Jim's Saga Scooter Trouble

[Weldangrind]

I spent time on this scooter this weekend to help out my buddy (and Pastor), because his scooter simply wouldn't start after he laid it down during a left turn.

In the past, we had already swapped the very restrictive air box to an open element air filter, much like a Uni pod. We also experimented with a high performance CDI, but we had not made any other performance mods.

I took the carb off and removed the jets, so I could buy some different sizes at the local Honda dealer. Based on a little research on www.scrappydogscooters.com, it is likely that the pilot jet is a #35, and the main jet is clearly marked as #80. I found a #38 and #40 at Honda, but I'll need to order a larger main jet.

I installed the #40, cleaned the carb, set the float level and re-installed it. It still wouldn't start. I loaded the scooter in my trailer and took it home.

I was quite focused on finding what might have been affected by a minor crash. With that in mind (and Reveeen's suggestion that the catalytic converter might be in the muffler), I took the muffler off for some exploratory surgery.

This is the stock muffler, replete with flashy bits:



This is the outlet spout, which is an obvious restriction:



Here's the inlet end, and it looked to me like the catalyst might be right there in the pipe transition. I scored it for reference, so I can weld it back together after.



Nope, no catalyst there. They actually used four different tube sizes to transition to the muffler. :roll: This is a shot looking into the tube, after I chopped the muffler off:



Here's where I cut the end cap off and peeked in to see how it was set up. Didn't learn much.



I removed the support bracket and chopped the inlet cap off to have a look. The cat was hiding in there.



Here's a side view of the convoluted arrangement within the muffler inner chamber. Exhaust passes through the cat, makes a u-turn back into the chamber and then exits via several small holes. The exhaust then find its way out of the exit spout.



How can an engine even run like this? Especially one that's only 50cc to begin with.



Here's my solution. Weld my recently liberated Beast muffler on. It's a decent muffler for a small displacement engine, and it's perfectly matched to the scooter pipe size (I've cut Beast mufflers apart before).



It'll get some paint tomorrow. It still wouldn't start. :evil:

What could be affected by a crash? I swapped out the CDI (twice), the regulator (twice) and the ignition coil (twice). Still no joy. I filled up the tank to see if it needed more head pressure. Nothing. I checked and double-checked every connector. Still nothing. I pulled the cover off of the flywheel to examine the pickup; I spotted the timing marks on the side. I started thinking about the ignition timing, but dismissed that idea.

By now, the reader has probably figured out what took me all afternoon. The timing marks finally clued me in: maybe the valves needed adjustment. Yep, the exhaust valve was really tight, so it was leaking pressure, rather than allowing compression to build. I set it at 0.004" and confirmed that the intake was also at 0.004", reassembled it and hit the button.

It fired right up. I took it for a victory cruise, and was rewarded with a wicked gunshot-like backfire upon coming to a stop. I turned the mixture screw in a bit (it is now 1/2 turn out from seated), and the backfiring went away. I took it for another cruise, and I was able to maintain 70 km/h at about 9000 rpm on level grade. It has never been able to attain that speed in the past.

Son of Weldangrind took it for a quick blast around the block as well, and he was all smiles upon his return.

Here's the happy scooter: