Technical Q and A for classic motorcycle maintenance and repair.
Editor’s note: In the July/August 2015 issue, we published a letter from reader Bill Adams, who wanted to powder coat the frame on his bike and wanted advice. Tech Q & A guru Keith Fellenstein has his own thoughts on the subject, and shared them in that issue. In response, we received several letters from readers, too long to print in the following issue. We’ve included them here in their entirety, along with the original letter that kicked off the discussion and a comment from Keith Fellenstein.
The original question and answer:
Q: I have a question that I thought you might be able to help me with, or at least steer me in the right direction. I’m restoring a 1984 Kawasaki ZX750E Turbo, and I’d like to have the frame powder coated. The problem is the factory applied federal standards stickers near the steering head. They would be destroyed in the powder coating process, but they would also be destroyed in trying to remove them. Do you know if these have to remain on an older, restored motorcycle, or can they be removed? I could take photos of them and have them reproduced and re-apply them, but I don’t know if that’s legal, or if legality needs to be considered in this case. Do you have any info on this in your experience? I appreciate any help you can give me, whether directly or from another source that you know. — Bill Adams/Pleasant Plain, Ohio
A: You may not like my answer, but here goes. I’m not a fan of powder coating frames for a number of reasons, some mechanical and some cosmetic. Let’s start with the mechanical. The thickness of the coating can interfere with refitting engine and frame components if you are not completely obsessive in masking off all the bolt bosses and threaded openings before having the frame done. More significantly, the flexibility and thickness of the coating can mask corrosion under the coating, and hide fractures in welds and other areas of the frame that you don’t want hidden. Those are my major concerns. A minor concern is that when, not if, the frame gets chipped, you can easily touch up paint, but powder coating, not so much. To your main concern, I don’t know of a way to protect the frame labels from the heat needed to fuse the powder coating. With many states increasing scrutiny of VIN numbers on older bikes, it becomes imperative to make the inspector’s job easier so you don’t spend time arguing with them over proper frame/engine numbering. My recommendation is to find a good paint shop and enamel the frame. Thanks for reading my column, and I’m sorry if this isn’t what you wanted to hear. MC
Dear Mr. Fellenstein:
I am afraid that I must dispute your comments in the 2015 July/August issue. They are very misleading, if not just wrong. I am very familiar with powder coating motorcycle frames and other parts. Maybe your comments are a reflection of some very poor powder coaters who just didn't know how to best go through the process very well.
I have had dozens of frames powder coated and have never once run into the problems you describe, of having rust or corrosion pop up under the powder coating. Also, if there are cracks, they show up quite well in the preparation process.
The electrostatic process of applying the powder coating was developed here in Warsaw, Indiana, so our local powder coaters have a good background in the process. A complete understanding of the process really helps get the job done correctly. Let me explain the process as it should be done.
First, every bit of oil and grease must be removed. Threaded holes should have a bolt screwed into the hole just far enough to be flush on the back side of the part. I use old bolts and machine screws with bad heads. Block off the steering head after the bearing races have been removed with a long threaded rod, 2 large washers and 2 nuts. Do the same for swingarm bearing holes in the frame.
The entire frame must be sand-blasted thoroughly. Special care must be taken to remove all rust and possible flux around welds. This will make any cracks or rusted through part very visible and they must be repaired before going any farther.
After sand blasting, the part must be very thoroughly washed in hot, soapy water, rinsed and then dried under heat, if possible. Any water will hinder proper coating.
When the parts are sand blasted and are dry, the parts are hung up and the powder blown on. The powder and the parts are charged with DC voltage in opposite poles. The powder with the opposite charge of the part is attracted to the part in an even manner. There are no sags or drips since it is evenly coated.
At this point, any touching the part is forbidden since it will disturb the even coating of powder.
The parts are then baked in an oven at over 400 degrees F until the powder melts and adheres to the part. After the part is cooled, it is ready to be used. No further curing or finishing is required.
Also, parts powder coated may be painted after just sanding lightly with 400 or 600 grit wet or dry sand paper. Powder coaters have a huge number of colors, but some special colors are not available.
I have a 1965 Ducati tank, powder coated black with the silver part painted right over the sanded black powder coat. A clear coat over that and the decals makes it look just like the original paint.
If you have any comments, I would like to see them. I think a follow up in Motorcycle Classics is necessary. I am writing this because there is so much misinformation out there that needs corrected.
James Townsend, Past President
Vintage Japanese Motorcycle Club
I have to be in total disagreement with your advice in not powder painting Bill Adams’ frame. We have restored over 100 bikes. The frames we had powder painted are much better quality and last much longer than enamel. Bear in mind that we do all the prep and masking and the painting is done by a professional who knows how particular we are. Powder coating can be repaired with the correct epoxy paint. As you well know, paint jobs and chrome plating are no better than the preparation.
Concerning the stickers near the steering head, they can be replicated to look exactly like the original if you get the correct person to do it. If you so desire I would be glad to correspond with Mr. Adams and give him information on how we prep the frame.
I like reading Keith’s Garage in every issue. I have picked up some very useful information. Keep up the good work.
Keith Fellenstein responds:
My experience with powder coated frames is from the point of dealing with the effects of bad work. As pointed out in the letters above, preparation is everything. Thanks to everyone for taking the time and effort to write on this.