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Suzuki DR 350 General Maintenance And Tune Up


Drive Chain Maintenance

The drive chain is possibly one of the most often serviced items on your Suzuki DR 350.

The first step is to clean the bike, taking care not to direct jets of water from a pressure washer at the chain as that could force water into the chain's internals, displacing lubricant. Instead, after washing the bike, use a wire brush to remove caked-on dirt, grease or rust. If you're running an O-ring chain, skip this step as you'll damage the O-rings, which will degrade their protective capability. If you feel you must clean your O-ring chain, simply wipe it off with a rag and know that you're merely cleaning it for aesthetic reasons.

Make sure the chain is adjusted correctly.  You can look down the chain from the rear of the bike and see if the rollers and links run exactly straight back from the countershaft to the rear sprocket. If an adjustment is necessary, use a steel tape measure to double-check the distance from, say, the swing arm pivot to the rear axle, and measure both sides. If it's not equal on both sides, you'll find accelerated wear of both the chain and sprockets. Wear on the inner and/or outer edges of the sprocket teeth indicates the sprockets are not aligned.

Also, make sure that the chain tension is properly set with approximately 3 fingers fitting between the chain and the swing arm.

Now take a close up look at the master link. The master link clip is basically a thin, U-shaped piece of metal, and the closed end must point in the direction of chain travel. If the open end is the leading end, chances are it'll catch on something and pop off-with the master link following suit shortly thereafter. Muddy conditions can grind the clip down and render it unreliable, so replace one that's worn down too far. Make sure it's not bent, too.  It's a good idea to have an extra master link in your dirt bike parts inventory.

Now you can lubricate the chain. Spray the inside of the chain near the countershaft sprocket while spinning the rear wheel. This helps minimize lubricant flinging off. If you have an O-ring chain, use a light-viscosity lube to prevent surface rust and keep the rubber O-rings pliable. The reason for this is that O-ring chains are pre-lubricated and those O-rings help keep lube in and debris-and external lube-out. Do not use penetrating-oil-type lubes, including WD-40. These sprays contain solvents that can damage the O-rings or even wash away the factory grease.  WD-40 works perfectly fine on non O-ring chains and of course there are a myriad of aftermarket brands of different types of chain lubricants from wax to spray.

While you are servicing your chain, you need to examine both sprockets. Look to see if the sprocket's teeth are excessively worn-especially if they're hook-shaped or exhibit high wear on the inner and/or outer sides-chances are the chain needs to be replaced. And if you replace the chain, you should also replace both sprockets at the same time. These three items wear as a set.  You can often times find a package deal where you can purchase both sprockets and the appropriate chain for a combo package price.  If you are in the market to purchase a chain or chain combo set you might consider purchasing these items from my friend right HERE.  Rick will give you a good price and he will give you the best customer service ever.  Be sure to tell him GMAN sent you!

Suzuki DR 350 Oil Change

How often you change your oil and filter is very important and varies depending on the use of the bike.  If you have a Dual Sport Model and you ride it very calmly you could go a 1,000 miles before really needing to change the oil.  If you aggressively ride and abuse your DR off road then you may consider changing the oil every 8 hours of hard riding and change the oil filter with every other oil change. 

In either case, you can keep a visual eye on the appearance of the oil and you can let this be somewhat of an indicator as to the amount of life the oil has left in it.  One thing is sure, and that is, when it comes to oil changes, it's always best to error on the side of doing them more often than to error in not doing them frequently enough. 

Within the DR engine there are many components where you have hardened steel mated against aluminum surfaces.  The lubricating effect of the oil and the machined in clearances are the only things insuring that the harder metal components do not damage the softer aluminum components.  This is particularly true of the upper end and valve train and additionally these are the first components to be starved if the oil level is low.

The oil change is quite simple and you won't mind repeating the procedure as often as needed. 

Find the oil drain plug on the bottom of the crankcase.  If you have an off road model with a factory skid plate, there will be an access hole to the drain plug located in the skid plate.  Remove that drain plug and drain the crankcase.  Reinsert the drain plug snugly but do not over tighten.

Now find the secondary oil drain plug located on the front of the frame down tube.  Remove it and drain the oil that is trapped in the frame.  Reinsert the frame drain plug snugly but do not over tighten.  Word of caution:  When you remove the drain plug in the frame the oil may exit with a surprising amount of enthusiasm.  Be prepared for this by having a container at the ready and place the container in front of the frame drain plug when you remove it.  I've seen the oil literally shoot almost straight out of the frame hole and make a mess of things.


Here Is A Picture Of The Frame Drain Plug

Now you are ready to change the oil filter.  On the engine side cover you will see the oil filter housing cover with 3 8mm headed bolts attaching it.  It says SUZUKI right on the front of it.  Remove the three bolts, the cover, the old oil filter, and the oil filter spring. 

Suzuki DR 350 Oil Filter Cover Picture

Now install the new oil filter.  Be sure that you note that the oil filter has two flat ends.  One end has a hole in it and and the other end is flat metal with a spot on it to help locate the spring. 

Be sure to install the oil filter with the oil filter hole facing the engine and the oil filter flat metal part pointing out towards the spring and oil filter cover. 

Now be sure to correctly install the spring in between of the oil filter and the oil filter cover.  You can see where it is suppose to go as it has it's own little place made for it in the center of the flat metal part of the oil filter and also in the center of the oil filter cover.

Now you are ready to re-install the oil filter cover.  Make sure that the rubber O-ring is hand wiped with fresh oil creating a film of lubrication to help prevent it from bonding to the aluminum during heat and cool cycles. 

If you have difficulty keeping the O-ring in the groove in the oil filter cover you can use a tiny smudge of wheel bearing grease in the groove to help keep the O-ring in proper position during re-assembly. 

Put the oil filter cover back into position being careful to compress the oil filter spring and the oil filter into their correct positions.  Now simply snug the oil filter cover bolts and don't over tighten them.

Now you can add 2 quarts of your choice of engine oil.  If you want to go the extra mile you can remove or unplug the spark plug and kick over / electric start spin the engine to cause the new dry oil filter to fill up and pressurize.  You can do this pre-prime procedure before you actually "fire up" the engine to pre-lubricate the motor.  It's not mandatory but it doesn't hurt either.  I would positively recommend this pre-prime procedure if you have had the cases split or if the crankcase has been drained of it's oil for any length of time. 

I'm not going to go into the depths of the different choices and opinions concerning different types of oils.  But for simple reference make a note of this.  During a normal oil change with oil filter replacement use 2 quarts of oil then check the level.  During a normal oil change without the filter replacement use 1 5/8 quarts of oil then check the oil level.  If you've had the cases split and the internals are dry then use 2 1/4 quarts of oil then check the oil level.

 Always allow the DR plenty of run time before you check the dip stick.  Otherwise, you will likely get a false low oil reading and you will have the potential of accidentally over filling the oil.  I cover this as a known DR problem in more detail HERE , so, if you are interested in the oil over filling phenomenon please follow the link and read all about it.  


Suzuki DR 350 Valve Adjustment Procedure

When you need to adjust your valves you will find it to be a bit tedious and difficult.  You will find it to be frustratingly difficult without a handy little tool.  Go to RonAyers.Com
and order part # 09917-14910. It is a $4.23 dollar tool that is designed for adjusting the DR valves.  It is a small yellow handled tool that holds the square end of the valve adjusting screw so you can tighten the lock nut with precision.

To check the valve adjustment you will find two oval covers on the very top of the cylinder head right under the gas tank.

One oval cover is in the front and one is in the back.  They each have two bolts in them and the front one has a little metal bracket for the spark plug wire.

Simply remove both covers to gain access to the valve train.  
Take your feeler gauges and BEND the last 1/2" of them to aid in getting them under the rocker tip.

Remove the left side engine case plug and the smaller plug on the left side engine case that is on the front of the case.  Insert a 19mm socket through the big hole and rotate the crankshaft.  View through the small hole and find a "T" and also a line next to the "T".  Center this line in the small hole and this will set the motor at top dead center.  MAKE SURE THAT WHEN YOU SET THE MOTOR AT T.D.C. that all the valves have some play in them.  IF THEY DON"T>>then rotate the motor 360 degrees and align the t.d.c. mark and then recheck to make sure the valves now have play in them.  (it is possible to line up the t.d.c. mark and be on an exhaust stroke instead of a compression stroke.  The valves must be adjusted on the compression stroke AND NOT the exhaust stroke.

Now with the motor at top dead center you can measure the valve clearances.  I like to measure both intakes and both exhausts at the same time.  I also like to feel the same amount of drag on both feeler gauges when both of the valves are set evenly.  Also, I like to insert the feeler gauge and rotate the motor.  Sometimes when you rotate the motor away from t.d.c. you will GAIN a little clearance in the valves.  You want to check and set the valve clearance WHEREVER you have the most clearance EVEN IF IT DOESN"T HAPPEN to be EXACTLY at top dead center.  Also, on the models with auto-decompression release MAKE SURE that when you set the exhaust valves that you are not on the decompression release of the cam or it will throw your valve adjustment off by about .020".  

As far as tools required you need to buy 2 feeler gauge sets.  You will also need to make or purchase (as described above) a tool to fit on the square end of the valve adjustment stem.   Some people use a screw with a square drive in the end of a piece of wood.  I chose to buy the Suzuki adjuster tool cause it was less than 5 bucks and I use it all the time and it was well worth the investment.

As far as recommended clearances, that varies from early model to late model.  If you need the valve clearance specifications please follow this link to my factory Suzuki specification gallery.  Click Right Here to Proceed to the Suzuki Factory Specs 

Suzuki DR 350 Brake Fluid Maintenance

This is an important but often over looked maintenance item on the Suzuki DR 350.  If you ride your DR very mildly then you need to plan on doing this procedure about once a year.  If you ride your DR aggressively and you raise the brake fluid temperature into the hot range then you need to replace the fluid much more often. 

The brake fluid tends to break down and become degraded and contaminated over time.  The more heat the brake fluid sees the more this process is accelerated.  Over time the brake fluid can absorb a certain amount of moisture which degrades the brake fluid.  Also, over time, heat and cool cycles also degrade the brake fluid. 

As the brake fluid degrades it becomes more easily compressible and or spongy feeling.  Also, as the brake fluid degrades it also will boil and become non functional at lower temperatures.  Extremely degraded brake fluid can even damage or negatively effect major break components such as brake lines, master cylinder, caliper, etc.

Fortunately, the procedure for replacing the DR's brake fluid is very straight forward and very simple. 

To service the front brake fluid start off by removing the master cylinder cover on the handlebars.  Then install a clear plastic hose onto the bleeder valve that is located on the front brake caliper.  Now route that clear hose into a container that is appropriate to accommodate the old brake fluid. 

Now you need to have your new brake fluid ready, in hand, and have the lid open and be ready to pour it.  With the new brake fluid staged and ready to go, open the bleeder valve on the front brake caliper.  This should allow the brake fluid to gravity bleed from the master cylinder and flow out of the caliper bleeder, through the clear hose, and into your container. 

If your bike doesn't gravity bleed then there may be a blockage within the bladder of the rubber brakes lines or elsewhere, and that blockage problem will need to be analyzed, diagnosed, and repaired.

Now you should see the old brake fluid leaving the caliper bleeder and you should notice that simultaneously, the brake fluid level within the master cylinder is slowly dropping to match.  Now all you have to do is let the brake fluid level drop in the master cylinder and then refill it with new fluid.  Let the level drop over halfway before adding more new fluid but be careful and don't let the master cylinder brake fluid level drop too low or you will get air into the brake system.   Keep letting the level drop and keep adding more new fluid.  Continue to do this and flush the old fluid out thoroughly.  You can see through the clear tube to have a good indication of when you have flushed enough brake fluid through the system to be finished.

Once you are satisfied with the flush procedure, then just simply snug up the caliper bleeder screw and remove the clear hose.  Now re-install the master cylinder cover and  have someone apply and hold the front brake lever and quickly crack the caliper bleeder open and then re-close the bleeder while fluid is still squirting out. 

There should not be any air or air bubbles escaping at this time but only clear brake fluid.    If there is air or air bubbles escaping, then simply repeat the bleed procedure, and have your friend apply the brake again and re-crack and re-tighten the bleeder until there is no air.

Now you are ready to double check the brake function and make sure that the brake is working properly.  If everything is okay then  remove the master cylinder cover and bring the brake fluid level up to the full mark and then re-install the brake cover and clean up the mess and you are finished. 

When filling up the brake master cylinders be SURE that you don't OVER FILL them.  When you install the brake fluid it will be at room temperature.  When this brake fluid heats up it's going to expand.  If you do not leave room for this thermal expansion then you may experience involuntary application of the brake calipers.  If the brake fluid expands and has no where to go it has no choice but to begin to apply the brakes.

The procedure for the rear brake is so identical to the front brake procedure that I am not going to detail it out.  Just apply the above mentioned procedure to the rear brakes and you will be in good shape.

Suzuki DR 350 Wheel Spoke Maintenance

The Suzuki DR 350 wheel spokes need to be checked for proper tension frequently.  It is important that you keep them snug at all times.  Otherwise, them may become so loose without you knowing it, that you will be forced to re-true the entire wheel assembly. 

The Dual Sport Wheel Spokes and the Off Road Wheel Spokes are nearly identical except for the fact that the Off Road Model has aluminum spoke nipples, whereas the Dual Sport Model has steel spoke nipples.

You need to pickup an inexpensive spoke wrench for this procedure.  They are available at many places and will probably cost you around $10-$15.  Get a decent quality spoke nipple wrench or otherwise you may "round off" your spoke nipples with a poor quality too.  You really do need a good quality tool since, sometimes, it may take a considerable amount  of force to break loose or rotate a spoke nipple that has become stuck or seized.

Every couple of rides you should be checking your spoke tension.  Simply set the bike up onto an inverted, empty five gallon bucket, or bike stand if you have one. 

 Now slowly rotate the wheels and lightly strike the spokes one by one with a medium sized wrench.  The spokes should produce a sort of "ring" sound to them and not a dull "thud sound".

Any spokes that sound loose should be checked first.  Use your spoke nipple wrench to see if you can snug up the loose sounding spokes with the spoke nipples.  Pay close attention to which way your are turning the spoke nipple.  If you are looking "down" the spoke AND "towards" the rim then you need to turn the spoke nipple "counter-clockwise" to tighten the spoke.

After you've removed the play from the loose sounding spokes make another trip around the wheel "ringing" the spokes again.  Repeat the procedure as necessary.  Be careful not to over tighten the spokes.  As you snug the spoke nipple, DO NOT apply considerable force but instead snug it up gently.  If you pay attention, you will be able to "feel" when you've removed the existing play in the spoke, as the spoke nipple will become much harder to turn just at the point where all of the free play is removed.

Once all of the spokes "ring" okay then just make two trips around the rim and gently snug each and every spoke nipple with an equal amount of gentle force. 

If you stay on top of your wheel spoke tension you will likely avoid ever having to re-true the wheel assembly.  If for some reason you ever do need to re-true your wheel assembly feel free to read my thorough write up on that procedure HERE.


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