Monday, 28 December 2020

W/NG - getting rid of the fouling problem

A week before Christmas I needed a haircut, so I took the opportunity of a sunny day to take the W/NG on its first decent run since the engine rebuild, having replaced the 0.107 needle jet with a (correct) 0.106. It took me 30 miles to foul a new W8AC, instead of 3; for the trip back I changed to a used B5HS which took me another 30 miles until it too showed signs of fouling.

It was all my fault. When it arrived from Italy, the W/NG had a 276 fitted and I renewed the needle jet for the 276 because the one in it was knackered, and all was well. Then I found a really good 275 body, marked for a W/NG and I swapped the needle jet and main jet into it with a new slide and needle. Of course, the 276 uses a 107 needle jet and the 275 needs a 106 so I had unwittingly installed the wrong one, so finding that improved the situation.

Back to the present, and with hair trimmed, I rode back to the coast and it was surprisingly dark when I got home. On the way, I pondered other elements that I had swapped from the old carburetter and realised I had no way of knowing whether my main jet was indeed a 120 (it is stamped 120) or had been tampered with. I ordered a new main jet when I got back. I suspected someone had attacked the 120 since it was smoking when I took this picture and had fouled the Bosch plug on the way down. 

It was a good run though and she was humming along getting to 50 easily on the flat, though of course I am being very careful not to stress the newly rebuilt engine.

A few days later, a package from Hitchcock's arrived - I have taken to buying Amal spares from Hitchcock's, since their postage and packing costs, a flat fee, are more reasonable than Burlen's. 

It's a matter of a few minutes work to change a main jet, and have a look at what I found. The question we have to ask ourselves is when is a 120 main jet not a 120 main jet? And, as you can see from the picture, when someone has stuck a drill through it!

Afterwards, I took the old W/NG on a short run to Cromer and it has now stopped smoking and is much more sprightly. I'm hoping the fuel consumption might be better, and it will stop eating spark plugs! I've done about 35 miles on the old B5HS so far, so it's definitely improving but I've installed an old Lodge HN out of the Huntmaster to see what happens. The B5HS is certainly not as light as I would expect it to be when you consider that it is too hot a plug for this engine.

QR50 - Frame: can't see the wood for the trees

Something has bugged me about this bike for a while, something I couldn't quite put my finger on. It started with a Honda publicity picture showing an exciting red dirt bike, typical of their 80's dirt bikes, and a dirty old relic in an ebay picture which strangely gave no hint of Honda's magic.

One day, fitting the silencer and trying to determine the right position relative to the frame and engine I saw what I had been missing. Take a look:

I had been using this picture to scale the size of the silencer:

Seeing it for the first time, I realised why the seat didn't fit properly and how the rear wheel had come to wear a hole in the mudguard. It took half an hour to get the bike off the bench, lift the frame off the engine and remove the forks. 

I put the frame in the vice, holding the rear frame loop on one side and applied some heat - the frame soon moved, and I flipped it over to bend the other side. I made the bends gradually, turning the frame each time so that I could be sure that the bends were going in the right place and that I did not overdo it. 

The seat now fits properly, with the rear bolt holes aligned with the frame lug. 

Sunday, 20 December 2020

Mini-Lathe - Cutting fluid feed

Doing a lot of parting for the various fasteners I am making at the moment led me to contemplate improving the manual drip oil bottle approach I have to feeding cutting fluid, which led me to eBay and YouTube to see what others were doing. A bit of slow-time at the computer led me to a simple drip feed oiler solution and as I’m lucky enough to have a lifetime of oddments knocking around the workshop, I thought I could easily build something without spending any money.

The solution started with a bit of 3/16” copper brake pipe, which I bent into a ‘question mark’ shape, squaring one end and filing a shallow angle on the other. It’s held by a piece of black Acetal round bar, cross drilled 3/16”. The plastic bar is very short, about 3/4”, and has a strong circular magnet attached to it with an M5 countersunk screw which is threaded directly into the Acetal:

The copper pipe is shaped so that the magnet can sit out of site behind the splashback. There is a pvc tube (fish tank air line) attached to the copper tube which leads to a valve, again a fish tank component: 

The valve is metal, to avoid any compatibility problems with cutting fluids and plastics and is there to shut off or restrict the flow of oil. The fluid comes from a washing up liquid bottle (told you it was cheap) hanging on a hook on the wall and full of oil:

 Fully open, the oil drips at a reasonable rate:

Tuesday, 8 December 2020

FH - Swinging Arm bushes

A while ago, last May in fact I removed the SilentBloc swinging arm bearings and I wrote about it here. Since then, lots of things have got in the way - not only the Honda stuff, the QR50 and the CX500 but also the rear mudguard and the oil filter for the FH and of course the W/NG engine rebuild. Anyhow, as regular readers will know, the oil filter is done and I am on to the swinging arm. I'm doing this next as I want to check the oil filter will fit (and can be re-fitted) with the FERC in place and I can't do that without the swinging arm fitted, so here goes.

Before I start, the inspiration for this job, the details of the bushes and indeed the spindle (and it's machining) came from Steve Carter, who's done more miles on Huntmasters than probably anyone alive today and who is a stalwart member of the AOMCC and a daily contributor to the AOMCC forum.

Thanks Steve.

So, I have two oil filled bronze bushes measuring 22 mm ID x 32 mm OD x 50 mm long that I bought from Simply Bearings under the part number AM2232-50. The cleaned out journals for the old SilentBloc bushes measure exactly 1 1/4", which is 31.75 mm and we will want an interference fit of maybe 0.002" or 0.05 mm.

Well, you know what is coming next don't you. Charlie will start banging on about the virtues of his mini-lathe. What puzzled me for a while was how to hold the bushes to machine the outside diameters to size - I considered expanding mandrels, grub screws in a mandrel and Loctite. I was nervous of using Loctite as the these bushes are porous and I was worried about getting the bush off the mandrel.

As it happened, I just went for it and did it. This Ever Build cyanoacrylate is old and cold and may not work very well but I put a 1/4" wide ring of it around the 22 mm mandrel and slid the bush on - in a few minutes it was set.

I machined the bushes quickly and easily to size using the power feed and a carbide tipped left hand tool running at about 400 rpm. and it cut beautifully with no complaints from the glue. Actually, the cutting forces probably don't test the glue very much as this bronze is quite soft.

When considering fits, I had thought about cutting a clearance fit and using Loctite 603 Bearing Retainer, but discarded the idea as I should be able to machine a reasonable interference fit and not require a liquid retainer. As it turned out, this worked beautifully with the first bush which had a medium driving fit, but I cut the second one slightly undersize so I used some retainer with that. They both held up to the reaming forces.

The mandrel knocked out very easily and the bushes were pushed in flush with the end of the swinging arm tube, since I knew that there was minimal end float with the swinging arm in the frame:

The spindle material I got from Steve was 7/8", which is about 22.25 mm so we needed to ream the bushes. The spindle needs to carry the original stud through the middle, which created a problem - my lathe is not long enough to drill out a suitable round bar, nor does it have the capacity to pass such a bar through the lathe spindle. This is where Steve comes in again - he had a bit of bar long enough to provide spindles for two of his bikes, mine and another friend’s so he ended up making four. All I had to do was trim it to length to suit my frame, which I could do with a fixed steady. 

With the reaming done, I could oil and fit the spindle - fortunately it fitted both sides simultaneously with out any adjustment, so I was lucky - I had taken no precautions to align the bush I was reaming with the other bush.

The fit is great - there is no play that I can feel on the bench, though it may be a different story when the bike is on the ground.

Last thing I need to do is fit a grease nipple, though I want to assemble the arm back in the bike so I can see where to put the nipple for best access.