Maxim. Does it use motor oil and transmission oil or just one fluid?

Are you wanting the size of the hex bolt head or the thread size and bolt length? Most oil pan plug bolts are either 17mm (5/8th socket) or 19mm (3/4" socket) bolt heads.

transmission filter in the bottom of transmission bolted to valve body.you need a large drain pan.place drain plug under transmission oil pan.remove transmission oil pan drain plug.let all transmission fluid drain out then screw back drain plug in oil pan.then you need to remove transmission oil pan then remove filter and replace pan gasket also.make sure you have right amount transmission fluid on hand.buy extra because if you short of fluid you cant drive car if fluid level too low.make sure you get the right amount fluid.torque pan bolts to 96 inch pounds.

Your oil filter is located underneath the motor. There is a round cover 4" to 5" in diameter next to the drain bolt. The cover is part #1 and the oil filter bolt holding it on is part #4 on the diagram. http://www.bikebandit.com/houseofmotorcycles/1983-yamaha-xs400k/o/m8258#sch208022 To change your oil you will need 3 quarts of oil, a filter, and a new aluminum drain plug washer. You can reuse the old drain plug washer if it has not been squished out of shape. Your motorcycle comes from Yamaha usually with 20w-40 mineral base motorcycle oil. You can use any oil that is JASO MA certified motorcycle oil. 10w-40 for cold climate. 20w-50 for warm climate/touring. Car oils use different additives and may cause scoring in certain types of cam bearings. Do not use any oil that says " Energy Conserving " on the label . It will shorten the life of your wet clutch and transmission gears. If you choose Synthetic oils, they will help your bike run cooler and shift easier. Pour in 2.5 quarts of oil to reach the high mark on the dip stick or inspection window. Make sure the motorcycle is upright or on the center stand when checking the level . You will probably need 3 quarts to hit the high mark. Run the motor for a minute or two to fill the oil filter compartment with oil. Now recheck the oil level and top up as needed. If you want to try an inexpensive full synthetic oil that is JASO MA rated 15w-40 Shell Rotella T Synthetic fits the bill at about $22 per gallon. All brands/manufacturers make a motorcycle oil. Some are very hard to find. Just make sure that the oil you pick has the JASO MA Japanese engine Rating to protect your motorcycle engine.

Engine Oil
Grade 1......API*Maximum Performance Signature Series 0W-30 100% Synthetic Motor Oil (SSOQT) Signature Series 0W-30 100% Synthetic Motor Oil (SSOQT)
Drain Interval Information
Maximum Performance SAE 5W-30 Synthetic Motor Oil (ASLQT) SAE 5W-30 Synthetic Motor Oil (ASLQT)
Drain Interval Information
Performance Plus XL 5W-30 Synthetic Motor Oil (XLFQT) XL 5W-30 Synthetic Motor Oil (XLFQT)
Drain Interval Information
Performance Synthetic 5W30 OE Motor Oil (OEFQT) Synthetic 5W30 OE Motor Oil (OEFQT)
Drain Interval Information
Above 19 F......10W-30
All TEMPS......5W-30 [1]
Manual Transmission,......SLF [2]
Synthetic Multi-Vehicle Automatic Transmission Fluid (ATFQT)
Torque-Drive Synthetic Transmission Fluid (ATD1G)
Automatic Transmission,MP6......AF3
Synthetic Multi-Vehicle Automatic Transmission Fluid (ATFQT)
Torque-Drive Synthetic Transmission Fluid (ATD1G)
Automatic Transmission,MP7......AF3
Synthetic Multi-Vehicle Automatic Transmission Fluid (ATFQT)
Torque-Drive Synthetic Transmission Fluid (ATD1G)

Looking under the bike up at the motor you'll see 2 drain plugs, 1 is motor and 1 is transmission.
Its easy to determine which is which because the transmission plug is vertical and the motor is horizontal.
Also you can drain the oil tank from the oil tank drain line which is plugged by a nipple on the frame. On the kickstand side of the bike, behind transmission.

There are two plugs on the bottom of the transmission, one for the engine oil, one for the tranny lube. The engine oil drain is the one that is closest to the left front corner of the oil pan. The other plug is the transmission.

The engine requires three quarts of oil, the tranny takes 20-24 ounces of oil.. Check the engine oil with the bike on the side stand. There are two marks on the dipstick. The upper mark is the "FULL HOT", the lower mark is the 'FULL COLD" mark. Keep the oil level between these two marks and do not overfill.

On the transmission, on the right side of the transmission, you'll see a chrome clutch release cover. It's behind the exhaust system. There is a plug that takes a 3/8" Allen or Hex key to remove. Check the oil level with the bike standing straight up.

As for what lubricants to use, I always use nothing but Harley-Davidson oil. 20W50 Syn 3 oil in the engine, transmission, and primary on 2000 and later model bikes. However, you can use other oils such as Amsoil, Royal Purple, Mobil, Motor Factory, and many others. Synthetic or petroleum based, your choice. Check the website of the manufacturer that you wish to use.

Good Luck
Steve

Uh Oh, makes me wonder what did happen.

On the bottom of the transmission, rear part behind the engine, are two drain plugs. The plug that is almost in the center of the oil pan is the transmission oil drain while the drain plug farther to front and on the left of the oil pan is the oil drain plug. If you remove this plug, the engine oil will drain out. Once it is finished draining, replace the plug and tighten.

On the right side of the bike right where the engine and transmission come together is a round cap with knurling on the edge. If you pull up on it, it will come out and has a dipstick attached. Pour three quarts of oil where the plug came from if you changed the filter too. If you didn't change the filter, only pour two quarts and 14 ounces of oil into the tank.

Now start the bike and let it run a few minutes and check the oil level. Notice on the dipstick that there are two full marks. One is FULL COLD and the ohter is FULL HOT. Top the oil off with the bike on the side stand, do not overfill.

If you drained the oil out of the transmission, you can refill it at the chorme end cap on the transmission on the right side of the bike. It has a plug in it that requires a 7/16" hex or allen key to remove. It too has a dipstick. Fill the transmission with 20-24 ounces of H-D transmission lube or Syn3 oil.

To change the primary oil, stand the bike as straight up as you can do safely. At the very rear of the primary down on the bottom, there is a drain plug. Remvove it and drain the primary oil. Remove the large round derby cover by removing the five screws that holds it on. Replace the drain plug and tighten. If you look at the clutch assembly, you see the aluminum outer shell. Just inside this is a black disc, the clutch diaphragm spring. Fill the primary with H-D primary lube or Syn3 until the oil level is just up to this level, do not overfill or the clutch will drag. It usually takes 36-44 ounces of oil.

To change the oil filter, simply screw the old one off, clean up the mess, and screw the new one on, tighten 3/4 after it makes contact.

Good Luck

There are three areas that you have to service, engine oil, primary oil, and transmission.

To change the engine oil, underneath the transmission, you'll find two drain plugs. The drain plug nearest the left side of the engine is the the engine oil drain. Warm the engine a bit and drain the oil. Change the oil filter. This is a messy job so put something down to catch the oil as it runs out of the filter. Replace drain plug and refill with oil.

The plug nearest the center of the transmission is the transmission drain. Remove the plug to drain the transmission. Once drained replace the plug and refill the transmission through the transmission fill hole in the chrome cover on the right side of the transmission.

To change the primary oil, underneath the primary outer cover very near the rear of this cover is a small drain plug. It takes a Torx wrench to get the plug out. Remove the plug to drain the oil from the primary. Remove the derby cover over the clutch. Refill with oil through the derby cover hole.

Your bike probably came with H-D Syn3 oil. You can replace the oil with this or any other oil as long as it carries a rating for use in a diesel engine. Here, it must have an API code of "C", example "SJ/CG4". Four quarts of engine oil, Add three quarts of oil and check. Fill to proper level with the fourth. Your dipstick is marked with a "Full Cold" and "Full Hot" mark. Fill to "Full Cold" mark and check again after warming up the engine.

Use Syn3 in the primary or 30 weight oil, 40-44 ounces. With the bike standing nearly straight up, the fluid level should be to the bottom of the clutch spring, large black disc in the center of the clutch. It's a diaphragm type spring.


Use Syn3 in the transmission, 20-24 fluid ounces. Check with the dip stick again with the bike standing straight up.

Change oil and, filters regularly; lube the throttle cables and, all moving parts drain the fuel tank and, replace the fuel filter every year, or; when needed. never leave fuel in the bike when you store it without using "stabil" only check your ignition with a timing light get a maintenance schedule from the bike's manufacturer and, follow it.

on left side looking forward near cyliner is the filler plag
there is a drain plug under the motor it will be the biggest bolt you see
you cant compromise on oil quality just use high viscosity & dont mix brands! stick with just one! the reason is the chemicl compounds sometimes are in conflict