Service
SERVICE
We welcome your technical questions and comments, and will publish those we think are of interest to our readers. Because of the volume of mail received, we cannot return any personal replies. Please limit your "Service" letters to technical subjects only, and keep them as brief as possible. Send them to: "Service," CYCLE WORLD. 1499 Monrovia Ave., Newport Beach. Calif. 92663.
YAMAHA PIPE
Would you please inform me if there are any companies that make expansion chambers for a 1977 RD400 Yamaha. I’ve looked in many motorcycle catalogs and haven’t found any special performance exhaust systems for my bike.
Joe T. Hadachek Dysart, Iowa
An excellent set of expansion chambers for your bike is available through DG Performance Specialties, Dept. CW 1170 Van Horne, Anaheim, Calif. 92806. Go back and check your March, 1978 Cycle World and you 'll see where a set of DG pipes eut 0.9 sec. off 'the quarter mile time and added 6 mph to the trap speed of a test RD350.
CLEAN AIR SPECIAL
I own a Suzuki GS1000EC with a manufacture date of 4-'78. I am planning to move to San Diego. California. Is there way to legally install Mikuni 29mm smoothbore carbs with K&N filters and also meet California regulations when register my bike in the state?
David Wright
Silver Spring. Md.
Depending on who you talk to, you get a different answer on this one. Even the people at the California Air Resources Board, which is responsible for the state emission laws, aren't clear on this. Federal law prohibits a motorcycle dealer or independent mechanic from installing non-approved emissions-related equipment on a motorcycle made after January 1, 1978. However, there is no federal law against an owner installing such equipment himself. California has its own emission laws that prohibit an individual from installing non-approved equipment on an emission-regulated motorcycle. If you installed the carbs before moving to California, technically you wouldn't have violated the section of California law that prohibits installation of the carbs. But other state laws require all the emissionrelated equipment to be operational in order to register a motor vehicle in California. At this time, however, there is no enforcement procedure in California for motorcycles. There is a requirement for automobiles to inspected prior to any new registration change of registration, but motorcycfrf don't have to be inspected prior to registration, at least not yet. There have beet? suggestions that motorcycles be inspected for emissions conformance, but it's not law yet.
What this all means is that you might violating a California regulation by regk tering the Suzuki with smoothbore carbs installed, but no one is going to catch you3
GULPING GAS
I own a 1978 Suzuki GS75OEC. I have~ pair of Conti Twins front and rear, a Vette SS fairing and get gas mileage of3l.5 mp~ About 80 percent of my riding is highwa~ riding between 55 and 65 mph in top geal I don't ride the bike hard, I've got 5000 mi on it and the Contis show almost no wear The bike has an excellent service recorc and the oil is changed every 1000 mi. 1t~ been to the dealer four times while under warranty but all he could offer was “must be the fairing.” 1 took the fairing off and ran three more tanks of premium gas through it and the mileage rose to 32 mph. When I took the bike back he said tha mileage was “an idiosyncrasy of the bike.” With a new riding season approaching,*! am planning a tour to Alaska but don't look forward to a string of fuel stops every 115 mi. Any suggestions you have would be appreciated.
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Bill McGowan ^
Nashua, New Hampshire
Your mileage is abnormally low for the type of riding you do. A variety of GS 750s used by Cycle World riders have run over 40 mpg under normal use. Based on the information provided, there's no way of knowing exactly what is wrong with the motorcycle but there are a number of points to check.
Start out by making sure the cycle U tuned to specifications. That should have been taken care of by your trips to the dealer. Beyond that, make sure the ignition advance mechanism is working properly, providing 17° BTDC below 1500 rpm and 37° BTDC over 2500 rpm. Check camshaft timing to the crankshaft position. Careful attention should be paid to the carburetors. It 's possible that the dealer set the curbs to Type 1 specs and the motorcycle may have Type II or 111 curbs. Type 1 curbs were installed on model numbers 10001-11346 and 12357-12417. Some mechanics adjust the fuel jet screw in the carburetors richer than stock to minimize part-throttle hesitation. If the fuel jet screw is bottomed ouj hard when adjusting, the jet can be damaged, another item to check.
Although it's unlikely to be the problem, make sure the odometer is accurate. If it doesn't stack up the correct number of miles, your figures will be off. Different gearing could reduce gas mileage or improve it. If you are satisfied with the acceleration ana pulling power of the 750, you might consider taller gearing via a larger countershaft sprocket.
Even with a 100 mi. gas range, you should be able to make the trip to A task a, providing you ride the Alaska Highway. Gas stations are never more than 100 mi. apart on tht road. BS
