Checking the Flywheel magneto

Well having reassembled the motor with new barrel, piston rings and small end bush, I naturally tried to start it. SADLY no joy and my first thought was a lack of spark. An easy test and yup- dead as a dodo. These old bikes have frequently fallen out of use through coil failure, but in this case the bike motor had siezed solid and so probably running (and therefore sparking) up to that point! I'm hoping this is just a contact breaker problem so best to check, clean and reset them as a first step.

Well you can check them visually and adjust through the flywheel but a proper check means removing this to get a good look and do a thorough clean. I'd expected to be able to use a Quickly flywheel puller but this doesn't fit. Luckily my Sealey set of pullers had one that does the job.

Removing the flywheel with an M25 1.5 externally threaded puller

The coils are rather more complex than the Quickly with an extra coil situated above the ignition coil. This I am told is to supply the horn.

The contact breakers do look corroded and dirty

Points look corroded and dirty so I cleaned them thoroughly. I could check that they worked using a magneto timing box.

points closed

Points open!

I  refitted the flywheel,  checked and found I could now get a spark (iridium plug).

Before trying to start I wanted to change the gearbox oil- the filler-level plug was easily identified.

The drain up was a little more mysterious

The drain plug is in the right position and has a sealing washer- but it's a bolt not a plug and does cross a crankcase join which I don't want to weaken. However I received confirmation that this is the right plug so changing oil is next on the list.

The manual states SAE80 Gear oil. This doesn't seem to exist any more but its not the same as SAE80 crankcase oil. I opted for this modern substitute.

Well draining the old oil showed that in fact there had been no oil in the gearbox for heaven knows how long. I refilled using an oil can to squirt in the oil above until it started to trickle out of the fill hole when the can spout was removed.

replacing the piston and barrel

The old piston may well have been usable, but the trauma of its removal from the barrel had left marks on the crown. 

Similarly the barrel would be usable but really needs reboring and rechroming to be sure it would last.

 Luckily I was fortunate to get one of the last new old stock piston and barrel kits from Germany. 

Testing the old gudgeon pin revealed wear in the small end. The pin itself wasn't greatly worn but the bush was. There was no up-down  play but there was a tilting effect when the pin was tilted in the vertical plane. If you tried the same movement in the horizontal plane then tilt was barely perceptible. This told me that the reciprocating motion of the piston has taken its toll on the bush and even though it might be OK for a while, it's going to need changing.

I assembled a hotchpotch mixture of pressure pieces to use with some M6 studding to press the small end bush out. Rurning a small stepped adapter to locate inside the bush and press on it- but small enough to pass through the conrod eye. I used a narrow tube (old Quickly gudgeon pin) behind it to get the length of push. The assemblage is shown below after bush removal, and the bush itself is indicated by the pencil. Obviously these items were assembled around the con rod to press the bush out and into the short tube section opposite. It worked fine but I think would have been better with M8 studding and probably a centre piece to keep the studding and tubing in line as pressure is applied 

 Unfortunately I could find no NOS bushes and no remanufactured examples either. I decided I would need to make one although my chances of making anything better than the worn original are debatable. 

I have prepared by ordering some reamers at 11.9 and 12mm to test but in fact fate intervened and I found this odd looking bush advertised as an NSU Quickly small end on ebay.

This had a number I didn't recognise but even with no clear sense of scale this looked a bit too big for the Quickly. The label has also had the "ly" obliterated and a "50" added. All this made me wonder if its actually a Quick 50 bush mislabelled. It was supplied by Alphaautomotive who seem no longer to be with us- at least as a parts manufacturer (superceded apparently as Alpha Bearings") but I was able to track down an old NSU applications list for them.

Or zooming in-

You can see they list two bikes under NSU 49cc... the Quickly (1954-68) and the the Quickly 50 (1963-66). These bikes use different bearings so, as the Quickly used the same bearings throughout its life, I'm assuming that "Quickly 50" is simply a transcription error for "Quick 50". If so then this confirms that the odd number SE229 does seem to be for my bike. The manufacturing period is also in agreement. Finally I asked the seller to supply the diameter of the bush which he recorded as15mm. Again this suits the Quick 50 but is too large for the 13mm NSU Quickly equivalent. I therefore bought this bush and if its correct then I'll take its dimensions to use-as a pattern before fitting it.

One point that always worries me us that the bush has to be right but not too tight.... so how tight?I measured the bush removed from this bike at 15.039mm and the conrod eye 14.9. Obviously in fitting and removing the old bush it will have been crushed a little and probably hasn't expanded to its full size on removal. Nonetheless this indicates some 0.139mm of crush which seems enormous- I usually reckon about 1/1000th or 0.015mm in this case. However doing the same calculation for the Quickly small end and conrod eye shows the (extracted) bush at 13.016 and the conrod eye at 12.9- in other words 0.116mm of crush or a very similar value. There was however quite a wide variation. Maybe more squish is needed because the bush is hollow and so deforms easily.  Perhaps it therefore needs more squish than say a solid pin to make sure its tight. Of course I'm measuring the con rod eye with calipers and the bush OD with a micrometer so the accuracy may be a little suspect.

My plan is to first drill a  phosphor bronze rod to as close to the gudgeon pin od as possible without the sides becoming weak. I will then turn the exterior down to slightly larger than the diameter of the control rod little end eye. I can then insert the bush into the con rod eye, drill through the lubrication holes and then progressively ream out the bore until it accepts the new pin as a smooth sliding fit. I think if I try to ream it out too far before inserting it in the conrod, its walls will be too thin to take the⁷ machining.

The OD of the inserted bush measured in position  is very close to 15mm, so I ordered 90mm length of 15.8.mm phosphor bronze rod. I hope this will be manufactured accurately enough to turn down but just in case I also bought a length of 19mm. In either case 90mm length should allow me to make a few attempts.

Here is the new bush. In its virgin (non inserted) state it measures 15mm in length, 15.126mm in width (ie OD) and 11.95mm ID. Neither the old nor the new Gudgeon pin would fit this in its unreamed state although both fitted nicely into the old bush which was only 0.03mm larger in ID. Clearly this sliding fit is a close run thing. The bush started out at 15.125 mm OD and the extracted bush is 15.04 so some 0.08mm of squish?

I cleaned up around the crankcase mouth 

... and removed the barrel studs to make sure I could get a clean joint for the cylinder base gasket- although this also improves access for changing the small end and piston.

Inserted new bush using drawbolts- tapered side first as a lead in. Ensure both bush and eye are clean and lubricated. 

The new bush had no lube holes so these were drilled through using the conrod holes as a guide- great care to remove any swarf. Use a vacuum extraction.

Finally ream the bore. I used two adjustable reamers starting with an H3 7/16 t 15/32 

and finishing with type ST4 15/32 TO 17/32. It's essential to test the reamer in the old bush before using it to make sure you don't go too large and check gudgeon pin fit after each pass. When I'd got a smooth sliding fit I could check the bore with a fixed reamer and it looks like for future reference a fixed 12mm reamer should be just fine.

As an added complications I found that not all 12mm reamers are the same! I have 3 and only one (h8) reamer the bush correctly so o really its probably best to stick to the adjustable and use care.

Nice sliding fit. I had to clean out the cylinder studding threads before the studs would screw back fully. Note that the piston is directional. It was supplied in the new barrel and I've not removed it. As supped the arrow on the crown pointed forward: a check with the fb group showed that this is correct, the arrow would usually point towards the exhaust (ie forwards).

Piston in barrel as supplied

.. and refitted to the Con rod, barrel added. 

The piston was supplied with one gudgeon pin clip already in place. I warmed the piston with a hot air gun and chilled the pin in the freezer before fitting it through the piston and conrod from the cutout side. Don't forget to add the new Gudgeon pin clip in this side and to line the ring gaps up with the piston groove pegs before fitting the barrel. I mark the position of the pegs on the crown  as you can't see them during the fitting process. I can then check "by feel" to make sure that the ring gap is positioned directly under this mark as I feed the piston into the barrel. It's not necessary to use a ring compressor, you can squeeze with your fingers to pop the rings in as the barrel is lowered.

Exhaust to Cylinder head mounting ring nut

The exhaust is mounted to the head by a ring nut compressing the flange on the end of the exhaust against a sealing washer. Unfortunately I do not have the rig nut and replacements are if the order of £40. Since they have to come from Germany they will incur high postage costs. Its cheaper to try to make one. As best as I can  determine the ring nut is threaded externally to M37 pitch 1.5. The internal hole has to accept the exhaust tube and should be app. 32 mm. I decided to try and produce something using thick walled (3mm) 38mm od mild steel tube which I can turn down to 37 and thread to 1.5 on the lathe.

I was able to make a collar although it is rather thin and leaves a gap around the exhaust pipe.

Nonetheless the pipe could be fitted incorporating a compression washer between exhaust flange and cylinder head. 

The replacement pipe is a little too long vertically and it was necessary to remove one of the silencer mounting bolts so that the silencer could be angled downwards to join the downpipe. In the long run I will probably make some hanger spacers to lower the silencer appx 2 cm so that it can join the downpipe and run horizontally without strain.

Replacing the carburettor mounting inlet manifold

The carburettor manifold was missing from this bike. Its a cunningly designed tube of aluminium that connects the carb to the cylinder, adapting for the height difference between carb outlet and barrel inlet port via a bend. It also changes the shape from the round Carb mouth to the squared off shape of the port. Finally it does all this with smooth curves so as not to obstruct the flow. My fabrication skills are not up to making one of these so I searched for a replacement. The fb group told me that a Puch inlet manifold will fit the barrel although it's angle is wrong, the cutouts don't match and it will need longer mounting studs. I'll have to see if I can make it work. Currently my plan is to modify the Puch part making an adapter from the barrel. 

This is the Puch part as supplied- it's rubber covered aluminium and the bulk of the angle is created in the rubber extension.

I cutback the rubber

and removed as much of the extension as I could.

The fit is close but the angle is clearly still mismatched. This could be adjusted with a cunning rubber tube union but its asking  lot to find one with different diameters at each end let alone the bend required for angle adjustment.

The only answer was to remove more of the Puch part to try and improve the angle match. Eventually I had no alternative but to slice practically of the manifold off the mounting flange and then insert a new tube to connect to the carb.

This is the stub of the Puch part. Unfortunately it's a tapered opening the cylinder side being a larger hole than the carb side.

I started with a length of 22mm aluminium tubing and turned it down over a 5cm length to the smaller opening diameter. I could then taper this dimension (8 deg taper) to the larger diameter so the the tube would slip snugly through the Puch manifold and engage in the tapered hole. All I needed to do then was reduce the length of the full width section to fit flush in the manifold and lie against the cylinder. Finally I turned down the projecting end until it would fit into the silicone tubing I have available.

Final turned aluminium tube note flare at left hand side to fit into the puch manifold and the reduced diameter at the right to fit into the tubing available to connect to the carburettor.

Turned tubing inserted

..and machined flush at the rear.

Assembled connector. I fixed the tube in place (hopefully airtight) using high temperature Loctite joining compound.

The silicone hose I have available is left over from a former project (Lotus Excel). It usefully features two different sizes joined by a 60 degree bend. I can trim the narrow end to join to my new adapter whilst the wider end should fit the carburettor outlet. This tubing even has a bend and so should fit the joint geometry very well. However- there is no avoiding the fact that building the adapter in this way has reduced the area and thus the amount of mixture able to enter the cylinder. This will reduce performance but at this stage, when a replacement part is not available, it should at least enable me to get the motor running.

Silicone tubing- narrow end already trimmed.

Trimmed and installed. Need to take it off to fit the gasket and hose clips. 

Hopefully in the fullness of time I will find an original part and if not then I'll eventually need to revise this adapter but use wider aluminium tubing TIG welded to the union plate. Currently this is beyond my expertise.

The carburettor Bing 1/16/61

The carburettor is a Bing 16mm (type 22 no 1/16/61) that is attached to the bike via rubber mountings; a mushroom shaped one connects to the air filter behind and a cylindrical hose connects to the intake manifold tube in front. Both held by wire clips. On my bike the intake manifold is missing so the carb is removed by simply unscrewing the large wire clip binding it to the air filter mushroom. The screw and nut that hold the wire clip are removed and the clip can be bent out of the way. Note fuel intake isnt visible since fuel enters behind the carb. Note also that the float chamber is at the base.

Slipping the wire clip

The rubber mushroom is a tight fit but levers off the rear of the carb.

And levering off the rubber mushroom

The carb is then held by the throttle cable passing through the carburettor cap. Note adjuster on the cable, the choke slide and the two attachment screws.

Top of carburettor

The screws are loosened but remain captive in the cap. The cap comes off under tension of the throttle slide spring below.

Withdrawing the throttle slide and choke

As the cap comes up you can see that the choke slide is hooked onto both the choke actuating pin and throttle slide as in the NSU Quickly. The throttle cable passes through the spring and is retained in the base of the throttle slide.

Withdrawal continued

The needle is in the base of the slide and visible as the slide pulls free.The following shows the view inside the carb body

Looking inside carb body- needle valve at the base.

Whilst the next shows the throttle and choke slides as they are assembled onto the choke slider rod and throttle cable.

Articulation of throttle slide and choke slide

The cable is held by its nipple passing through the base of the slide. Compress the spring slightly to allow the cable nipple to slip out of the slide and it can then by switched to the pass through hole and withdrawn from the top of the slide. Here the pass-through and retention holes are both visible after the cable has been removed.

Pass through and nipple retention holes in base of slide.

Inside the slide the spring base equalisation washer and needle clip are visible. The different widths of the pass though (wider) and retention (narrower) cable holes are evident.

Needle clip and spring base washer.

There was no gasket under the carburettor cap and I feel sure that there should have been one here. This was the first clue that the carb has been disassembled previously. I later found it was very clean internally. I'd expected it to be quite choked.

Inside cap-choke plunger on left, cross wire locates in raised and lowered positions using "figure of 8" clip

Choke pin jammed with some sort of debris which needed to be removed.

No gasket below cap

The choke sliding pin was however jammed solid and needed to be freed with carb cleaner and wd40 until it could slide smoothly between the two locking positions where grooves on the pin engage with a locking cross wire and clip fixed in the underside of the cap. Above- pin now free to slide.

Idle speed adjustment screw is visible above the float chamber. Returning to the body I removed the idle control screw and its spring, thats the round headed screw shown here. The hex nut being the clamping screw holding the tube stump that should connect via a hose to the intake manifold. 

Idle speed screw (round head)

Idle speed screw and spring removed. It had been fitted at 1/2 turn from fully screwed in but I suspect this is a meaningless setting that probably postdates the engines failure.

Idle speed screw and spring removed

I could then turn the carb over and address the float chamber. The float chamber unscrews with a 14mm spanner. The whole bowl unscrews from the carb body revealing the ring shaped float inside.

Removing float bowl

Looking inside the float chamber its clear that fuel should pass through the two small holes each side of the central column. An additional hole halfway up the column also admits fuel. The column is screwed onto the main jet housing so fuel is actually extracted from this small chamber at the base. Its not clear whether there should be a filter in this small chamber although there was none on disassembly. There was a little sediment at the base of this small chamber which I cleaned out before checking that the entry holes were clear.

Inside float bowl, note two base entry holes top/bottom of Central bore. Some sediment at base.

Before removing the jet it was safest to remove the float . This was held by a short pivot pin which was carefully tapped through. The following show a few general views of the float in its assembled position.

Float in situ

Note that the main jet penetrates through the column up the centre of the ring float, and the float chamber screws onto the outside of the jet-surrounding column.

Float in situ

The float is retained by a sliding pin through two lugs in the carb body.

Float pivot pin

This needs to be carefully tapped down using a drift. Strange witness marks on the float body so I'll check it for leakage.

Tapping pivot pin down- complete process with very fine drift.

The process was completed using half of a split pin that could pass through the lugs without enlarging the holes. Once the pin was through far enough the float could be lifted off.

Needle tapped out and float removed

... and the needle removed from the fuel entry needle valve. This was a solid brass needle and has a flat base. In some carbs the needle is hung downwards from the float and fuel enters from below but in this carb the needle sits above the float and fuel enters the float chamber from above. Ideally I'd replace with a viton tipped needle, but this only seems available for the hanging needle type.

Removing the needle

It was also evident that the groove here seems designed for a flat O ring (41x45x1.5mm). This carb had rhe remnants of some form of composit  compressed paper washer in the groove which were difficult to remove.

Once the float and needle have been removed the main jet can be unscrewed. It needs a carefully chosen screwdriver and I found an angled one fitted perfectly. I unscrewed the jet which is a small threaded plug screwed into the long brass holder. I unscrewed the jet and the holder came with it.

Unscrewing the main jet

The main jet and holder can then be removed and cleaned by blasting through with carb cleaner. If necessary the jet itself can be removed from the holder by holding the hex section of the holder in a vice or wrench.  I found no real debris in the carb although the main jet was blocked.

Withdrawing jet and jet holder as a unit

The individual carb components were then thoroughly cleaned and all the passages cleaned out with carb cleaner and put in my ultrasonic cleaner. The main jet was cleaned and re screwed into the carb body. the Idle speed adjuster returned with its spring. I slipped the needle valve into the valve body and then refitted the float to keep it in place. Easier now the pivot pin has been polished (below). I checked that the needle sealed by blowing through the fuel inlet whilst inverting and righting the carb body. When the float pressed on the needle, passage of air was blocked. This is a good sign but it remains to be seen whether the float will successfully regulate the flow of fuel.

On reassembly I noticed that both the choke pin and float pivot pin were very tight in the body. In time this would damage the float lugs as the pin is fitted and removed so I polished both in Emery cloth by rotating them in a Dremell until they were a smooth sliding fit.

Here the choke pin is held in a dremmel for polishing against Emery cloth

I am concerned that I will be dismantling this carb again  fairly soon as I am using a substitute float bowl seal (see on) and I have changed neither needle nor the needle valve seat. I noted a mark in the valve seat and so it's possible this is going to leak. The pic below shows the view inside the needle seat and the scratch is visible inside the valve seat at around the 6 oclock position. Note cleaned O ring grooves.

Looking inside needle valve (right). Note scratch or mark in base around 6 o clock position... zoom in.

New valve seats are available- as are new needles, but from Germany and so expensive since Brexit. Also there is no straight access to drive out the needle seat ...

Looking down fuel entry hole...needle valve body visible in base but there is no direct line to tap the valve body out.

... so if it needs to be renewed the most likely way would be to cut a thread inside it and use a bolt to tug it out with a small impact hammer.

Note that there is a small basket filter inside the fuel pipe connector which also needs to be removed and cleaned. I replaced the fuel inlet using a new fibre washer.

Basket filter removed from inside fuel spigot 

I also found that the cable adjuster would not screw fully into the carb cap. This could be deliberate, perhaps to prevent air leaks, but since the tapping passes right through, the tight point being in the middle, it seems likely to be simply a damaged thread rather than a deliberately truncated one. The thread is M6 fine (0.75 putch) so I retapped the carb cap allowing the adjuster to screw along all of its length.

Having finished cleaning I started reassembly. The float chamber requires a square or flat O ring 41x45x1.5mm in size. These are surprisingly hard to come by so I used a round 41x45 nitrile O ring. This seems to seal but I suspect will need replacing each time the bowl is removed.

Round O ring

O ring installed- looks like it will seal.

I cut a paper gasket to go beneath the carburettor cap- very fiddly but it can be done. I sprayed some paper with a light coat of black paint, inverted the carb into the wet paint and then stamped out a few gasket outlines. I stamped the holes with a punch and then carefully cut the fiddly bits with a scalpel.

Stamping gasket shape on gasket paper.

Gasket cut out

I then reassembled the carb- as follows; fit the gasket to the cap, place the needle and spring seat washer into the throttle slide, aligning the grooves with the holes. Put the spring inside. Feed the throttle cable through the cable adjuster in the cap and insert it through the spring into the larger hole in the throttle slide base. Flick it to the smaller hole to retain. Finally fit the preassembled carb body onto the cap ensuring the gasket is still in position. To do this fit the choke slide onto the choke pin and engage its lug into the slot in the throttle slide. Carefully feed both into the carb body ensuring that the throttle slide engages with its location pin in  the carb body and that the needle enters the orifice in the carb base. Slide home and tighten the 2 cap screws. Finally tighten the mushroom clamp.

Reassembled and cleaned carburettor

Cleaned carburettor refitted.