1970 Honda SL100

Actually John, POS is a pretty apt description of the before condition.

Don, wasn't meaning to diss yur new ride, glad to see we basically agree about the description. :D

The green crud in the carb is the same as I found in Dr. Z's float bowl last Thursday. Not nearly as much, tho. It's some sticky goo, had to pull the float needle with a pair of needle nose. No other clogs noted.

Keep us poSTed on yur progress. This project and the other thread about the rebuilt ST keep me inspired to do my own work.
 
Well, I reached the end of the road on this project. I was going to change the oil today and couldn't make the drain plug budge. I took a closer look and there was some type of adhesive between the bolt and the crankcase. It was hard, but I couldn't tell what it was. I got a bigger socket wrench and gave it another shot and it came loose, but the adhesive was JB weld or something similar. The crankcase had been broken and fixed by gluing the drain bolt into the case. At this point I think I'm finished unless I can find a case really cheap.
 
After thinking about it I ordered a set off ebay. I hope they're usable.
 
Hope so too!

I found this thread as I picked up a 1970 SL 100 last week end. (Google 1970 SL 100)
Thought I would follow along & see where your finding parts etc.
My bike is orig, but has the early KO smaller kick start shaft that broke off 10-20 yrs ago.
If your in there and have the smaller shaft, the 71 and on larger version is said to fit with larger case seal & kick starter.
Not sure if I am going to split the case or have someone else do it.
Here is a shot of the shaft.
Oh, tried to fire it up yesterday, only to find gas leaking from the petcock and carb, LOL LOL
Ordered a new petcock, will have to go through the carb.

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I had the broken kick-start shaft on my SL100 many years ago (1972?) No need to split the cases to replace the orginal shaft, don't know about the fatter one.
 
Really?
Thats great news!
Any details? (If you had a 72, you had the fatter one)
Feel free to E-mail or PM me.
Thanks again

MCM
 
Mine was a 70, broken in 72. It was the "skinny" one. But, I think the shaft sticks into the cases at the left end, but is mostly inside the right side cover, easy to remove without splitting the cases. My memory is a little foggy but I know we didn't split the cases.
 
Really?
Thats great news!
Any details? (If you had a 72, you had the fatter one)
Feel free to E-mail or PM me.
Thanks again

MCM

I've never done it, but the Clymer manual makes it sound like you have to.

1. Apply assembly grease to the thrust washer and hold it against the rachet.
2.Install the assembled shaft into the crankcase. Insert the end of the rachet spring into the hole in the crankcase.
3. Hook the return spring into the recess in the crankcase.
4. Reassemble the crankcase as described in this chapter.

I tried to figure out if it could be done without splitting the cases, but its all in the sequence and its difficult to determine if steps could be left out. Maybe as you are doing it you could make that determination.
 
I read the same thing. Would be nice though!

Got to keep these little guys on the road!

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Well, I gotta take it back. Looks like the cases must be split to replace that shaft. My foggy memory cleared a little this afternoon. First, it wasn't my SL100 that had the broken shaft, it was my first wife's CB-100. The SL100 came later. And, we sold the CB with the broken shaft. Same engine in those two.

I did replace a shift shaft on my 67 CL-160 without splitting the cases.

Rumaged around in my book case just now and found the Clymer manual for the 70-72 100 thru 250 singles. There is a chapter on converting the XL250 for motocross and off-road use. :D
 
I'm going to persevere on thid one just because,

I also found my next project.

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I decided to just rebuild the entire engine. I ordered a set of cases off of e-bay and will just transfer all the parts off the old engine on to the new cases.

I took the old engine out of the frame and took it to the bench to disassemble it. Before I even got the engine out of the bike, I found more problems.

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One of the exhaust studs is broken it off, the pipe hid the problem. This motor has been through ****.

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All the screws and bolts look like this.

Now I've got a new head and cylinder on the way and the new cases have arrived, but they also show signs of poor maintenance.

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This is the oil drain bolt. I'm surprised the threads weren't stripped out of the case.

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You can see how squished the crush washer was here.

I'll spend the next week disassembling the old engine and getting the new cases and head ready. I'm going to take the head and cylinder to a machine shop to make sure everything is okay and figure out what size piston and rings I need. I've also got to figure what size rotor puller I need.
 
Made some progress today. The new ebay cases had been seperated since the crank and tranny was missing, but **** if three of the screws weren't frozen.

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This is what they looked like, I couldn't get them out even with an impact driver.

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After several heat cycles with a propane torch and three nights soaking with liquid wrench one finally came loose. I was afraid I'd break the easyout if I put any more pressure on it so I decided to drill a little larger hole and use a bigger easy out on the other two.

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I got one more out like that.

Then I realized that the threads only went into the other case and if I drilled out the head of the screw I could just pull the cases apart.

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I wish I'd done this in the beginning!

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The new cases.

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This is the cam chain tensioner, it has to be removed to bead blast the cases.

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This mechanism pushes down on the tensioner which bows to tension the chain.

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I cleaned up the gasket surface with a dull scraper. I'll take them to the machine shop when I take the head and cylinder. I'll have them pull the two bearings and then bead blast the cases in preparation for painting. You can see the original machining on the bottom gasket surface of the case.

Then I went to work on the engine. The oil filter, the oil pump and the clutch have to be removed from the right side.


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The oil filter.

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Once you remove three copper screws there is a special bolt holding it on the shaft.

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The socket you need for most of the early Honda bikes.

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The nut removed from the oil filter. This is a centrifical filter which spins the oil to seperate it from sludge. Not much of a filter, no wonder the oil change interval is 1000 miles.

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The filter sits on a splined shaft. I used the penney to keep the crankshaft from turning while I removed the bolt.

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This is the oil screen which sits on the opposite of the oil filter. All the oil passes through this screen before entering the filter. I think I need a new one.

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Two bolts hold on the oil pump cover. I like these ratcheting wrenches.

I'll finish taking off the oil pump and remove the clutch tomorrow.
 
Funny those screws were so frozen if the cases had been split to remove the crank.

Big job but it'll run eventually. Keep it up.
 
Funny those screws were so frozen if the cases had been split to remove the crank.

Big job but it'll run eventually. Keep it up.

I couldn't figure out why they weren't loose, who would screw them back in that tight?
 
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.

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

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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.

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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.

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The removal steps.

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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.

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

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Everything is off the right side of the engine.

On to the head.

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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.

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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.

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The head removed.

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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.

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piston and rings don't look good.

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

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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.

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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.

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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.
 
I once rebuilt one of those engines, and SL 125. Virtually identical except slightl bigger spigot, bore, and stroke. Had to replace the rod, not available from Honda separately but some bike shop in Cali had all the individual parts. That was in about 1975 tho.
 
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.

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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.

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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.

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Before

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After

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can you tell which one has been bead blasted?

I even tried it on the petcock.

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Before

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Halfway

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

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These two looked alike when I started.

Now I'm looking for anything aluminum to blast!
 
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