Sumotrack

[Ratranger]

So I'm new to the forum and to having an XS but not new to bikes, or modifying them. Picked up a 78 yesterday off of offerup for $100. Hasn't run in years, bad charging system. Odo shows 17k miles and engine turns free and has good compression, will pull out my tester and get exact numbers on that.

Plans are to turn it into a street tracker/frankenbike. I already have 2 fzr400 3tj swingarms from my last bike, so monoshock is in the plans. Front end might go with a brace or I might swap to a newer front end. I definitely want spoked wheels.

78 xs 650 by vw_drag, on Flickr

 

[Gcraay]

Welcome and good luck.

 

[fredintoon]

Hi Ratranger and welcome,
Congratulations on finding a $100 bargain.
Don't submit to peer pressure and spend a fortune on aftermarket charging and ignition systems until you've thoroughly checked that the stock electrics are TOTALLY fubar.
Non-working stock electrics are almost always easy to fix for not much money.
Just about any design XS650 wheels will fit into your bike although I reckon the '73 thru '76 deep groove aluminum rim wire wheels are the best looking.
Alas that the only other disk brake rear wire wheel is the 16" chrome rim megaspoke but IMHO those wheels are no better looking than the 7-spoke cast wheels and you can't run tubeless on them.
All the other rear wire wheels have drum brakes. If you want to give up on having a rear disk brake to run wire wheels, OK.

 

[Ratranger]

The entire electrical system has been attacked by someone with no knowledge. Thankfully it appears they never got in the engine, but all wiring outside of it is pretty trashed.

For wheels I'm probably going to use a rear wheel from a drz400sm as it uses the same diameter axle as the fzr. That makes it simple with only needing to fab spacers.

 

[lakeview]

Rear wheel swaps are often complicated by the very small rear sprocket that must be used on the XS.

 

[fredintoon]

The entire electrical system has been attacked by someone with no knowledge. Thankfully it appears they never got in the engine, but all wiring outside of it is pretty trashed.
For wheels I'm probably going to use a rear wheel from a drz400sm as it uses the same diameter axle as the fzr. That makes it simple with only needing to fab spacers.

Hi Ratranger,
did the dreaded PO only attack the wiring or did the electrical components also suffer?
Your '78 has fewer "mystery modules" than my '84 but I have learned that each one of them has to be in working order and correctly wired
(even if you've no idea what they do or why Yamaha put them there in the first place) or the bike won't run properly.
And if there's wire wheels that you like from a different bike, go for it!
But heed lakeview's caveat, the rear hub has to have a small enough bolt circle to install down to a 30T rear sprocket.
Note that others on this list have dealt with similar problems and you can most likely find all your answers by using the list's "search" button.

 

[Ratranger]

Atleast the regulator looks pretty rusty and banged up. I ordered a shop manual, but I am afraid there are parts of the electrical system that are just plain missing.

I understand I am setting myself up for a harder time than needed in some areas, but sometimes I like the challenge of what I can accomplish using my lathe, minor access to a mill, and basic tools. I have plenty to learn and plan on doing a fair amount of reading to hopefully reduce the extra labor of making a new path where it isn't needed.

 

[fredintoon]

Hi Ratranger,
some of the XS650's electrical components ain't where a person would think to look for them.
The '78's rectifier is bolted underneath the battery carrier.
It's there for a good reason, it's the most vibration-free area on the bike, but who'd of thought to look there for it?
Oops, just checked your bike's photo. It ain't got no battery carrier. Unless it's in a parts pile someplace.

 

[Ratranger]

I got the carbs, fenders, and most of the original lights with it. But no seat and the points are in a coffee can that had water in it at some point.

I'm tempted to use something like a microsquirt and a 36-1 wheel on the cam to run LS coils. I have a megasquirt2 on my engine swapped spitfire so I know what can of works that would open.

 

[bighairyralph]

Microsquirt would be really cool, but ask yourself first - do you want a motorcycle that runs and rides or another can of works injection project? If you like worms, have an awesome time. Personally, I'd rather use them for fishing.

If you want a ride, keep it tried and true.

 

[Ratranger]

Megasquirt is pretty simple. My spitfire is running full sequential fuel and spark with lq9 coils set up as coil on plug. When the weather is nice I commute 60 miles a day getting 30mpg. Big thing is getting the timing map set right.

And honestly unless you get used carbs and good deals I could do a microsquirt with LS coils and gsxr throttle bodies for about the same as a pamco and a set of VM carbs.

But first things first is to get the engine running without mods.

 

[Ratranger]

Started collecting parts for a PMA conversion. Banshee stator mount got here so I used a waterjet at work to cut a mount plate out of 6061.

Have to pick up a new impact driver, in the last few moves mine vanished.

 

[Ratranger]

Ok, pulled out my gauge and did a compression test. Both cylinders came out at 110psi. So compression is good.
For the PMA swap I ended up ordering a flywheel puller, so that is on hold until it arrives. Since I have time I threw the banshee flywheel on my lathe and lightened it.

I also cleaned the carbs, thankfully there wasn't a huge amount of varnish in them. Now I am waiting on the puller and then it will be time to set timing and try firing it up.

 

[littlebill31]

110, compression is not good. It's bad
With a warm engine, carbs off or butterflies open, it is 165 rebuilt, but 150 is real good if stock/used.
145 is minimum.
Since it has been sitting, the cylinder and rings are probably rusty. If you get it running, it will wipe off that rust and compression will increase. Unless something else is going on. Possible stuck valve or valve not seating is another common issue.

 

[59Tebo]

Try the "squirting some oil into the cylinders to help the rings seal better" trick and see if your compression comes up. Littlebill is right, 110 is bad, especially for a motor with only 17K on it. And Fredintoon hit it right on the head: make it run with the stock parts first. There's plenty of time to get crazy with your overhaul later...

 

[littlebill31]

I agree. Save the money for fixing stuff, not adding.
You never know what might be wrong. Once you start getting into problems that the previous owner failed to repair, the price starts going up. Bikes are parked for a reason. Could be the owner stopped riding. Could be the crank came apart. You never know.

 

[5twins]

110 may not be too bad if the test was done on a cold motor.

 

[grizld1]

Yep. And if the motor sat for a long while compression will probably rise after it's gotten some use. Sounds like you have a good plan and know what you're doing, Ranger. I look forward to following your progress.

 

[Ratranger]

Cold motor, no carbs, no exhaust, used the kick starter as the wiring is trashed. No oil in cylinders before test. Manual says 139psi on a warm engine, so next I will find my bore scope and take a look down in the cylinders and see if there is damage that will be a problem.

Right now the only thing I am changing is the charging system. I was told the bike was parked because it stopped charging, and when they couldn't figure it out the bike just sat. They definitely hacked the wiring trying to figure it out. So I will probably do a simple ignition only wiring job after I clean and set the points to test them and the coils, then I will try to start it. If it starts or not will decide which way I go from here.

I tend to make big plans as soon as I get a project, and as I get into them things get dialed back. Running EFI would be fun, and simpler than many people think it would be. But that doesn't make it easy, or more reliable than time tested parts. Right now before I even look at tires or a chain I want to hear the engine run.

 

[theDQG]

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