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Discussion Starter · #1 ·
That's next on my to-do list (well, after I clean and lube the chain :p). The underside of my bike has quite a bit of rust, how do I clean/treat it and prevent it from coming back?

rust.jpg
rust 2.jpg
 

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You can try 0000 steel wool. Seemed to work very well on my Scrambler pipes. There is also a product called Quick-Glo that I use all the time. Works very, very well.
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Discussion Starter · #3 · (Edited)
Thanks! My amazon cart is full of stuff for the motorcycle right now, my wife is going to kill me :-D Would you suggest the fine type or the original for heavy use? Maybe start with fine and try the original if it's not strong enough? I don't want to scratch anything...

So you use the steel wool first to remove the heavy rust deposits, and then the quick-glo? I'm watching videos online and wow, it does seem to work wonders, although I think in my case the areas I took pictures of are probably too far gone. We'll see...
 

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There are mechanical and chemical methods for removing rust, and yes as you said keeping it from coming back is a big deal.

I'm a big believer in vinegar (regular 5% white vinegar from your kitchen) to remove rust. If you can remove a part to soak and scrub it works well. For parts you cannot remove and scrub I recommend a sponge to soak the rusty area and a cheap aluminum pan from the dollar store to catch the mess. Work outdoors and start early, wash the bottom of your rusty bits with a vinegar soaked sponge every 20-30 minutes, use a mirror to view your progress. Add some elbow gease with green scotchbrite between sponges full of vinegar to accelerate the process. Basically the vinegar is a low concentration of acetic acid which will convert the oxidized iron into soluable salts which can be scrubbed away, eventually leaving clean steel. The problem with clean steel is it will rust, likely soon. That's a good time to neutralize the acid with a mix of baking soda and water, and then dry the pipes. I recommend a towel dry and running the engine to dry the pipes thoroughly. Then you'll want to apply some sort of protective finish to the bottom of the pipes, there are high temp etching primers and high temp finishes available. Wipe the bottom of the pipes down with a prep solvent, mask off everything you don't want painted, chock the wheels front and rear and have a strong helper tip the bike over to the side opposite the one you're painting. While the pipes are still warm but not hot spray primer, follow the directions on the can for dry time between coats, then spray topcoat after correct dry time interval, perhaps 2 top coats.
Be aware of view angles, if you don't want this paint seen keep it down low in the shadow.
The bottom of your pipes will be well protected from exterior rust. It may be easier to take the pipes off the bike, perhaps that is something for later on.
 

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I would take the exhaust off the bike, clean it up and paint it with VHT engine aluminum paint. It's not like anybody would see it under there anyway.
 

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I'd take the exhaust off too, but I'm not sure Olivier is interested in that, so I didn't go there.
 

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Discussion Starter · #7 ·
Well yeah I'm not sure I want to go all the way :p I mean if this was a '73 CB350 then yeah I'd take it all apart, because I'd feel like I had to, but I don't really think it's the case here. But I don't know, maybe it's easy to do it, I have no idea! :-D
 

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Thanks! My amazon cart is full of stuff for the motorcycle right now, my wife is going to kill me :-D Would you suggest the fine type or the original for heavy use? Maybe start with fine and try the original if it's not strong enough? I don't want to scratch anything...

So you use the steel wool first to remove the heavy rust deposits, and then the quick-glo? I'm watching videos online and wow, it does seem to work wonders, although I think in my case the areas I took pictures of are probably too far gone. We'll see...
Thats how I did mine. There are other ways as mentioned on this thread but i believe this makes less of a mess. Just some old rags and the Quick-Glo. If you end up using steel wool make sure its 0000 grade. Good Luck.
 

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I'm not gonna say I'm sold on Quick-glo especially to keep pipes from rusting again, but this guy shows some good results.
(Honda twin content!)

 

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Discussion Starter · #10 ·
It seems to work really well for light rust deposits from the videos I've seen (like wow!!!!! well). I'll report back next weekend for the heavy stuff...
 

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Discussion Starter · #12 ·
Still not sure at which point the steel wool should be involved though. Should I use it with the quick-glo where the rust is quite thick? Or use it before, then let dry and then go at it with cloth + quick-glo?

If I take the suspension off, are there some gaskets that need to be replaced with new ones, or can everything go back on (assumings gaskets look OK)?
 

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Still not sure at which point the steel wool should be involved though. Should I use it with the quick-glo where the rust is quite thick? Or use it before, then let dry and then go at it with cloth + quick-glo?

If I take the suspension off, are there some gaskets that need to be replaced with new ones, or can everything go back on (assumings gaskets look OK)?
Knock off the heavy stuff with the steel wool first and then use the quick glo.
 

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There's no gaskets with the suspension, just the swing arm grease seals which should be fine for millions of years.
 

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Discussion Starter · #15 ·
Ooof, I need to get more sleep, I meant exhaust, not suspension... sorry.
 

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Discussion Starter · #18 · (Edited)
I would take the exhaust off the bike, clean it up and paint it with VHT engine aluminum paint. It's not like anybody would see it under there anyway.
Well I ended up doing just that tonight, I looked in the service manual and it didn't look all that complicated, so... makes it easier, and since I want to clean the chain this week-end (plus I can't ride tomorrow since it's going to rain here) it'll make it all easier. I'm surprised there is so much rust though, I mean, I guess it's 11 years old, so there's that, but still, the MD DMV must have kept those in the rain or something. The collars in particular are very rusted, I may order some replacements. Some fasteners I want to replace too (see below)... that being said, where the rust is not too severe, the quick-glo is working really well.

First it looks like there are some welded plugs alongside the length of the exhaust. I think one of them has rusted through, and the other one is in the process, I can't imagine there are supposed to be holes under there. Is there a good way to plug them?
Rusted through hole_.jpg
Rusting Hole_.jpg

Second I wonder if I can safely remove these screws and replace them with clean, un-rusted ones. There's no trick, right? No nut that's going to fall off inside the exhaust so I won't be able to reattach these plates? These rusted bolt heads look like crap...
Protection Plate.jpg

I'm also thinking about replacing this bolt, it looks like it's rusting through...
Fastener - middle.jpg

Anyway, this is how it looked like before I started going at it. It's starting to look better already, but that middle member is pretty far gone. I took some steel whool to it and it's starting to look better, but the connections to the exhaust pipes in particular are pretty bad. I'll post more pictures tomorrow once I'm done cleaning it. And yes, nobody can see it... so I'm thinking about painting it with something to stop the rust and prevent it from coming back. VHT aluminum paint would be a good choice? It looks like it's pretty prone to rusting, which I guess makes sense considering where it's located... BTW the pipes near the engine do look a bit discolored... blue-ish and yellow-ish a little, hope it's not too bad a sign.
Underside - before.jpg
Top side - before.jpg
 

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Discussion Starter · #19 ·
One thing I didn't think ahead of time though: I don't (yet) have a replacement for the two copper gaskets. I hope to find one at a motorcycle store today, but if I don't and I have to order one online, which will take a few days to be delivered, is it OK to ride re-using the old gaskets until the new ones arrive? They may take a few days and I don't want not to be able to ride in the meantime...

I see a fair amount of black soot/deposit at the exit of the exhaust and also where it connects to the engine, is that normal? Or a sign that the carb mixture isn't right?
 

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I'd have warned you to have a new set of exhaust gaskets on hand if I had the foggiest idea you were going to unbolt your exhaust from the engine.
Here's some on ebay, I've bought from this seller before. https://www.ebay.com/itm/2-Exhaust-Pipe-Gaskets-Fits-HONDA-CB250-Nighthawk-250-1991-1997-2000-2008/282077470749?fits=Model%3ANighthawk+250%7CSubmodel%3ACB250&epid=28003210841&hash=item41ad20a01d:g:lEUAAOSwjXRXbFhN

Removing those screws or that bolt may not be easy (or necessary) being rusty they'll give you a good fight and may wind up breaking off anyway.
Remove the rust if you can't stand looking at it and paint them with high temp paint and a small brush, a couple of coats should do.

Exhaust studs at the cylinder head on these are notorious for breaking while unbolting the pipes.
You may or may not be able to reuse your old gaskets, the exhaust shouldn't bolt up as tight as can be, it only should be tight enough to seal.
 
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