Difference between revisions of "Rebuilding a Minarelli V1"

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[[Category: Minarelli]]
[[Category: Minarelli]]
[[Category: Engine Rebuild and Top End Repair Tutorials|Minarelli]]

Revision as of 23:49, 30 March 2014


Tools (prior to removal of engine):

    1. 8mm box wrench
    2. 10mm box wrench
    3. 13mm box wrench
    4. 13mm socket and driver
    5. 17mm box wrench
    6. Flat head screw driver

Start with the removal of the pedal arms. Don't bother with the pedals unless they need to be replaced. Use the 10mm box wrench (or socket and driver) to remove the pedals. Sometimes PB Blaster helps a rusty, stubborn arm.

On the clutch side, use a 10mm box wrench to hold the bottom of the clutch cable knarp/anchor bolt thing, and use an 8mm box wrench to loosen the top bolt. Pull the cable out of the bolt.

On the sprocket side, leave the chain attached. Use a flathead to jam in between the chain and the sprocket teeth (TEEF!). This keeps the sprocket from moving while you use a 17mm box wrench to break the sprocket nut loose. Lefty-loosey on this one. PB Blaster is helpful for a tenacious nut.

Using a 13mm box wrench AND a 13mm socket and driver, you can loosen the three engine bolts. 13mm is standard, but bolt size can vary between models. Remove the front and bottom bolts first, and the central one last.

If you haven't done so, now would be a good time to drain the oil from the clutch case. The drain bolt is at the bottom, to the left of the shorty clutch bolt and is usually a Phillips head screw.


Tools (everything you might need): V1toolsall.jpg

    1. Spark plug wrench/socket
    2. Philips head scrooldriver
    3. Flat head screw driver
    4. 19mm box wrench (or adjustable wrench)
    5. 17mm box wrench
    6. 10mm socket and driver
    7. 13mm socket and driver
    8. 15mm socket and driver
    9. 5mm allen wrench
    10. Circlip pliers
    11. Piston stop (for non-hi comp heads, or use a rope for hi-comp, angled plug heads)
    12. Rubber mallet
    13. 19mm x 1mm flywheel puller (for CEV flywheels, 21mm x 1mm for Bosch)
    14. Clutch puller (an e50 one will work)
    15. Case splitter...If you don't have one, a BFH (Big Fuckin' Hammer) and a punch will be your best frandz.
    16. MAPP or Propane torch (optional)
    17. Torque wrench (optional for you'z fancy mechanics)
    18. two-three zip ties
  • Pro tip: The manual says to remove the cylinder first. Don't do this. The top end is the last thing to remove before splitting the cases. Why? Chances are you don't have that OEM Minarelli flywheel or clutch holder tool. Instead, you can use a piston stop to keep the flywheel and clutch assembly from moving when you break the clutch nut/clutch and flywheel loose.

Remove sparkplug. Insert piston stop in spark plug hole. Rotate flywheel to 'stop' the piston.

  • Pro-tip: If you are using a rope (for high-comp heads or thrifty mechanics), turn your flywheel just past TDC BEFORE you put the rope in the cylinder, then pack as much rope as you can into the hole. This ensures that the rope does not get snagged between your piston and cylinder ports when you go to break the flywheel or clutch nut loose (which could lead to a broken ring).

Note that the flywheel timing marks in the pic are at roughly 12 and 1 o'clock. The screwdriver in the pic represents an imaginary point on the flywheel that aligns with the timing mark on the case. This is the position you want your flywheel to be if you are using the rope trick.


I usually start by pulling the flywheel. Use a 13mm (sometimes 14mm) socket and driver to remove the flywheel nut. Lefty-loosey on this one. Screw in the flywheel puller. Use the 19mm or adjustable wrench to tighten the puller bolt. It takes a lil' muscle, and it'll makes a loud POP when it's free. Make sure the flywheel key doesn't get lost.

Take yer flat head screwdriver, align it on the edge of the stator plate, and tap a mark in both the stator plate and the case (one edge of the screwdriver should touch the stator plate, and the other edge should be on the case). This acts as a quick reference for timing marks so you don't have to dick around with timing it once it goes back together.


Now use a philips head and remove the two or three screws holding the plate.

  • Pro tip: Put yer flywheel nut, stator bolts, and woodruff key in yer flywheel. Violà! It's a magnetic thingy-holder!

Alright, flip the engine over to the clutch side.

  • Pro tip: Drain it first, ya egg-nor-rame-us.

Using a 5mm allen wrench, remove the 7 clutch cover bolts. Don't forget the lil' guy by the drain bolt. Tap with rubber mallet to remove clutch cover. Oil WILL spill out.

  • Pro tip: It's best to use a cookie sheet or large pan under the engine so yer not stuck working in a puddle of nasty 40-year-old ND-20 oil.

Using a flat head, pry the starter plate circlip off. Watch yer face! These things like to sproing! Place it and the starter plate, cap, and spring in the clutch cover for safe keeping. Inspect the starter plate bearing at this time. If it is smashed or worn, check out this sweet lil' starter plate link to learn how to fix it. Pryclutch.jpg

Using a 15mm socket and driver, remove the clutch nut. THIS MAY BE A RIGHTY-LOOSEY THREAD!! Turn it clockwise to loosen it! Occassionally, they are regular thread/lefty-loosey. Aren't ya glad you used that piston stop?!?

Ok, here's the tricky part...When you put the clutch puller in, make sure the two bolts that thread into the clutch are pretty tight. DO NOT OVERTIGHTEN, AND DO NOT UNDER-TIGHTEN. Hand tighten them, then use the 5mm allen wrench to give them a turn or two until they resist. Don't force them.

  • Pro tip: Use a MAPP gas or propane torch to heat around the clutch and crank. A good 30 seconds or 1 min should suffice. IT'S GONNA BE HOT! NO TOUCHY!


Tighten that puller with a 19mm box wrench or an adjustable wrench. There is a fine line between tight and fucked. You should not break a sweat tightening the puller down. If you do, you might strip the threads in the clutch and then it's Bummertown. Use that rubber mallet or BFH and give the puller a few hearty taps. You are not Thor, so don't smash on the damn thing. Check to make sure those two bolts that thread into the clutch are still tight. A loud and startling POP usually indicates you have successfully pulled the clutch from the crank. A loud and startling POP with a limp puller usually indicates ya done did stripped the clutch thread(s). That's a different chapter. Better find someone who can weld.

  • Pro tip: Use your intuition. If you are realllly cranking down on the puller, and that clutch is creakin' but not poppin', back off, use a lil' more heat or even some PB Blaster (not both at the same time), and a few exuberant whacks with your rubber mallet or BFH. Make sure your puller bolts are tight. Be patient and calm, don't manhandle the situation. Pulling a stripped v1 clutch off is the worst thing ever.

Ok, clutch is (hopefully) off. Clutchoff.jpg

Keep track of yer shims and circlips by zip tying everything together in the order that it was removed. Right to left: Remove clutch, circlip, shim, clutch bell, bushing, shim, in that order. Clutchorder.jpg

On the reduction gear side, from right to left: Remove circlip and shim from the lil' drive gear, the lil' drive gear (clutch drive gear according to the service manual), another circlip, another shim, and finally that big reduction gear. There is no shim behind that big reduction gear guy. Zip tie it all in order as it was removed. Primaryshims.jpg

Once all the tranny bits are removed, use a 10mm socket and driver to remove the 4 nuts on the top end. Slide the cylinder off to expose piston. Remove piston circlips by grapping the 'tail' of the circlip and twisting while pulling. Don't forget to remove that old base gasket.

  • Pro tip: To remove the piston wrist pin, wedge a shop towel around the piston to keep it from slappin' around while yer tapping out the pin. Use one of those multi-tool screwdriver things without the bit, or a 10mm socket to GENTLY tap it out. PB Blaster also helps.

Pinextraction.jpg Ok, that's done, now flip the engine to expose the magneto side again. Remove the 11 allen bolts (the 6 crankcase bolts I affectionately nicknamed 'The Six Sisters' and 5 case bolts affectionately nicknamed 'The Five Brothers'). All 11 bolts are the same size, (M6 x 30mm) so don't sweat it if you mix them up. If you have a case splitter, you gotta flip it over to the clutch side and the splitter inserts in the right and top of the case with 3 bolts. They should be aligned with the case so that the big central bolt is over the crank. If you ain't got dat splitter, use a punch and a BFH on the CLUTCH SIDE crank, then on the pedal shaft, then on the crank until the cases are split.

  • Pro tip: DO NOT USE A BFH DIRECTLY ON THE SHAFTS OR CRANK. You'll mushroom that shit out so fast. Just be patient and make sure you get a proper sized punch to use. DO NOT USE A SCREW DRIVER TO PRY THE CASES APART.

Punchsplitter.jpg SHIMS...here's where they all fall out. V1Splitcases.jpg

There's a crank shim that ALWAYS lives on the magneto side of the crank. The v1 service manual does not show this shim in the exploded diagram, but it's there. Some engines even have two of those lil' buggers! Whoa! Crankshim.jpg

There are two shims, one on each side of the idler gears. These are the ones that usually fall out first and are dreadfully discovered by the v1 novice. Have no fear! The fatter one goes on the side of the smaller gear, the thinner one on the side of the bigger gear (tip to help you remember: the shim's thickness is opposite of the gear size). Idlershims.jpg

Pedal shaft has two equal sized shims, one on either side. Easy. Pedalshaft.jpg

On the output shaft (you know, where the sprocket lives), there is a wide, flat shim that goes BETWEEN the oil seal and the bearing (on the inside of the case), and a smaller one that goes between the bearing and the teeth (TEEF!) on the output shaft. They don't come out from splitting the cases. The smaller one might fall out if the output shaft falls out in the splitting process. The wider, flatter one comes out when the output shaft bearing comes out. Make sure the wider guy is placed in the case PRIOR to pressing/drifting a new bearing or ya gotta waste that fresh bearing to put that shim back in if you forget. Outputshaft.jpg

REPLACE YOUR BEARINGS AND SEALS Bearing sizes are 6203 (C3, non-shielded) for the crankcase, and 6202 (C3, non-shielded) for the output shaft and transmission cases. Oil seals: You'll need two 17 x 35 x 8 (or 17 x 35 x 7 which is stock) and three 15 x 24 x 5. Using a seal puller to remove a seal: Pullingseal.jpg

Use your BFH and an approximate size socket to drift the old bearings out. Here's a pic of everything removed (note, this is a V1L, but other than the presence of a reed block track in the crankcase, the internals are the same as the V1). Barecases.jpg

CONGRATS! You just successfully tore down your Minarelli v1! Now let's re-assemble!

  • Pro-tip: At this time, throw your bearings in the freezer and go have a celebratory beer or root beer (for the kids). Keep those bearings in the freezer for a minimum of 30 minutes.


The best DIY method for installing bearings is use your MAPP or Propane torch to heat the cases, then drift the cold bearings in place. BE CAREFUL! THE CASES ARE GOING TO BE RIDICULOUSLY HOT! Keep flame away from shop rags or any flammable liquids you may have previously used around your rebuild area.

The best place to direct the torch flame isnt on the bearing race itself, it's on the case around the bearing race. If the cases are heated properly, the 6203 bearings will literally fall off your finger and into the bearing race without having to touch your hammer. The 6202 bearings are a little more stubborn, and often need some persuation with a BFH and a socket that covers the entire outter race of the bearing.

  • Pro tip: DON'T HULK THE GD BEARINGS INTO PLACE. If they are being stubborn, use more heat, not more smash.

OIL SEALS I usually install them once the shafts are in place, but you can put them in before you join the cases with the shafts in place. A lil' PB Blaster around the inner and outter lip of the seal helps it slide into the race easier. Just make sure ya don't displace the spring when you install your shafts through the seals. You wanna use a socket large enough to cover the diameter of the seal. Don't smash it too far down in the race. This can bind the bearings and make for a sad engine. Have patience and tap it lightly to make sure it is seated even and flush...About 1mm from the top of the race lip is perf.

Lay the magneto side case half on the bench, and assemble the crank and output shaft on that side. Lay the clutch side case with the clutch side down on the bench. Insert the pedal shaft, idler pin/gears, and the center gasket on the clutch side and join the case with the magneto side on top and the clutch side on the bottom. The trickiest part is getting the pedal gears to mesh evenly without the pedal return gear losing its place in the case.

  • Pro tip: If your cases have about 1/4" gap in them and don't seem to be going back together, your pedal gear teeth are probably not meshing, the pedal return gear is not sitting flush, and/or the pedal return gear's pin is not seated correctly in the case. Just tap the pedal shaft slightly to re-open the cases. You can usually finagle the gears into place with your fingers or a screw driver. Watch for falling shims (the idler gears are usually the culprits).

Replace the 6 crankcase bolts in a criss-cross pattern first, then tighten the remaining 5 case bolts in the same pattern. Tighten all 11 bolts with a torque wrench to 8.7 ft. lbs.

  • Pro tip: 8.7 ft. lbs. is roughly 'hand tight.' This means the bolt is tightened down one or two turns past the point of resistance. Tight's tight and too tight's broke.

Replace top end, piston, circlips, etc. Rule of thumb! Most pistons are marked with a arrow on the piston crown. This arrow USUALLY points to the exhaust. There are kits in which the arrow points up toward the intake. If you are unsure, take a look at your piston ring pins. They are manufactured to glide over the cylinder wall. If the pins glide over a transfer port(s), chances are, the piston is in upside-down. Make sure to renew yer gaskets and yer circlips! Check that the piston clears the ports on both TDC (Top Dead Center) and BDC (Bottom Dead Center). Adjust your base gasket if needed. Tighten cylinder studs to 8.7 ft. lbs.

Assemble the stator plate, making sure to align the mark you made on the stator with the same mark you made on the case. This is your APPROXIMATE reference point for timing your engine. You may still need to adjust your point gap and/or stator position to get the engine timed correctly. Tighten the two or three stator bolts.

You can replace the flywheel key and flywheel at this time. Tighten that sucka to 34.7 ft. lbs.

Flip dat bitch over and assemble the transmission. Start on your left with that big reduction gear. Remember, that big guy does NOT have a shim behind it. Apply shim, cirlip, lil' drive gear, shim, and circlip. These gears should not have much wiggle to them.

Regarding the clutch shim...This is the first thing that goes on the crank during reassembly of the clutch before your brass bushing goes on. Do not lose or mix up this shim as it is vital to keeping a healthy transmission in a v1.

  • Pro tip: If the brass bushing easily slides over the crank, it is worn and must be renewed. If your clutch bell has a significant amount of wiggle once it has been assembled on the crank, your bushing is most likely shot, or your clutch shimming is off.

This bushing may be difficult to push onto the crank. The best way to get it on is to wrap a rag around it and use loosely-fitted vise grips or similiar to twist it onto the crank. Be careful not to allow the teeth of the vise grip to bite deeply into the bushing. You could use a socket to drive it down on the shaft, but you risk mushrooming it out and having a hard time fitting your clutch bell over it. Once the bushing is situated, place the clutch bell, shim, and circlip over the shaft. Does the clutch bell wiggle, or have a bit of play on the crank? If so, your bushing may be worn or your shimming may be off. You want as little play in the bell as you can realistically get.

  • Pro tip: Have you investigated your clutch yet? If you have aftermarket springs or new material on your clutch shoes, did you remember to tack weld the 4 pins that hold the clutch shoes in place? I've seen these pins work their way loose even on stock clutches!

Tackedclutch.jpg Have you checked to make sure the taper is not worn on either the clutch or the crank? A worn taper will manifest itself once the clutch is put on the shaft and tightened into place. It will not spin separately from the clutch bell, and will keep the bell engaged. Sometimes, a new crank or a machined taper will be the only thing to correct this problem.

If everything checks out, put dat clutch back in and tighten 'er down to 21.7ft. lbs! Remember, this nut is usually reverse thread (lefty-tighty)!

  • Pro tip: A lil' dab of locktight on the end of the crank threads will keep the clutch nut from spinning off the crank.

Alright! Put the starter plate spring, cap, plate, and locking ring back into place. Use one hand to hold the lock ring down, and a flathead screw driver to pop the rest of it into its groove. You shouldn't have anymore than 1mm of play in this starter plate. Remember to replace your clutch gasket!

  • Pro tip: Use Ed's gasket mod to make oil changes and drainage easier!

Edgasketmod.jpg Re-assemble the clutch bolts. In case you need to refresh these bolts, the sizes are M6 x 35mm. The lil' shorty guy is an M6 x 15mm. Tighten in a criss-cross pattern. Torque to 8.7 ft. lbs.

Assembly is done! Now put dat hunka-junk back on yer bike! Start with the central engine bolt, then the front and bottom bolts. Make sure to use washers and tighten these bolts down like a boss!

REPLACE YER CLUTCH CABLE! Trim off any frayed ends so it's easier to slip the cable through the knarp/anchor bolt. Use a pair of channel locks to push the starter lever forward until it no longer moves. Hold that position with the channel locks, then pull the rest of the cable taught with your free hand. Keep the starter lever in place with the channel locks. Use an 8mm box wrench to SLIGHTLY tighten down the clutch cable anchor bolt. Once it is slightly tightened, put down the channel locks.

Grab that 10mm box wrench, and with the 10mm box wrench on the bottom of the anchor bolt and the 8mm box wrench on the top of that bolt, tighten the cable...NOT TOO HARD! Don't crush that cable, bro! Clutchcabletools.jpg

  • Pro tip: Make sure the case-mounted clutch cable adjuster is adjusted all the way in before you attach the cable. You can use a small 8 or 10mm wrench to make cable tension adjustments once the cable is attached to the anchor bolt/knarp thingy.

Check the clutch cable engagement. The lever should be buttery and soft, but you should not be able to touch the lever to the handlebars. The lever should not be so tight as to feel stiff or crunchy.

  • Pro tip: Kitted v1's may have a lil' clutch slip to them. This is normal, and unless you mod yer starter plate pads, you might as well get used to it.

WIRING! Quick hardwire...if the three wires that come out of your magneto are blue, red, and black; Take the blue wire and ground it to your engine block. You will not have a brake light by doing this. Why? Because those Eye-Tail-Yunz thought it would be smart to include a saftey feature that killed the bike when the brake light burned out. By grounding that wire, it eliminates that annoying gremlin. It sucks when you go to ride yer moped and the damn thing won't start because Safety Cat™ showed up when you didn't notice and put a stop to your mopedalcycling fun.

The black wire operates your headlight/tail light/horn/speedo light. It does not operate the brake light. You will need to make sure you have two separate grounds for your headlight and tail light. Usually, the headlight is grounded through the 'ears' that hold the headlight bucket, and the tail light has a short ground that goes to the frame. It doesn't work to tie these grounds together, so don't even try. The lil' red wire goes to your high tension coil AND to your kill switch.

If you have a black, green, yellow schematic comin' out of your magneto; Take the green wire and ground it to your engine block. Again, this means you will not have a brake light. The yellow wire operates your headlight/tail light/horn/speedo, and should be wired and grounded like it's described above. The black wire goes to your high tension coil and also to your kill switch.

  • Pro tip: LEDs make great tail and stop lights because they are bright and do no draw much power. You can even use a halogen bulb for your headlight since the LEDs will leave so much extra current. Be bright, be seen, and stop blowin' headlight bulbs, ya idjit.

If you gotta have a stop light, you can use the Minarelli wiring guide to get creative. I've kept the blue (or green wire) grounded, and use the headlight circuit to power my stop light on some of my bikes. It works well if you are running LEDs, but not so much for incandescent bulbs. You'll need Tomos brake switches (open circuit switch) to make it work this way.

Alright! Put some oil in yer gearbox and some gas in yer tank! You'z ready to blast off!

  • Pro tip: Minarellis use almost a quart of oil in their gearbox. Use SAE NON-DETERGENT 30 oil. Why? 'Cuz the other stuff gets foamy and breaks down under high heat, makin' yer clutch a sad lump of metal. Most auto stores carry it, but you'll only find it in the lawnmower/outboard section.

If you didn't before, treat yer ol' Hardly Davidson to a new spark plug. NGK B6HS are where it's at. Have yer local auto parts store get ya a big ol' box of these things. The product order number is 7534.

Good luck and happy riding!