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


Suzuki TS185 Suggestions

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 email with “Keith’s Garage” as the subject.

Suzuki TS185 suggestions

A: A number of readers wrote in to help me with the question in the November/December issue about the Suzuki TS185. I’ll let them add what I missed in my troubleshooting. Thanks for the help, I appreciate it.

From: Gene O’Meara Jr. “I read the magazine cover to cover like most readers. I noted something that caught my attention in your column, regarding jetting issues for a reader’s TS185 and its tendency to blubber at 5/8 to full throttle. I just thought I would pass on my experience renovating a 1975 Suzuki TS250. It was having similar symptoms, and after removing and working on the carburetor more than a dozen times, I finally decided to buy a second carb from an eBay source. Sure enough, the bike exhibited the exact same symptoms and I was forced to open my thinking to other areas. Eventually I found the problem: a collapsed spark arrestor in the rear of the exhaust pipe, causing back pressure. The bike could not breathe properly. It was a little torpedo-shaped thing with twisted metal to deflect the sparks. The welds had broken after 40-plus years. So I tacked it back together and re-assembled it, and on the first test ride that bike took off like a scared cat.”

From: Tim Sickel. “In reference to the problem Steve is having, it could be that the spark arrestor in the back of the muffler needs to be cleaned or removed. Having owned three of these I found this to be a recurring issue. We would remove them and it did make a big difference in the way they ran.

From: Vincent Palazzo. “Regarding the Suzuki TS185 blubber above 5/8 throttle. I suggest checking and/or replacing the jet needle and needle jet. On old bikes these items wear due to the constant back-and-forth movement of the needle. The hole in the top of the jet needle is probably elongated, with corresponding wear on the needle jet. This causes a rich condition above 1/2 throttle that you can’t jet out unless you go so lean that you will cause the engine to seize.

Kawasaki GPz550 Carburetor Suggestions

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 email with “Keith’s Garage” as the subject.

Kawasaki GPz550 suggestions

A: It looks like I’m going to let my readers do the bulk of my work this issue. On the subject of the Kawasaki GPz550 from November/December 2019 issue, I heard from a few of you with helpful advice.

From: Vincent Palazzo. “It may not be carburetion. An ignition control module can fail in such a manner that you still get spark, but it won’t advance or retard. His bike is less sophisticated in that it still has a mechanical advance on the right crankshaft end. The weights and/or rotor may be rusted/stuck in the retarded position. Since it won’t rev, I’d be willing to bet spark timing is not advancing. This will cause all the symptoms Mr. Herchenroder noted.”

From: Tom Batchelor of Moto-Resto in Florida. “I think I have a suggestion for the other Keith (Keith Herchenroder) who wrote in about his GPz550 carb issue in the November/December 2019 Keith’s Garage column. I’m guessing you may still have his contact info. Please tell him he likely needs to shorten the CV carb diaphragm springs in regards to length. This was a mandatory operation on my Bandit 1200 Stage 2 setup from Holeshot Performance, and it’s required on a lot of other intake/exhaust modified CV carb bikes. Tell him I can’t give him an exact amount to cut them down to; however, what I’d do is start with 12mm off the length and try that; and go up to 25 mm. But I’d have to know the nominal length of the spring first to make an educated suggestion.”

1970 Triumph T120 Fork Leg Thoughts

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 email with “Keith’s Garage” as the subject.

Fork leg thoughts

Q: I am putting my 1970 Triumph T120 fork legs back together after some work on them. I want to make sure that they don’t leak where the dust covers mate with the lower legs (at the threaded junction). A friend said any good silicone sealer would work. Do you think Permatex High-Temp RTV Silicone Gasket Maker would be appropriate? I just happen to have some in my shop. I guess the issue is whether that would make it too hard to undo them down the road? I enjoy your column. Keep the rubber side down.

Crocker Bennett/via email

A: I too would be concerned about disassembling them the next time. If you go this route I’d only smear a little on a few threads, not the entire threaded portion. I wonder if Anti-Seize would work? It’s a heavy grease. Kill two birds with one stone perhaps?

Positive or Negative Ground for 1973 Triumph TR7RV?

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 email with “Keith’s Garage” as the subject.

Positive or negative?

Q: How would I determine if my 1973 Triumph TR7RV is positive or negative ground? I assumed that it was positive ground, but I hooked it up that way and it blew the 30-amp inline fuse on the negative cable. I do not know a lot about these British bikes. Thanks.

G. Manning/via email

A: First off, use a 15-amp fuse, as the ratings are different between British and U.S. fuses and a 30-amp British fuse as called for in the rider manual is a 15-amp American fuse. Next, the fused negative cable goes on the negative post, the positive post (red wire usually) goes directly to ground. If it still blows fuses after these changes, there is something else wrong with it. All this advice assumes it’s got the standard plate rectifier and Zener diode voltage regulator. If it has an aftermarket regulator/rectifier combo it may be a little more difficult to troubleshoot. Let me know if this fixes the problem.

Positive or Negative Ground for 1973 Triumph TR7RV?

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 email with “Keith’s Garage” as the subject.

Q: How would I determine if my 1973 Triumph TR7RV is positive or negative ground? I assumed that it was positive ground, but I hooked it up that way and it blew the 30-amp inline fuse on the negative cable. I do not know a lot about these British bikes. Thanks.

G. Manning/via email

A: First off, use a 15-amp fuse, as the ratings are different between British and U.S. fuses and a 30-amp British fuse as called for in the rider manual is a 15-amp American fuse. Next, the fused negative cable goes on the negative post, the positive post (red wire usually) goes directly to ground. If it still blows fuses after these changes, there is something else wrong with it. All this advice assumes it’s got the standard plate rectifier and Zener diode voltage regulator. If it has an aftermarket regulator/rectifier combo it may be a little more difficult to troubleshoot. Let me know if this fixes the problem.

1976 Suzuki GT750A Cylinder Problem

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 email with “Keith’s Garage” as the subject.

Ignition or carburetion?

Q: I have a question about my restored 1976 Suzuki GT750A. I did a complete engine overhaul on the bike, split the cases and had the crank rebuilt, including new oil seals. The CV carbs were also rebuilt. It has happened twice now during a ride that all of a sudden I lose power on one cylinder completely. It runs on only two cylinders for a bit and while I can keep the engine going on two cylinders and play with the throttle a bit all of a sudden it kicks back in and operates like nothing happened. Could this be an ignition issue or carb issue?

Jerry Gooren, Hayden, Idaho

A: Since it’s always the same cylinder, and the easiest thing to check would be ignition, I’d start like this: Rewire the coil from the constantly bad cylinder to one of the others, and swap that cylinder’s coil to the bad one. See if the problem migrates to the newly assigned cylinder. If so, you have a bad coil. If the problem remains with the original bad cylinder, then you should check that cylinder’s carburetor and mountings.

1978 Kawasaki KZ650C Mikuni Mixture

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 email with “Keith’s Garage” as the subject.

 

Mikuni mixture

Q: I could use some help setting the mixture on my carburetors for my 1978 Kawasaki KZ650C. How many turns out on the air/fuel mixture screw do you go to adjust a Mikuni carb? Remember there are four carbs on this bike.

Brian Rhenlun/via email

A: It’s almost universal that idle mixture screws are set at 1.5 turns from gently closed. Start there and turn them all out 1/2 turn and see if the idle speeds up. If it does, go a further 1/2 and check again. If no improvement try a 1/2 turn in from your start position and do the same test. Once you have figured out the right direction, fine tune in 1/4 turn increments. Once you have the fastest idle, use the idle speed screw that controls all four carburetors at once to set the correct speed. After that you may need to go back and double check the mixture. It can take a while to get it just right.







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