SOHC.co.uk Forums > CB500/550

Engine Painting Disaster - Help!

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Spitfire:
I did a similar thing in that my silver VHT paint went golden, I set the oven in centigrade not Fahrenheit.

Cheers

Dennis

Oddjob:
The spots are caused by oil in the metal coming to the surface due to the heat. You need to start again I'm afraid. Use some sort of acid to get rid of the oil in the metal before repainting. And take the rockers out next time. That's just more oil vapour being released.

exvalvesetdabbler:
I used vht engine enamel many years ago, it was branded sperex back the before holts bought them out. Just branded VHT now and not to be confused with simoniz.
It didn't need a primer and it's stayed on aside from where I have been careless with spanners.

You need to wash with  paint thinners or acetone, bake it in the oven  at 100C, then solvent wash again. This will bring out any oil from the pores in the casting or corrosion pits which is probably what is causing some paint to lift.  When baking paint, dry overnight and then put it into a cold oven and slowly ramp up to 100C in stages then hold at that temp for half hour.

Regards
Dave

Bryanj:
Sprex black was the go to for exhaustd back in the 70's

Neilw:
Thanks for all of your suggestions.  I can't face stripping the paint off and starting again, it's a huge job to do manually for the whole of the top end.

As it's only cosmetic, I think I'll lightly sand all the components and give them another coat or two of VHT. As for baking, i'll try the incremental increases and do them separately so I don't get any cross-contamination, i'll try a small test piece first to see if that works.

I know it's not the perfect solution and may come back with issues in the future, but I'm not planning on riding more than a few 100 miles a yr. Trust me what i have now is 1000% better than what was there before.

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