1970 SL100

[bmcdonau]

I removed all the parts I can off the bottom end and took off the top end today. I'm stuck until I get the rotor puller I ordered from Motion Pro. I halfheartedly looked for a 16 mm 1.5 bolt today, but no one seems to stock one that large.





The clutch was pretty easy to get off, pull out the actuator, loosen four bolts and slip off this collar that holds the springs.



Then this circlip comes off and off comes the clutch basket along with the steel and fiber plates. This was a wierd looking circlip--there weren't any holes in the end to grab.



This is next item to come off, its called the external shift mechanism. The engine shift actually exits the case on the right side and uses this mechanism to connect to the shift shaft which then transverses the entire engine and comes out on the left. I guess the bottom end of this engine dates from the time when things shifted on the right.





The removal steps.



this is one of the things you have to be aware of when you take things apart. That little nub looks like its molded into that bushing sticking out of the case.



In reality, its a small piece of metal which is easily lost if you don't know it comes out.



Everything is off the right side of the engine.

Off with its head.

















Removing the points and mechanical advancer to pull the cam. More of the same type of screw heads. I had to get out the easy out again.



removing the head only required removing four acorn nuts and one long bolt plus disconnecting the cam tensioner. This is the bolt that secured the cam tensioner. More hamfisted mechanics. I don't know why this bolt didn't strip out the threads from the head or break off in the head.



The head removed.



I turned the crank and the piston movement popped the cylinder off the cases. Cool, I've had to fight some of these for hours to get the head off. Multicylinder bikes can take days.



piston and rings don't look good.





Neither does the cam tensioner. The guide which goes on the other side looked pretty good though.



This is the journal in the head where the cam rides. Its gouged and scored. Luckily, I bought another head when I bought the cylinder. They came off the same bike and I thought it'd be a good idea to keep them as a set.



I wiggled the piston to see if it had any play in the wrist pin and it did. Problem is I don't know if its the pin, the conneting rod or the piston. I probably should replace all three if I can find the parts. It all depends what the machine shop tells me about the cylinder bore.





the piston and rod look bad.

I have to get my head around the parts I'll need and I'm terriable at making lists.

The rotor puller should be in Wednesday and I can split the cases and take out the crank. This is a two piece crank and I'll need the machine shop to take it apart and replace the connecting rod if I go that route.

Stay tuned.

[The Big Spank Daddy]

It just amazes we how we ever got stuff like this done back in the day. Modern tools are such a time and part saver today. I remember whenever I got a new bike buying an Allen head screw kit to replace the all the Phillips headed screws on the engine. Those kits where a popular sale item over the parts counter back then.

Now today, we have all kinds of easy outs, special drill bits, cobalt drill bits, Drill Doctors to perfectly sharpen those drill bits, cordless drills and impact drivers, etc. I’d be lost at work without them.

[bmcdonau]

I'm taking the cylinder and case to the machine shop on Monday. I need them to measure the bore and tell me if I can just hone it and use the standard piston I have or if I'll need a rebore with new piston and rings. I'll also get them to remove the bearing fom the left side of the crankcase.



Today I did an inventory of the gasket kit I bought and found its pretty complete, but there are lots of o-rings which weren't supplied. I'll have to order about 8 different ones for things like the clutch lever.





I usually send stuff out to be sand blasted, but I've never been able to refinish aluminum parts to look like new so I decided to get a blast cabinet. This one from Harbor Freight was only $119 and I also picked up some glass bead which says its for aluminum.

Once I got the cabinet set up I cleaned up three of the case parts to be blasted. This thing uses a lot of air, but it works really nicely.



Before



After



can you tell which one has been bead blasted?

I even tried it on the petcock.



Before



Halfway



Finished. A new gasket kit and this will look and work like new.



These two looked alike when I started.

Now I'm looking for anything aluminum to blast!

[DaveC]

Soda is suppose to be a good medium to use on soft metals. Carb bodies and such.

[bmcdonau]

Originally Posted by DaveC

Soda is suppose to be a good medium to use on soft metals. Carb bodies and such.

That's what the guys on the SOHC forum use, but that seems expensive since you need about 5-10 lbs at a time. I also bought some crushed walnut shells which is the same consistency.

[owtcast]

Wow. I wish I had your patience and tenacity. Looking good.

[The Big Spank Daddy]

I bought a sand blast cabinet several years ago. Its great for the exact stuff your doing. However, the media itself tends to break down into a finer dust. Make sure you thuroughly clean all the parts afterwards.

[Buellboy]

Brings back lots of memories of my SL race dirt bikes of the early seventies.
Replaced lots of pieces on hopped up SL100-SL175's chasing two strokes.

[bmcdonau]

Originally Posted by The Big Spank Daddy

I bought a sand blast cabinet several years ago. Its great for the exact stuff your doing. However, the media itself tends to break down into a finer dust. Make sure you thuroughly clean all the parts afterwards.

I noticed that, I'll be sure to clean everything thoroughly. I removed the bearings from the cases so I wouldn't have to worry about cleaning them up.

[bmcdonau]

I dropped the cylinder, head and left case at the machine shop on Monday. He said the bore looked iffy so we'll see if I need a quick hone or a honest to goodness overbore. The valves are good, but I'm having the clearances checked, valve seal (only one) replace and valves lapped. There is only one valve seal, on the exhaust valve. Weird design.

There was a guy in there with a crank from a Ford 460 and he recognized the head right away as he was a certified Honda mechanic in another life. He said there was only one valve seal because the inlet valve was cooled by fuel and didn't need a seal. I guess when you are building these little bikes you have to cut costs every where you can to make a profit. How much does a valve seal cost? Multiply it by about a million world-wide and you're talking about real money.

[The Big Spank Daddy]

Yep, we have a lot of John Deere engines like that. At first I thought I was seeing things. Then a long time mechanic explained it to me that they were made that way.

[Shadman]

I have a good condition SL100 motor in a box in my garage. Been there for 5 years, never really knew what to do with it. Now I know....give it you. I am 90% sure it's an SL100, but it may be an SL125. I'm gonna go check it out right now and post up what I find. Sorry I just found your thread now.

I can give it to someone in Big Bend this weekend who maybe can get it back to you in SA. I'm in Houston.

Peter

[Shadman]

OK here is the bad news...it's not an SL100 motor. And it has leaked most of it's oil out in the tub thru the cam sprocket cover.

[Shadman]

...but the good news it all looks to be as I remember it...good working condition, turns over freely, no external damage, should run with carb and electrics. And it is a CB100 motor. Should be a direct bolt in and identical parts swap. I could also bring it to San Antonio on March 11th - 12th when I am visiting my brother.

Peter

[bmcdonau]

Originally Posted by Shadman

...but the good news it all looks to be as I remember it...good working condition, turns over freely, no external damage, should run with carb and electrics. And it is a CB100 motor. Should be a direct bolt in and identical parts swap. I could also bring it to San Antonio on March 11th - 12th when I am visiting my brother.

Peter

I'll take it! Thank's Peter. March is good, thanks again.

[bmcdonau]

Well, the 16mm rotor puller I ordered from Motion Pro didn't fit, it was too large and they don't list a 14mm one. I looked on e-bay and found one for $8.99 with free shipping and it was here by Saturday.



Here it is installed, you just turn it and it pulls the rotor off the crank.



once the rotor was off, you have to take the woodruff key off the crank.



There's nothing behind the rotor and stator except the cam chain tensioner.



After the tensioner is out all you have to do is take the case screws out and split the cases.



That was another exercise of pure joy. Not! More stuck screws. This time I used a big easy out and didn't worry about it breaking or the heads coming off the screws.



The crankshaft. The left case pulls off and the tranny and kickstart shaft stay in the right half.



Kickstart



Transmission.

the left case and cylinder and head are still at the machine shop. they should be back this week. Regardless of what I found out about the cylinder, piston and rings, I'll be able to put the bottom end back together this week.

[bmcdonau]

I'm at a bit of a standstill right now. I use Clay's machine shop on South Presa in San Antonio and they do a great job. Its a bit of an old fashioned place as it looks like machine shops I visited with my dad. They have one guy who does the motorcycle work and he's been sick. Hopefully he'll be back next week.

In the mean time I picked up a parts bike with two engines in Ft. Worth today. I needed the frame and handle bars, but I think I can probably build another engine out of the two.

[bmcdonau]

I finally got the parts back from the machine shop today. All good news, the piston is reusable and the bore is good and stock size. The exhaust valve seal was replaced and the valves lapped. I'll be painting the cases and rebuilding the bottom end this week. I ordered new standard size rings and some misc parts I need to finish the motor. Hopefully I'll be done in a couple weeks.

[Coolhand]

Wow, excellent thread. Thanks a bunch

[SL350]

Yea, this is going to be a new bike, top to bottom. Nice to see so much attention to getting it right.