Frequently Asked Questions

 

What is the best two-stroke oil to use?

What is the best transmission oil?

What should I do to eliminate clutch slip?

What about carb kits?

How should I jet for pipes & filter changes?

How can I get rid of "surging"?

Why don't my turn signals flash?

What brand tires should I use?

What size tires should I use?

What expansion chambers are best?

How can I improve handling?

Oil leaks?

What sparkplug is best to use?

 

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What is the best two-stroke oil to use?

There is no good single answer as everyone has their own opinion... kind of like "what's your favorite color?".
Most any modern two stroke oil is better than anything that was offered in 1970. 

There are a few things to note:
Synthetics or semi-synthetics smoke less than dino type oils and, generally, have lower ash content.
Some full synthetics will not prevent moisture corrosion when bike has been sitting for long periods.
Castor based oils are known to gum up rings.
Oils are rated for "air cooled" and "water cooled".  "Air cooled" oil is designed for higher operating temperatures than "Water cooled".
Any oil rated TC-W3 or JASO FC (or better) is good oil.
Make sure oil is designed for injector use unless you premix.

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What is the best transmission oil?

Even though the owner manual specifies 30W motor oil, it is not the best or even a good thing to use in your transmission.  Modern motor oils are filled with additives that your clutch may not like.  Dino based, 80W gear oil is a better alternative.  A lot of folks think 80W gear oil would be thick like syrup... not so.  80W gear oil is similar to 30W motor oil in viscosity.  Any dino based 80W or 85W gear oil with a GL-5 rating is suitable.
Viscosity Table

Many choose to use ATF in their transmissions.  ATF lacks the shear strength and pressure qualities of gear oils.

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What should I do to eliminate clutch slip?

Clutch should not slip with a stock motor if everything is done correctly.
-Fibers must be within specs. Fibers with slanted cuts should be mounted so oil is thrown outward.
(Note: It is reported that some Barnett fibers will swell with heat.)
-Steels should be deglazed.
-Automotive motor oil should NOT be used. Use 80-90wt dino gear oil without additives or oil specifically designated for motorcycle wet clutches. It will take a while to see results when replacing automotive oil with a preferable variety.
-Clutch pressure plate must be properly aligned with basket. http://3cyl.com/mraxl/partid/clutch/clbasket.htm
-Clutch release and cable must be properly adjusted. http://www.3cyl.com/mraxl/manuals/maint/section5.htm#clutch adj    http://3cyl.com/mraxl/tunerwisdom/clutch_adjustment.htm
Note: Defective/broken/worn clutch release can cause adjustment problems.

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What about carb kits?

Carb kits have been known to cause a lot of grief because of inexact dimensions and tolerances of various kit parts.  Needles and jets contained in kits may not be the same as those originally supplied.  Genuine Mikuni parts are recommended.  The fuel valve and gaskets in kits can be used without reservation and can frequently be purchased in a kit with less expense that buying the parts individually.  If you do choose to use kit jets, etc., be sure to save the original parts to cure any problems created from kit parts.

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How should I jet for pipes & filter changes?

Jetting is an individual thing.  There are a lot of variables that are unique to an individual bike at a specific location.  There is no pat answer.  A lot depends on the specific type of chambers and filters used.  It is imperative that the carbs are thoroughly cleaned.  If all of the information at http://kawtriple.com/mraxl/carbtuning.htm is read and understood, proper jetting can be achieved.  It is largely a time consuming trial and error process.  Pilot jet should not require change.  It should be noted that "rebuild kits" may contain jets and needles that are NOT suitable for use in any application.

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How can I get rid of "surging"?

"Surging" is caused from a lean mixture condition.  It is a characteristic of H2's at small throttle position.  Surging can be minimized by careful sync of carbs and setting of air screws.  After air screws are set for maximum rpm according to procedure, you can try setting them richer by as much as 1/4 turn.  It may also be desirable to fit a richer slide.  Removing 0.020" from the flat at the bottom of the slide is near equivalent to fitting next size richer slide.  A loose chain and/or loose rubber drive hub dampers will emphasize surging.

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Why don't my turn signals flash?

The bulbs in the signals MUST be at least 23 watt bulbs for the flasher to properly function.  In addition, a fully charged battery is desirable.
If aftermarket or LED signals are used it will require that the flasher is replaced with an electronic type flasher where bulb current is not required for the flasher to work.

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What brand tires should I use?

Opinions vary but, in general, the cheap priced tires give poor performance, especially in wet weather conditions.  Bridgestone BT45 & S11 are good tires for the money.  Quality tires can improve handling and may save your a$$.

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What size tires should I use?

Modern metric tire sizes are now used for most tires today.  For S series, use 90 or 100 widths and 110 for the rear.  For H series, use 100 for front and 120 for rear.  Any larger tire on the rear may rub chainguard and detract from handling.  Be aware that manufactures do have recommended tire sizes for specific rim widths.  Chart

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How can I improve handling?

New swingarm bushings, roller bearings for headstock, quality tires, and tight spokes are good things for all Triples.  The H series can show improvement by installing longer (1-1 1/2") rear shocks and 18" front wheel.
Early H1 front to rear tracking has been found to be in error. Ref: H1B Cycle Guide Review

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Oil Leaks?

Most oils leaks result from reusing aluminum crush washers at the oil pump banjo fittings. The crush washers are not designed to be reused. Replacing them with Stat-O-Seal or Dowdy washers is a good fix. Very little torque is required for a good seal when using this type washer. Excessive torque can easily strip the threads in the pump housing.

Another common leak, especially on H2's is a transmission leak at the rear of the motor leaving a pool of fluid under the bike. This is caused by temperature differences and resulting pressure buildup in the transmission. The oil leaks from the vent at the back of the motor. This can be fixed or reduced by turning the vent nipple up, removing the O-ring on the dipstick, or drilling a small vent hole in the dipstick.

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What expansion chambers are best?

That depends on what you want and your riding preferences.

The concept of expansion chambers is that the design reflects sound waves back into the cylinder providing an extra "boost" in performance. They are usually tuned for a specific rpm range. It is vastly different than that of 4-stroke exhaust.

Most traditional "skinny" pipes are designed with a "hit" at higher rpms. Some of these chambers will allow very high revs and are accompanied with a weak torque output at lower rpms. Newer "fat " pipe designs will give a smoother power delivery with increased torque at lower rpms.

Stinger designed pipes are very loud and not intended for street use.

Expansion chambers, when properly designed, are for a specific bore and stroke of piston/cylinder. Therefore, putting a set of pipes designed for a 500 and installed on a 400 will not work as well as a set designed for a 400.

The only brand of expansion chambers to be leery of are Wirges chambers. Not only are they lacking in performance (H series Street) but many have an internal baffle that can clog and severely limit engine performance. The only way to clean the internal baffle is to cut the pipes open.

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What sparkplug is best to use?

All triples will run fine with the preferred NGK B9HS plug. NGK B9HV (Gold Palladium) or NGK B9HIX (Iridium version) are less likely to foul, especially good for points ignition models. NGK B8HS was spec'ed for 400 models which is a slightly hotter plug. Usually B8's are used where there is a lot of low speed, in town, riding. It is a misnomer that a hotter plug delivers a stronger spark... it does not.

BR9HS plugs should be avoided. The "R" in the number indicates it is a resistor plug. They are especially poor to use with points ignition systems.

Extended reach plugs can cause engine damage unless non stock heads designed for their use are fitted. B9ES is an extended reach plug as noted by the "E" in the number.

Early H1's spec'ed with surface gapped plugs (BUHX) will run fine with B9HS plugs and are preferred.

Other brands of equivalent plugs have been used with varied results.

In addition, resistor sparkplug caps should not be used.

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