SWM Jumbo PWK install details and photos

[drca]

I’ve finally found the time to start working on the SWM 350 Jumbo I picked up last spring.

The previous owner had installed an electronic ignition that failed on him, so he reverted back to the stock point ignition. I reached out to the manufacturer (Rex’s Speed Shop in the UK), sent them the unit for testing, and, sure enough, the electronic ignition module was dead (which, according to them, never happens!!!). I got a replacement ($$), installed it, and got it all set up. The installation is pretty straightforward—you just need the right flywheel puller (which, of course, I didn’t have! 😒).

Next, I replaced the rear shocks. The bike had aftermarket Works Performance units that felt tired are no longer supported, so I swapped them out for a set of new shiny Falcon shocks (steel version), tuned to my weight.

I also installed HFS fork cartridges that I had ordered.  Installation pretty straightforward too.

Then came the carburetor. The only time I ran the bike, it was running horribly rich and leaking gas. So, the Dell’Orto PHBH 28 BS was due for a full rebuild and some new jets. But then I realized I had a spare Keihin PWK 28 lying around. Since all my other trials bikes use this carb, I am pretty familiar with it and I have a full set of jets for it. Would it fit? A quick check said YES 😋.

Off to the 3D printer I went, and a couple of hours later, I had a prototype mount—duct tape and all! I used the standard jetting I run in my modern trials bikes (280cc): a 125 main and a 48 pilot jet.

Took the bike out of the garage, put some gas in the tank, choke on... kick... The darn thing started 2nd  kick 🤩 and after warming up and a couple of adjustments on the air screw it ran like a champ! Yeah!

Next is finalizing the mounting and getting a trials appropriate needle (that particular carb was came off a MX bike and is running a MX needle).  And oh yeah... fix these horrible foot pegs! These have to be the worst even fitted on a trials bike.

I'll test ride it at the trials park tomorrow and see how much improved it is compared to the previous time I ran it.

Yeah, I know it's probably possible to make the bike run as well with the Dell'Orto than with the PWK, but in my experience (having done the swap on a couple of Gas Gas TXT Pro) the PWK is much easier to work with, get parts for, and tune.  But other people experience might be different.

Now, some people are going to say all these mods might not be permitted in Vintage trials competition (hydraulic clutch, D-slide carb in particular I think).  Well, here (West Coast USA) for the local club events I am going to run, the class I'll run is "twin shocks, air cooled, drum brakes".  Anything beyond that is permitted. 😁

Happy trails.