What I think I have here is

Should be able to id the year from the frame and engine numbers - there's a table in the tech section? Then you can see if it's a '78 with '81 wheels or whatever.
 
Following the advice from @Raymondo, @gggGary, @Superjet, and @lakeview, I decided to slowdown with pulling the motor. With it being a sunny 37 degrees I decided to take it out for a spin and start working on fix list. Bike fired right up but idle was a little high once off choke. When adjusting the idle I noticed this. Electrical tape was used for the seal from the air box to throttle body. Can't believe I missed that.

I pulled some of the tape off, you can see dirt was getting past. I'm not totally bummed as I was planning to pull the motor when I bought it.

I'm coming from the woods riding world and this would basically mean instant top end. Wondering now if I should go back to the original plan of pulling the motor?

Monday the manual arrives and with that I hope to see what parts I'm missing.
carb intake.jpeg
 
Yes, you're missing the rubber ring that fits between the airbox and carb. There's a tension spring on it too. Unfortunately, you can' buy that stuff new anymore, you'd need to scrounge used ones. Something else worth checking is the rubber sleeve between the two airboxes, a crossover between them. That often rots out and again, is N.L.A. These were some of the issues I faced with mine, along with the boxes being all rusty from battery acid drips. It was just a whole lot simpler and easier to switch to pods.
 
Wondering now if I should go back to the original plan of pulling the motor?

I would still investigate further. There is no proof yet that the engine needs a top end especially if only tape holding on to airbox. Keep digging in and come up with true compression numbers. Dont give up!
 
I would still investigate further. There is no proof yet that the engine needs a top end especially if only tape holding on to airbox. Keep digging in and come up with true compression numbers. Dont give up!

But once I pick up the scissors I just have the urge to run. Ok, I’m not that bad. I will borrow a tester and see if I can get that done tonight or tomorrow.
 
The stance looks good with smaller rear wheel because the forks are pushed up to the handle bars.

Hi 'Chance,
BTDT. Swapped wire wheels into my artillery wheeled Special (aesthetics) and swapped them back (practicality).
No visible stance change. Only difference was the narrower 18" rear tire let the bike corner better but made it
more straight line skittish.
A 16" rim is smaller than an 18" rim but the outside diameters of their stock tires are eff nigh the same.
You can get the same nose-down stance and save the front fender from further damage
by putting the forks back to normal and fitting longer rear shocks.
 
A 16" rim is smaller than an 18" rim but the outside diameters of their stock tires are eff nigh the same.
That’s what is the question. I’ve looked over many tires now in side by side comparisons in bike shops and stats online and I’m convinced there is about an inch+ diameter difference between the 16” & 18” choices
 
Hi 'Chance,
BTDT. Swapped wire wheels into my artillery wheeled Special (aesthetics) and swapped them back (practicality).
No visible stance change. Only difference was the narrower 18" rear tire let the bike corner better but made it
more straight line skittish.
A 16" rim is smaller than an 18" rim but the outside diameters of their stock tires are eff nigh the same.
You can get the same nose-down stance and save the front fender from further damage
by putting the forks back to normal and fitting longer rear shocks.

Thanks, if I bump into a deal on some standard wheels I will probably pick them up.
 
Shocks are on the list if I keep the 16", I'm 6'4" a little extra height is also good for comfort.
That right there gives reason to consider all the tire and shock choices carefully. It is clear that you are not going to personally benefit from a lower than stock XS Standard at all.
Keep thinking it thru . I am as well and it is a tough one as the fat 16” is a tempting look.
 
There is definitely a difference in the wheel/tire diameters. The bike will be more difficult to put on the centerstand with a 16" wheel. That tells you right there that it's sitting lower and has to be lifted more to get it on the stand. With the bike on the stand with a 16" wheel, you can pretty much slide a 2 x 4 under the tire. With an 18" wheel, the space under the tire is about half that.
 
There is definitely a difference in the wheel/tire diameters. The bike will be more difficult to put on the centerstand with a 16" wheel. That tells you right there that it's sitting lower and has to be lifted more to get it on the stand. With the bike on the stand with a 16" wheel, you can pretty much slide a 2 x 4 under the tire. With an 18" wheel, the space under the tire is about half that.

This bike has no center stand, probably for the reason above.
 
That's too bad. You'll learn pretty quickly that a centerstand is a wonderful thing to have when it comes time for servicing things like the wheels/tires. Heck, it's just great to have for any service work as the bike is more level and stable when on it. Usually, it's mostly hidden from view by the exhaust system. Your cut-off shortie pipes are probably the reason it got removed. It just looked too out of place hanging out in the open. As far as the exhaust goes, the bike will run best with a 2 into 2 using long mufflers. Gently tapered megaphones are good but we're at a bit of a loss now since MikesXS quit making their good ones. They used to have a wonderful muffler for these.
 
That's too bad. You'll learn pretty quickly that a centerstand is a wonderful thing to have when it comes time for servicing things like the wheels/tires. As far as the exhaust goes, the bike will run best with a 2 into 2 using long mufflers. Gently tapered megaphones are good but we're at a bit of a loss now since MikesXS quit making their good ones. They used to have a wonderful muffler for these.

Center stand is on the list. It was all I could do to lift the rear end to get it over the hump going on and off the trailer. Certainly not in dirt bike land any more, I’m not tossing this thing on a stand with a arm lift and push with the hip.

If I keep this as a runner I was looking at Mikesxs XS1 standard exhaust, any experience with that? It’s pricey, so not going make that call anytime soon.
 
I don't think the XS1 headpipes will mount up properly on your later frame. I think the lower pipe mounts are in a different spot. But, you could probably fit the XS1 mufflers to a set of later headpipes.
 
I'm in with the not tear down the engine crowd. If it ain't broke don't fix it.
When it's running does it seem to blow smoke out the side with the missing air filter parts?
As far as sucking in dirty air in through that taped up air filter, it isn't like being out in the dirt. Roads are much cleaner than out in the dirt.
Another thing with the center stand. Keep it greased, works much better. I doubt it was greased since it left the factory.
Not hard to run the tire up on a 2.4 to help get it up on the stand.
The longer shocks and sliding the fork tubes back down helps too.
Leo
 
@Superjet and @Raymondo, The compression test numbers are in and the winner is the left cylinder coming in at 123 PSI, the right side at 120 PSI. That is cold with throttle full open and full charge on battery (12.7 volts). Recharged battery in between tests. I just received my Clymer manual and haven't found the PSI range in there yet. From searching here it looks like I should be up around 135 PSI.
 
You'll get better readings on a warm or hot engine. Ideal is up around 150.
 
IMHO those numbers are fine. Nearly the same both sides. Tested compression on mine and got similar numbers after a top end rebuild - that was a cold engine and me not realising the throttle should be open. Time to worry is if the number is below 100 psi or if one side is way below the other.
 
Ck filters.... compression test.. I do cold and warm... not more then 10% readings apart. That will give you a idea as to the health of the engine. How many miles indicated ?
Top end job, 2nd over, seals, gaskets... valve job, do'n most of it yourself... $750-1000.oo.. but then it cascades from there.. might as well pull clutch plates.. replace or service... starter spring... rebuild carbs. Remove the points.. toss in magic box....
I'd only do all this and more... if it's going to be a "keeper"....
 
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