Kawasaki Carburetor Problems and Triumph Valve Adjustment

Motorcycle maintenance, repair and performance tips

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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 your subject.

Q: I love your magazine, but one thing it needs is a question and answer section. Most of the new bikes do nothing for me, but I subscribe to one of the new magazines mostly for the service section. A question and answer section in a magazine gives people a place to find out fixes to problems and a feeling of camaraderie with other enthusiasts. It would be a great addition to your mag. — D. Seymour/via e-mail

A:You’re not alone in your wish for a question and answer section in the magazine; it’s a column readers have been asking for more and more lately. As luck would have it, we’ve found just the guy to help you sort out your classic conundrums. Meet Keith Fellenstein, a longtime classic bike enthusiast and the proprietor of Geezer’s Garage, a classic bike repair shop Keith runs out of his Kansas home.

We’ve been wanting to put this column together for some time, but were waiting for the right guy to come along. We think Keith, with his years of experience wrenching everything from aged Aermacchis to jaded Jawas and nasty Nortons, is just that guy. Keith’s not a factory-trained tech. Like many of us, he’s worked his way to a place of knowledge the old-fashioned way; by getting his hands dirty and figuring it out. At the end of the day, there’s no substitute for experience, and Keith has it by the bucket load.

Rough running KZ750

Q: Last summer, my 1982 Kawasaki KZ750H with 15,500 miles on it started running a little rough. One morning, I went to the garage and found gas on the floor around my bike. The vacuum operated fuel shutoff had failed. I purchased a repair kit for the shutoff, changed the oil and filter (due to gas filling the crankcase), removed the carbs to replace the needles and seat, replaced the spark plugs, and ran a compression test, with all cylinders showing 125psi. Up until this, the engine had run fine. After replacing these parts the engine would run well under acceleration, but cruising it would miss and feel like it was just going to die.

I removed the carbs way too many times, making sure all the passages were clean and all the adjustments were right. I can now rebuild one of these carbs in my sleep! Nothing seemed to help, so I went to the electrics. I checked the timing and the timing advance unit — it was rusted and would not advance, so I repaired it. I then substituted known good coils from a friend’s bike, with no change. I then synchronized the carbs, and after attempting this several times I noticed no change.

Going over all that I had done, I realized that probably when I took the carbs off the first time the rubber carb insulators had lost their seal at the head. I replaced them and now the engine fires up very quickly. It hasn’t started this easy since my problems first began. I also replaced the gasoline in case it might contain ethanol, but it still had the cruise problem. I removed the air filter and cover, and now the cruise problem is almost gone, I can barely feel the hesitation. I am going to install separate air cleaners and see what happens. According to my repair manual (which I have memorized), this means that I have a rich mixture condition. Why do I now have a rich mixture when all I did was clean the carbs? — Matt/Wichita, Kan.

A:Matt, I think you hit the nail on the head when you realized the carb insulators weren’t sealing to the heads anymore. That was my first thought when you said the bike would miss at cruising speed (light throttle). You don’t say, but did you buy new insulators or used ones? I ask because old cracked rubber insulators can cause a lean condition throughout the power band. A quick test is to spray some WD-40 on the insulators as the machine is running. Any change in idle speed will indicate an air leak. You say the cruising problem is almost eliminated by removing the air cleaner. Ensure the air cleaner is clean and not clogged, and that all the lines to the air injection system are intact, or if removed, properly plugged. Check the rubber diaphragms in the carburetors for cracks, and make sure the float heights are correct; they could have changed when you replaced the needle and seats. I’m glad you fixed the advance unit, but I don’t think your problem is electrical. I think once you confirm all your base carburetor settings are right, and that you don’t have any air leaks, you’ll find you’ve solved your problem.

Triumph valve adjustment

Q: I ride a 1971 Triumph TR6 650. The manual says to set the valves cold, with the intake set at 0.002 inch and the exhaust at 0.004 inch. My question is, it’s hard reaching in to set the valves and I’ve always had a hard time getting those tight clearances right. I’ve always heard that valve clearances tighten up as an engine warms up, so I’ve been in the habit of setting them loose, with the intake at 0.008 and the exhaust at 0.010. A friend of mine says this is a bad idea, that I’m running the risk of burning the valves. It seems to run just fine, and I don’t notice that it’s any louder than other 650s I’ve heard running. So my question is, am I risking damage to my engine setting the valves this way? If there is a risk, what is it, or is this just an old wives’ tale? — George/Yellowknife, NT, Canada

A:I know exactly what you mean about the difficulty in reaching the valves on Triumph vertical twins. No, you don’t run the risk of burning valves by running loose valve tolerances. Loose tolerances actually allow the valve to stay seated longer, allowing more heat to transfer from the valve to the seat. What you do give up is flow and some high end power. That said, 0.008 and 0.010 is a little loose; too much clearance and you risk wear to the cam face, rocker arm and valve tip as these parts slam into each other at higher RPMs. I’d be more comfortable with 0.004 and 0.006.

Kawasaki carb parts

Q: I just purchased a 1982 Kawasaki KZ1100A with 30,000 miles that needs all four Mikuni BS34SS carburetors rebuilt. Do you know any company that has NOS parts or one that specializes in obsolete parts like the rubber diaphragms? My Kawi has the full Vetter touring package, with frame-mounted front fairing, removable saddlebags/luggage, and the large back fender luggage trunk with passenger backrest. I’m a religious off-the-rack reader of every issue you put out! — Glenn/Bridger, Mont.

A: It looks like you can get all the parts you need to rebuild your carbs, but make sure those diaphragms need replacing before you shell out the $$$ to replace them. To the best of our knowledge they’re only available NOS, and they come complete with the piston. Bike Bandit shows them at $173.17 each, while Kawasaki Parts House shows them for $154.14. All the other carb parts seem to be affordable. MC