Got a free project XS400, or so I think?

[josh_makesstuff]

Hello all, first post, I received a free project bike and after running the VIN, all it returned was the year (1981) and that it's a Yamaha. I was told that it is a XS400, but the bike has changed idle hands a few times. Anyone know how to look up the model? VIN: JYA4R500XBA016963

I received it mid-cafe racer mod and am tearing it down to see what needs attention. This is my first motorcycle rebuild (FAA mechanic) and I'm getting stuck on some of the Yamaha-specific items.

1: The timing point cover has a phillips screw in one hole and some sort of plug preventing it from coming off in the other. Is that something broken?

2. It was intended to be a kick-start only bike (starter & solenoid is removed). I've heard that this means it doesn't need a battery; is this true? I figured it would be needed to run lights and whatnot before it cranks up.

3. Are there any hard-learned lessons that I should look out for? I plan on redoing the bare-bones wiring and replacing most of the older bent up parts.

Thanks!

Josh

 

[XS4004lyfe]

All these fucking jokers buying vintage bikes and getting halfway through a cafe racer build piss me off. I see SO MANY FUCKING half done cafe racers.

Such a damned shame. That and wanna be bobber builders. Like holy shit.

 

[NewHavenMike]

Welcome. Youve got some work ahead. Start reading the manuals or just buy one.

JYA4R500XBA016963. I think JYA is Japan designation, so 4R5 would be the model prefix.

Youll get a mix of model prefixes that will probably work on your bike. Partzilla is a good resource for getting part numbers and buying parts and looking at the parts diagrams

The point cover is probably capped so you cant alter timing. You should be able to remove it.

The bike needs a battery to generate the magnetic field for power which will start and run the bike so keep a good one. No battery=nothing happening.

Hard-learned lessons, sure, dont get curious. Dont take the engine apart for any reason. Start with the engine though. Remove the inspection caps on the head and spray some oil on the lifters. I use fogging oil spray because it mists on everything and that will get the cam oiled. I would remove the carbs and exhaust and spray oil in there too and also in the spark plug holes. See if it has oil and fill it if you need to.

After everything is oiled and kick it over a couple times to get everything moving, hopefully if you get power and spark you can pour some gas in the plug holes and see if it kicks over. If it wants to start then I would continue with the engine and get it running before I fixed the rest of the bike.

I can see you will need new fork tubes.

 

[XS4004lyfe]

Damn Mike you just spoke some TRUTH.

I fucked an engine up by playing with it too much, crammed a valve real good.

 

[Matthew Friez]

All these fucking jokers buying vintage bikes and getting halfway through a cafe racer build piss me off. I see SO MANY FUCKING half done cafe racers.

Such a damned shame. That and wanna be bobber builders. Like holy shit.

Some of us lose time. I started mine 11 years ago and as of 2 weeks ago was a pile of random parts. Got laid off of work because of the rona and got back too it. We’re not all the same.

 

[MoonClipper]

Looking forward to your progress on this bike! As was said, a battery is needed. I'm not sure about these bikes, but I do know on some bikes and other vehicles running the engine without a battery will damage the regulator, so be careful about that.