Author Topic: engine discoloration (Read 9048 times)

loonymoon · « **on:** May 30, 2005, 09:10:15 AM »

Hi!

I have a 1973 CB350/4 and although the bike is in excellent condition overall, I have noticed that the engine casings seem to be getting more an more discolored . On some panels (like the crankcase) there seems to be a lacquer which has yellowed and is peeling with age, other panels have blackish marks on them. I am loathe to take the engine to pieces and strip the whole thing as the bike runs like a dream and to be honest I haven't the time or money.
So far haven't tried to remove the lacquer as I think it's probably providing some protection to the metal. However I would like to make the engine look nicer so - does anyone have any suggestions as to what I could use to remove the worst of the discoloration without stripping the engine? I thought about using an abrasive metal polish but was scared it may do more harm than good. I think this discoloration is a common occurence and is just a feature of age and use with these engines but I would love it if my engine were as shiny as the rest of the bike!!

Paul · « **Reply #1 on:** May 30, 2005, 01:07:04 PM »

unfortunatly, from what I can gather, the yellowing lacquer is there to stay unless you remove the coating itself, all the polishing in the world will just give you nice shiney yellow lacquer. Some feel the sight of the lacquer shows originality and shows the bike has not been unduely ripped. (Some of the lads may suggest aircraft paint stripper or something....hold tough for more.

loonymoon · « **Reply #2 on:** May 31, 2005, 12:18:12 AM »

Yep that's pretty much what I thought. I've left it 7 years so far I guess I can live with it for longer. I don't want the bike to look like a fully restored "museum piece" as it gets ridden a fair amount and the originality of it adds character!! Thanks for your suggestions anyway!!

loonymoon · « **Reply #3 on:** June 21, 2006, 05:24:41 AM »

Ok I thought it was time to resurrect my old post.

I'd like to polish up the engine (well what I can get to without taking it out of the frame anyway) and remove some of the darkening that's been going on. I don't mind about the yellowed laquer so much as, i agree, this is a sign of originality!!

So what's the best thing I can use to polish up the engine casings (and lacquer) that won't damage the metal and will protect it from corrosion? Bearing in mind that I am in the UK and some products may be unavailable or be different here!!

byurko · « **Reply #4 on:** June 21, 2006, 05:55:35 AM »

I'm in the process of polishing now... First I sand all the crap off w/ 150grit followed by 220grit. Then I wet-sand with 600grit, 1000grit and the 2000grit. I've been using Autosol afterwards with excellent results! http://www.totalmotorcycle.com/reviews/AutosolReview.htm I'd like to seal it with ZoopSeal, but cost is $99. Not sure if it works that good!

I originally bought a bench grinder/polisher, but didn't work as well. Maybe others can share different results.

The good thing w/ your CB350 is that you can remove the valve cover w/out pulling the engine (me thinks?). I had to pull mine to get to it, but it gave me the opportunity to check everything out as well. I just can't help seeing something mechanical and not taking it apart to see how everything works!!

Good luck!

Bryan

ProTeal55 · « **Reply #5 on:** June 21, 2006, 12:09:56 PM »

Take a 3M Scotch-Brite pad to it, and make it look like raw alum. like I did.

A "touch-up" is just a quick scuff away

loonymoon · « **Reply #6 on:** August 22, 2006, 02:29:32 AM »

Hey guy's. I've decided to have a go at polishing up my old bike's engine. I decided not to go straight for the sanding and tried just autosol and my dad's Dremel. I spent a good 3 hours or so polishing and re-polishing and blimey - how much black stuff came off?!?! It definately looks better now and more like the original colour and in most places (apart from the top of the cylinder heads on either side) it's removed the yellow discolouration. However a lot of the old lacquer still remains - which I guess I won't get off unless I wet-n dry it.

I attach the before and after shots of one of the engine casings. I have bought a new can of high temp engine laqcuer but as there's still some old lacquer on the engine I think I might have to resort to the sanding... I might try a fine-grade wet and dry paper. Although I am half thinking I'll leave it as it is as it shows the originality of the bike and doesn't look TOO bad now..

The only bits I'm mainly concerned about are the bits at the top of the cylinder heads. They are very yellowed with old lacquer where they have been exposed to light (underneath the tank is fine) and have "spiders" of oxidation, the autosol didn't remove the discolouration and as the oxidation was under the old laqcuer it didn't do much for the "spidering". I was a bit unsure whether to use an abrasive on this as I'm not sure whether this part is actually painted and I don't want to have to take the engine out of the bike to re-paint it.

nippon · « **Reply #7 on:** August 22, 2006, 03:07:13 AM »

Currently, that's my job, too.
Removed the dent's and scratches with a dremel,
then sanded wet with 320, 600, 800, 1200.
Polished with wax and elbow grease.

loonymoon · « **Reply #8 on:** August 22, 2006, 04:46:08 AM »

Wow, that's impressive!

I suspect it's a lot easier if not on the bike. I've now bought the wet-n-dry paper so I'm going to have another go at shortly...
Still not sure what to do about the cylinder heads though.. to sand or not to sand...?

DME · « **Reply #9 on:** August 22, 2006, 05:06:44 AM »

Quote from: nippon on August 22, 2006, 03:07:13 AM

Currently, that's my job, too.
Removed the dent's and scratches with a dremel,
then sanded wet with 320, 600, 800, 1200.
Polished with wax and elbow grease.

Very nice work, Nippon

Cheers
Daniel

nippon · « **Reply #10 on:** August 22, 2006, 05:55:56 AM »

Thanks, DME.
One question: Did you paint your cylinders or are they just sanded?
if yes, any problems with the durability of the color on the cylinders?
I have disassembled my engine completley in order to do a new paint job,
(VHT primer and #118) but i'm not sure if I should paint the cylinders,
too or just sand blasting.
Your carbs are looking exactly like mine after cleaning and polishing.

nippon.

BobbyR · « **Reply #11 on:** August 22, 2006, 06:28:29 AM »

If it is indeed lacquer that has yellowed, that can be dissolved with denatured alcohol. Dissolving it is much easier than sanding, and it will leave you with a surface you can polish using a cheap buffer on an electric drill and red rubbing compound. For deep pits you will need to sand first then polish.

techy5025 · « **Reply #12 on:** August 22, 2006, 09:53:26 AM »

Nippon...what tool did you use in the dremel tool to remove the dents
and scratches. Do you realise you could make a nice living just polishing
stuff for guys (and gals!) here on the board.

Really impressive.

Jim

Short Round · « **Reply #13 on:** August 22, 2006, 10:36:12 AM »

if you dont want to go through all theo trouble of sanding and dremel, use Scotch-Brite, when in doubt Scotch-Brite!!!

nippon · « **Reply #14 on:** August 22, 2006, 12:36:36 PM »

I took the one as shoewed in the pic with 120 first.
After that you have to sand it with 320 and a sanding block to remove the unevenness.
The next steps are wet sanding.

techy5025 · « **Reply #15 on:** August 22, 2006, 12:37:40 PM »

.............are we talking about taking Scotch-Brite in our hands and manually
getting into all the tight spots on this cover. Sounds like lots of time and
effort. Is Scotch-Brite able to remove those deep scratches? I haven't used
it but it must be more abrasive then 150 grid sandpaper.

Jim

supersport_CB400F · « **Reply #16 on:** August 22, 2006, 01:01:26 PM »

Quote from: Littleitaly52 on August 22, 2006, 10:36:12 AM

if you dont want to go through all theo trouble of sanding and dremel, use Scotch-Brite, when in doubt Scotch-Brite!!!

I used Scotch Brite before I painted

DME · « **Reply #17 on:** August 23, 2006, 02:20:30 AM »

Quote from: nippon on August 22, 2006, 05:55:56 AM

Thanks, DME.
One question: Did you paint your cylinders or are they just sanded?
if yes, any problems with the durability of the color on the cylinders?
I have disassembled my engine completley in order to do a new paint job,
(VHT primer and #118) but i'm not sure if I should paint the cylinders,
too or just sand blasting.
Your carbs are looking exactly like mine after cleaning and polishing.

nippon.

I glassblasted my cases, cylinders and cylinderhead when the engine was apart for the rebuild.

Cleaned it, cleaned it again, and again, and again to get ALL the glassbeads out of every nook and cranny.

You also need to go over all holes with a tap to get the grit out of the threads.

I painted the cases head and cylinders with this paint: http://www.motip.com/?page=23&id=550

Did not use any primer, just sprayed it on.

The paint was left to harden during the chassis build, so it sat for two months....

I have used the bike all summer and the paint is holding up great! No flaking or discoloration, no nothing.

It went a little soft with the heat on the first runs but now its hard as a rock and very easy to clean.

I haven´t had any gasspills yet and i would not use any chemicals harsher than a mild detergent on it. Don´t need to as the filth just washes of with a spunge soap...

Would I use again? Yes!

I´ve heard a lot of good things about VHT paints, but they don´t sell them in Sweden.... Some problems with toxicity, appearently

I´m going to rip my carbs apart this winter to get a fresher look on the carb bodies. Someone here had boiled them in water and lemonjuice and they turned out like new

Please post some more pics of your project or Email them to me! Looks inspiring

Cheers
Daniel

loonymoon · « **Reply #18 on:** August 23, 2006, 03:37:07 AM »

I tried sanding some bits of my bike. I didn't want to take my bike apart so I have everything but the tank and side covers on the bike at the mo so it's very difficult getting into the nooks and cranies, but even what i've done so far looks far better than yellowed blistering lacquer with black spiders!!

Most of it came up quite well although some bits of lacquer remain on the tops of the cylinder heads around the bolts. I'm going to try a very carefully applied non-acidic gel-type paint stripper to try to dissolve the remaining lacquer (can't get hold of denatured alcohol!) - might try it on a part that's less noticable first though to make sure it doesn't do funny things to aluminium!!

This was never meant to be a restoration - just a tarting up - however I can see that finding a place to stop may be difficult!! However not-disassembling the bike may help me find a natural stopping point as there's only so much you can do..!!

EDIT- later that afternoon -

Yes the stripper worked really well (oo-er). I just applied it with a cotton bud and was really careful about it... Still haven't got it 100% off all the panels as was scared to go too near any rubber or bits that may have gasket s or frame paintwork near, but hey - it still looks sort of original and untouched whilst looking a LOT better than before which is kind of the effect I was after...

I'm now wondering whether to try the new lacquer I've got or whether it'll look strange because the engine parts aren't 100% clean still. I'm just a bit worried that the exposed metal will corrode faster. Any thoughts?

Thanks for the all the previous tips guys- Lovely work you lot have been doing too - when yours are finished I'm sure they'll make my tarted up engine look like it's been at the bottom of the sea for 30 years. The parts you've shown make it look like that already!!

loonymoon · « **Reply #19 on:** August 23, 2006, 12:59:16 PM »

Quote from: techy5025 on August 22, 2006, 12:37:40 PM

.............are we talking about taking Scotch-Brite in our hands and manually
getting into all the tight spots on this cover. Sounds like lots of time and
effort. Is Scotch-Brite able to remove those deep scratches? I haven't used
it but it must be more abrasive then 150 grid sandpaper.

Jim

Yes I was wondering about this too. I'm not sure what kind of scotchbrite you're talking about, as I just associate them with pot scourers and surely very abrasive!
Even with the 1200grit wet sanding I can still see scratch marks on one of the parts I sanded - not too bad after autosol but still noticable if you look close. Probably need to go to 2000 grit and perhaps take a LOT longer over it. My poor little arms started aching and I was too scared to use a drill as knowing me I'd let it fling off and hit another part of the bike (another problem with trying to do this without taking the bike to bits), I even had this problem a bit with the dremel every now and then it would catch and suddenly lurch sideways, and i'm afraid I created a few scratches and pits this way $:-\$ .

Perhaps someone should write an idiots guide to engine polishing - with methods for on bike tarting up and off bike restoration with the order in which things should be done as I screwed it up a few times by using the dremel and various attachments and then sanding and then thinking I should have sanded first etc and doing everything again!

supersport_CB400F · « **Reply #20 on:** August 23, 2006, 02:00:49 PM »

You can get different grades of Scotch Brite, I use black for tough stuff down to red with Autosol for polishing, I like it more than using paper.

nippon · « **Reply #21 on:** August 23, 2006, 03:27:58 PM »

Don't you have a wife for the sanding job?
If you want the brilliance, after sanding you have to polish with wax
and at least with Autosol or everything else.
In order to avoid oxidation, you have to use a sealer like Liquid Glass.
Believe me, I have not disassembled the engine only for polishing,
I had to replace the primary chains and several parts, so I went to
restore the engine covers.

nippon

loonymoon · « **Reply #22 on:** August 24, 2006, 02:50:23 AM »

Quote from: nippon on August 23, 2006, 03:27:58 PM

Don't you have a wife for the sanding job?
If you want the brilliance, after sanding you have to polish with wax
and at least with Autosol or everything else.
In order to avoid oxidation, you have to use a sealer like Liquid Glass.
Believe me, I have not disassembled the engine only for polishing,
I had to replace the primary chains and several parts, so I went to
restore the engine covers.

nippon

::)LOL- if I was married I would be the wife...!!

What sort of wax are you using - standard car wax or a special metal wax?
Would love to see pics of your bike when it's finished!

USN20 · « **Reply #23 on:** August 24, 2006, 08:10:25 AM »

To protect your aluminum from oxidation try Meguires #20 as it holds up pretty well compared to regular car wax. I've been using it with good results. Apply liberally, let dry and wipe off. Then use a old tooth brush to remove the excess from the crevices and around the screw heads.

http://www.meguiars.com/?pro-liquid-car-waxes/Polymer-Sealant

nippon · « **Reply #24 on:** August 24, 2006, 09:13:24 AM »

autsch,...sorry!
Please take a look at the pics, these tools I have used.
It's a special wax for aluminum and metal polishing.

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Author Topic: engine discoloration (Read 9048 times)

byurko

supersport_CB400F

supersport_CB400F

USN20