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1977, Yamaha, XS750
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Discussion Starter · #1 ·
Hello everyone obviously I’m new here but I just wanted to post some pictures of my new bike. This is my first bike and I am a tall guy (6’5”) so I was worried about fitting but honestly it’s comfortable. I only paid 500$ and it does run and drive. I am having some problems with cold starting and the electric starter really doesn’t start the engine so I have to get a nice leg workout with the kickstarter. It idles kind of rough and likes to die when cold. Sometimes the rpm’s stick at like 2500-3000 rpm’s but the throttle doesn’t and the front brake lever doesn’t activate the rear brake lights, the turn signals don’t work at all and the lights stay on all the time, none of the lights to illuminate the gauges work the Speedo is like 10-15 mph fast so It says I’m goong 70 but really going like 55-60. But besides that it shifts good and on the freeway I drove it 85 miles the first day I bought it and I’m instantly in love with this bike. I am ASE certified to work on cars and currently work for Chevrolet in the service department. I know about engines and I am a mechanical guy but I don’t know everything and don’t know anything about bikes besides the basics. Feel free to let me know your thoughts and I will definitely have questions thank you and nice to be here
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Your front forks are in need of service & that's not something you want to let slide and while you are in there, it would be amazing if your front wheel bearings are not past due for replacement. Those two service items will make a huge difference to improve the motorcycles handling performance and the cost is not prohibitive, you're looking at about 200$ in parts.
 

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1977, Yamaha, XS750
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Discussion Starter · #3 ·
Your front forks are in need of service & that's not something you want to let slide and while you are in there, it would be amazing if your front wheel bearings are not past due for replacement. Those two service items will make a huge difference to improve the motorcycles handling performance and the cost is not prohibitive, you're looking at about 200$ in parts.
Yeah I noticed they were leaking I already ordered my repair manual and I know I have to get to those forks asap. Thanks for pointing out the forks and the bearing though I now this bike needs a lot of work but I am here for as much help as I can get
 

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Front fork service is The most over-looked service item on most used motorcycles. It's easy to service forks once you've done them a few times, but highly advise you find somebody familiar with working on forks the first time out so they can show you how it's done. If you ride them with worn fork slide bushings and dirty grit in the oil, the lower fork legs will wear oval on the inside bore and that will ultimately destroy them.
Wheel bearings are critical to both the steering and to braking. If the wheel bearings are no good, the brakes will not work good. That's what makes those items a particularly high priority.

... the motorcycle should not be considered road worthy if the forks are leaking oil onto the brakes.
 

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Tires should be on the list, the shocks look like they are leaking as well. Brake system should be rebuilt, new lines. Generally electrical issues on old bikes are from bad grounds or contacts or jury rigged wiring harnesses.
I don't know the velocity stack arrangement between the carbs and the cylinder (on a Honda they are rubber) but check that they are seated and sealed properly. Or not cracked if they are rubber.
 

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Does it have Hitachi or Mikuni carbs?
The Hitachi are a PITA but there are more parts available for them now than there were in 1978.
Apart from a weak second gear (probably fixed under warranty years ago?) it's a pretty nice motor.
Not having original air box is probably the cause of hard starting?
 
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Discussion Starter · #10 ·
Does it have Hitachi or Mikuni carbs?
The Hitachi are a PITA but there are more parts available for them now than there were in 1978.
Apart from a weak second gear (probably fixed under warranty years ago?) it's a pretty nice motor.
Not having original air box is probably the cause of hard starting?
Mikuni carbs and idk there’s this vacuum line on each carb that goes to nothing and is plugged also.
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Discussion Starter · #11 ·
It appears to be missing an air intake system. OP for your own safety and others that bike really should be serviced before riding it, it needs some love.
I talked to a nearby bike shop and asked about the fork seals and they can get them in 3-5 business days but they don’t have the top caps shown in my photos? And I don’t know the proper name? Dust caps? I was also wondering if I should just change to a newer fork setup off of an GSX-R?
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I talked to a nearby bike shop and asked about the fork seals and they can get them in 3-5 business days but they don’t have the top caps shown in my photos? And I don’t know the proper name? Dust caps? I was also wondering if I should just change to a newer fork setup off of an GSX-R? View attachment 106787
The size of the fork seal is determined by the diameter of the stanchion tube. Measure the stanchion tube in millimetres and that's the size of fork seal you seek. The other dimensions are the height and outside diameter of the seal which are usually not very special. It's the bushings that will be harder to source.

Changing your old used forks out for used forks taken off a newer bigger motorcycle with completely different suspension design is kind of a stupid idea, you might better just go buy a bigger newer motorcycle and ride that.

Yes the part you can see is the dust cap and that is the least important part there. The slide bushings are most critical followed by the oil seal. If the bushings are faulty the oil seal can never work. The dust seals could be replaced by fork gaiters and that would work just as good.
 

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... those vacuum lines should not just end like that, somebody has messed with it.
You might want to check your crankcase ventilation, somebody probably killed that too.
 

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Google says XS-750 2D (1977) forks are 36mm
Replacement seals are useless if the slide bushings are worn out. Take it apart and service it before you buy parts, that way you know what you need.
Clean the forks inside and out just as you would clean a gun, forks need to be spotless clean throughout and all the parts fit precisely prior to reassembly. Collect the old oil draining into a clear glass container and examine that for water, metal shavings or nylon plastic debris.
Use between 5w and 10w fork oil when you replace it, & don't go thinking that heavy weight oil is better, it rarely is.
 

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Here's what a set of fork bushings look like,
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note the wear on the black nylon coating reveals the brass colour of the metal beneath it in some places.
This is the part that wears out and results in your fork seals leaking.
 

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I downloaded the service manual for that bike from the Carl Salter site and the forks look like they are less serviceable then most, you should definitely disassemble everything and inspect parts for wear, you might not need much. You should also download that service manual and read it completely. The photo reproductions are not very good but it contains a lot of critical information.
 
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