The Service Dept
THE SERVICE DEPT
JODY NICHOLAS
COOKED XL250 PISTON
This letter is in response to a problem I encountered with the new model XL250 Honda. Although I don’t have many miles on it, in terms of those who burn up the road, I have quite a few hours on it and can attest to the handling both on and off-road as super.
The problem involved a badly cooked piston and aluminum-plated cylinder. I guess my first mistake was using 20W-40 oil. I have used this oit in the previous Hondas I’ve owned, with no trouble at alt. This is the first larger Single that I have owned, the others being Twins or the single model 90.
The dealer says lack of lubrication and pushing it on the road were the contributing factors. I was running it from 45 to 55 mph and 4500 to 5500 rpm, varying the speed constantly. I now use the dealer-recommended oil which is a nationally known brand of 40W racing oil. He recommends, locally, 40W for summer (or 50W if very hot) and 30W for winter.
The Honda warranty and quick dealer service had me back on the “wheels” in no time. I was surprised he had the parts this soon.
D.E. Kelsey
Lind, Wash.
Our conversations with the engineers at American Honda confirm our suspicions that your piston problem doesn’t have much to do with the engine oil. They firmly recommend the 10-40 oil as used in other Honda models. We’re inclined to think that the use of too warm a heat range plug, combined with high rpm road use, and possible lean carburetor jetting, may have caused your problem.
Remember that this machine has two jobs: to operate slowly in off-road
situations and operate fast on the road. One spark plug can’t do both perfectly. If you anticipate being on the road 50 percent or more of the time, you would do best to run with a slightly colder plug-an 8 instead of a 7 in the case of the XL250-even though the bike may misfire for a few seconds above 6000 rpm after an extended period of low rpm running.
Further, break-in is extremely critical on the XL250, which feels, and is, quite tight when new. Give that new piston a chance and do not exceed 4500 to 5000 rpm in any gear for at least 500 miles.
CAREFREE FUN
Ten years ago I sold a Triumph Thunderbird. The carefree fun enjoyed by an owner of one of those mild-mannered, good handling machines has been sorely missed although I’ve owned a variety of machines since.
A week ago I purchased a 1968 Triumph Daytona (500cc) and I would like to calm it down. It seems to me that this would be an ideal rig for my needs.
If you have information concerning the de-tuning of a Triumph 500 (Daytona or Trophy) please let me know how to obtain it.
Kent To ugh er y
Or eland, Penn.
The Triumph Thunderbird was indeed a docile and long-winded machine, but the demand for more spirited machinery drove it out of production.
De-tuning your Triumph Daytona is a fairly complicated job if you go the full route, but it can be calmed down a little without too much expense.
The first thing I would do would be to buy a single carburetor manifold (Part No. E 7578) and install one of the carburetors that came off your machine. This modification will give easier starting and smoother carburetion.
With the high quality of all gasolines available in the United States today there is no reason to lower the compression ratio from the standard 9:1.
The next modification is a bit more involved and concerns altering the camshaft timing. The Triumph workshop manual (Part No. 99-0948) describes the process in detail, but this should be left to a qualified service technician at your local Triumph dealer as several special pullers and special tools are required to do the job properly.
SLIPPING CLUTCH
I am at present the proud owner of a 1972 Norton Commando, I’ve had it for four months and am very pleased with it so far. Only two troubles have developed. The first was a rare problem in Nortons, as my dealer told me. The oil in the oit tank drained into the crankcase completely in a single night. My dealer said that it was common for Nortons to do this on two to three weeks sitting. He got on the phone to Norton Villiers (I am stationed in England) and the trouble was isolated to the oil pump, the pump was repaired and it’s been fine ever since.
My present problem is that my clutch slips at high speeds and at high torque. As it only has 4000 miles on it, I am at a loss for explanation. Is it the disc segments or is it the spring diaphragm? Is it possible to buy a special clutch spring diaphragm for racing to rectify the trouble or should I just replace the clutch segments? The engine is a “Combat” engine and develops 65 bhp at 6500 rpm and my clutch starts to slip at just over 5000 rpm in either third or fourth gear under hard throttle. Any advice would be greatly welcome.
Sgt. Edward J. Vahovick
New York, N. Y.
The diaphragm spring-type clutch used by Norton is fully capable of handling more than the 65 bhp developed by the Combat engine and has a life expectancy of many more than 4000 miles.
But it is susceptible to the same ills as almost any motorcycle clutch which runs in an oil bath in the primary chaincase. Certain of the techniques which should be used when operating a motorcycle with this type of clutch are not too obvious, but should be employed if maximum clutch life is to be realized.
One of the most common mistakes motorcyclists make is to sit for long periods of time with the clutch disengaged and the motorcycle in gear, as at a stoplight. When the clutch is disengaged with the engine running and the transmission is in gear, the outer clutch case and the drive plates (the solid metal ones on the Norton) are revolving while the driven plates (the fiber-disc plates) are stationary.
Even with the proper clutch adjustment there is a film of oil separating the clutch plates which will heat up, disperse itself and allow the plates to become hot enough to damage themselves. A dry-type clutch is not nearly as susceptible to this phenomenon, but shouldn’t be held disengaged for long periods of time either.
A trick used by many motorcyclists is to select neutral just before stopping at a stoplight or an intersection. This helps to keep the clutch cool and to prevent the plates from swelling from becoming too hot.
Another important aid to extended clutch life and freedom from clutch slipping is to keep the clutch cable properly adjusted. There should be at least 5/16-in. of free play between the clutch lever and its holder at the handlebar and just a perceptible amount of play between the clutch pushrod and its operating lever inside the transmission case outer covering. This clearance will prevent the clutch from slipping by reason of relieving pressure on the diaphragm spring.
It is quite possible that the fiber plates on your machine have been damaged by heat and must be replaced. [oj
