New to 650s

[Chris fertig]

Hey guys I'm new to the yamaha 650 scene and was wondering if I could get some pointers or help. I just recently picked up a 77 XS that has been hard tailed already. But that's it. It came with three incomplete engines and about 7 boxes of random and duplicate parts for it. I want to try and tackle this build on my own and am confident I can but I sure could use some pointers before I dive in to this engine and ignition. Any help is appreciated. Thanks in advance

 

[Hyde]

Hey Chris, welcome! But too much of a general ask in your post, not sure what you're looking for asssitance with. Folks here will be more than happy to help ya out though.

Did those 3 engines by chance come with 1 manual? Lol.

 

[5twins]

I guess the first step would be to see if any of those 3 engines are a match to the frame. Check the numbers on the steering neck against the engine numbers. The engine serial number is on the front of the case by the front mount .....

If you find a match, that's the one I would try to renovate.

 

[Chris fertig]

Hey Chris, welcome! But too much of a general ask in your post, not sure what you're looking for asssitance with. Folks here will be more than happy to help ya out though.

Did those 3 engines by chance come with 1 manual? Lol.

Yes sir they did come with a manual. I guess what I'm asking is if there are any tips or tricks when it comes to putting these engines back together or watch out for this or make sure you do this. That kind of thing.

 

[Chris fertig]

I guess the first step would be to see if any of those 3 engines are a match to the frame. Check the numbers on the steering neck against the engine numbers. The engine serial number is on the front of the case by the front mount .....

If you find a match, that's the one I would try to renovate.

None of them match which I hope doesn't lead to problems tagging it

 

[5twins]

I guess the big question is what does the number on the title match, the frame or one of those motors? I think they usually base titles on the frame number. If you were pulled over and they checked numbers, I think they would look at the frame.

 

[XSLeo]

If any of the engines are complete I would start by checking compression and maybe a leak down test. This would give you some idea if they will run. If none are together. It's time for a bit of checking the parts you have for wear. Your manual should explain how to check things like crank true, rod big end play, rod small end play.
It will tell you how to measure cylinders for wear, over size, out of round and taper. Same for pistons and rings.
If you don't have the tools or skills to do this measuring of the cylinders, most engine shops can do this for a small fee.
Your book tells how to determine piston to cylinder gap, you may get lucky and find you have a good match between some of your pistons and cylinders.
Leo

 

[5twins]

You'll also want to determine the years, or close to it, of the motors you have. There was a big change to motor internals in '74. '73 and older motors have different cams, cam chain, pistons & rings, rods, among other things. Many of the internal parts won't swap. And a note on the heads - heads and their top covers are a matched set, machined together to accept the bearings and valve covers. Don't mix them up. They will have matching numbers stamped in them on the front .....

 

[650Skull]

As well as the cases...........no's should match. Don't have a pic of them both

 

[lakeview]

Check to see if the hard tail installation is done safely; welded and ready to go or just tacked? Put together a roller and as you work things may become clearer.

 

[kshansen]

As well as the cases...........no's should match. Don't have a pic of them bothView attachment 105490

There has been a little discussion over on the XS400 forum about cases. There is at least one person saying you can replace the lower half off one engine with one off a different engine. I know I would not try doing it unless it was a last resort. Not sure if there is some major difference in the way they were machined. The 400's used plain bearings and not the roller/ball type used in the 650's.

 

[Chris fertig]

That is ALOT for all the replies guys it has helped big time. For the most part I'm really trying to familiarize myself with how this motor works so I can figure out what goes where because the book deosnt tell you everything. For example what runs my oil pump and where does it connect to. But this is what I have so far. None of my numbers match but the trans top and bottom came together so they match

 

[5twins]

If the top cover doesn't match the head then it may not fit properly and seal up. It doesn't look like it fits very well in your pic.

I'm pretty sure the oil pump is driven by the crank. It is mounted in the lower front area of the right side cover, under the big gear .....

The small worm gear on top of the big gear drives the tach. If someone removed these gears, your oil pump won't work.

 

[Chris fertig]

If the top cover doesn't match the head then it may not fit properly and seal up. It doesn't look like it fits very well in your pic.

I'm pretty sure the oil pump is driven by the crank. It is mounted in the lower front area of the right side cover, under the big gear .....

The small worm gear on top of the big gear drives the tach. If someone removed these gears, your oil pump won't work.

They are just sitting loosely on top of each other that's why the look like they don't fit. What drives the tach gear is it a cable?

 

[Chris fertig]

Ok I figured out it is I fact a cable now I'm just trying to figure out what runs/ spins the cable

 

[5twins]

The cable attaches to the top of that long rod. The crank turns the oil pump, the oil pump turns the tach drive rod, and the rod turns the cable .....

The cable operates the tach, the instrument itself. It doesn't turn or operate anything down in the case. All that stuff is what makes the cable spin.

 

[Chris fertig]

Ok. So the tach gear literally on drives your tachometer and nothing else.

 

[5twins]

Yes, I guess that's all it does. Some guys eliminate their tach. Then they think they can take all that stuff out of the case. Well, you can pull a couple of the parts like the rod and the little worm gear, but that big gear on the oil pump has to stay or you'll disable it. Then the motor will burn up in short order because there's no oil circulating through it. I've always said if you're going to be stupid, it helps if you're rich, because being stupid can get very expensive, lol.

 

[Chris fertig]

Perfect. Thanks for helping with that.
For the time being I only have one other question. I bought the upgraded PMA charging system will I need the factory wiring harness for That? The guy I bought it from tossed all the original wiring.

 

[650Skull]

Hey Chris, Engines and heads are assembled then the holes are bored in them. this is why they number the individual components for matching.............when they bore the holes there is a slight difference between every engine may only be a mm or so..........Yes it has been done before, and in some cases, (pun), they will be so close to a match a seal can be formed...................in other cases they can't and may as well be called Triumphs..........These mismatch's don't look much but a seal wont work on these.



also note in the first pic the sealant used on the rocker cover has blobs protruding into the engine...........one of those breaks off and gets stuck in an oil gallery the engine is going to get cooked somewhere.........if it is in the oil feed to the crank it is a complete rebuild..........


On the Tach drive, i always tell people to keep the Tach........... If the Tach stops working on a ride.....stop....check to see if the cable is damaged/broken, if the cable is your probably good to carry on...........If the cable isn't broken/damaged, it means the oil pump is.......get a truck...........the Tacho give you a heads up............