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Tech Corner
Technical Q and A for classic motorcycle maintenance and repair.

Seized Cylinder on a Suzuki GT550

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 your questions to: Keith's Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with "Keith's Garage" as the subject.

Q: I have the chance to buy a reasonably nice Suzuki GT550. I believe it is a 1976 model — one of the later disc-brake bikes — but the center cylinder on this triple is seized and I wondered if you have any thoughts on the best way to free it up?
— Peter/via email

A: You can do a simple test to see if it is the piston seized in the bore (somewhat common and fixable) or a seized main bearing (unlikely, but probably a deal killer). If the seller will let you, take off the left side engine cover, and with the appropriate size wrench gently turn the nut at the end of the crankshaft back and forth. If there is some movement you can assume the main bearing is free. If it passes that test and you buy it, the next step will be to pull off the cylinder heads and have a look at the middle cylinder. If the piston is up you won't be able to tell much, but if it is down you should be able to see if the bore is scored or scuffed, indicating a seizure while running. If none of the transfer ports are visible yet there is some room in the cylinder to hold liquid, the shade tree mechanic fix is to pour in a mixture of ATF and acetone and let it sit. After a decent interval of several days, you can again try to turn the crankshaft with the wrench, looking to see if the center piston moves at all. If the center piston isn't at TDC you can also try tapping the center piston with a suitable sized wooden dowel and hammer. Easy does it. Repeat the solvent, wrench and tapping until you achieve success. Once it's free, you can confirm if you'll need a new piston or other work to get it running. Good luck!

Norton Commando Clutch Setup

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, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with "Keith's Garage" as the subject.

Q: I have a beautiful 1975 Norton Mark III Commando that is nearly unrideable due to a clutch/shifter issue that my local vintage mechanic has been unsuccessful at fixing. The clutch does not fully disengage when you pull in the clutch lever. The 1 to 2, and 2 to 3 upshifts are very hard, particularly when the bike is warmed up. Downshifting is worse, as pulling in the clutch to downshift does not fully release the clutch (i.e., even with the clutch lever pulled in, the transmission engages immediately when you shift down). Sometimes on a 4 to 3 or 3 to 2 downshift it hits what seems to be a false neutral, but sometimes blipping the throttle gets a gear to engage from the false neutral. To stop this quirky Commando I need to pull in the clutch lever, apply the brakes, and blip the throttle to "break" the clutch loose. Otherwise I'm "power-braking," which is of course not ideal. Unfortunately, I lack the skills to troubleshoot and solve the problem. — Christopher Belling/New York

A: The Norton Commando clutch is usually pretty easy to set right, but there are a few things to check. First among them is the stack height, the total thickness of all the plain plates, friction plates and pressure plate. For your 1975 model the height should be close to 1.027 inches. If the height isn't correct, you'll notice it with either a dragging clutch like you describe or a difficult pull at the clutch lever. It's possible that over the years there has been some mismatching of parts between a 750 and 850 clutch. The diaphragm spring and clutch basket are the same across the models, but the number and thicknesses of the plain and friction plates is different. For the 850 the friction plates should be 0.121 inches thick and the plain plates should be 0.080 inches thick, with the pressure plate being 0.102 inches thick. The 850 has five friction plates and four plain plates, while the 750 has four and three, respectively. Another common problem is a notched basket or clutch hub. This will tend to keep the plates in contact with each other even when the clutch is pulled in. To complicate things further, the plates can build up oil residue and stick to each other. On the right side of the bike, you should open the inspection cover of the gearbox to make sure of two things. One, that the clutch release lock ring is in all the way and tight, and two, that the cable to the clutch rod actuation lever hasn't fallen out of position. It can fall down when the clutch pack and rod is removed. To make a long story boring, I think you'll need to tear down the clutch and check everything to see what's out of spec.

Triumph Trident Boyer Ignition Troubles

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, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with "Keith's Garage" as the subject.

Q: I recently purchased a classic Triumph Trident with wiring problems. The biggest problem at the moment is that the Boyer ignition doesn't compute to hook the coils in series. When tested, there is a voltage drop until near nothing on the last coil. Do I have coil problems? The other problem is the flasher that is hot all the time, the left turn signal works but not the right. — Gene McKillips/via email

A: I agree, at first glance wiring coils in series just looks wrong. The difference between points ignition and electronic ignition on the Trident is that the three sets of points fire each coil in sequence, while most electronic ignitions fire all the coils simultaneously. That's called wasted spark ignition, since in the case of the Trident only one cylinder will be on the compression stroke while the rest are on some degree of exhaust stroke. If you are still using the original coils, the problem with wiring all the coils in series is the voltage drop becomes a problem; the coils don't fire properly or at all. Where you once had three 12-volt coils, each wired separately, now you need — ideally — three 4-volt coils wired serially in order for each coil to receive enough voltage to fire properly. The Boyer instructions call for using 6-volt coils. If you make that switch you should be OK. I have to say that of all the bikes I own, an electronic ignition makes the most sense on my Trident. As to your left signal problem, grounding those old Lucas stalks is a common problem. The originals back in the day had a ground wire running from the socket to the metal pipe connecting them to the bike frame. Modern copies rely on the chrome plating on the plastic to ground the socket. As you might imagine, this fails over time due to corrosion and flaking chrome on the plastic.

No Spark on a Husqvarna 250 WR

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, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with "Keith's Garage" as the subject.

Q: I just bought a 1972 Husqvarna 250 WR. It has been sitting in a heated basement since 1975. It was never raced and is all original. It even still has the original tires. What it doesn't have is spark. I got a flywheel puller, but I have not removed the flywheel yet. Using a multimeter, I'm getting a reading of 4.32 ohms on the original coil. I'm not sure how to test the stator or if that is the correct next step? — Randy Kuser/via email

A: It sounds to me like the coil is fine, so next I would rotate the flywheel until I could see the points through one of the flywheel slots. They're bound to be corroded from sitting and may not be conducting properly. You can take a thin piece of card stock like a business card and pull it through the points to clean them a little bit. Spray a little contact cleaner on the points and switch to a clean strip of card stock and repeat until the card is clean. You may find you now have spark.

Motorcycle Lift Recommendations

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, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with "Keith's Garage" as the subject.

Q: Can you tell me what to look for in a good motorcycle lift for home maintenance? — David Geiger/via email

A: Thanks for a great question. Which of course raises other questions, because what lift you buy depends on what kind of work you'll mostly use it for. I usually see two different types of lifts, the platform lift and the parallelogram lift. If you have the room for it, you can't beat a platform lift. If your space is limited, the other type takes up less space and is usually light enough to lean up against the garage wall. I use both, depending on the work at hand. If I'm replacing old tires, the parallelogram lift allows me to remove both wheels at once, handy for me because I don't have tire changing equipment and take all my tire business to another local shop. If I'm working on a long-term revival, the platform lift gives me room to place parts removed from the machine and lets me raise the bike up high enough to work on it comfortably. I started out with a Harbor Freight lift over 10 years ago, and that lift is still being used at editor Backus' shop. I replaced it with a Titan air-operated lift because I got tired of pumping the Harbor Freight lift up manually several times a day when I was working on multiple bikes.

Most if not all the platform lifts will have a rear wheel drop-out for tire work. Most if not all the platform lifts will come with an adequate front wheel chock, but if you use them much you will want something better. I've got a Condor Pit Stop/Trailer Stop. It works perfectly.

Autolube Oil Mix Ratio Questions

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, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with "Keith's Garage" as the subject.

Q: I recently purchased a 1966 Yamaha 305 Big Bear. I had one of these when I was a teen and found it to be almost indestructible. I am wanting to reduce the oil mix ratio on the Autolube oil system. I have looked at several shop manuals and the factory only shows one setting. There is a pin that aligns with a mark on the pump and is adjusted with the throttle cable. I think that by using a synthetic 2-stroke oil (Amsoil) that I can reduce the oil mixture ratio, thereby reducing exhaust smoke and increase spark plug life, as well as improve overall performance. What are your thoughts on this, and what procedure would you recommend? — John Botts/Ponca City, Oklahoma

A: My usual solution to oil injection problems has been to bypass the pump if possible, and pre-mix to your desired ratio. The Yamaha manuals I have mention removal of the oil injection system as an option for competition and suggest a 40:1 gas/oil ratio. I have little experience here in changing the pump output, so I thought I'd get some expert advice from the folks at HVCcycle, 2-stroke specialists in Nebraska. Brad Obidowski from HVCcycle says: "Keep in mind the oil in the mix has to lubricate the crankcase main bearings too, so be careful you don't cause yourself engine problems chasing less smoke. Modern low ash oils burn better, leave less residue, smoke less, and protect better anyway. If you do decide to change the autolube pump, 0.012-0.015 inch is the standard shim gap. You need to reduce this to reduce the amount of oil. I's mostly guesswork once you deviate from the factory settings." He also mentions that trying to adjust the flow by modifying the cable pull could result in too little oil at higher rpms, causing problems. Reducing the amount the cable pulls will leave the output of the pump at an idle state longer, thus reducing the needed extra oil at cruising speed. Adjusting the shim stack keeps the oil delivery constant with the required throttle position and rpm range. My final advice would be to set it up as stock. Too many problems arise from getting the mix wrong.

Pitted Master Cylinder Fixes

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, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with "Keith's Garage" as the subject.

Q: A couple of issues ago, I fielded a question about a pitted master cylinder on a Honda, where the part in question wasn't available as a replacement. I mentioned that I didn't know of any places that offered sleeves for Hondas, though I knew of plenty for British bikes. Several readers wrote back with places they knew of that offered that service. Proof, if any were needed, that motorcycle gearheads are the best people. Here's a sampling. Thanks to everyone who wrote in with solutions to the problem. — Keith Fellenstein

A: I had a similar situation on my 1980 Suzuki GS1000 even though it is used regularly. The infamous pitted bore, and since the bike is pretty much made out of unobtainium I had it sleeved. In my case I used White Post Restorations. They installed a brass sleeve of the original bore size and now it's better than new with no more corrosion issues. — Floyd Webb/via email

A: In your response regarding the CBX master cylinder, you said you didn't know of any companies that provide sleeving service for Hondas or any other brand master cylinders. I have run into this issue on several of the vintage metric bikes I work on. There is a company in Minneapolis, Minnesota, that can sleeve pretty much any metric master cylinder as long as it's within the dimensions of the special European stainless steel tubing they stock. They bore out the cylinder, press in the stainless sleeve and then hone out the inner diameter to match the original inner diameter so OEM or aftermarket stock cylinder components will fit right in. Contact Brake & Equipment Warehouse. — Earl Johnson/via email