Working on two fronts

Spent some of the weekend working on two of the bikes; the SC500 and its long awaited engine rebuild and the timing on the Husqvarna WR250.

SC500

Going back to April, I’d damaged the cases on the SC500 at the Llanthony Clyro meeting, following a failure of one of the dog gears. Lack of oil seeming to be the reason for the failure. The cases had been repaired and I’d reassembled the bottom, but decided at getting another bottom end.

With the acquisition of the replacement from California Connections / AP Motorcycles , I’d started looking at the rebuild. The original crank had a damaged rotor nut thread when I had it, and getting it out of the crankcase didn’t improve matters too much either. Therefore used the crank that came with the new cases.

Though I’d rebuilt the engine originally, getting the crank out of the cases turned into an epic and needed the use of plenty of heat, and my oven, in order to get it down. The balancer shaft had already been removed from the replacement case and therefore I’m guessing it had been raced at somepoint in the past.

Rebuild went okay, but left with a couple of issues that need resolving:
• the rotor for the PVL ignition was catching on the stator and though there is some room for adjustment, I couldn’t get it to run true and it therefore goes solid when you tighten the stator plate.
• the clutch basket is excellent hasn’t got the wear the original has, though it seems a little reluctant to get into place.

Husky WR250

I’d done a brief look at the bike after picking it up and the main issue was the lack of a working ignition. It may have been DK who’d look to put a Motoplat ignition coil on the bike with the Femsa stator and rotor in order to make it work, but that wasn’t going to the solution.

Some research had shown that for WR’s of the period, with the larger crank ends, that PowerDynamo ignition was the way to go. They may not provide greater performance, but as experience as shown, there’s nothing like a modern electronic ignition to transform a bike. The PowerDynamo kit – has the signification advantage in that it supports lighting kit. The WR250 RT was a road-legal bike, and using their AC kit, getting a rear light and headlamp in place isn’t going to be an issue. They do an DC kits also, but don’t have a battery and unlikely to fit indicators.

The ignition got delivered 3 days after ordering, and although the 20 euro delivery charge to the UK wasn’t cheap it worked.

Installation was pretty straightforward, though the LH thread rotor nut supplied wasn’t correct (maybe this is for the RT model only ?), so reused the existing nut and a couple of washers. The block connects aren’t the best and the PVL kits are better quality. That said, after resoldering some new connectors on, the bike actually fired first kick (see below on other items)

Timing the ignition wasn’t too bad, but Husky timing information (from both the Clymer and Haynes manuals I’d acquired) is in degrees BTDC, rather than mm’s of piston travel. Therefore borrow Tamara’s protactor, and chalked up the measurements on flywheel. It’s clockwise rotation, so the firing mark is 22 degrees anticlockwise of TDC, ie to the right of the TDC mark. Therefore, got the piston to TDC and then aligned the flywheel, before tightening the nut and then checking it to ensure the crank hadn’t moved.

Working out the Timing

The Mikuni carb had been left with petrol in it, so after a quick look, decided to bolt on the matching carb from the Yamaha MX250. A strip and clean on the agenda, if I can battle my way through the smell of stale petrol, my favourite. Though the original carb was a Bing, I’m not going to be loosing sleep on its orginality.

Also ended up using the plastic tank from the Yam, as the whilst externally in good external condition, there was some rust inside the Husky tank, maybe the difference of a bike from Colorado rather than one from California. I doesn’t look too bad, but will need an application of brick cleaner and maybe some stones rattled around inside it as part of the clean up. Petrol tap needs de-gumming.

A running Husqvarna

The engine ran okay, but a bit noisy and I’ll plan on doing the bearings and seals once I’ve finished the 500 engine currently on the bench. However, optimism abounds once you actually get the thing running, however briefly.

In terms of other parts, the bike needs:
– lighting. This is going to be non-trivial to get the original Husky units, but I’ll probably go on the hunt for some period replacements. There are some good aftermarket D250/400 headlamp repo’s which will fit nicely and will work with the 12v output.
– cables, need a front brake cable, for the full width hub that’s fitted and a new throttle cable.
– brake pads; not essential but to be sourced
– seals and bearings; the engine is going to need a rebuild, but it’s in the queue along with the SC500 and another MX250 engine that needs doing.
– tank sealant, will probably find something to line the tank.

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