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


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.

1971 Triumph T150 Electric Start Conversion

Motorcycle Classics tech expert Keith Fellenstein
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.

Triumph T150 electric start

Q: I was reading your article in a recent copy of Motorcycle Classics about converting a Triumph T150 to electric start. I have a 1971 T150 and would like to do the same. Can you provide me with more information as to where I can buy the components (kit form?) or who might do the conversion for me?

John Damon

A: It used to be easier to find the parts from the 1975 Trident needed to convert the earlier models to electric start. Then the idea became popular and now parts are scarce. You need the clutch basket from a T160, or a late model T150 clutch basket and the ring gear that goes on it. L.P. Williams in England has the ring gear if you have the clutch basket. I believe you can have earlier clutch baskets machined to take the ring gear, which is an interference fit on the basket.

Next you need the inner clutch cover from a T160. A quick search of eBay shows there are none currently available there. David Madigan is manufacturing a cover, but it is in the early stages and not for sale as far as I know.

Finally you need a starter motor and again David Madigan is the best source. Oh, one more thing I forgot, you need three of the early Amal concentric float bowls, the ones without the drain plug. They’re needed because the T150 engine doesn’t slope forward like the T160/R3 engine, so there’s no clearance between the starter and carburetors. You’ll have to search around the various British parts shops for those. I think I’d start by contacting David at the email address above. I hope this helps. I sure enjoy my Trident more with the electric foot.

Suzuki T20 Fiberglass Tank

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 T20 GP kit

Q: I have a NOS GP kit temporarily set on one of my T20 projects, just to get a visual. It is two projects away from starting and I’d planned to Caswell coat the tank for ethanol protection. It will get ridden several times a year and taken to our Western VJMC rally. The tank will be drained when not ridden. My understanding is the Caswell product can be used to protect fiberglass tanks from our wonderful Cal-ethanol “gasoline.” I’ve used it successfully on a couple of needy steel tanks. You recommended that Joe M. replace his GP tank with a steel one, and if it was never coated, I would agree. My tank has never been used and appears very solid. Would you have any reservations about my plan? I can hardly wait to get the first, of three, T20s together with the GP kit and stainless Higgspeed pipes on the road.

Mike Corcoran/via email

A:If it’s a virgin tank, I’d have no reservations coating it in order to use it. Just go completely by the instructions. Being a bit paranoid, I’d probably see if there was enough in the kit to do two tanks, and do a double coat in case there were any voids in the first coat. The tunnel can be particularly hard to coat properly. Another problem area is the interface between the fiberglass and the metal bungs for the petcock taps. It will be difficult to get the perfect seal between the glass and metal. I’m not saying it can’t be done, but it could be a problem. A couple of people with Norton fiberglass tanks have gone to the extreme of cutting the bottom out and coating the parts, then reassembling to assure complete coverage.

Kawasaki GPz550 Carburetor 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 email with “Keith’s Garage” as the subject.

Q: Before I shove this bike off a tall cliff, I figured I should ping you on your vast experience! I’m working on a 1982 GPz550 which is close to complete, except that I can’t seem to be able to sort out a carburetor issue. It has the dreaded TK CV carbs. I have been through the carbs too many times already and all jets are clear, passages flow carb cleaner and air, float levels checked.

It has pod filters and an aftermarket 4-into-1 exhaust (I wish it had the standard exhaust, but that is the way it came). I have a Dynatek Stage 3 ignition. I have a 1983 GPz550 which runs great, and I set these carbs up using that bike’s setup as a starting point.
It has new plugs, wires, and I changed the igniter with a spare I have.

The bike starts easily (too easily, actually) and will run at lower engine speeds, but begins to die when you open the throttle, and will spit and buck when you close the throttle. Initially it felt like a lean condition, except that the plugs came out black and sooty — classic rich condition.

I have the slide needles in the leanest position, but nothing seems to make any difference. No amount of changing jets or adjustments appears to make any difference.
I did notice that if I manually hold open two of the slides (need the other hand for the throttle!) it seems to clear out and rev more cleanly. It almost seems like the slides aren’t opening quickly enough to flow the necessary air.

The diaphragms appear good and the slides do lift with the throttle. I’m wondering if the needle jets need to be a leaner size, or am I missing something else I should be looking into? Any thoughts would be appreciated — that cliff is moving closer and closer! Thanks!

Keith Herchenroder

A: I think you’re on to something with the slides. Many times those staging kits come with new jets for the diaphragm metering too. Is it possible the wrong jets were installed there, choking down the CV slide response? If you have the carburetors set up to match the other GPz550 in your stable you could compare them. P.S. My experience is only half-vast at best ... MC

Suzuki GS450 Stuck Wheel

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: I am trying to get my 1981 Suzuki GS450 into shape to transport via trailer from Minnesota to Florida to give to my daughter’s boyfriend to restore. The bike needs work. Right now the electrics are not working right, so I can’t get it started or even light up the lights.

The biggest issue right now is even though I think I shifted it into neutral (engine not running), I can not get it to roll forward or reverse easily so I can get it up on a trailer. With effort, I can get it to roll backwards very slowly feeling a lot of resistance in the rear tire as it turns.

With a lot of effort we can push it forward, but the rear tire does not turn. It just drags along. Any ideas on what we can do to get the rear wheel turning freely so I can easily get it loaded on a trailer?

Thanks very much for any thoughts.

—  Rick Ross/via email

A: I’d start by really loosening up the rear brake linkage and see if that helps. If that doesn’t, you’ll probably have to take the rear wheel off to visually inspect the brakes and drum, and maybe the rear wheel bearings.

Suzuki TS185 Jetting Issue

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: A year ago I picked up a nice 1975 Suzuki TS185 and have been restoring and riding it, reminding me of my youth. I owned a 1972 and 1974 185 along with many other RM and TS models when they were new models.

My problem is the bike runs very nice, but from maybe 5/8 to full throttle it seems to blubber. My thinking was that it must have the wrong main jet, but I checked and it has the correct No. 125 jet. I did find and repair a couple small exhaust pipe cracks.

I have moved the needle clip up and down but now I am stumped. I have the carb somewhat apart and soaking in cleaner now and a new No. 125 jet has arrived in the mail. Do you have any suggestions? I am having a great time tinkering with the bike, but this is making me pull my hair out. Thanks.

—  Steve Foley/via email

A: Steve, you may have the correct numbered jet installed, but do you know if it is in original condition? Back in the day of expensive, hard-to-find parts and bad information, many a main jet was drilled out thinking that more gas means go faster. Try your replacement jet and see if that makes a difference, if not try a No. 120 or No. 115 and see if that changes things. Don’t go too lean too fast, that leads to piston seizure.







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