QuestionI bought it reciently in great condition from my cousin in Denver,Co. I live in N.E.Kansas. The bike seems to run great but friends say I should re-jet the carb for lower altitude because it will run too lean here. How do I know if I need to do this or not? Is there a way to tell if it is running too lean? Thanks for your help!
AnswerHi Phil,
Jetting is usually required with about every 1000 feet change in elevation.
Visit NGK's website and learn about reading the appearance of spark plugs. "www.ngk.com/sparkplug411.asp" Click the left menu topics and compare your plugs with images on their site. Review the tech intel on plugs and keep an eye on the appearance of your plugs.
Engines run best just lean. It may be dialed in for optimum power and no changes required.
Ideal plug colors are light shades of tan/brown. If the plugs engine side insulator appears whiter than tan, it's okay. Check NGK's site and study the images showing excessively lean plugs.
For our convenience, always include your email address as part of your question as requested and explained in my instructions. I return test information files by email.
Respectfully,
Mark Shively
(samle tech file minus images)
Introduction to Spark Plug Reading
The appearance of the firing-end of a spark plug graphically reflects the condition of an engine, the suitability of the spark plug heat rating, and whether or not the carburetor and ignition timing are properly adjusted.
This information is intended to assist you in correctly choosing your spark plugs and determining the performance condition of your engine.
Wet plug firing-ends such as those shown in Figures 1 ~ 2 are normally attributed to one of the following causes:
1) Excessive choking.
2) Trouble within the ignition system.
3) Oil pumping past worn piston rings and valve guides.
The causes of sooty plugs like those shown in Figures 3, 4 and 5 are usually the result of:
1) A plug with too high heat rating is being used and the firing-end does not reach its self-cleaning temperature (above 400-450 degrees) due to light load conditions.
2) Use of a too rich air-fuel mixture of richer than 8:1 ~ 10:1
3) Trouble in the ignition system.
4) An improperly functioning cooling system resulting in excessive cooling.
The firing-end burns illustrated in Figures 25, 26 and 27 may be a result of:
1) Too low heat rating, permitting the plug to exceed the highest limit for optimum operating temperature of over 850 ~ 1000 degrees due to excessively heavy load operations.
2) A too lean air-fuel mixture.
3) Ignition timing too over advanced.
4) Abnormal combustion such as knocking.
5) Cooling system trouble, which causes engine overheating.
Overheating conditions shown is Figures 28 and 29 are due to intense knocking and pre-ignition following situations identical to those in Figures 25, 26 and 27 where increased temperature of the spark plug firing-end results in melting of the electrode.
