Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

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8/26/2015

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Stiff clutch

Q: I have a 1975 Norton 850 Commando that I bought recently. It sat for many years, but runs very good, and it only has 7,700 miles on it. My problem is the clutch is so hard to operate that I can hardly ride it in stop-and-go traffic. In 15-20 minutes my hand is cramped up. It will also not go into neutral when running, but it goes right in when I stop the engine. I have lubed the cable and made sure it is routed with nice smooth bends.

A Norton specialist says nothing is wrong with the clutch, even though it seems it is the problem. I have had many different bikes over the last 40-odd years, but I’ve never had a clutch this hard to operate. Help! Thank you. — Thomas White/via email

A: There are several factors that can make the Norton diaphragm clutch hard to operate. You’ve dealt with one of the easiest, which is cable routing and lubrication. A major factor in how easy or hard it is to pull the clutch is the clutch stack height, the combined thickness of the metal plain plates and the composite friction plates in between them. It doesn’t take much friction plate wear to move the clutch from easy to hard to pull. How new are the friction plates? Also, Old Britts in Enumclaw, Washington, sells plain plates of varying thicknesses that you can use in combination with new friction plates to get to that sweet spot where the clutch is easy to pull, but doesn’t slip. If all else fails, Colorado Norton Works has a hydraulic conversion kit. It’s pricey at $459, but solves the problem permanently. Colorado Norton Works also has a less expensive clutch kit for $205 that keeps it mechanical, but claims to fix the hard pull. Good luck. MC



8/13/2015

Motorcycle Classics tech expert Keith Fellenstein

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

The responses:

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.

Sincerely,
James Townsend, Past President
Vintage Japanese Motorcycle Club


Hi Keith,

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.

Dale Keesecker
Washington, Kansas


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.



7/22/2015

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Frame powder coating

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



7/8/2015

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

KTM 250MX Starting Troubles

Q: I have a 1986 KTM 250MX and am unable to start it using the kickstarter. I have installed a new spark plug, and the carburetor is clean. The timing is correct, and I’ve installed a new power reed. It will start if it’s pulled behind a four-wheeler. — Clair Raible/Black River, New York

A: Without seeing the bike, I can only guess, but for a 2-stroke, starting troubles that are overcome by pull starting usually point to bad crank seals. Once you have it running, will it idle reasonably, or does it die? That’s another pointer to crank seals. If you can do a pressure test, you should be able to pinpoint the problem easily. If it idles once you have it started, it may be poor compression. Again, a pressure test will give you the answer. See our How-To in the March/April 2015 issue or online. MC



6/24/2015

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Synchronizing Carburetors

Q: I have a question regarding “syncing” carburetors. Some gurus can synchronize them by ear, and I’ve met mechanics who are just incredible and use all their senses to accomplish the extraordinary. How does syncing contribute to performance? Usually, I measure the slides with the carbs on the bench with drill bits, selecting a size that just fits between the horn and the slide, and average the two (or three or four). Are there unique factors with individual cylinders that require a “power on” vacuum test, or am I good to go? I suggest to your readers to start a scrapbook, as I have with your articles. I look through the table of contents when I’m stumped and lo and behold, you’ve already done the work for me. — Mike Peterson/Chetek, Wisconsin

A: In a multicarburetor setup, synchronizing ensures that each carburetor is providing the same amount of fuel and volume of air at the same rpm. That in turn keeps the cylinders working in unison, with no cylinder working harder than the other. This, along with engine timing, contributes to an engine that runs smoothly and accelerates at its best. What you’re describing is generally referred to as “bench syncing” and it is a necessary first step whenever you have disassembled a multicarb setup. Depending on whether you’re dealing with CV carbs or direct slide carbs, the technique is a little different. On direct slide carbs such as the Amals on British Triumphs and Nortons, you can use the wire-gauge method you outline, using the idle stop screw to get the initial opening the same. Assuming you have the carbs off the bike, you can try this. For CV carbs, I keep a few 1/4-inch ball bearings on hand. I place them in the throat of the carburetor and open the butterflies. If the balls drop simultaneously, the butterfly valves are synced. Once that’s done, you need to make sure the cables are pulling identically for all the carbs. You can check at wide open throttle to see if the slides are all the way up to the same degree, but you can’t really tell if the intermediate range is matched. This is the range where you’ll spend most of your riding time. The easiest way to do that is with vacuum gauges. MC



6/10/2015

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Triumph cylinder

Q: I just started a total restoration of a Triumph Trident. The engine took on some water at some point, and I’m not sure if it is going to be worth the investment to rebuild it. My first question is, what size and type of wrench do I need to take off the cylinder? These are odd looking bolts. Also, the piston rings are fused to the cylinder walls. I have them soaking in penetrating oil, but so far I have not had any luck in freeing them up. — Jim T./via email

A: Those odd-looking nuts have 12 points and you need a box wrench to loosen them. A 13mm wrench works, but a 1/2-inch wrench fits better. Sometimes you have to grind down the thickness of the wrench to fit in the narrow space between the bottom fin and the nut. You may also have to grind down the circumference of the wrench for clearance between it and the cylinder base. For your seized engine, a 50/50 mix of ATF and acetone is reported to work well as a penetrating solvent. Applying heat cyclically can also help break things loose. If you’ve recently used the ATF/acetone mix, use a heat gun rather than a torch; a torch would be OK after the acetone evaporates. Don’t use MAP gas; it gets hot enough to melt aluminum. Propane should be safe if you keep the torch moving. Aluminum gives no warning; one second it looks fine and the next it’s melting. Alternating between hot and cold should create enough expansion differential that the rings will eventually break free of the cylinder walls. Applying a little torque to the crankshaft nut helps break it free, too. Remove the primary cover to access the crankshaft nut. Patience is your friend. MC



5/27/2015

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Honda carbs

Q: I have a 1981 Honda GL500 with 61,225 miles. The bike starts and runs up to about 4,500rpm, then breaks up and runs really rough. In terms of problem solving, I’ve done all of the typical tune-up items including replacing the air and fuel filters, and the spark plugs. I have also cleaned the carburetors. None of this solved the problem. After research on a CX500/GL500 forum, a member suggested replacing the spark plug wires and the coils, which I changed. This didn’t solve my problem either. I then located your article on CDI units and their function, and it seemed like the logical solution since I’m losing high-end. After changing both to a set ostensibly from a low-mileage bike, it still didn’t solve the problem. Do you have any suggestions? — Phil Quattrone/via email

A: Running problems with the CX/GL 500/650 bikes can be difficult to pinpoint, as there are several troublesome systems that can cause your symptoms. One of the toughest problems to solve is carburetion. The CX/GL Keihin carbs can be difficult to clean completely. See our article in the March/April issue about the CX500. The owner of that bike has written a comprehensive book on thoroughly cleaning and disassembling CX/GL Keihin carburetors. MC



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