Waconia Charity Build 2016

[wankel303]

So here are some photos of the teardown from last night.  I have to admit, it was a bit nostalgic for me dismantling this engine.   When I was 15, the first snowmobile I ever bought had this same engine ( but it wasn't correct for the chassis).  I ran it anyway and put countless hours back in the woods exploring unmarked trails, getting stuck, cruising the trails at a maximum of 40mph ( on the really long, straight and smooth stretches).   I ran that old JLO until it just didn't have the compression to get me around anymore.  Well, anyone who wrenches on JLOs is aware of the "quirks of disassembly" ; how much you have to take apart to get at this and that, hard to remove things etc.  These all came flooding back and I  had to get out the special JLO tools I made for these occasions all those years ago.  But I digress, here is the disassembly:

As with just about any engine, the recoil was the first item to come off.  I was pleasantly surprised to find the old foam dust seal was still stuck on the recoil hub.  When engines are wrenched on frequently, these are usually the first things to go which makes me think this thing hasn't had too many visits the small engine shop.  Unfortunately, it wasn't salvageable and disintegrated as soon as I touched it, literally.





The starter cup was removed next and again, I was pleasantly surprised to find all of the proper shims still in place, untouched.  Often, these are forgotten upon reassembly.



The next step is to remove the fan shroud and here is the first of the "quirks" I mentioned.  There are a series of bolts that secure the fan housing to crank case half and in order to remove one of them, the carburetor has to come off.  Anyone who has wrenched on any JLO equipped a Tillotson HD, is aware of how difficult it is to remove the mag side carburetor bolt.  These are a thin 17mm nut.  So many of these are chewed up along the edges from the tips of screw drivers "chiseling" on them in order to tighten them up.  Well, here is the solution to that issue.  The very first tool I made for the JLO.  It's nothing fancy, but it works wonderfully.





With the carburetor off, you can now remove the fan housing cover as well as the cylinder head shroud.  The 297 is the only JLO single that used a one-peice cylinder head shroud and to remove it, you need to remove the exhaust manifold, carburetor and intake.  You can see the bolt I was referring to earlier, the one that you needed to remove the carburetor in order to get access to, on the right side of the photo below.  The engine has the insulating intake adapter which is a good thing.  JLO singles can get pretty warm when run hard and I have had a few in the past vapor lock on me due to the intake adapter being aluminum rather than an insulating material like this one. 





All clean inside and only very minimal signs of our favorite furry friends ever being in there.



One bolt was missing on the shroud which is the first sign I have had that someone might have been into this motor before.



The flywheel nut is 28mm and after removing it, I set up to remove the flywheel.  There is a right way and a wrong way to pull a JLO flywheel.  The wrong was would be to throw a harmonic balancer puller on the three starter cup bolts and pull.  The result is a broken flywheel everytime or damaged ignition components from threading in the bolts too far.  This is the right way:

Remove the flywheel nut:



Grease up the puller, both threads and tip:



Install the puller and remove the flywheel:





The flywheel is nice and clean inside:



Like the flywheel, the stator assembly is nice and clean and appears to be all original.  I will investigate the wire splice and verify originality when I get into the stator to freshen it up later on.



Once the stator is out, we're in all the way on the magneto side.  The magneto side crank seal looked good and felt nice and soft but since we're in this far already, it will be replaced.



The next step is to remove top end and it's time to remove the head and see what lies within.  Only 5 nuts secure the head in place and when properly seated, they require a gentle rap on the side to pop 'em loose.  The properly installed head, as this one was, has a spacer and locking washer between the head and nut.



Well now we know that this old engine has been to the shop at least once.  Originally this head gasket would have been copper but this one is a composite style.  I can see some lettering on the underside of the head as well with a clear letter "W" implying a "Winderosa" brand head gasket.  It appears as though some one has scraped some of the buildup from the piston crown as well.



Now I can remove the cylinder and have a peek but this is another one of those "quirks".  The cylinder is held on by 4, 17mm nuts on each corner.  The stud they use is too tall to fit a conventional open end wrench between the end and the cooling fins so again, use the same homemade wrench as was used on the carburetor to loosen them up.  Access to the magneto side bolts is gained through the opening in the magneto side fan housing.  Hopefully, now it becomes apparent why I disassembled it in this particular sequence.  I was a little negligent in my photo taking during this particular step but hopefully, can get the idea from the picture below:



The cylinder showed some signs of moisture and rust had set in.  I am going to attempt to hone this out but we'll see how it turns out.  I am cautiously optimistic and we'll deal with it if it ends up needing a fresh bore.



I removed the piston next and in most cases, a piston puller would be used here.  After removing the circlips, you'd install the puller and draw it out of the PTO side of the piston.  Sometimes, if you're feeling strong, you can push it out with your fingers and when you can no longer reach it, installing a socket that is slightly smaller than the pin can allow you push it the rest of the way out.  That's what I did here.  I could move it with my fingers so I figure I could remove it entirely without the puller.  JLOs use spacers on each side of the wrist pin needle bearing so you need to be aware that they'll drop once the pin is out. You just have to have your other hand there ready to catch them when they fall.  Also note that there is a recess on one side of the spacer.  The recess is meant to fit against the needle cage bearing.  If you have them flipped around, they won't fit back in the piston. 





This piston is pretty gummed up.  Seems the mixture was pretty rich but the piston looked great except for a little discoloration from ring blow-by.  Very little if any scoring.  I am hoping it's re-useable but I won't know until I clean it up.   If not, we may need a piston for the old bird.



There isn't much left to it from here.  From the magneto side now, the next step is to remove the socket head capscrews that hold the two halves together.  These require a 6mm allen wrench.  After removing these, I re-installed the flywheel nut on the magneto side of the crank until it was flush with the end.  A couple of raps on the end with the rubber mallet and you'll see a gap open up between the cases.  Once the gap forms, I used a plastic wedge to gently wiggle the PTO side free from the crank.  Once the PTO side was free, a few more raps on the crank end, and the crank pops free from the MAG side case.  If these were stubborn, applying heat with a heat gun to the case halves with a heat gun directly onto the exterior of the crank bearing seats, expands the aluminum cases enough to let the bearing slide loose.  When I go to re-assemble this engine, I will probably heat both case sides like this and also leave the crank in the freezer over night to contract the bearings a little more yet.  This just ensures an easier assembly since once the crank is trued, I don't want to be rapping on it at all during assembly.





Since I did rap the end of the crank, something I try to do very, very sparingly, I will check the runout on it before I re-assemble.  JLO engines are built quite beefy as you can see.  Big bearings, big counter weights, big pins, big bolts,,...just heavy duty stuff.  It's no wonder they're considered workhorses rather than speed demons.  So considering the strength of the rap, and the mallet material, I doubt I have induced any issues to the crank alignment but it's always better to be safe than sorry.



So we're completely dismantled at this point.  My next steps are to clean everything up.  Stay tuned for further updates.

[Vintagesleds.com]

[dirtman]

lookin good so far!  glad to hear the crank bearings roll nice.   let me know how the cylinder looks...       we're on the 6 month countdown till Waconia now!     

dirtman

[wankel303]

How is the rest of the chassis coming along?  Is it back from Polaris now?

[dirtman]

talked with Aaron (ajjohns)  for a few minutes the other day, he's almost done with the fab repairs on the chassis, said all the parts are blasted and ready for paint. the skis are done and look GREAT!   

dirtman

[wankel303]

I finished up some cleaning last night.

The cases cleaned up very well, inside and out.





The piston cleaned up nice as well.  I am somewhat of an "old-school" snowmobile guy.  I was taught that a piston should "sing" if it was any good.  By "sing" I mean when you drag your fingernail down the side, the aluminum will ring as your fingernail zips over all of the micro grooves machined into it.  This piston still sings nice even across the rusty-stained area below the exhaust port.  I see no reason it can't be re-used,...with a new set of rings installed of course.



The cylinder work is done as well.  After a good cleaning, I removed the head studs to make honing a bit easier.



The bore cleaned up very nicely. Considering what we started with ( see picture in previous post) and I am very happy with the results.



There is one tiny scratch, about 3/4" long near one of the transfer ports that didn't come out.  You can see it in the picture below.  It's pretty thin and shallow and I honestly doubt it'll affect the performance of the engine even in the slightest bit considering it's location.  If it was a chrome bore, I would certainly be concerned but this old cast iron lump, not so much.  It looks to me as though something came through the transfer port.  There isn't any corresponding damage on the piston or the rings.  At this point, I am planning on leaving it in there but if you guys think it should go, just let me know and we'll go the overbore route.  I have run JLOs with cylinders in far, far worse shape than this one.

[Rex Rules]

LOOKS GOOD WANKEL303,  I SAY USE IT AS IS. 

[wankel303]

10:4 over and out.  I'll use it as is.  I dropped the crankshaft into the deep freezer last night so we'll be putting the crankcase halves together tonight.  Stay tuned for more photos.

[dirtman]

sounds GREAT Mike,     i think there was something i was supposed to check and see if i had for you.....   know what it was?   

dirtman

[wankel303]

I think it was a carburetor kit for the Tillotson Hd....it has the small, side mounted fuel pump.

[wankel303]

The pace it picking up now on the re-assembly.  I spend a few more minutes last night cleaning up the cases, ensuring that the bearing seats were free of dirt and/or debris.  I ran a q-tip with some solvent on the tip around the seats just to be sure there wasn't anything in there that would hold the bearings proud from their seats. 



After that, I fired up the heat gun and applied some heat to the PTO side crank case half.  I usually just  heat these enough so the entire case half is just a bit too hot to touch with your bare hand and I apply the heat as evenly as possible both inside and outside of the bearing seat.



Once it's up to temp and I have a leather glove on my left hand, I dig the crankshaft out from the freezer and slip it into the PTO side case half.  It slips right in without the slightest bit of struggle.  From  here, I let t he PTO side assembly acclimate back to room temperature.  I went and made dinner and by the time my pizza and beer were gone, it was back to room temp.  The whole unit went back into the freezer then for a few hours.



After an hour or so, I began prepping the MAG side crank case half.   There is a gasket on these JLOs between the halves and it can be a bugger to install straight when you're working with hot parts.  I applied a little Aviation Form-A-Gasket to the MAG side case to serve a gasket tack and hold it in place. After it was in place, I applied a skim coat to the other side of the gasket as well.  This will help hold it in place when I slide the two halves togther.



Just like the other side, fired up the heat gun and began the pre-heat treatment for the MAG side crank case.  Same process....even heat, inside and out.



Once it was hot, the PTO side assembly was retrieved from the freezer and the two halves slid together.  The case gasket has a portion the bridges across the crank.  This gets trimmed off nice and flush with the cases.  Once together, I installed the 6mm socket  head cap screws just snug.  I will torque these once the cases acclimate again.





From here, I can install the piston.  JLOs have spacers on either side of the wrist pin bearing.  These can be a bugger sometimes to line up and you need to be aware that they only go one way.  To make it easier, use a socket or another wrist pin, to help with the alignment.  Once it's all aligned, slide the new wrist pin through.  After cleaning the cosmolene off, a new wrist pin bearing, spacers, and a new wrist pin was used here.  It's nice and snug!  The last step was to install the wrist pin cir-clips.  Always install these at either the 12 o'clock position or the 6 o'clock position....oh...and one more thing, at this point, also make sure that the arrow at the top of the piston is pointing to the exhaust.  These engines don't run well with the piston on backwards. ;-)





I was moving along pretty quickly at this point when I realized that I should have checked the piston ring gap before I installed the piston.  Getting the rings square in the cylinder can sometimes be tricky and it's critical to get the measurement right.  Pushing the rings down the bore with the piston is an easy way to get them squared up.  Unfortunately, I had already installed the piston,..fortunately, I had a spare 297 Wiseco Std. around that was missing it's rings.  I measured ring gap of the old rings first and found 0.042" on the top of the bore and 0.045" at the bottom of the stroke.  Seems pretty large to me but these were used rings too.  The new rings were measured next and I got 0.021" at the top of the stroke and 0.024" at the bottom of the stroke.  This is inline with the rule of thumb for 0.004"-0.007" per inch of bore ( which is 2.953" for the 297....i.e.....0.021"/2.953 = 0.0071").  To be safe, I dug through all of my old JLO manuals and couldn't find a ring gap spec anywhere so if anyone knows for certain what the ring gap spec is for these engines, I would appreciate the information.  I think we'll be safe with where we're at but I would prefer to sleep well at night knowing we did this thing right.

[KKWILL]

Coming along nicely.   


I think that "end gap" is about perfect. 

[wankel303]

After checking then double checking that the circlips were fully seated, I prepped the base and base gasket for installation.  Again, I used the Aviation Form-A-Gasket as a gasket tack and for a little extra seal insurance.  Once the gasket was in, I gave the top surface a light coat as well.





I prepped the cylinder for installation by lightly coated the skirt area with oil.   



Setting that aside, I installed what I use as a ring compressor but it's really just a large worm gear hose clamp.  I prefer to use these because you don't need to mind the clamp with one hand like you would with a traditional spring clamp ring compressor.  It takes a technique to really be able to use them well but once you get it, they're the easiest way to install rings IMHO.  The key is to tighten them just enough to get the rings into the cylinder.  Leaving a space above the lands, when you can, helps a lot as well.  The most important part when using any ring compressor is to ensure that the pins in the piston are not beneath the rings.  If they are, you'll break a ring the moment you try to compress them. 

The hose clamps are especially handy with big heavy cast iron cylinders or big one lunger cylinders where you need two hands to support the cylinder.  In the cases of big heavy cylinders, I would place some plastic spacers ( old pieces of slides) beneath the piston but this JLO wasn't very heavy so I skipped that step.





With that, the cylinder slid nicely and smoothly into place.  So far, this motor is beautifully tight.

[wankel303]

I had to go back to the washtub for a bit and clean up the next parts needed for the assembly.  The cylinder head, and head shroud were next on my list as well as the flywheel.  Of the three parts, the flywheel took the most to get cleaned up.  All three turned out quite nice.







With the parts cleaned up, I could continue with the re-assembly.  After re-torquing the case screws, up 7 ft-lbs in 30% increments, I packed the lip of both crank seals with grease and installed them.  I try to keep the outter diameter of the crank seal as clean and dry as possible.  The seals do hold back a few lbs of compression force when the piston travels down in the cylinder and having a seal pop out due to greasy fingers during the install is one of those things that can easily have been prevented.







A new, NOS head gasket was installed followed by the head. 



As with all heads, a cris-crossing pattern was used to ensure equal torque across the board.  JLOs have a spacer- lock washer- nut sequence for head installation.  Each bolts get this combination.  The nuts are 13mm and are the torque spec for these is 28-32 ft-lbs.  Seems hefty but this is one of the features of these old JLOs that makes them a tank of a motor.   The spacer is actually important here as it distributes the force at each bolt evenly.  I have a few heads from other JLOs with cracks running through the bolt holes and I suspect that it's the force concentration created by the lock-washer used without the spacer that causes the cracks.  I apply the torque in steps about 30% increments so I don't warp the head during the installation, in this case, it's 10 ft-lb increments.  As a comparison, the Kawasaki KT and T4 single cylinder motors use the same size studs, but are only "torqued" to 16 ft-lbs and there are only 4 of them versus the 5 on the JLO.  Same for the 190 series Hirth engines ( except the 194R).  The Hirths only have 4 bolt heads and received 18 ft-lbs.

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Now that the seals are in, it was time to rebuild the stator assembly.  I always do the works; plug wire, points and condenser.  While I'm in there, if there are any wiring quality issues, it's best to hit them now.  In the case of this stator assembly, the lighting leads were kinda short, had a few bare spots, and the primary lead had a crimped connector on it.  The crimped connector was cut off then the new wire soldered and shrink wrapped to ensure a solid and short-proof connection from here on.  The same treatment was given to the lighting leads.  Once these were patched up, the condenser was de-soldered, removed, replaced then re-soldered in place.  The points were removed and a a new set installed.







The plug wire is standard copper core wire and it simply screws onto the threaded stud recessed on the primary ignition coil.  I used the old wire to gauge the proper length and then gave myself 2 additional inches to work with.   Where the wires ran from the contact points and coils through the stator plate, a small section of shrink wrap was pretty rotten.  To prevent these wires from chaffing, I re-installed a new section of wrap.



The completed rebuild of the stator assembly was ready for installation.  I installed a new grommet through the case for the plug wire.  The other grommets were equally rotten and I visited the hardware store for the new, proper sized ones.  These can be installed later but it's best to do it before installing the stator assembly and flywheel so you can ensure the grommet it fully engaged with the case.



Stay tuned,....next up: timing the JLO!

[sled_hed]

As usual awesome work and explanation wankel.!

[Gilson435]

No question Wankel was the right man for the job! Nice work