Britbike forum Forums Projects started by Britbike forum members Members bike projects '37 Rudge Ulster

…the front brake cables adjusters locking plate was missing. So using a sketch with the original dimensions it was simply a case of bending a strip the 15swg sheet steel to make a replacement. Or at least it should have been!, but due to the tight angles it was necessary to make a special tool to add to my collection of single use tools that I have made, used once and will probably never use again. I fitted new adjusters and spring with the new locking plate.

Hi Bryan, reading your thread with great interest, like former one about a Velo. Just got a request / question from a guy from Poland who just bought 2 Specials from a friend of his father. Both bikes were modified with telescopic front suspensions so he is looking for 2 front forks and more knowledge about bikes and methods of restoring them. Would like to show him your thread and a source you quoted in the one of the first posts. I think he has his work cut for him, but he restores old bikes professionally ( just not English bikes being quite rare in Poland ) so probably needs all the help possible. Not sure about his English, but if its good perhaps he could contact you personally, if you agree.
This is what he bought:

Hi Adam, PM sent with contact info.

…the carburettor looks to be pretty original and the PO had it professionally sleeved and new slide, needle, copper float, float needle, jet and fittings installed. The sleeve job looks to have been done to a high standard and I have the receipt for the work. Cosmetically the plating on the body had seen better days, so I removed it using fine emery cloth then various grades of wet and dry on the brass body. This was initially planned as preparation for replating, but I quite like the raw brass look against the bronze head so I may end up not plating it. I made replacement mounting bolts while the parts were in the ultrasonic cleaner and will order a heat isolating spacer and new top ring for final assembly.

...I finally got back to work on the Rudge project after an extended period of travel and then getting my other bikes serviceable for use this riding season.

The dry-build pre-assembly is more-or-less complete and I will now start to get parts sent off for painting, powder coating and plating.

First job was to get the girder forks removed and checked.

An hour in the garden with nitromors and a wire brush in the die grinder soon had the paint removed. I then set them up on a mandrill between centres on the lathe and checked the alignment using a digital level. The alignment between each set of spindle bolt holes and wheel axle drop out plates was within 0.1 deg, so all good.

I then did a dye penetrant flaw detection inspection to check for cracks of broken brazed joints. This also proved to be OK.

The spindle bolts and shackle bushes were measured. The spindles were found to be straight within half a thou', there was some radial wear on 2 of the spindles ranging from 0.002" to 0.003" outside of original factory manufacturing tolerances. The others were within tolerance with wear of <0.002" but this wear was out of round. The plan is to replace all 4 spindle bolts.

The shackle bushes were found to be worn, ranging from a total clearance of 0.004" to 0.008", and worn oval, so these will also be replaced.

Hi Bry,
I rebuilt a set from a 38 Special recently, the worst wear was in the eyes of the shackles and the top spindle hole in the fork legs
I had to bore and sleeve these, a tricky operation to keep everything lined up
15thou oversize spindles are available from Paul Horton (UK) which can sometimes rescue these without the need for sleeving

John

Thanks John, yes the top shackle eyes are worn on mine also, which surprised me a bit as the spindle doesn’t turn in these. Also, curiously the wear is tapered from ~0.001” on the outside to ~0.006” on the inside. I did see Paul’s oversized spindles on his website. I’ve not decided if I’ll make my own yet, but with the current cost of EN16T bar, Paul’s are looking like a good option.

The set up for boring must be tricky due to the geometry of the shackle? I may try an adjustable reamer with a pilot, which I’ll need anyway for the bushes if going >0.5” with an oversize spindle.

Bryan

...with the tanks, mudguards, toolbox etc. dropped off at the painter, I started getting the parts that will be sent for powder coating prepared.

The fork shackle legs were checked for parallelism. The upper one initially was showing a slight misalignment, but this was found to be just uneven wear on the bushes supporting the test mandrill. I line reamed these oversize and true to remove the wear (they will be replaced anyway) and on rechecking the shackle was found to be OK.

The upper steering head bearing cup was removed from the frame using an expanding puller and slide hammer. The lower one needed a bit more hydraulic persuasion.

The paint was removed from the frame using chemical stripper and a rotary wire brush. After a visual examination and alignment check I performed a dye penetrant inspection for cracks or other surface flaws. None were detected.

...in preparing, photographing and documenting the parts that will be sent out for powder coating, some minor repairs were necessary.

The gearbox plates had some local deformation on the edge where the centre stand contacts when deployed and the stand had a corner piece of one of the foot pads broken off. All were repaired by welding, filing and power filing.

...another small repair, but a very worthwhile one to prevent kickstart rubbers slipping off on the rare occasion that a British bike needs multiple kicks to start :-).

The kickstart pin was pointing slightly downward when in the operating position. The cause was excessive wear on the pivot bolt - the holes are ok - and wear on the pin face where it contacts the lever. So a new bolt was made and the worn area built up with weld and filed to the correct height and profile.

…with the frame and associated parts ready to go off for powder coating, I made a start on the engine.

As the temperature inside the shed had been more-or-less at a constant 20degC most of the evening, it was a good time to measure the barrel and piston. The barrel is in good condition and had been vapour blasted when I received it. There is no scoring or significant marks on the bore, but there is a detectable step at the top of the swept area on the exhaust side. I therefore added a measurement location to the top, middle and bottom positions at the step. The piston is a Specialloid brand and marked STD +0.040”. There is evidence of previous pick-up on the piston.

I calibrated my bore gauge - fitted with a digital indicator with a resolution of 0.000mm – using a stack of gauge blocks held in an accessory kit holder, for the bore measurements. The piston was measured using a micrometer. I measured in mm and calculated the clearances in inches for ease of reference (at least for me).

A height gauge on a granite surface plate was used to measure the barrel height.

Below is the complete table of measurements and calculated values. The piston clearance is >0.011” and the step has ~0.004” wear. As I see it, my options are as follows:

1. Lightly hone the barrel, fit new rings and run as is. I will likely not do this due to the condition of the piston from previous pick-up, the ~0.004” step in the barrel and the quite generous clearance, which I don’t believe is all wear. The previous pick-up and likely increased piston clearance are possibly related.

2. Try and find a +0.060” Ulster piston and rebore. This is my preference, but I have not found one yet, although I’ve only looked online and not started calling around yet.

3. Fit a liner and return to STD or +0.020”. This may be a necessary option if I can only find a smaller piston.

4. Fit a +0.060” BSA Gold Star piston. I have read about others having success with this but will need to investigate further before deciding. If this is a workable option, it would be preferrable to fitting a liner.

Any advice or shared experience on the above options would be gratefully received.

Hi Bry
The Gold Star piston is your best option, modern low expansion alloy if you buy an Omega or Wisco
The old Specialloid and Covmo pistons need at least 8 thou clearance to avoid seizure (some still will give trouble at .008)
I found a liner from a Ferguson35 four cylinder (copper belly) is a suitable size for Rudge 500's (cheap as chips)

John

Thanks John, that looks like the direction i'm heading (+0.060" GS).

What clearance do you use for an Omega or Wisco?

Bry

Hi Bry
From memory they have 4 thou clearance for a GS ?
I would give it 5-6 thou because of the iron cylinder vs the GS alloy one
I did one about a year ago, I will ask the owner what clearance we settled on,
It is going really well now, he was plagued with seizures using an original piston even though it had almost 10 thou clearance

John

Thanks John, this helps a lot, what type of GS piston did you use with regard to compression ratio? I believe they are available in different options.

Bry