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brocktoon 10-11-2012 02:46 PM

'73 R75/5 - Almost back on the road
I've spent about a year rehabbing a '73 R75/5 with a freebie R75/6 as a donor bike. The /6 was in better condition internally despite having been parked outside in a San Francisco backyard for a few years, so that should give you some idea of the /5's condition as it was found.

Last night I finally hooked up the battery. Lo, and behold:


There are still plenty of problems, among them:
  • Left side turn signal doesn't flash, just activates signal indicator light (as pictured)
  • Headlight only works when dimmer switch is activated
  • Horn doesn't work, though it does when connected directly to battery leads
  • Ignition and light switch is touch-and-go, and won't fully engage without jiggling
  • Beacon 1 LED tail light seems to be at full brightness all the time. Neither brake switch works
  • Neutral indicator doesn't work, though it tests fine with the multimeter
  • Can't get my iPhone to pair with it over Bluetooth. Tried for about an hour. WTF?

Needless to say I've got a lot of work ahead of me, but it was the first sign of life I've gotten since I started working on it a year ago.

Cordless 10-11-2012 04:06 PM

Zombie AWAKE!
Congratulations on your success. Any sign of life in these former zombie bikes is a very encouraging sign.

If it's a brake light that is on all the time you've either got a wiring connection change to make or your brake activation switch (usually the rear brake switch in my experience) is activated all the time. You say neither brake switch activates the rear light but how do you know if the rear light is on full bright all the time?

What's the rest of the bike look like?

How close is it to running and being on the road?

ignatz72 10-11-2012 04:18 PM


Originally Posted by brocktoon (Post 19797411)
  • Can't get my iPhone to pair with it over Bluetooth. Tried for about an hour. WTF?

/5s don't support A2DP, only DUN (Dial Up Networking) connections. Even then, mono only.

brocktoon 10-12-2012 12:16 AM


Originally Posted by Cordless (Post 19797936)
If it's a brake light that is on all the time you've either got a wiring connection change to make or your brake activation switch (usually the rear brake switch in my experience) is activated all the time.

You were right! The front brake wasn't adjusted properly. The brake light works now, as do the turn signals -- separate issue.

Most of the other problems are sorting themselves out as I go, but it looks like the ignition/light switch is going to be an ongoing battle. The key doesn't want to stay in. I'd like to pull it out and clean it, but the tabs holding the unit into the shell look fragile as hell. I can just see one of them snapping off after being bent one too many times.

I may just go with the ignition switch upgrade from Rocky Point cycle, or try to roll my own.


Originally Posted by Cordless (Post 19797936)
What's the rest of the bike look like?

How close is it to running and being on the road?

Doesn't look like much at the moment.

It's close to being on the road. Everything is there. I just have to put it together. The swing arm and final drive are up next for installation.


Originally Posted by Ignatz72
/5s don't support A2DP, only DUN (Dial Up Networking) connections. Even then, mono only.

Wish I would've known that BEFORE i sunk a year and $$ into this project. How am I supposed to voice-activate my heated lap blanket?!?!?

Bill Harris 10-12-2012 02:15 AM

You've come light-years with it cosmetically. Good show!

The main light switch is reliable, uber-funky and expensive at over $200. The mounting tabs are quaint and do break if you're not careful. I've had my board out 4-5 times the last 39 years and I fear that the tabs may go south the next time-- I'm looking at fabricating some sort of bolt-on adapter for the board.

Look at Duane Ausherman's website-- it is /2 related, but has many /5 items of interest. Like the switch board care&feeding.

You've got a few wiring issues to be sorted out. Nothing major, just tedious. If the main harness is in sad shape, you might want to consider replacing it. At a current price of $70-ish it's a bargain and a candidate for a big price jump.

Otherwise, keep chipping away-- there's a motorcycle in there. And keep posting...


disston 10-12-2012 03:19 AM

That bike is on the road. You have enough. If 90% is working that's enough in my book. Don't need lights or brake lights or any of that other stuff. Just don't go very far. :freaky

You're right the Blue Tooth hook up is bothersome.

REALGRAVEROBBER 10-12-2012 10:04 AM

Inspiring post, same bike in my garage. Refreshing it over the coming winter. Time for my first refurbish-thread!

"Finish one thing before you start another" can be a helpful mantra for getting a classic bike safely on the road. One bike at a time... My $0.02.

brocktoon 10-18-2012 10:53 PM

I finally got to a point where I could try starting it up.

I took the bike out under the cloak of night -- the better to hide my inevitable shame. I filled it up with gas and found out the left side is leaking fuel like crazy. Undeterred, I pressed the starter button. I got a nice KA-THUNK, but no turning. I plan on checking the starter relay, and have a starter rebuild kit from EME waiting in the wings.

Still undeterred, I gave it a few kicks. I found out it's not much of a motorcycle, but as a bird caller it's not half bad: audio link.

That sound is not me sobbing. That's the bike. I promise.

I need to do a detailed run-through of the electrics, as there are a few gremlins yet. I finally got the headlight/parking light to work, but they remained on even with the key pulled out of the ignition switch. I had to pull the ground cable to get them to turn off. which is not SOP, I gather.

All in all, a frustrating couple of days.

Bill Harris 10-19-2012 04:23 AM

Like I said, "keep chipping away-- there's a motorcycle in there. And keep posting..."

On the starter, pull the starter cover and "activate" the starter manually-- pull the black wire with the Faston terminal from the solenoid and jump between the big battery cable and that now-bare tab on the solenoid. See if the starter turns over, and how vigorously. BE SURE the bike is in neutral. :deal

The turkey gobble? That is the crankcase breather. It's working. :eek1


disston 10-19-2012 08:50 AM

I suppose the clicking noises were the kick starter lever being pressed down? The other faint noise is often described as a turkey gobble sound, it is the breather, identified by Bill earlier. Since you got the turkey gobble and didn't even get it started yet I guess, maybe, we can assume good compression.

Check for spark.

brocktoon 10-19-2012 10:07 AM

The clicking noises are the kick start lever coming back up from engagement, and clacking as it turns the rear of the input shaft. That was one I learned when rebuilding the gearbox.

Compression seems good, so I guess it's down to two things: spark (as recommended) and a proper fuel/air mixture -- and not having an audience around when I try and start it, of course.

Ok, noob question regarding fuel/air: the carburetor should be jetted according to its model, and not to the bike it will be used on, correct? That is to say, I have Bing 64/32/11-/12 carbs, which were originally intended for the R90/6. My carbs have the correct jets in them for the /11-/12 model according to the Bing manual. However, I noticed the carbs for the R75/5 had smaller jets. I should use the stock jets for the /11-/12 carbs, not the jets used on the R75/5 carbs, right?

Does that make any sense?

UPDATE: No spark.

disston 10-19-2012 01:16 PM

You need the jets for a 750 engine. I would think for the /7 or /6 R75 would work best. But I don't think that this will keep you from starting. The R90 jets will work fine to get it going. They will probably make smoke after it warms up and even if not I wouldn't leave them in because the extra rich running washes oil off the cylinder walls. this is not a problem for right now though. Just make rejetting the carbs next, after getting started. and don't forget.

The carbs are actually the same. It's the jets that are changed to fit the engine.

brocktoon 10-23-2012 11:46 AM

Thanks for the clarification. I'll pick up new main jets, needle jets, idle jets, and move the jet needles up one clip to match the R75/6 specs.

I was still getting a KA-THUNK when pressing the starter button and no spark when kicking, so I stared at the wiring diagrams for a few hours, tested the ignition coils with a multimeter, replaced the brushes and bushings on the starter, and generally cleaned the shit out of the the housing and all electrical connections. Still nothing but a ka-thunk. Then yesterday I woke up and for some reason my first thought was "Am I hooking the cable from the starter solenoid to the positive or negative battery terminal?" I went out to the workshop in my pajamas and, sure enough, I was hooking it up to the negative terminal. God only knows why. I switched it to positive and:

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Also getting a nice spark, which means I can start it up in the near future. That being the case, I started reading engine break-in threads for Nikasil cylinders. Jesus, I had no idea how important the first few minutes after first start-up would be. My initial plan of just trying to get it to start are now officially abandoned. I'm going to try to start it up right the first time, which means immediately taking it for a ride, apparently.

Remaining issues before it's road-worthy:

1. Gearbox is leaking oil from the back cover. I'm going to try conventional 80w90 to see if it helps. It currently has full synthetic.
2. Half the bulbs in the instrument panel are burned out, so an all-new replacement set of LEDs from are on the way.
3. Find and fix the fuel line leak.
4. The tire is rubbing against the swingarm.
5. ?????????
6. Profit

disston 10-23-2012 01:03 PM

You have Nikasil cylinders? On a 750? So I guess you had these coated, they aren't BMW are they?

Synthetic oil will often leak in places that Dino oil doesn't. If nothing else the Dino will leak slower. Many riders do want to use Synthetic oils but they cause problems in many areas of an Airhead. You should research before making any changes to Synthetic. We actually get along fine with the old fashioned Dino oils and they are more digestible. :freaky

There is a most controversial subject concerning engine oil. The Old Line is that engine oil needs ZDDP and you don't get it in Synthetic. However the leaks can usually be stopped by replacing all the seals and some riders do use the modern oils.

I use only Dino oils.

If you have a fatter tire on the rear there is a longer top hat spacer that sometimes will keep it from rubbing. I'll try to look up the part number later. (I think this works on a /5. I have the longer spacer on a /6)

brocktoon 10-23-2012 01:33 PM

Yep, they're Nikasil plated. The original barrels were well-worn and smooth. I had the choice of boring to 1st over, getting the 1000cc Siebenrock kit, or Nik plating. I had a conversation with my Airhead mechanic about it. His take was that a 1st over bore is basically just buying time. The new bore wouldn't last as long as the original, and the work + new pistons would be costly. He wasn't a fan of the Siebenrock kit, so he advised Nikasil plating.

If dino gearbox oil doesn't do much to help, the plan is to pull the transmission, remove the rear cover, re-clean the mating surfaces, and place the cover against a granite machinist's plate to see if there's any discernible warping. If it is warped, well, I guess I'm screwed.

I may have the longer top hat spacer from my /6 parts bike. I'll take a peek tonight. I have a big tube swing arm at the powder coater's, so once that's done it's going on the bike anyway.

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