Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Honda enthusiast on March 22, 2024, 10:04:49 PM
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Hi folks
The temperature in the workshop is ten degrees and I can probably get it up to 15 with a heater, would that be ok for the vht 231d to air dry if applied in thin coats? I do have two 1 KW bodyshop infrared lamps , was thinking of using them to cure it as opposed to doing it in the oven....any ideas?
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15° to air cure is fine. Never cured under lamps as we always cure in an oven, so can't comment on that. But, the heat needs to be all around the part to oven cure it evenly.
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When I first got my 750, the main case paint had been damaged by carb leaks and the previous owner had repainted with VHT, which would wipe off with any petrol on a rag.
When I worked on the engine, I wanted to repaint it. Although it was out of the frame, I only had the head and cylinder block off, so I couldn't put it in an oven!
I took it back to bare metal with brass brushes in a Dremel. Lightly scuffed it with 800 grit paper, to giive a better key. Then did a light coat of etch primer and left it a day to dry, light coat of VHT silver, left it to dry, then warmed up the case with an electric paint stripper on low, let it cool. This step took about an hour going over the case in sections. No idea if it achieved anything other than making me feel good! Then finally, I sprayed a light coat of engine clear lacquer. Let it harden for a couple of weeks, before it went back into the frame.
All was from aerosols. All in November/December, with a fan heater in the garage. Each time i made sure the engine case was at room temp (not hot), by gently heating with my paint stripper and the paint was kept in the house between uses.
It was a labour of love, for sure. Not quick. But, 1,000 miles in, so far it is standing up very well to riding and cleaning, much better than just the VHT. The odd stone chip off the front tyre. A lot of cleaning, due to winter muck. Still looks fresh. However, I did have an episode where petrol leaked from the carbs. A small area was damaged. Only the lacquer was affected and I cleaned it off, masked everywhere off and misted the affected area. Good as new.
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Thanks Julie and Martin, I'm glad you say it's doable 😁 it would be a shame to have to wait till July/ August....I've just bought a 3kw fan heater from Amazon and along with my 2kw space heater should have a good enough temperature.
Thanks both 😎👍
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I would also make sure the paint cans are not cold. I was advised once to stick the cans in warm water to heat them, but I didn;t fancy putting a pressurised can into anything hot...so I just bring them in the house the day before I want to use them to warm them up. As well as the curing process, aerosols don't like cold or damp conditions, and the paint may not atomise properly leading to spattery paint.
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I regularly place rattle cans in hot water when it's cold and have never had an issue. In the summer I have had them get to hot to touch when left in the van and they haven't popped. The same can't be said for tubes of gripfill I had three tubes decide to glue themselves and the shelves contents firmly in place
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I don't want the cylinder liners to move while in the oven...on the K7 the head is bolted to the cylinders with M6 bolts and I was going to do that and place it right way up in the oven...so the tops of the liners are against the cylinder head...
Would that work folks or is there a better way?
Hubert
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I don't want the cylinder liners to move while in the oven...on the K7 the head is bolted to the cylinders with M6 bolts and I was going to do that and place it right way up in the oven...so the tops of the liners are against the cylinder head...
Would that work folks or is there a better way?
Hubert
Surely this is the very hottest part of the engine and as such a few hours of riding might do the job okay?
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I agree it will soon bake with the engine running.
I have read that similar paints will effectively become curred by air drying alone provided it is a decent room temperature of 20-22 deg C except it takes some 3-4 months as the solvent eventually completely evaporates.
Oven baking just accelerates the drying time to reach full cure down to a hour or two.
When my BiL painted his Fireblade engine he just left it to cure for several months in the summer - it was differnt brand of paint from the USA. The information does not support my BiL claims although I believe he sought further information from the supplier.https://www.frost.co.uk/vht-cast-iron-engine-enamel/?gclid=Cj0KCQjwmdGYBhDRARIsABmSEePCbaToXB0usEPUkOpLCJlcM6IJMXOzWiGj0maZBRi7auTU2W44CSAaAoV7EALw_wcB
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Thanks both, I'll bake it anyway while my wife's out 😜
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After you have baked the block make sure you cook a few sausages in the oven afterwards to mask the aroma. ;D ;D ;D
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I always prefer to use a catalyzed paint as they cure via chemical reaction not evaporation. They also will not dissolve with solvents or gasoline. Poof can paint will dissolve and oxidize no matter how long they have cured.
As they never truly "cure"
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Is Simoniz Engine Enamel considered the best paint to get?
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After you have baked the block make sure you cook a few sausages in the oven afterwards to mask the aroma. ;D ;D ;D
My dear wife is out from ten thirty to six, enough time to bake with the kitchen windows open and leave no traces of smell. Golden opportunity strike while the oven is hot 😂 She's lovely in every way and has a good sense of smell so i might be rueing doing it this evening, Ted ...hope not but the evil deed will have been successfully done ✅
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After you have baked the block make sure you cook a few sausages in the oven afterwards to mask the aroma. ;D ;D ;D
My dear wife is out from ten thirty to six, enough time to bake with the kitchen windows open and leave no traces of smell. Golden opportunity strike while the oven is hot 😂 She's lovely in every way and has a good sense of smell so i might be rueing doing it this evening, Ted ...hope not but the evil deed will have been successfully done ✅
Flowers and chocolates on the table for when she gets home, they mask all bad smells and quell anger. Happy wife, happy life (and good luck in the Bake-off) ;)
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After you have baked the block make sure you cook a few sausages in the oven afterwards to mask the aroma. ;D ;D ;D
My dear wife is out from ten thirty to six, enough time to bake with the kitchen windows open and leave no traces of smell. Golden opportunity strike while the oven is hot 😂 She's lovely in every way and has a good sense of smell so i might be rueing doing it this evening, Ted ...hope not but the evil deed will have been successfully done ✅
Flowers and chocolates on the table for when she gets home, they mask all bad smells and quell anger. Happy wife, happy life (and good luck in the Bake-off) ;)
If I did that, she'd be convinced I was having an affair.
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After a little wait to make sure, dear wife was not coming back I carried in my lower case and...... 😖😜 It wouldn't fit!!! Our AEG oven has a name he's called Herman the German ( AEG) and is approaching thirty years old...ovens must have got bigger over the years...
I've tried the fingernail test and it's fully dry so I'm going to try heating it with the two 1kw Anest Iwata short wave infrared lamps I have....better than nought 😁😞
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My 500 casing fitted in our AEG oven just fine here is the proof in the pudding.(https://live.staticflickr.com/65535/52632263712_9e60d4f007_o.jpg) (https://flic.kr/p/2obW7jC)PXL_20230117_140852031 (https://flic.kr/p/2obW7jC) by Macabe Thiele (https://www.flickr.com/photos/187487200@N03/), on Flickr
As part of my domestic negociations I obtained planning permission to use the oven as long as I cleaned it afterwards.
I did not want discolouration of silver engine paint so cleaned the oven first. After reading the destructions I saw it had a Pyrotechnic Cleaning Cycle. The smell of this cleaning cycle was truy terrible, after manually cleaning the racks with the oven looking brand new I had to submit to further concessions. I agreed to do the bake off whilst Whilst Wendy was at work!
Result. 8) 8) 8)
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...ovens must have got bigger over the years...
Why not seek help from your local social circle, one of your mates must have a bigger oven! ;D
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My 500 casing fitted in our AEG oven just fine here is the proof in the pudding.(https://live.staticflickr.com/65535/52632263712_9e60d4f007_o.jpg) (https://flic.kr/p/2obW7jC)PXL_20230117_140852031 (https://flic.kr/p/2obW7jC) by Macabe Thiele (https://www.flickr.com/photos/187487200@N03/), on Flickr
As part of my domestic negociations I obtained planning permission to use the oven as long as I cleaned it afterwards.
I did not want discolouration of silver engine paint so cleaned the oven first. After reading the destructions I saw it had a Pyrotechnic Cleaning Cycle. The smell of this cleaning cycle was truy terrible, after manually cleaning the racks with the oven looking brand new I had to submit to further concessions. I agreed to do the bake off whilst Whilst Wendy was at work!
Result. 8) 8) 8)
I'm truly jealous , Ted, well done at least you came clean !
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Four months ago I took the engine back to bare metal. I painted my cases with a light coat of etch primer, then 2 light coats of Simoniz VHT silver and then 2 light coats of clear engine lacquer. I was concerned about cooling, so I only applied 2 light coats of the Simoniz VHT silver to the cylinder barrel fins, no primer orr lacquer. I didn't oven bake any of it.
On the first wash, after a couple of rides, I noticed some paint coming off the cylinder barrel, but not the cases, when I towel dried it. So I've been blow drying ever since.
This week, having had about 20 heat cycles through the motor, I tested the fins and they now seem fine, no paint transfer. I expect, without the oven treatment, it needed a few heat cycles and some time to fully cure. I'm hopeful it'll be robust now.
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Four months ago I took the engine back to bare metal. I painted my cases with a light coat of etch primer, then 2 light coats of Simoniz VHT silver and then 2 light coats of clear engine lacquer. I was concerned about cooling, so I only applied 2 light coats of the Simoniz VHT silver to the cylinder barrel fins, no primer orr lacquer. I didn't oven bake any of it.
On the first wash, after a couple of rides, I noticed some paint coming off the cylinder barrel, but not the cases, when I towel dried it. So I've been blow drying ever since.
This week, having had about 20 heat cycles through the motor, I tested the fins and they now seem fine, no paint transfer. I expect, without the oven treatment, it needed a few heat cycles and some time to fully cure. I'm hopeful it'll be robust now.
Yes, that's how I'm going with mine, from past experience it's the front of the engine which is exposed to water spray and road dirt so I'll try and harden that up with the heat lamp....no rush, I'll get there and like you say the heat cycles will do the rest. I'm still considering doing the outside breeze block oven method by Ashmoto.
As a matter of interest do you have a Moto Martin 6?
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No, my name's Martin and I have a K6 CB750! :)
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I only had the head and cylinder block off, so I couldn't put it in an oven!
I took it back to bare metal with brass brushes in a Dremel.
Thanks for posting this. I am thinking of doing something similar with my 550 rebuild. I plan to rebuild the top end but not the bottom end which seems fairly sound apart from the paint. Do you have any tips for removing the old paint other than using a dremel & brass brushes? I was thinking of using a Scotchbrite pad or wheel to prep the surface before etch primer.
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I don't think a scotchbrite pad will be aggressive enough. May be wrong, but I would expect that to be a long job and lots of pads. 240 grit wet and dry, used dry, might be better, but the creases and corners will be tricky, if you try to get all the paint off. I found the dremel, used with the flexible extension head and a range of brass brushes, worked quickly, got into nooks and crannies and didn't damage the alloy. I then went over once with some wet and dry to key it. Took me 2 to 3 hours to do and another hour to brush clear all the little brass tines off the floor. You do go through the brass brushes in that job.
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It might look a bit daunting before you start but it works well with wet and dry...if you can find somewhere to soda blasting it that's the best bet...
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I don't think a scotchbrite pad will be aggressive enough. May be wrong, but I would expect that to be a long job and lots of pads. 240 grit wet and dry, used dry, might be better, but the creases and corners will be tricky, if you try to get all the paint off. I found the dremel, used with the flexible extension head and a range of brass brushes, worked quickly, got into nooks and crannies and didn't damage the alloy. I then went over once with some wet and dry to key it. Took me 2 to 3 hours to do and another hour to brush clear all the little brass tines off the floor. You do go through the brass brushes in that job.
Thanks. Im pondering over my engine before I take it out the frame next weekend. When you painted the assembled bottom end how did you deal with the bolts in the casings? Did you remove them in sections and re-torque after painting or mask them in some way? Thanks, mike
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Mike, I replied to your PM. In short, masking tape pushed to a crisp edge with a Stanley/razor blade. Good crisp result, until you get a microscope on it!