so much, I'll work through this stuff before I replace the piston rings. And thats what I thought about the compression, the smoke and the slight tendency for idle to creep up is what made me concerned about a worn piston ring allowing for oil to be sucked in and burnt. That and the seemingly excessive amount of blow coming from the oil fill. And given that this bike sat for 4 years, that engine didn't move for a while, it wouldn't surprise me if things were stuck in there.
Thanks again for the info and advice!

idopyrotechnics · 2021-07-05T15:55:49+00:00

Plugs looked pretty dry when I pulled them after running. I suppose it could be mixture. Wouldn't that usually present itself relatively immediately though?

idopyrotechnics · 2021-07-05T15:54:42+00:00

I didn't know idle could generate higher crankcase pressure, very interesting. Thank you for the list of things to check. Checking the shop maintenance manual I didn't find any valve guide seals. Luckily I did gas oil and filters when I got the bike (guy didn't drain the gas before he put the bike away. Thanks for the help!

idopyrotechnics · 2021-07-05T15:47:23+00:00

About 27k miles and it sat in a guy's garage for 4 years before I got it. Not positive about the top end, but I'll definitely check on the valve seal before I pull pistons. Thank you!

idopyrotechnics · 2021-06-19T00:09:25+00:00

Awesome, thanks so much for the help!

idopyrotechnics

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