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.
LEAKING Z
After boring my 900 Kawasaki out to 1015 cc and installing 10.5:1 pistons I have developed an oil leak problem. It appears to come from between the cylinders and head and also through the holes where "the cylinder studs pass through the cylinders and head.
I assembled this motor and used a new O-ring around the cam chain opening. The head gasket is all aluminum and reusable and was assembled with silicone sealer recommended by the local Kawasaki dealer.
I know special cylinders are made to combat this problem, but I would rather not spend that much money. Is there an inexpensive fix?
Ron Simmons Akron, Penn.
A number of things can cause Z-l head gaskets to leak oil. The first one we would suspect is the reusable aluminum head gasket. You can sometimes use a metal gasket for more than one head removal and get away with it, but it’s generally not a good idea. Small changes in head position can cause oil to leak past old flat spots in the metal. The 900 and 1000 racers at nearby Champion Kawasaki claim the stock head gasket, a composite of fiber and metal, is hard to beat and works very well with a 1015 kit.
The center O-ring is another trouble spot. O-rings that have not been stored flat can be twisted or springy and lift out of their grooves and become pinched during engine assembly. Local shops report a high incidence of this in home engine rebuilds.
If the O-ring is in place and the gasket is doing its job, the most common source of oil between Kawasaki heads and barrels, as well as around the base gasket, is oil seepage past the stud threads in the cases. The oil seeps up into the stud cavity in the barrel and head and flows around the gasket surface. One way to check for the offending stud or studs is to groove the bottom of a head stud washer, clean the area around the stud, install the washer and nut and check to see if new oil wells up around the stud and flows out through the groove in the washer.
If it does, the only lasting cure is to remove the head and barrels and the cylinder studs, using a stud puller or the doublenut method, cleaning the threads on the studs and cases and reinstalling the studs with Loctite. The red Loctite Lock & Seal works very well for this, and the type of Loctite formulated for hydraulic fittings works even better.
CX WARRANTY
I am wondering if you have heard of a problem of camshaft and cam chain wear on 1978-1979 Honda CX500s. I own a ’78 with 14,000 mi. on the odometer, and have oil changes at 1000 to 1500 mi. intervals. The Honda dealer has two other ’79s with the same problem, but with only 7500 mi. on them. I have contacted Honda consumer service, but they said no problem existed. If you have heard of a problem could you inform me, as well as other CX owners.
Steve Jung
Random Lake, Wise.
We’ve heard of no problems with camshaft wear on the CX500. The early CXs, however, did have a cam chain tensioner problem because a bolt that held down one end of the tensioner blade was torqued against a rubber surface, so when the rubber lost its spring the bolt loosened up. This problem existed on bikes with frame numbers from 2000001 to 2034366 and was corrected at the factory by the end of 1978. Honda still has a warranty open on that repair, if it hasn’t already been done on your bike. The factory asked dealers who performed this repair to make three punch marks in the shape of a triangle next to the serial numbers on the side of engines when the work was completed, so this is one way to check if you bought the bike used.
HOT OR NOT BEEMER
A few months ago I purchased a new 1981 BMW R100RS. I noticed that no matter how hard or long I rode the bike the thermostat, to my a knowledge, never did open. The oil cooler never felt at all warm to the touch, so I assumed it was not opening properly.
When I approached one of the shop’s mechanics about the problem he said the thermostat would not open until the bike was at a standstill in traffic for a long time. What good is an $8000 machine if the thermostat doesn’t open until the oil is overheated and on its way to breaking down?
James Shouse Camden, Ohio
As on many machines now equipped with oil coolers, the BMW’s oil cooler is there more for insurance (and racy looks) than out of necessity. BMWs, and most other bikes, seldom if ever produce sump temperatures that are anywhere near the danger level for oil breakdown or mechanical damage to occur—except under road racing conditions, or as your mechanic mentioned, if the engine is allowed to idle too long. Air— cooled motorcycle engines ^ need that flow of air over the cooling fins to maintain proper temperature, and as long as they have that, their oil temperatures are usually lower than those of water— cooled automobile engine running at the same road speeds, on the same grade of climb, etc. If your BMW oil cooler were A flowing much oil under normal riding conditions, the oil would probably be cooled below the most efficient operating temperature for the engine.
TRIUMPH PING
I presently own a 1976 Triumph Bon--if neville. As you probably know, this particular motorcycle, in order to operate at optimum level, must use a high octane fuel. Unfortunately fuel of a sufficiently high octane is either non-existent or extremely hard to find. I have been using an octane booster with my fuel in order to^, compensate but I find this procedure highly inconvenient. Is there a method that would alter my engine in such a way as to allow it to operate on the leaded gas now being sold? I am aware that BMW offers base gasket kits to lower the compression of their earlier models. But I have yet to see something similar offered for ^Triumphs. Any information which can help me in my plight will be greatly appreciated. James Gorski Keesler AFB, Mich.
Big D Cycle, 3600 W. Davis, Dallas, Texas, stocks Venolia forged pistons with a compression ratio of 7.5:1 for the 750 Triumphs, down from 7.9:1 with the stock pistons. Jack Wilson of Big D had to custom order a limited number of these pistons sets from Venolia, so at $73.24 each, they are considerably more expensive than the production item. Other than lower compression pistons, there is presently no good way to reduce the pinging tendency on the 750, except for careful throttle control and checking to see that your ignition is not too far advanced. Our Triumph shop connections tell us that extra base gaskets will not make a significant enough difference on the relatively narrow Ibore 750 to be worth the trouble of installation. Jack Wilson has plans to modify Triumph heads to accept a second spark plug, as some companies are now doing with BMW heads, but hasn’t yet worked out the details.
JPOINTLESS MZ
My 1968 ISDT MZ175 has lost the temper on the points spring. Where the heck can I get a service manual and some parts? I’ve looked in the U.S. and W. Germany but I fear that nothing can be got out of E. Germany. G. Nooteboom ^ Corvallis, Ore.
We've looked too, and can't find a U.S. source for MZ parts. Can't speak for E. Germany and MZ, but many of the Czech bikes use Bosch points, so it is possible the MZ does also. If there is a Bosch part number on the points, you may be able to match them up with something off another German motorcycle or automobile. Bar ring that, it may be possible to adapt a set of motorcycle or automotive parts tofit by drilling, filing, etc. If you want to give it a try, Bertus Motorcycles, 1340 N. Hacien da Blvd., La Puente, Calif 91744, has vol unteered to take a look at your MZ points nd see if they can be matched up with something from their stock of CZ and Jawa parts.
RELUCTANT XL
m I have a 1979 Honda XL 185S. My problem is that the engine refuses to start unless I inject gas into the cylinder via the spark plug hole. Even then it runs for jusC a few seconds. I left the bike for three months without running it. I have checked all the fuel lines for clogging, checked the action of the carb, and cleaned the air filter to no avail. Could you please give me some hints at getting it started. Also, could you give me the name and address of a company from which I can purchase a degree wheel. Mike Geletka Miami, Fla.
If your bike was running well before its three month storage, the most likely problem is a gummed or clogged passage or jet in the primary circuit of the carb. The only fix for this is to remove and disassemble the carb, soak the body and jets in carb cleaner and blow out all the passages with compressed air. If the gas in your tank is also three months old, it would be a good idea to drain the tank and get some fresh gasoline.
You can order a degree wheel through Accessory Mart, 5218 Wooster Rd., Cincinnati, Ohio 45226.
BIMMER BATTERY
I own a 1977 BMW RIOOS and had been plagued by battery failures (two in 30 months). Although I take good care of the battery, I was told by two different dealers in my area that this was not an unusual occurrence in the /7 series BMW, particularly the lOOOcc models. I had no qualms about buying either the OEM Varta at over $100 or the recommended replacement Yuasa at about $65, however Eve used both these batteries and they were the very ones that failed when, after a year, the weather grew cold (as is wont to happen in N.Y.)
After determining that the charging system was in order, I decided to solve the problem for good. The solution involved the removal of the battery box and its modification by cutting it in half between the middle and end mounting holes, adding 5/16 in. to its length. The mounting holes are then elongated and the box installed. Next I purchased a #9603 Sears Diehard. This battery, designed for golf carts, has nearly twice the ampere hrs. (42) as either the Varta (28) or the Yuasa (24). It also carries a one year warranty, and the peace of mind of knowing that if you do have a battery problem anywhere in the U.S. there’s bound to be a Sears store nearby. Price of the battery was $57.99 plus tax.
The bike now starts with the temperature well below freezing, even when it’s been sitting for several weeks, on the first try, and I am able to restart the bike as often as I wish. Bruce Gerard New York, N.Y.
ROPE TRICK
I am writing you concerning the control of minor oil leaks in head gaskets as are reported on the Honda 750 models. A piece of cotton rope, about an inch long and large enough diameter to jam between the fins, has been of help in controlling the leak on my 750. This procedure also helped a lot with an old Sportster. The rope is removed with needle nose pliers when the bike is washed and a new piece: jammed in. The rope seems to absorb some oil and perhaps makes a hot spot which causes enough local metal expansion to reseal the gasket. George A. Hahn, M.D. Sacramento, Calif.
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IT CLUTCH CREEP
I own a 1978 IT175 and lately I’ve been having trouble with the clutch. The bike has a little over 1000 mi. on it. The cycle creeps when the lever is pulled in. Shifting, especially downshifting, has become difficult. I have made repeated internal adjustments following the owner’s manual instructions. This helps temporarily, but after about half an hour of riding the bike starts to creep again.
I asked the dealer about the problem, but he said it was typical of enduro bikes. When I first bought the bike, however, I did not have the problem. Please tell me what you think the problem might be and how I could cure it. Terry Decker Clearwater, Fla.
Your problem is most likely caused by overheated and warped steel clutch plates. It’s very easy to slip the clutch a bit too hard when the engine is hot and burn a plate. One or more warped plates will take up the clearance when the clutch is disengaged and cause it to drag. Adjustment sometimes helps temporarily, as it has in your case, but as soon as the bike heats up again the plates expand to take up the extra space. Damaged friction discs or worn finger grooves in the outer clutch basket can also cause clutch drag, but these problems are much less likely on a machine with only 1000 mi. on it.
Remove the clutch plates and look for black or blue coloring in the steel, indicating heat damage. A good way to check the plates for flatness is to lay them on a thick piece of glass and try to rock them to see if they are bowed. You should not be able to slip a 0.005 in. feeler gauge under any part of the plate. The steel clutch plates deepest in the basket, or closest to the engine, are the most likely to be damaged. Plates are relatively cheap, and any that are not flat should be replaced.
GUZZI T
After owning several two-strokes I have finally arrived by purchasing a 1975 Moto Guzzi 850T. I have several service questions you may be able to answer.
(1) The tech manual for the Guzzi 850 calls for the same size tires front and rear. I am now running a 3.65-18 on the front which requires lower than recommended pressure to maintain an adequate contact patch. I would like to replace it with a Continental 4.25-18 to match the rear. Can this be done without causing handling'' or safety problems?
(2) I have been informed that the rear end whine present, greater under load while nonexistent under no load, is typical of the 850T. Is this in fact the case, or is it indicative of future trouble?
(3) I have been informed that the GuzzL front forks will not hold the pressure of air assist. I know that no air assist kits are made for the Guzzi, but I don’t believe it would be too difficult to have a set of air caps machined. _ K Harry Thode Omaha, Neb.
The tech manual you have may contain information applicable to a different Guzzi model, such as the Eldorado. The 850T came with a 3.50-18 front and a 4.10-18 rear, very nearly the same size except for a small profile difference, but smaller than those on the Eldorado. If you presently have a 4.25-18 Continental on the rear, however, there is no need to go to an equally large tire on the front. Your 3.65-18, a low section profile tire, is actually just a little smaller than the standard 3.50-18 recommended tire. The 850T works very well with standard size tires installed (one of our staff owns one) and steers and handles best with a 3.50-18 on the front. A larger front tire will merely reduce steering feel and increase the likelihood of “cupping” or uneven tire wear as you put miles on the tire. Your best bet is to put a standard 3.50-18 on the front and when the rear wears out, go back to a 4.10-18. Tire pressures should be kept at recommended specs. Lowering tire pressure will not significantly increase the contact patch unless the pressure is so low the tire is dangerous to ride on, due to heat buildup and sidewall distortion.
Rear end noise in the Guzzi isn’t normal or a common problem, though we have seen cases of gearbox whine at high mileage. If the noise is not severe, however, ring and pinion gears will usually last a long time (with proper lubrication) without getting much worse. But keep an eye, and an ear, on it. If the noise grows louder, some rear end repair is probably in order.
Unless you want to soften the front forks considerably by installing lighter springs and using air caps to give more progressive compression to the front end, there is no real advantage to installing air caps on the 850. In stock form the fork springs are an excellent compromise between compliance and excessive fork dive, while providing very good handling characteristics. If thè springs have sacked with age, you may want to replace them or increase the preload with spacers under the spring caps. ES
