Rebel Moby's Words of Wisdom
DISCLAIMER: This is by no means meant to be an exhaustive summary of his helpful posts. For the most part, I have focused on his Motobecane-related posts. If someone wants to clean this up, please feel free. (as of 4 Dec 2010, he has made 432 posts in the repair forum (i did not search other forums) under the user name Rebelmob). You would be amazed how many times he has answered the same questions.
- 50V spokes
most imported Mobys had 80mm Prior hubs front and back. 38 spokes each wheel. 3mm x 172mm is the size for Prior 80mm rears 3mm x 166mm is the size for Prior 80mm front Atom front wheel 36 each 178mmx2,7mm
- 50V Belt
I use Three Five brand of V belt – cheap soft rubber on polyester cords that wear quickly but the price is low and being soft rubber they really cling well to the pulleys.
- Plug Wrench
 I have a couple of cheapo Kmart spark plug socket wrenches (sort of made out of metal tube) that I chopped in half to fit between the plug and the frame. Then just grab the socket with a vice grip.
- For your new (to you) Moby
Get the Novi nut off by dremel and get a replacement then get rid of the no spark situation – clean the points, change the condenser, replace the bonding strap between the motor and the external coil – try it then. If it has been sitting more then 1 year without running give the carter a leakdown test to make sure the seals are not finished. While a bike sits the thin oil film between the crank and the crank seals deteriorates and actually will glue the seal to the shaft. The slight tear in the seal can leave enough of a leak that the motor will not catch unless you spin the heck out of it – and that is the only way she will fire up.
- Clutch/Magneto puller
The puller should be 26×1,00 for flywheel and 24×1,00 for clutch
- Removing the Magneto
 Novi nut is a lefty. I found best to hold the flywheel still by the flywheel. Put a #72 hose clamp around the flywheel, cut a piece of wood 18 inch long and place it between the clamp’s nut and the floor, use the 3/8 straight bar and give it some gentle taps on the end of the bar to loosen the nut.
- Cleaning a rusty tank
To clean the tank take out the petcock and replace it with a cork, get some washers and tie them to a string, drop the tied washers in the tank with some kerosene or diesel, shake the heck out of the bike, get a friend to shake the bike with you, have a bike shaking party, pull the washers out and flush the crap out of the tank with more kerosene or diesel.
- Refittting tire
Soap or talc. Use spoons. Push the bead across from where you are running the spoons to the middle of the rim.
- what causes a plug to be oily?
Usually too much oil in the premix or plug too cold or plug misfire or jet too rich or flooding/weeping carb
- 50V sprockets
Most common sizes are 10, 11, 12, 13 front gears and 38, 44, 48 and 54 rears.
- spark fires when kill switch is pressed
Either a bad ground or bad condenser. Change the condenser and add a bonding strap between the motor and the frame – that should fix the trouble.
- removing rear wheel bearing
Heat and patience – also you need to get the drift in there and tap around the outer edge of the bearing not sort of the edge.
- Your new (to you) Moby
Best to open up the fuel bowl on the bottom of the carb and get the number off the jet. Keep in mind there is about 50ml of fuel in the bowl, so have rags ready. Best to check to make sure what jet you have and then take her out for a nice long ride. Do a plug chop to check that you are getting enough fuel. Too little fuel and she will seize, which is more of a heartache then fouling plugs from too much fuel. Too much fuel will slow you down so you would probably need to adjust the jetting so you can get the full potential of the motor. With a SHA14:12 in proper tune you should be getting 30mph easy on flat land. Bigger the # the larger the orifice and the more fuel is delivered. Also just check your dataplate on the steering tube of the frame to make sure you have a 30mph Moby. The 25mph is the top speed according to the original equipment. A little bit of modifications will get you up into the 30mph range. The date on the tag is when the design was registered in France and not necessarily the year of manufacture. If the title says 1971 to agree with that then best keep it that way. If you are curious then check on the old Gurtner, either on the flat above the fuel bowl or on the bowl is the Gurtner carb model and date.
- weak spark
If the bonding strap is arcing to the engine then the terminal point on the engine is not good.
- The AR2-10 rev 737
is indeed a 10mm Gurtner, you may not need a new intake if you measure the inside diameter of the old intake. It should be at least 12mm, some are 10mm, 12mm and 13mm on the stock motors. If it is the 12 or 13mm then you can get a collar to adapt the SHA directly to the intake. jets I used a 53 on one and a 55 on another so it is in that range.
- Old Raleighs
have the AV7-Dbe, the pipe on the Raleigh mopeds is the old trapdoor mufflers. These are easier breathing then the blunderbus if cleaned out.
If you have the original carb it is a Gurtner BA or an AR2-10, either way it is a 10mm, installing a 12mm carb would be a good idea. Installing anything bigger would not work too well.
- crank thread
Clutch side is right hand thread – only the Novi nut and the huge variator nut are lefties.
- Tail lights
take a lot of vibration – did you try 12v 5w for the tail? 12v bulbs have a thicker filament and can take more shaking then a 6v.
- Removing crank bearings
Warm thm up in the oven at 350 for an hour and just tap the carter half against a block of softwood and they usually will just pop out. Sometime you meed to put in a screwdriver and give them a little tap. While the carter is still warm pop out the seal, that needs a screwdriver to convince it to move though.
- Rear shocks
On a Moby they are just a spring with no damping oil. If they are not retracting you can invert them and give them a good spraying with penetrating oil and leave them stand upside down until the oil starts to weep out then right side up them. That will loosen them up if they are not too jammed.
- Refitting condenser
Easiest is just cut the wire on the existing condenser or remove it and the wire completely. Splice the new condenser into the wire which goes from the points to the ignition coil. Done.
is the worst thing ever invented as far as 2 strokes are concerned – you should put some bluing (or marker pen) on the heads sealing surface and give it a pass on the flat surface and look for the low spot, same for the top of the cylinder. Petcock is straight thread so you might need to replace the oring that seals it to the tank.
- DIY Gasket
Go to a hobby store and get some copper sheet and cut a gasket, anneal it and stuff it in. Can do the same with aluminium but it is not as reusable as the copper sheet. I have gaskets which are years n years old made of copper, just reanneal them and stuff then back in if you open the motor.
- Low Compression
I would be suspect of head gasket leaks if you had low compression, the piston picture does not show any blow-by at the rings, even between 1 and 2 ring there is no brown which would be the witness of leaky rings.
Just wondering if you have tried to replace the condenser and the plug cap first? These items are known problem areas for many points ignitions. Also if you are using a resistor sparkplug this will effectively snuff out the spark as the plug cap is a resistor cap. Coils are NOVI 127850 Blue, NOVI 125820 Grey, NOVI 126850 White. The ignition coil is 125820 Grey. You can get a replacement from LeSolex for 15 Euro plus shipping or the entire stator plate for 40 Euro plus shipping Another idea is to get an aftermarket CDI from 1977Mopeds
- Removing the Magneto flywheel
Use a strap wrench on the flywheel and the 3/8 straight bar on the Novi nut, the nut is left thread so turn it backwards to loosen. If you do not have a strap wrench you can use a #72 hose clamp and place a piece of wood between the clamp and the floor to hold the flywheel still… assuming the motor is still on the bike… Actually the size is 10mm which is 0.019 bigger then 3/8 inch. Rope in the piston works well as long as the nut has not been forced too much. If you flat spot the needle bearings or mains the engine will growl at you. If you crack the cage in the gudgeon bearing it can spit out a needle and ruin your engine.
- Set the timing
Set the timing by putting piston at 2mm BTDC Rotate cam clockwise until points are full open Adjust points to 0,35-0,40mm open Rotate cam clockwise until points close Then continue to rotate cam until the points just start to open Use a piece of cigarette paper as a feeler gauge for finding ‘just open’ Make sure your piston is still at 2mm BTDC Give the cam a sharp whack with a block of softwood to lock it on the crankshaft where it is just opening. Put on the Novi nut and tighten it to 35 ft lbs.
- Leak down seal test
You should be getting 0,5-0,6ATM (14-18 inches) vacuum on a 250ml draw (8-10 ounces) so if the vacuum pump you have does not displace at least 16 ounce or 1/2 litre you will not be able to draw enough to test the seal. A leak in the carter or in the intake tract or coupling between the carb and motor will allow too much air to dilute the charge. It would be same as running with a jet too small or a float level too low.
- Crank seals
No debate needed – on 2 strokes garter springs should face outside the carter. On 4 strokes, transmissions, wheels etc they should be in backwards with the garters inside the casings. It is to prevent road dirt and dust from being inhaled around the seals and not the springs. If you find the springs are on the inside then you are definitely not in virgin territory.
Variator is held in place by virtue of the two circlips and the shim washers. Some are sloppy feeling and some seem tight. As long as it it not touching the carter you are good to go.
- Driven Pulley
Looking at the condition of the driven pulley and the slight rust on it I would suggest you look at the variator and make sure the sliding cheek can actually slide easy. If the action is not smooth then it will get hung up trying to move towards the fixed cheek. Also remove the grease nipple in the center of the crankshaft and use a straightened paperclip to dig in the grease hole to make sure the grease has not separated over time. Repack it with general purpose grease if it is empty or if there is waxy old grease in there scoop out as much as you can and repack it.
If you have floody carb then first make sure the seat where the needle goes is super clean, brass needle into a brass seat needs to be spotless clean. If she is still floody then set the plastic float so there is more pointy end showing. But measure first so you have a starting place in case you get the float real low and it still is not sealing, then it is a dirt problem and you will need to start over. If you need less pointy end then only change the length by grabing the not pointy end with needle nose pliers and pulling. If you try to push the pointy end it will not be so pointy and a bend there can make it into a perma-leaker. If your patience wears too thin – just get a SHA 14:12 cable choke carb – slap it on and you are off and running (viton tipped needle is not as tempermental).
Depending on the year you are looking at either 8w or 12w total 120x Novi output on the lighting coil. You are not going to have any spectacular lighting stock from a Moby – sadly – get a battery powered add on or go CDI for the stronger lighting coil.
- Your new (to you) Moby
Check timing is set to 1,5mm to 2mm BTDC and maximum opening for points is 0,35mm to 0,40mm. Gap the plug tight to 0,38 if you have mostly high speed in mind, tight sparks easier at the top end but fouls easier at slow speed. Make sure the carb is not floody – leave her sit for a while and see if she has dribble of gas from the throat, if the float is leaky or set too high (if it is plastic float) it will run excess fuel.
- moby runs then dies
Partially blocked fuel system – you can empty the bowl faster then it can fill.
- Your new (to you) Moby
If it making a lot of heat the spi seals could be worn and leaking air into the carter. Do a leakdown to check if you are getting extra air in a seal or gasket on the motor.
- Air Leak Test
Get a suction gun – looks like a giant syringe you can get them at the car parts place – and a vacuum/pressure gauge and a tee fitting and a piece of hose. Put the tee fitting into the hose and a short piece connecting one outlet to the vacuum/pressure gauge and the other to the intake. Put the suction gun at 1/2 stroke. Put the motor at TDC. Pull the vacuum gun until you get at least 14 inch on the vacuum gauge and hold it there, the only place that should be sucking air is slightly on the exhause, anywhere else is a vacuum leak. Then push the vacuum gauge to do same for pressurization. If it does hsssss anywhere else except the exhause then it is a pressure leak. You can use liquid dish soap on joints and seals and look for bubbles if there is a hsssss you can not find. Seals turn hard from lack of use so it is not too surprising to have a old low miles pristine moped with leaky seals and a ratty high mileage one still having perfect carter pumping. Change all of the seals not just one side – or you end up with one that is good for years and the other good for … a week … maybe two … maybe a month and a half … maybe right up until the night before the best rally ever… just change them
- 50V key
Key are same blanks as old Samsonite luggage -- Samsonite luggage squair head key blanks have the same profile as the original Motobecane locks.
There are two screws are under the decals, one at each end of the chrome part – about 75mm from each end. Some one at Mabecane forum was talking about reproducing the Moby decals, dont know how far he got on that…
- Your new (to you) Moby (AV44)
The AV44 should be timed at 2mm btdc. If you have spark the condenser is probably good. To set the timing you need the cam puller. Put the engine at 2mm BTDC and rotate just the cam clockwise until the points are open widest then adjust them to 0,35 – 0,40mm. Then rotate the cam only clockwise until the points close and put a piece of printer paper between the points to work as a feeler gauge. Continue rotating the cam clockwise until the paper is only just let go by the points. Give the cam a knock with a piece of wood to lock it to the crank. Put the flywheel back on and torque the Novi nut to 35 ft lbs.
- Your new (to you) Moby (BG43)
You should have a Novi nut that is right hand thread not left thread or someone swapped out the original engine on you.
That is an AV7 Galet motor which runs backwards so… Put the engine at 2mm BTDC and rotate just the cam counter-clockwise until the points are open widest then adjust them to 0,35 0,40mm. Then rotate the cam only counter-clockwise until the points close and put a piece of printer paper between the points to work as a feeler gauge. Continue rotating the cam counter-clockwise until the paper is only just let go by the points. Give the cam a knock with a piece of wood to lock it to the crank. Put the flywheel back on and torque the Novi nut to 35 ft lbs. The other weak point on the Galet motors is the tiny spring between the spark coil and the plug wire. You need to clean the contact area of the coil and the spring to ensure good contact between the two.
- Speed Classes
Up to 1978 in USA the headstock tag with the serial number was marked 20 25 or 30mph – then they had a number for the speed rating in 1978-79 A=30 B=25 C=20 – then in 1980 and onwards they changed it to A=20 B=25 C=30. If the engine dies and the motor is harder to turn by hand (gloves if you try to turn the genny – it will be HOT) then you could be leaning out from semi blocked fuel system. Spark plug will also be light coloured. If you remove the plug from the engine and try pedaling over the motor do you still get a bright blue spark when it has gone kaput from being hot?
- Your new (to you) Moby
Running for a short time and dieing sounds like a fuel issue. Have to clean the carb and fuel screen in the tank. Motor not driving the wheel – does the belt move or not? Does the outside of the clutch move with the cover or not? Does the driven wheel move or not? Does the chain move at all? Does the engine speed up when you twist the throttle or does it run at the same speed? If the engine spools up but the belt and wheel does not move faster then the clutch is slipping, if the belt seems to move faster but the wheel does not then the belt is slipping.
- AV85 driven pulley bearings
Make a bearing puller with a piece of threaded rod, washers and a large deep socket. Bearings are a pair of HK1612
- SP50 Belt
SP50 takes a wider belt then the 50V. The correct belt you need 18×955 or 18×960 which would be Ventico D243CR or Hutchinson 5354.
- DIY torque wrench
to check for 11 ft lbs – use a 12 inch ratchet or bar and a fish scale and pull with the scale hooked on the handle until it reaches 11 lbs OR use a 6 inch ratchet or bar scale and pull with the scale hooked on the handle until it reaches 22 lbs.
Stock AV7 and AV10 are 39×2mm, AV35 and AV77 are 39×2.5mm, AV3 are 39×3mm Remember to check the ends are the correct pin configuration. All new rings need to be end gap checked and filed for clearance.
- To set the timing with the spark plug timing tool.
Put the motor at top dead center and thread the timing tool into the spark plug hole. Turn the tool until it makes contact with the piston at top dead center. Then turn the motor 90 degrees counter clockwise. Turn the timing tool in 1 1/2 turns. Turn the engine clockwise until the piston touches the timing tool. Turn the cam clockwise until the points are at maximum gap. Adjust the gap with the points screw to have 0,35 – 0,40mm and tighten screw Turn clockwise cam until points close. Put a piece of cigarette paper between the points contacts. Turn cam clockwise until cigarette paper can be pulled out. Place a piece of wood on the cam so it does not get damaged and lock cam to crankshaft with a tap of a hammer. Install the flywheel onto the cam and the Novi nut. Torque the Novi nut to 30-35 ft lbs. Remove the timing tool.
- DIY Gaskets
Aluminium works good for head gaskets but not all gaskets. Copper works great for head gaskets and exhause gaskets. The rest of the gaskets use gasket paper, cardboard or butcher paper unless you are putting together newer casings that call for 3bond. RTV is for cars and sealing around the shower so the neighbour in the apartment below you does not get a leaky ceiling and gets the landlord on your case.
The gray wire from the genny is all you need for the coil, run it directly to the coil. You also need to have a bonding strap between the engine and the frame. If this configuration does not produce a nice thick blue spark then open up the genny and clean the points and give it another try. If that does not produce a spark then disconnect the original condenser and add an external condenser. Attach the pigtail from the new condo to the gray wire going to the external coil and use one of the coil bolts as a mounting point for the new condo.
- stripped carb threads
For emergency repair you can splinter a toothpick and cram in into the trashed hole and force the machine screw into the hole, the wood is soft enough to self tap threads into itself and wedge the machine screw.
SP50 has a AV7 v2,5 the serial says 1964 not 1960 – that is the date the design was filed in France and not the manufacture date. Takes the standard Moby bearings and spi seals.
AV85* The Gurtner BA carbs with the darn right angle jets are a pain to get unstuck. You can running some penetrating oil from the jet side and the throttle bore and draw it in with some gentle heat by placing the carb into a double boiler for 30 minutes to get it to 100C then it should be expanded and lubed enough to tap out or pull out if the cable is still attached.
- Removing pedal crank pins
Back off the nut 2 turns on the pedal arm cotters, use a 7 or 8mm socket to shield the remaining threads and whack it good with a hammer it will start to release the death grip the dang little pin has on the pedal arms. When it shifts a bit then back off the nut another two turns and whack it again with the socket as a shield for the threads. Sometimes takes 3 or 4 tries like that and the dang thing will just come out. A two jaw puller, a bearing splitter or a pickle fork will pull the arms from the pedal shaft if they are really stubborn. A bit of heat will help the arms to relax and let go of the shaft.
- Timing and Gap
Do not mix up the timing and the gap – they are two different settings. First turn the cam until the points are widest open and set the gap. Then set the piston to 1,5-2mm advance and turn the cam forward until the points are just starting to open. You can use a cigarette paper as a feeler gauge for “just starting to open”. Seriously go over a new2you bike from one end to the other. Check the tire pressure and everything is lubed and properly adjusted, all the electrics have good contact, look for leaks or oil stains between casings, check the wheels roll freely and the brakes are properly adjusted. Sometimes there is something else not right that will rob us of enjoying our bikes as we ponder the motors performance…
- A Gurtner kit
will consist of a figure 8 gasket, an oring and a small gasket for the cover screw. Gurtners need to be well cleaned – the float valve is brass on brass so only a small piece of crap will mess it up and it will flood constantly. Poor performance issues is usually the diffuser enrichment holes are blocked or vent holes blocked. Cleaning details are at Mabecanes site –
- Checking for chain wear
Check that your chain is not worn – the motor side is 1/2 inch pitch so measure with a tape measure for 12 inches of length. If it is over 1/16 past the 12 inch mark on the tape the chain is no longer good. #41 chain from Princess Auto will fit the motor side.
- Wheel allignment
Center the wheel alignment by working on the motor side first, pull it back and allow 1/2 to 3/4 inch total up and down slack and secure that side. Loosen the tensioner for the pedal side and place the wheel centered in the swingarm and secure the pedal side. Adjust the sensioner to allow 1/2 to 3/4 inch total up and down slack.
- Splitting the case
Heat is the way – I put the assembled carter into a double boiler after removing the casing bolts and 30 minutes later I just pull the whole thing apart – casings off the crank and bearings out – even though it is “only” 100 degrees C you would want to wear gloves because it will be heat soaked… same with the other suggestions on using heat.
- removing carbon build-up
Those tiny brass brushes for a dremel work really well on carbon build up – give the carbon a soak with some diesel and hit it up with the brush. If you have a lot of carbon you can give it another soak once the brush does not seem to cut it as fast.
- Crank nuts dimensions
According to Motobecane – Ecrou de blocage tambour est 11×1,00 a droite so it is M11×1 right hand thread on the clutch side Ecrou de blocage volante magnetique 11×1,00 a gauche so it is M11×1 left hand thread on the flywheel side
- Your new (to you) Moby
You need a flywheel/clutch puller, a bearing splitter, metric sockets and wrenches, a propane torch, and some patience. Buy a gasket kit, a pair of rings, two spi seals and a pair of crank bearings. Do not just change the seals, change the bearings at the same time and might as well do the rings – if the old rings and bearings are still good they make nice tree ornaments for December. You are not just splitting the cases – you are completely disassembling the motor. Sounds tragic at first but once you are done you will have a refreshed motor which will be ready for years or service and miles and miles of fun transportation.
- Bad Condenser
If you can feel the shock but not see the spark then you need to change the condenser or the coil. Start with the cheaper of the two – the condenser. The spark should be blue and bright enough that you should easily see it in the shadow of the ped.
- Testing a condenser
Take off the condenser and test it with a analog multimeter, connect the black to the casing and the red to the wire, the needle should deflect to the end of the scale and slowly climb back. If it does not deflect all the way or does not climb back the condenser is faulty. Disconnect the wires and wait then reconnect the black to the casing and red to the wire, this time the needle should not deflect, if it does even a bit then the condenser is faulty. Reverse the wires, it should deflect again to the end of the scale then climb slowly again. If it does not go all the way to the end or does not climb back then it is faulty. Condensers are not expensive, way less then a induction coil in the genny so it would be the first part to try if you have a weak spark and your points are clean and properly gapped and the plug is clean and properly gapped. Sorry – set the analog multimeter to ohms Analog – old school with a needle that goes back and forth Digital – actual digits to display the quantative values
If the rings are dimensionally same the they will fit and work. You need to make sure they have the correct ends. Always end gap rings – even on a new kit. Should be 0,1mm – 0,2mm (.004 – .008 inch) for 40mm bore. You could also order rings from AtoZ in UK – not expensive and they can get every moped ring ever
- moby reving up and down
Air leak, timing off or blocked vents on the Gurtner – unless you have swapped for a Dellorto carb then you are back to having to only chase down an air leak or timing off.
According to Novi the 120x genny should generate approximately 6 volts at 3000 rpm on the internal ignition coil. The lighting coils are rated at either 12 volt or 6 volt at 8 or 12 watts for either voltage depending on the coil.
Older Mobys have only 1 coil inside the Novi generator. Same as the later bikes the weak part of the system is the condenser which fails due to repeated heat soaking. Best is to replace it with an external condenser. You will need to make a bracket to mount an external condenser and also make a spot to feed the wire through the backing plate. Other weak point on the older ignition is the darn spring from hell which connects the coil to the coil wire. This spring can fail or become corroded and the spark either goes astray in the genny or just does not happen. When you get the genny open you will see if the wrapping on the ignition coil is stressed or not. If it is tired or you need other bits I would suggest to contact Brian Aplin at Aplins of Bristol.
- Your new (to you) Moby
Hope you are mixing 4% (25:1) two stroke on the older AV7D series motors. Mine are finicky on the mix – especially when hot or warmed up. Check the compression hot – getting a new set of rings also helps cure the hot troubles if that is the trouble. Rings can lose their springiness and the ring lands can coke up over time. Change out the “gasket in a tube” base gasket for a paper base gasket.
- DIY Butterfly hone
Make a butterfly hone from some plumbers sanding cloth and a piece of 1/4 metal dowel or tube. Cut a slice up the end of the tube or dowel so you can put in a strip of sanding cloth longer then the cylinder bore so it ends up like two flaps of sand paper. Chuck it in a drill and use some kerosene or diesel to wet the paper and just polish away the rust. If it is rusted it is not aluminium – it is steel – you can use drain opener to clean steel liners and chrome bores it but do not get it on any aluminium or it will immediately turn into crap.
- cleaning up spilled gas
Cat litter if there is a puddle still. Baking soda also works well if it is still damp. Trisodium phosphate, get it in the hardware store at the paint section, and water as hot as you can handle. Wear gloves and soak the floor and wipe it up quickly so it does not soak into the wood far. If you got it on the carpet also then use lemon dishwashing liquid, scrub to get it soaked and then use wet rags to get the soap out of the carpet then put the coffee table over the wet spot in a feeble attempt to not get in shit for messing with a carb in the livingroom.
You have 3 coils – top for lights, bottom is the internal ignition coil and the third that bridges the two is for the turn signals. Condenser would be outside of the genny which is where they belong anyhow – away from heat. By the look of the fire you may have the lights and flasher coil insulation melted, if they are they will produce barely any voltage. You do not need to pull the cam to remove the coils.
- Your new (to you) Moby
You can beef up the spring or you can remove two balls from the variator if it is a 4 ball. I would not suggest running a 3 ball with one missing that just puts the balance out and stresses the already undersize upper motor mounts.
- Testing coils
If you disconnect the new condenser and external coil, put a volt meter on the gray wire and on the casing and give the genny a spin - should have 4-8 volts depending on your spinning ability - if zero then the internal coil is kaput - if you have voltage then the external one is kaput.
- Refitting blunderbus exhaust
What pipe are you running on the engine? If it is stock the blunderbus exhause will work with the wiki port job as long as you resize the outlet of the pipe. The enterance to the pipe is 18mm so measure the height and width of your port window and check the area cross section math to make sure the exhause is not a restriction coming out of the window. You will also need to enlarge the outlet of the blunderbus, outlet should be at least 10mm and can go up to 12mm, depending on your window area. Also the timing is probably too advanced. With a higher compression ratio you need to gap plugs tighter, this is because air is a lousy conductor of electricity and you have more air per cc with higher compression. Gap your plugs tighter at 0,38mm (.019 inch) and set the timing to about 1,5mm (20 degrees) before top dead center. Stock is too restrictive, especially with the later blunderbus pipes which had the reverse baffle tube instead of the muffler balls. Area of 21 * 14 = 294, area of 18mm pipe is 255 so you are down sizing into the exhause. Change out the exhause tubes for a blank plate with a 10mm hole and see how she runs then, you can experiment with the hole sizes until you find the sweet spot, it will not be over 12mm, but it will be louder because there is no reverse baffle tube.
- DIY stripped temporary fix
Go to the dollar store and buy one of those thin metal cookie trays and cut a strip 13mm and make a sleeve to fit into the exhause where it it stripped. Make the sleeve so there is no more then 3 or 4 mm overlap. thread the exhause nut in carefully and you will get a tight seal so you can ride until you get a replacement cylinder.
END 4 DEC 2010
- Assorted Torque Ranges
It is not OCD to use a torque wrench, that is what you call proper standard practices. A lot of amateurs strip casings and ruin hardware tightening by feel.
Here are some torque specifications for Motobecane AV7 AV10 and Isodyne engines according to the Motobecane manuals.
Always use an antisieze compound on threads of any fastener that attaches directly to an aluminium case specially the upper carter bolts, exhaust big nut and spark plug.
Novi nut 30-36 ft-lb
Cylinder head nuts 11 – 13 ft-lb
SparkPlug – 18 ft-lb
Carter assembling bolts 9-11 ft-lb
Variator nut 18 ft-lb
Stator securing bolt 9 ft-lb
Clutch nut 13 ft-lb
Inlet pipe setscrew 9 ft-lb
Engine upper Flexibloc bolt 27 ft-lb
Engine rear Flexibloc bolt 27 ft-lb