20 Most Recent 1979 Yamaha XS 650 F Questions & Answers

try here it may help

http://www.xs11.com/forum/showthread.php?t=396

C'mon, you get it, right? You can research us up the subject in the annals of Yamaha. You can do it, take the jump into history, For one, I will applaud you if you can discover what hath Yamaha wrought.

sounds like the float in one or more carbs are stuck..you will hahe to remove the float bowls and check if the floats shut off the fuel supply..

Main drive gears. The bike is pretty old, so there is undoubtedly a wear pattern on the faces of the gears, especially the higher two gears. The crankshaft bearing may also be worn and need to be replaced. Does the engine whine only when the gears are engaged, or also when running in neutral?

You probably have varnish build up in the carburetors, causing restricted air flow, and therefore the engine is running too lean, especially on the right side, and a lean running engine will run hot at the exhaust. It only idles when the choke is on because the choke creates a richer fuel supply. A can or two of commercial fuel cleaner through the fuel supply may get the engine's jet's orifices cleaned out. Otherwise, overhaul the carbs.Hey, nice old bike, though. Good luck

No. That's the short answer. The long answer is that when the bike has sat for any length of time, over three months, say, the gaskets and O-rings will get dried out. Another problem is that on the older models bike, the rubber is very susceptible to ethanol, which will destroy those parts. Another problem is that after gasoline has sat for any length of time, it goes bad and will not burn well, if at all. Another problem is that when fuel sits for a long time, it creates varnish on the surfaces it touches, which is not so bad for the walls of the float chamber, but plays Old Harry with metering jet orifices, plugging them or restricting them, thus creating an overly lean fuel mixture. another problem is that if the gas tank has sat less than full, the less full the worse, because a fine rust forms on the interior wall of the tank, and therefore the fuel filters get clogged, and replacing fuel filters twelve times still won't clear the rust -- you have to dismount the tank and take it to a shop for clean up and having a protective coat sprayed onto the interior of the tank. As far as the fuel hoses, they all have to be replaced with a rubber or other material which will stand up to ethanol. I'd really like to have a 650, but there is a lot of work in resuscitating a motorcycle which has been in dead storage. For instance, you probably have varnish build up on the piston rings, which is why the engine doesn't turn over. When I have had this problem, sometimes fuel additives such as Sea Foam or Chemtool 16 or Marvel Mystery Oil will help free the pistons -- squirt a couple of ounces into each cylinder through the spark plug holes and let the bike sit over night, then try turning it by hand again. You can try this method for a couple of days. If it doesn't work, you'll probably have to pull the pistons and overhaul them and the inside of the cylinder walls. Good luck.

WHAT YOU HAVE IS A CHEMICAL REACTION THIS USUALY HAPPENS WHEN CELULOSE IN THE PAINT ATTACKS USUALY ACRYLIC PAINT WHEN THIS HAPPENS THE ONLY THING I WOULD RECOMEND IS HAVING THE FRAME OLD PAINT EITHER BURNED OFF WITH A BLOW TORCH OR HAVING IT SHOT BLASTED AND POWDER COATED WICH IS NOT THAT EXPENSIVE AND IT IS FAR SUPERIOR TO HAND SPRAYING AND LASTS FOR A VERY LONG TIME WITH A TOUGH FINISH

Might have to make a calculated work to mend the wire with a lead so as to be fixed back to the brush.
use of a good soldering iron with good wattage to remove old lead and fix the new one.

when you let those old bikes sit for a long time with gas in the cup it eats up the diagram inside.somtimes it is impossibile to get them to stop leaking. Have you tried to adjust the floats?

mixture or fuel regulating screw.The mix screws should come out. There's nothing holding them in once they're unscrewed all the way. They have a spring, washer, and o-ring on them that may be causing them to stick in the hole. If you cleaned the carbs using carb cleaner with the screws in place, that cleaner may have melted the o-rings. That could be what's holding the screws in. Unscrew them until you're sure the threads are disengaged then try grabbing them with some pliers and tugging them out.

You may not have gotten the passageway clear that these screws fit into and regulate fuel/air mix through. You really can't properly clean it with the screw in the way. That may be the cause of your misfire. Also, that little o-ring needs to be in there and in good shape for the screw to regulate flow properly.. Check fig:----
The 650 mix screw regulates the all ready made air/fuel mix that comes from the pilot jet. The strength of that mix can be altered by changing the pilot jet size on the BS38s. On the BS34s, it can be altered by changing the pilot jet size and/or the size of the air jet that feeds it.

The air/fuel mix from the pilot jet is delivered into the main bore through 4 tiny holes. 3 are clustered together about where the butterfly plate closes. These flow directly from the pilot jet and are unregulated. Whatever mix the jet sizes are producing will come out here. The 4th hole is off to the side (BS38) or ahead (BS34) of the 3 others and is the regulated feed from the mix screw. The mix screw gives you control and adjustment over approx. 25% of the feed from the pilot jet..Check fig:---
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Did you replace the vacuum diaphragm on the back of the petcock? That is usually the cause of fuelcock leaks on Yamaha's. Yamaha only offers the diaphragm in the complete petcock assembly. The only way to get a diaphragm separately is in the K&L petcock rebuild kit. Unless your leak is dirty carb/bad needle related and not petcock related.

looks like the float bowl is stickin-get some paint remover or acetone and clean it or bend the damage out-thats a classic bike keep it but buy a service manual

Hi, depending on the climate you live in. A general purpose 10W30, is a good all rounder. If its hotter, then a 20W50 oil. Dont know the exact quantity, but somewhere about 2 quarts, it should have a dipstick on the filler cap, so just add a little at a time, checking regularly. Dont forget the oil filter too, located behind the small round cover, on the right hand side engine case. Changing this will require a little more oil , mabey 2 &half quarts.
Good Luck

solid state is far more efficient than your original regulater do yourself a favour fit it up & enjoy the ride

how long since the coils & condensors were replaced if iether of these items are breaking down once they are hot the machine will comence to run poorly the fuse blowing is caused by the system building high resistance because the fuse is designed to fail at a predetermined ampage that is 15 amp fuses blow if they are subjected to a higher ampage than 15.you would be well advised to have reputable technician check your electrical system. good luck

if you cleaned and set the gap on your points check and make sure the you are getting power up to the points follow the path with your test light.
Power at points?
NO= follow the path to what every is not letting the power pass, fuse, broken wire ect..
YES = power out to coil?
NO=something is wrong with points may not be closed spin motor slowly stil nothing check that they are closing
YES = dose your test light flash when you spin the motor with test on the power wire at coil
NO= points are not opening adj and try agine
YES= change cond. and check for spark
Good Luck
Mark
C.C. Motorsports

probly need a new starter relay-located by batt n has the cables attached--also chec wiring for any flaws--I wood make sur batt cables r tite n clean-ur welcome olschooler

try bigger pipes also the vaccum tube that alows air into the tank maybe blocked ?? get back to me

You need to remove the seat and fuel tank first. Loosen the clamps on the back of all 4 carbs that the air box boots are connected to. Then do the same on the front of all 4 carbs that connect the carbs to the intake boots. Pull the carbs out of the boots and disconnect the choke and throttle cables. Now you got to take the carbs completly apart for a good cleaning and adjustment. If you feel this is to much for you to handle then take it to a good bike repair shop.