Winter project #2

[bosco659]

Well I thought I’d probably finish the Titan sooner than planned so I’ve added another bike to the stable. A 1978 Yamaha SR500 “Thumper”.

I just picked it up today and am trying to not work on it but it’s proving difficult to keep away. Here’s what I know:

The good:
- 10,000 km
- good tires - Avon Roadriders - like new
- new chain and sprockets
- new battery
- all parts to make the bike complete are included
- lots of compression (that’s another story)
- chrome in nice shape - needs a polish (scuff on muffler)
- good spark

Not so good:
- rear caliper siezed
- big dent in tank
- seat cover needs attention
- aluminum oxidized
- needs lots of cosmetic work
- not running (yet)
- side cover needs a bit of repair
- headlight needs attention
- left control for lights, signals, horn needs rewiring

The bike didn’t have oil in it and I’m not sure why. The bike came with 2.5L of oil - almost the correct amount). Perhaps an unfinished oil change? I put in a good dose of oil down the plug hole do it can soak in overnight.

The compression test - ever try kicking over 500cc to get a reading on the compression tester guage? Not so easily done and I eventually gave up. It is so hard to kick over I assume the numbers will be good. I will try squirting gas down the spark plug hole tomorrow to see if it will light up.

It looks like many of the parts on the bike are the same as an XS. That would be great and will simplify parts sourcing.

Here’s some pics….

 

[bosco659]

Looking for a couple of bits. Headlight bezel - just need the chrome piece and a Speedo chrome cover. Lmk what you have and $. Thx

 

[Signal]

Another great project looks like its mostly there just needs good tidy up. I have fond memories of my SR, they are not hard to start when you get the knack.

 

[Raymond]

Looks not too bad, been looked after, not much muck around the front sprocket, chain looks clean. Kicking them over helps to use the wee window on the cam box.

Back in the day, the M/c mags dissed them as horrible, slow and impossible to start. Well, that's coz lazy journalists didn't bother learning the starting technique - mine started first kick every time. The performance is what it is, adequate, it's not meant to be a rocket ship.

The CDI unit failed on mine and 3rd gear cog lost its engagement dog but other wise pretty reliable, and stripping the motor is pretty straightforward.

Will be following . . .

 

[Downeaster]

Ooooooh! One of the prettiest bikes Yama-Mama ever built. Following...

 

[Bob Wegman]

Great find. I have had my 80 SR since new. It will probably be the last bike I would ever sell. Mine has around 38,000 miles on it now. Just took the top end off for the first time and replaced the piston rings and valve seals, and cleaned up the valves. Been a great bike.
PS. There is a headlight for a 78 SR on the ; thekneeslider.com, website under Yamaha SR500 listings. Looks like it is located in Canada too.

 

[bosco659]

Great find. I have had my 80 SR since new. It will probably be the last bike I would ever sell. Mine has around 38,000 miles on it now. Just took the top end off for the first time and replaced the piston rings and valve seals, and cleaned up the valves. Been a great bike.
PS. There is a headlight for a 78 SR on the ; thekneeslider.com, website under Yamaha SR500 listings. Looks like it is located in Canada too.

Thanks Bob - that’s a great site . I just looked and there’s tons of parts there for both the SR500 and my Titan.

 

[bosco659]

For previous or current SR owners. How robust is the CDI unit? Is that something I should be looking for as a spare?

 

[bosco659]

Any tips or tricks to make the bike easier to start? I’ve seen some videos where owners kick the motor over up to 10X with ignition off and decompression on before attempting to start it.

 

[Jim]

Any tips or tricks to make the bike easier to start? I’ve seen some videos where owners kick the motor over up to 10X with ignition off and decompression on before attempting to start it.

It's a dry sump engine. Multiple kicks is just to scavenge the crankcase.

 

[Mailman]

Nice project!
I used to have an XT500, which has the same motor. There is a certain procedure to start them and it’s hard to do if you don’t follow it. I’d be happy to tell you it if you want, but if you’re already familiar I won’t clutter up your thread.

 

[bosco659]

Nice project!
I used to have an XT500, which has the same motor. There is a certain procedure to start them and it’s hard to do if you don’t follow it. I’d be happy to tell you it if you want, but if you’re already familiar I won’t clutter up your thread.

Please enlighten me Bob.

I have a sore knee now after kicking it too many times today.

Carb off, very clean inside. As expected nothing was snugged down tight. The carb was a bugger to get off. It’s back on to the head now. Gotta figure out how to make the airbox move back to get the rear coupler in. If I fight with it too much I may get a Uni pod filter. lol.

The only thing I found that was wrong was a wrinkled diaphragm (one of three). When assembled with the spring in place the diaphragm wrinkles and the wrinkles get squished between the cap and not. Possible vacuum leak?

The ball bearing for the choke detent is in the neighbours back yard now so I need to find a 3mm ball bearing.

I got it to stumble once but not again. That was with gas down the plug hole. Once I get the tank back on I may try again. Needs new fuel, vent and vacuum lines. Good news is the vacuum petcock works.

 

[Jim]

The ball bearing for the choke detent is in the neighbours back yard now so I need to find a 3mm ball bearing.

Gotta zerk fitting?
Take it apart... there's your ball bearing.

 

[Mailman]

I’ll preface this by saying that I bought my bike new and everything was factory new with no gremlins to be worked out.

So the drill was….
1. Pull the compression release and slowly rotate the kick start lever while watching the little glass window on the end of the camshaft cover,

The cam looks black but there is a shiny spot that appears in the window when the piston is almost up to top dead center. Stop when you see that shiny spot.
2. Flip the choke on
3. Turn on the key
4. Give it a good stomp on the kick starter. Never took more than one or two kicks, hot or cold.
You could give it a couple of kicks with the key off before going through this ritual, if you wanted, just to pull a little gas into the cylinder. But I never needed to.

Great! But what if it’s dark and you can’t see that little spot in the window?
Push the kick start lever down until it stops from hitting compression. Let the lever come back all the way to the top, then pull the compression release and slowly rotate the kick start down about half way and stop. ( That will put you right back to that sweet spot just below TDC )
Let the lever come back all the way to the top and you are ready for your stomp, same as before.

Trying to kick start this motor without using that compression release to get the piston in the right place will prove difficult and can get you some nasty kickbacks.

Note: I grabbed that photo off the internet and it shows an aftermarket lever on the front of the head for operating the compression release.

Hope this helps!
-Bob

 

[bosco659]

Gotta zerk fitting?
Take it apart... there's your ball bearing.


View attachment 377311

Thanks Jim! I’ll do some surgery tonight. I know people in this group know a lot of things by how would you know that bb dimension?

 

[Jim]

That little trick was taught to us by @robinc... may he rest in peace.

 

[bosco659]

I’ll preface this by saying that I bought my bike new and everything was factory new with no gremlins to be worked out.

So the drill was….
1. Pull the compression release and slowly rotate the kick start lever while watching the little glass window on the end of the camshaft cover,
View attachment 377312
The cam looks black but there is a shiny spot that appears in the window when the piston is almost up to top dead center. Stop when you see that shiny spot.
2. Flip the choke on
3. Turn on the key
4. Give it a good stomp on the kick starter. Never took more than one or two kicks, hot or cold.
You could give it a couple of kicks with the key off before going through this ritual, if you wanted, just to pull a little gas into the cylinder. But I never needed to.

Great! But what if it’s dark and you can’t see that little spot in the window?
Push the kick start lever down until it stops from hitting compression. Let the lever come back all the way to the top, then pull the compression release and slowly rotate the kick start down about half way and stop. ( That will put you right back to that sweet spot just below TDC )
Let the lever come back all the way to the top and you are ready for your stomp, same as before.

Trying to kick start this motor without using that compression release to get the piston in the right place will prove difficult and can get you some nasty kickbacks.

Note: I grabbed that photo off the internet and it shows an aftermarket lever on the front of the head for operating the compression release.

Hope this helps!
-Bob

Thanks Bob. I should be ready to try it again once I get the fuel lines sorted out. I got a sore knee already from some early morning testing.

 

[Jim]

I know people in this group know a lot of things by how would you know that bb dimension?

This one's a little over 2mm. I'm sure different brands have different sizes.
I lost the ones out of my BS34 choke detent. One of these has worked for about 7-8yrs now.

 

[bosco659]

Thx Jim.

I didn’t do a lot on the bike but I didn’t remain idle. Took the carb off - major pita and checked it out; reinstalled; Gorilla taped my seat back together; removed Speedo to look at the chrome cup so I can look for one at a swap meet this weekend; reinstalled one factory (not so pretty) signal light; replaced one fuel line; repaired cracked side cover (Amazons Chinese hot wire tool is great!); straightened gear shifter; replaced carb mount flange bolts with flanged headed bolts so clamps can grip metal carb holder properly.

 

[bosco659]

What are my options for replacing this rubber insulator (between chrome housing and Speedo). It decided to come apart in two pieces. I don’t think there’s enough left to glue together.