While waiting for bits for the QR50, I took the opportunity to refinish the horn for the Huntmaster. It tests OK in that it pulls a current and deflects the diaphragm, so some adjustment will have it working. Lucas catalogues are very useful. This is catalogue 716A, section F - six pages of horns and horn pushes. The application page tells you which part number you should have: In the case of my 1958 Huntmaster, it's a HF1441 model horn, part number 70048. The spares list tells us a bit about it: It's black, and looks like this: So, I had the correct horn (bought from eBay I think - it w ..read more

 With the little QR50 out of the way and the FH back on the bench, we can get on with the build. The barrel has been painted for a while, the bottom end is in the bike, there's no primary or timing side and no pistons. Off we go: First step is to fit a circlip to each piston; the gudgeon pins come out with some mild warming and are refitted just as easily. As you can see, I've put a large rag under the pistons as I don't want a circlip in the crankcase at this stage, and the pins go back in and the circlips go on without any drama. Next, we can refit the reground cam followers. I've gro ..read more

 After three years in the field, the little beast is back. The boys are complaining the bike has no power after ten minutes running and with busy lives, my son and daughter in law have no time to check it out - so it’s back to Grandad’s workshop. The Square Four is now off the bench to test the kickstart against the clutch, and then close up the clutch, refit the exhaust and test ride it. All went well with that, so the QR can go on the bench: The first thing to attend to, and rather alarming, is the fact that the fork top threaded inserts are both loose. Now, these had a ring machined ..read more

 After spending the winter rebuilding the gearbox and the clutch, I'm pleased to be finishing the job as the weather warms up. First job, before finally closing up the gearbox is to fit the kickstart stop rubber that has been waiting on the bench for literally years. I needed to remove the metal part of the stop and reduce the 1/2" OD to about 7/16" to get the rubber to go over it. I mangled one in the process of realising that, which delayed the job by a week: Next, when the kickstart is on and the gearchange mechanism is timed, I need to fill the gearbox. This is easier said than done ..read more

 While waiting for the kickstart rubber, I've degreased the FH barrel in the cleaning tank and given it  good scrub and scrape. Removing the rings from the new + 0.060" IMD pistons and testing them for fit reveals a nice 0.004" clearance in both barrels, per the IMD recommendation. Therefore, it's time for a coat of engine paint. This is the same stuff I used on the W/NG which seems to have survived OK ..read more

Are events coming back to bite us? In this recent post I commented on some intermittent clutch problems - maybe we are now finding the cause. Three of the four plates are like this, and the colour reveals they have been hot: This is a new set from AOMCC Gearbox spares, laser cut, a realistic price and flat as a pancake. We are getting near closing up now. All I need is a kickstart rebound stop, which is coming from Draganfly, and I can refit the kickstart and the gearbox end cover. Then I can test the kickstart and set up the clutch ..read more

 Over the last few days I've assembled the primary drive and the clutch, tightening the mainshaft nut in the process. I've installed the clutch spring studs with Loctite 271, the red thread locker. That won't come loose; originals were peened in place, but it's not 1950. Fitting the plates revealed some rocking. I pulled them all out again, and found that three of the four plain plates were distorted by up to 2 mm, and discoloured from heat. Geoff will send some new ones tomorrow ..read more

 Now we know what we have to do, we can get started with the rebuild helped by these lovely new bushes from Geoff at AOMCC Gearbox Spares First job is to remove the two Welch plugs over the layshaft and camshaft; I drill a hole in these and lever them out: With some heat in the casting, you can drift the layshaft and camshaft bushes out from the drive side: The sleeve gear bushes come out with a bit of tube; the new ones go in with a large flat drift. They go in quite easily with a hammer (you don't hit the bush directly), but it's times like this that I wish I had a press. The n ..read more

Starting the Square Four up mid winter is something I do at least once a week just to make sure it's all working, which it usually is - except when it isn't. This week I was met with an unexpected noise, like gear-dogs clashing - it sounds like it does when you put it into first gear. Listen to the sound, especially obvious around 28 seconds: The noise stops as you disengage the clutch (which is dragging badly) as the mainshaft slows to a stop. It's also not present if you run the bike in gear on the rear stand. Casting to the forum & FB world for advice, I ended up having a chat with AO ..read more

I'd been dreading this job, but needs must. I was forced to face up to it because I needed to get the Square Four on the lift in order to look at the gearbox before the riding season begins, and I didn't want to resort to holding the stand up with an aerolastic. The way I did this was to take a piece of 2" rolled angle and drill a 6 mm hole at one end; I put a long M6 screw in the hole, and the small eye of the stand spring over the screw. Then I took a bit of 1/2" round bar and used it to stretch the spring by levering it against the end of the vice; I put a 5/16" washer in each of the gaps b ..read more