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:

[Weldangrind]

After some sleep, it occurred to me that the AIR device is responsible for the back-firing, more so than the mixture screw. I removed it this morning and removed the muffler for a little flat black heat paint.

After work, I'll fabricate a block-off plate for the AIR device, re-mount the muffler and tune it again.

At the last test run, the torque off the line was acceptable, and the top speed was much improved. However, the mid-range is suffering a bit, and I attribute that to the stock variator. I'm considering new sliders / rollers, although a bigger main jet might solve the issue.

[FastDoc]

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

Another great example on how poorly adjusted valves show up in all sorts of odd problems.

Another thing that could have caused no starting after a crash could have been a damaged sidestand, brake, or clutch 'safety' kill switch, or the kill switch itself.

I took it for a victory cruise, and was rewarded with a wicked gunshot-like backfire upon coming to a stop.

Is that even legal in Canada? :wink:

[Weldangrind]

It was impressively loud.

in retrospect, it was because of the AIR device that was injecting oxygen into a low-restriction exhaust. That's gone now. A smog-ectomy, as Spud is fond of saying.

[FastDoc]

BTW, Weld, I should have mentioned right off the bat, good on you for helping your Pastor and friend.

[Weldangrind]

In your words Doc, happy to serve.

[Weldangrind]

Made a little more progress tonight after the disappointing Canucks in Boston game #6. :(

I removed the offending AIR device and dismantled it to form a block-off plate. Upon looking it over, I realized that it was already equipped with a large rubber hose, so I just removed it and plugged it with a bolt. It saves fabrication time for something that will never be seen, and it already has a decent gasket.

Here's the block-off plate that was recently liberated from the AIR device and plugged:



Here it is installed. Once the cover is back on, nobody will see it.



Since the AIR device is gone, it no longer needs a vacuum hose. As such, I removed both vacuum hoses and replaced them with one quality hose that simply goes from the vacuum source on the intake tube to the fuel valve. I also replaced the fuel line with good quality hose.

I took Reveeen's advice and routed the vent hose up high and out the back. I inserted an old automotive vacuum fitting on it for some mass and to achieve a 90. Any comments Reveeen? Is this suitable?



Tomorrow, I plan on welding small bungs onto the Beast muffler that will accept the original heat shield. It will offer some protection, and it will restore a little bling.

[Reveeen]

1) I cut the tube off flush (on the air injector plate) and stuck a pan head bolt in there. (just because that is what I had close to hand)
2) that's the idea with the vent tube, high and long.
3) when they backfire like that it means rich (but who cares?)

Wait until you encounter no spark with the side stand down.... I'd like to know who *thinks* this stuff up? (trust me here... you ONLY drive a bike away ONCE with the side stand down)

Isn't that a "sweetheart" of a muffler?

[Weldangrind]

Yeah, I found the no-spark symptom with the stand down. :roll:

The Beast muffler is so much better suited to this application. The sound is acceptable and not too "tinny", and the internal tubing matches the entry tubing.

Thanks for your feedback on the vent hose. Is a catch can a benefit?

[Reveeen]

Is a catch can a benefit?

A catch can provides 2 functions:
1) it's a bit more environmentally friendly
2) it provides a vent "maze", where stuff is slower to go out, and conversely, it slows up stuff from going in.

Motorcycles all vented directly to the atmosphere before the foolishness started. Probably an air filter of some kind would be a better choice, K+N makes one, for $22 (wasn't worth $22 to me). Maybe a piece of foam retained by an elastic band? But if you think about it: the oil vapor trying to escape would coat the tube walls and trap most stuff trying to invade. I could see making the great effort (or spending the $22) if you were operating under dusty conditions, but under most operating conditions it should be ok.

[Weldangrind]

Ok, I'll let it ride for now. If it starts to be a problem, maybe I can try a large fuel filter.

[Jim]

Originally Posted by Weldangrind

Made a little more progress tonight after the disappointing Canucks in Boston game #6. :(

Does this mean you've jumped on the band wagon?

[Weldangrind]

Not really, but it was a disappointing game. Here's to game seven!

[Weldangrind]

I finished welding the bungs onto the old Beast muffler, so I painted it and installed the original scooter heat shield. It looks ok.

I rode it over to Jim's house tonight, and I was able to cruise above 70 km/h! I actually passed three cars in a 60 zone. All of this is still with the stock #80 main jet, so I'm hoping for good things with the new 88 that's on the way. Curse the Canada Post delay. :(

Jim took it for a quick rip, and he couldn't stop grinning. He loves the exhaust note of the new Beast muffler, and he couldn't believe that he is now able to bury the speedometer (it only goes to 70). I'll report any changes after installing the new jet, if it ever arrives.

Here's the new heat shield on the Beast muffler:

[FastDoc]

Well done Weld!

Even Pastors are allowed to have fun. Mine drives an old 'Vette. 8)

I remember my buddy's Catholic priest when we were growing up. I was still Jewish at the time. The priest drove a Fiat Spyder. I though that was the coolest thing. My rabbi drove a Rambler. :roll:

If I ever become a Pastor I'd be sure to ride to church on a Chinabike. :wink: