My free SL350!

[NJ-Brett]

I love those old bikes.
I would love to get one and could kick myself for not picking up a rat one that was for sale close to my house last year.
It would be nice if they made a bike like the sl350 these days, that you could get parts for, etc.

For the last 5 years I was dual sporting a 1969 Daytona, but that motor has various issues that its hard to correct.
Parts were not a problem though...

I wonder if you could sort of convert a cb350 into an sl350 sort of bike.

[LC Garage]

"I wonder if you could sort of convert a cb350 into an sl350 sort of bike."

I think the short answer is YES. The early SL350's were really just converted CB/CL's, they even had the electric start. My first 350 was one of the early SL's and it was a great bike.

[Sniper X]

You aren't sure how impressed he is? Out on a limb here, but not very.....Cool dog for sure though!

[Mr. Vintage]

So this last spring I decided to dig into some maintenance items on the SL. The fork seals have leaked almost from the day I put them in, and the front brake de-adjusted itself. The fork seals were a sinch, but the front brake took a little research. If you don't have it adjusted right, the double-leading shoe brake becomes single-leading shoe and doesn't do much of anything. I did a little research, and it turns out you can only really adjust by feel - adjust the first shoe to barely drag, then adjust the second to barely drag twice as much. Seems to work much better.

Then it all went south. I released the timing chain tensioner, and something didn't feel right. So I pull the drain plug to change the oil and I have aluminum shavings, again, lots of them. Crap. Removing the tensioner spring from the back of the cylinder head, I found the remains of the tensioner pulley wedged in the hole:

You have to remove the top end to replace the tensioner so it's engine out:

So I need a new tensioner pulley. I considered the KA Performance slipper tensioner - I can't really fault the design, but I'm a glutton for punishment and really wanted to make something with my lathe. I had read somewhere that the chain pitch for a CB350 starter sprocket was the same as the timing chain. I dug a starter sprocket out of my archives and, copying the design of the disintegrated tensioner, I hollowed out the sprocket, and made a plain-bearing bushing and pin.

But I could never really convince myself this was a good idea. At redline this little pulley is spinning at something like 11,000rpm and it's only oiling is via whatever happens to spit on it from the chain. About this time I decided to disassemble the original tensioner to use its parts, and had somewhat of a revelation.

[Mr. Vintage]

The tensioner I bought as a replacement a few years ago was not a Honda part. The OEM piece is a needle bearing, so it requires hardly any oil for lubrivation - this is key given it's location. I'm not really sure whether the failure here was related the bearing, the rubber wheel, the age of the part, psychotic riding, or what - but the lesson here is that cheap aftermarket parts aren't always the greatest. Sometimes you learn the hard way (but at least you still learn something).

So I decided to make a new pulley out of nylon, actually Nylatron GSM which is impregnated with moly and should allow some degree of slip with minimal friction. I took some dimensions:

Then took off the rubber to use the bearing parts from the factory tensioner (it's in fine shape).

It took a few tries before I was happy with it, but the completed tensioner wheel was press fit on the bearing. I also made another pin, and peened the thing together. (The key here is aligning the holes in the pin and the bushing so what little oil this part sees makes it way into the needle bearing.) I made the wheel as big as would fit in the bracket, logic being that it would turn a little slower. What I didn't consider was that this would push the tensioner just out of the range of the spring assemby, so I had to shorten the spring plunger shaft just a bit to make it all work (I didn't manage a picture of that).

I also made a new bushing for the center of the kick-start idler - this is one of the parts that makes this SL bottom end unique from the CB/CL. The bushing was shot the first time I had the engine apart, but since the part is unaviliable I decided to live with it (I dremeled on it a bit in an attempt to keep the wobbling to a minimum). But with the lathe I roughed out a bearing from mild steel, press fit in the gear, and then machined the inside to size. Much better.



I also split the cases to replace the timing chain (again) and clean all the latest swarf out of the sump. I expected the old chain to be loose, but it was actually tight in places.

Engine back together!

[Mr. Vintage]

In short order I had it all back together and running briefly in the shop - it runs much smoother and quieter without the timing chain flopping like a rice noodle. Well heck, I need to ride this to work. On the way out the door yesterday:

A few miles down the road, while blissfully enjoying the ride, I happen to look down at the engine. Yikes! Oil is spewing everywhere! I immediately knew what had happened, as I did this before (I'm a bit slow sometimes) - the cam bearing gasket was in backwards. Oh well, I can fix this along the road. About then it starts to rain, hard - it hasn't rained here for 2-1/2 months. The mix of oil and water make everything brutally slippery, but I manage to get the gasket flipped.

I eyeball the tappets and figure I'll limp it home. But in my excitement to stop I left the ignition on and the battery is completely flat. I concede defeat (I have a meeting with the boss too), and have a friend come pick me up. I grab the van and a trailer and run it home. Note the oil slick!

This morning I charged the battery and readjusted the valves - bike runs great and all is copacetic. Just as well it didn't start as it was a full quart low (it only holds two). I'm anxious to really ride it somewhere, but this weekend I have to be in a wedding....

[Mr. Vintage]

[OldCoot]

Great write up. You sure are a patient man. Nice pics of a beautiful area, too.

My first bike (that I bought) was a red SL350... I think it was in '69... $800-$900 brand new. Did that 4-stroke redline at 9-10k?

[patiodadio]

Great looking bike ! Bravo for bringing a cool bike back to life !




.

[Mr. Vintage]

A couple weekends ago I took the SL on a 170 mile ride to the Dent Bridge in Idaho:


After riding my big bike a lot, it always surprises me how well the SL does for these kind of trips. As long as you don't have unrealistic expectations of going 70mph everywhere it has enough power to move you at a good clip, and even on the paved section can make pretty good time. It vibrates, but you get used that (i.e. go numb ) pretty quick. For what it lacks in suspension technology it makes up for in a low center of gravity and a comfortable riding position. It really excels on gravel forest roads, and all around it's just fun. And reliable, in a 70's Honda sort of way - it always needs some attention, but will get you home anyhow. It was missing under load for much of the trip - I think the oil streaming out of the points cover might be a good place to start troubleshooting that....

[BAGSTR]

[JasonLester]

Hello,

Love the bike and the rebuild. I have three SL350s. Dad had one in the 70s when he was in Alaska and we got these three to try to make 2 good ones out of. We both also ride KLR650s and have riden them to Alaska a couple times (actually the bikes are there now and I await my time to fly back up for the ride home)

So since I am missing my bike I figured I would revisit my SL350 and I stumbled on your thread... I love that there are people riding these. I hope to get our two going so we can ride them some...maybe even to AK.

[McJamie]

Originally Posted by Mr. Vintage

A couple weekends ago I took the SL on a 170 mile ride to the Dent Bridge in Idaho:


After riding my big bike a lot, it always surprises me how well the SL does for these kind of trips. As long as you don't have unrealistic expectations of going 70mph everywhere it has enough power to move you at a good clip, and even on the paved section can make pretty good time. It vibrates, but you get used that (i.e. go numb ) pretty quick. For what it lacks in suspension technology it makes up for in a low center of gravity and a comfortable riding position. It really excels on gravel forest roads, and all around it's just fun. And reliable, in a 70's Honda sort of way - it always needs some attention, but will get you home anyhow. It was missing under load for much of the trip - I think the oil streaming out of the points cover might be a good place to start troubleshooting that....

Keep riding it like it was intended to be. That's what it's for.

[woolsac]

Originally Posted by Mr. Vintage

After riding my big bike a lot, it always surprises me how well the SL does for these kind of trips. As long as you don't have unrealistic expectations of going 70mph everywhere it has enough power to move you at a good clip, and even on the paved section can make pretty good time. It vibrates, but you get used that (i.e. go numb ) pretty quick. For what it lacks in suspension technology it makes up for in a low center of gravity and a comfortable riding position. It really excels on gravel forest roads, and all around it's just fun. And reliable, in a 70's Honda sort of way - it always needs some attention, but will get you home anyhow. It was missing under load for much of the trip - I think the oil streaming out of the points cover might be a good place to start troubleshooting that....

Love the thread. Hope she's still kickin'

[Mr. Vintage]

Originally Posted by woolsac

Love the thread. Hope she's still kickin'

Yep, nothing epic - just to work and back lately. Working great!