Doctor, I've got no pulse!

[allenp42]

I’m guessing the difficulty on my crusty bike will be more than less, kinda like the difference between these two photos

Now and then I have encountered one that was little stubborn to remove. What I do is make sure the flywheel puller is screwed with several threads. Tightened the puller bolt pretty snug. Then removed the wrench/socket that you're using and tap on the bolt head with a hammer. I would not go go too hard though. This is one of those steps that is hard to describe but I think you'll get the feel of what to do. If it does not pop loose, tighten it a little more and repeat tapping with a hammer. It will eventually pop loose.

I never beat on the flywheel. Just seen too many with those battle wounds.

 

[69ST]

I've seen guys destroy parts due to a stubborn flywheel. The worst was a recent video of a flywheel & crank being destroyed in the process. Who would've imagined that was possible? Prior to that, the collateral damage award went to the guy who broke-off the end of a Nice crankshaft(!). IMO, none of this destruction is necessary. I rebuilt the aforementioned Nice 110, the flywheel was easily removed from the broken crank. With the 72cc motor, shown in the video...the "jump the shark" moment is pretty obvious; but, in all fairness, my view is a bit jaded since I've been wrenching on small engines for 50 years now.

The missing element is heat. Heating the flange, quickly, has never failed me yet. All it takes is a garden-variety propane torch, some care in aiming the heat (keeping it away from the crankshaft) and working quickly enough so that conduction doesn't undo your efforts by transferring heat energy to the crankshaft snout. (This same "trick" also work wonders on oil spinner cover/throwout bearing flange screws & stator screws.) Tapered holes respond well to rapid warming and, really, temps in the 200F range should be plenty. In a worst-case situation, a flywheel stuck like nothing I've yet encountered firsthand, I'd snug the flywheel puller as tightly as one would dare (stopping short of damaging the crank), then applying propane torch persuasion to the flange area. I expect that the puller will lose a little tension in the process, from thermal expansion...that can be used to your advantage, by retorquing the puller. When clearances tighten, as the metal parts cool, more pulling force would be applied. A few heating/cooling cycles should be sufficient to break a stubborn mechanical bond. Having said all of that, I seriously doubt you'll have to deal with anything remotely resembling this. The slightest bit of movement, along the crank snout, and the flywheel will lose its grip rapidly.

 

[airblazer]

Thanks for the tips guys. We’ll see if I have time to attempt this tomorrow.

 

[airblazer]

I got to spend a little time today disassembling the head. The rockers have two divots running the width of the surface that touches the cam - I assume that’s no bueno? The cam looks ok to me, but I have untrained eyes. How about the intake valve? It was covered in dust and dirt when I pulled it out. Racerx you mentioned Atomic Rebel’s looked 3x worn beyond what it should be - how does this one compare?

 

[cjpayne]

If in doubt about the rockers, replace them and chek the cam for any scoring(especially the head journals). If you do reuse the rockers, make sure they go back to the original places.

 

[airblazer]

If in doubt about the rockers, replace them and chek the cam for any scoring(especially the head journals). If you do reuse the rockers, make sure they go back to the original places.

I don’t know what qualifies the rockers as worn out. I suspect the grooves worn into the contact surfaces aren’t desirable. They’re not expensive to replace, although I’m curious why the current rockers have different numbers embossed on them - 33 & 26? Are they different from each other?
I also did a little work to de-gunk the cylinder jug. The inside looks very good to me, but I’d appreciate everyone’s opinion. Thanks

 

[Gary]

Ryan drag a finger nail over those dark spots in the cylinder wall,if it catches as if there are pitts there you could use a bore. If thats the case then you need to see how much that costs +shipping+ piston+ rings. Then check out the price of a new cylinder kit or a big bore kit - you might be surprised,some are very reasonable. I think those numbers on the rockers are most likely an identifier to the manufacturer. They probably cast them in bulk for example say 50 - if something goes wrong with the cast- say number 27 is bad,they can easily identify where to look in the process.

 

[69ST]

Not liking the look of that cylinder. The scoring at the bottom might not be as bad as it appears to be...but..."rust never sleeps" and that pitting, in the ring-swept part of the cylinder is probably worse (i.e. deeper) than it appears to be.

CJ is right about getting the rockers back in their original positions. As long as you don't have scoring & obvious wear on the contact surfaces, they should be okay to reuse. That said, the rockers, cam lobes, valve stem tips and lash adjusters all develop wear patterns over time. Once you start replacing parts, those patterns...which developed slowly, and matched...are disturbed. It won't hurt anything but can result in valvetrain noise(s) that vary by engine temp & rpm. That's the bad news; the good news is that, eventually, those parts will develop matching wear patterns as they break-in and things will quiet down.

Gary is right about the cost of a bore-up kit. Compared to overboring & restoring an old cylinder, it's usually a wash.

 

[airblazer]

There’s a big line around a third of cylinder wall that I can feel with my fingernail. The other rust spots/pits are less damning, but some don’t pass the fingernail test. So I assume this cylinder is a candidate for bore-up or pencil holder...
The rockers are also done as they have obvious wear patterns on them. The cam seems usable to me, no wear/corrosion on it like the rockers and cylinder. I don’t know what to look for as far as valve wear is concerned...any tips?
I’m in unexpected terrain now. I wasn’t expecting to have to replace the cylinder, which was probably naive. I intend to bring the bike back to operational status, not do a concours restoration. I haven’t shopped for replacement cylinders or bore-up kits. I’m not building a rocket, so stock or 88cc or some other size that works good with the stock carb are fine with me. Any suggestions on the right kit/parts would also be helpful. Thanks

 

[OLD CT]

The cam chain left it's mark on the cylinder. Don't forget to change the cam chain/ cam sprocket and the related rubber parts. Tunnel roller, tensioner roller and the little rubber tip.

 

[airblazer]

The cam chain left it's mark on the cylinder. Don't forget to change the cam chain/ cam sprocket and the related rubber parts. Tunnel roller, tensioner roller and the little rubber tip.

Thanks OLD CT. I bought all those parts when I saw the grooves the chain had made on the top and bottom of the tunnel (or whatever it’s called) where it runs.
I think I would like to use an 88cc bore up kit, but I want to retain stock appearance and original carb. There’s a lot of different options (and prices) online, so I’m busy trying to understand the differences...

 

[69ST]

The trailbikes kit is the most widely used; it's been around from the beginning, hands-down the most popular item. Paint the jug black and it'll look nearly stock. Obviously, the aluminum jug (iron sleeve) looks different, the fins are thinner & the texture is smoother than OE cast iron.

You can retain the stock induction assembly, complete. Just be sure to remove the restrictor cone, if present, from the inlet side airbox boot. Add the "fast road" cam, upsize the C/S sprocket 1 tooth and you should see high-40s once the motor is broken-in and the carb tweaked to perfection.

Dunno why I couldn't see the rocker pic until now. Those grooves were machined...and they appear to be outside the contact area. Cam lobes look decent, not liking the look of the rocker wear; not sure if I'm seeing camera artifacts or actual wear. New rockers are cheap. Valves look better than most, intake looks to be in the early stage(s) of becoming "tuliped"...the contact band is like 3x wider than it should be. I'd replace both valves and verify seat condition + contact bands - before lapping. If either is off (too high or too low) a light cut should be all that's needed to get them centered.

 

[Gary]

Ryan With the exception of gearing it down I did exactly what Bob has suggested-very happy with it. Did not bother at the time to paint the cylinder although now I probably would. I even pulled the diffuser out of the muffler. Don't know if that did anything but it sounds powerful

 

[airblazer]

The trailbikes kit is the most widely used; it's been around from the beginning, hands-down the most popular item.

Which vendor is trailbikes? Is it tbparts? Trail buddy? Tbolt? Maybe this is the kit you spoke of?

 

[69ST]

Which vendor is trailbikes? Is it tbparts? Trail buddy? Tbolt? Maybe this is the kit you spoke of?
View attachment 64577

Yep, that's it a.k.a. tbparts.com. Tbolt is one of their distributors, as is "the `doc", among others.

 

[airblazer]

I’ve made some real progress on engine tear down. I’ve completed all steps to split the cases, and have them split about 1-2mm apart all the way around by using a razor blade as was recommended here. Thanks Kirrbby again for your tear down videos on YouTube...there might be a lot of oily fingerprints on my iPad from pausing your video after each step. I had incredible luck, no stripped screws or other common problems during disassembly. I’m in the same boat as kennysyeti with the flywheel and stator - to me it looks like surface rust that should clean up ok. When I took the oil pump off I failed to notice that one screw is longer than the other two - anyone know what position it goes in?
You can see the 13 tooth sprocket and it’s very spent teeth in the background of the stator photos. The big sprocket on the rear wheel was the size of a dinner plate with 45-ish teeth, also spent. Would this combo be meant for hill climbing? Just trying to learn about the PO’s thought process. Thanks!

 

[kirrbby]

Thanks for kudos on my videos. I like to hear that folks watch them now and again. I need to make some more of those...it's pretty fun stuff.

Your flywheel looks VERY good to me. That little bit of rust on the magnets wont hurt anything. What you don't want is rust on that points cam...look at the stub that protrudes from the inside of the flywheel. It has a hole in the center where the crankshaft goes thru. Just outside of that is where the points "rubbing block" rides against the flywheel. The O.D. is NOT round...it actually has a high spot/lobe...it's a cam that pushes on the points rubbing block to open the points. THAT is where you worry about rust the most. Rough and rusty will always be wearing down the rubbing block and changing your points gap, basically wearing out your points. Your points cam looks pretty clean.

The screw at the very topmost part of your last picture is the longer one.

 

[Gary]

That might have been what he was doing,I have something like a 48 on mine just because hills is all I got. Looks like your getting the job done!

 

[OLD CT]

A 4 speed 45 tooth sprocket on a 3 speed auto can also be used to ''slow a kid down'' Whaddya think?

 

[69ST]

That's a really nice-looking and relatively clean alternator assembly. A little massaging with a fine Scotchbrite pad should take care of that light, surface, rust. If you can find crocus cloth, that'd be the ultimate for polishing the point cam. Fine Scotchbrite & a little oil will work fine. Once done, the cam will be greased and that'll keep if from rusting.