Introduction '72 R75/5 & '66 R60/2

[6bikegarage]

Hello all,
I'm an amateur mechanic trying to help a couple people out with their bikes, but as is often the case, finding I often need help myself. Just because I might know a little more than them doesn't mean I know what I need to.
I registered for this forum because I have a '72 airhead (I can't recall off the top of my head, but I believe it's an R75) with a some mild cafe mods and 5 speed transmission from an R100 plugged in coming into my workspace. I haven't even got this one in the garage yet so I don't even know what my questions are on that, but wondering if anyone has any knowledge of pre '70 airheads?

I have an aging neighbor who has more projects than time or ambition and I worry about him and his health so I'm trying to help him get a couple things running and hopefully moved on. One of his bikes is a '66 R60/2 and I currently have it in my garage. I set the timing and went through the carbs and it was running a week and a half ago (I posted a youtube video about it on my channel: "6 bike garage"), but it was losing power when going uphill. This last weekend I was trying to get the brakes to work a bit better and got the turn signals working again and was going to try another test ride to see if the brakes felt better, but now it doesn't want to stay running. It's will occasionally get up on both cylinders, but typically only wants to run on one and then dies. I seem to have good spark (even on the side that doesn't want to run right), there is a new air filter, and I have good fuel flow from the petcock, so I think it has to be carb related. I currently have the carbs set with a baseline set up (idle screw one turn in from just making contact with the slide and idle mix screw 1.5 turns out from bottom). It looks like the carbs were rebuilt at some point as they have plastic floats instead of the brass ones that were stock. The problem might be with these floats. They have wires across the top that slip into the notch on the float needle like the brass ones, but every time I've had it running, when I pull the float out, it has pulled out of the notch and is sitting about 1/4" below it. I'm at a loss as to how this is happening as it takes a fair amount of force to pull it out of the groove when snapped in. I'm also befuddled by the fact that it seemed like it was running well a week ago and now it isn't. Apologies, for asking about a pre-'70s bike here and y'all can tell me to get bent if this is taboo, but I'm grasping at straws a bit.

Cheers,
jason in Seattle

[6bikegarage]

I just found the part of the forum for pre-'70s bikes. Shaking my head at myself.

[Kurt in S.A.]

The plastic floats are a newish replacement for the older brass floats. The brass can stress crack which then lets fuel inside the float. Plastic floats have been around for maybe 5-8 years. There are two varieties based upon weight, one 11g and the other 7g. If the needle running down the center of the float is pulling out of the wire clips, I'm wondering if the float needle is sticking in the small well in the bottom of the float bowl. More likely is that the plastic floats have swollen and are scraping along the sides of the bowl. The first version of the floats were known to do that...my first set did that. The Ver 2.0 floats were better in the unleaded fuel. See if the floats move easily inside the bowl.

Kurt

[6bikegarage]

The plastic floats are a newish replacement for the older brass floats. The brass can stress crack which then lets fuel inside the float. Plastic floats have been around for maybe 5-8 years. There are two varieties based upon weight, one 11g and the other 7g. If the needle running down the center of the float is pulling out of the wire clips, I'm wondering if the float needle is sticking in the small well in the bottom of the float bowl. More likely is that the plastic floats have swollen and are scraping along the sides of the bowl. The first version of the floats were known to do that...my first set did that. The Ver 2.0 floats were better in the unleaded fuel. See if the floats move easily inside the bowl.

Kurt

Thank you for the thoughts. The floats didn't have any resistance when I pulled them out and they drop right back in so I don't think they are sticking at all. I've pulled them out about half a dozen times so far. I'll have to look at them again to see what the weight is (I saw markings on them that indicated what they were, but don't recall of the top of my head).

I saw somewhere that there should be 22mm from the bottom of the cap to the bottom of the needle valve lever when the valve is closed (float is all the way up), but I wander what the fuel level is supposed to be at. I've seen two different styles of washers or clips the push up against the lever and with different floats (plastic vs brass) and with plastic floats available in two weights, it seems like the 22mm dim wouldn't yield consistent fuel levels.

Thanks again,
jason in Seattle

[Kurt in S.A.]

According to my notes, the plastic floats in my /7 weight 7 gr. Not really sure if the float swelling is an issue, but just mention it. Might be interesting to soak the float in fuel and compare measurements across the large diameter and see if it changes before and after.

I've never figured out where the gas level should be. I've just trusted that when the needle is snapped into the wire holder on the float, the float is set at the correct height.

Kurt

[Kurt in S.A.]

I've started to review your video I found on youtube. One recommendation I have regards starting. I would not stand on the footpeg in order to reach the kicker. Over time, you will damage the support structure for the center stand which lets the rear tire touch the ground when on the stand. Currently you have some room under the rear tire as seen in the video. But standing on the center stand is something I wouldn't do. I start my R69S on the center stand, but my left foot is on the ground. I guess maybe I'm tall enough to reach the kicker that way.

Another thing I noticed was looking through the throat of the carb. That center section, which the needle goes through, has worked it's way up. That will restrict the lower movement of the slide. Duane Ausherman has suggested that this item needs to be pushed back down to more flush with the throat of the carb. It's just pressed in on a spline with the body of the carb.

A battery is not needed to run the bike. It is just a reserve to power the lights when the RPMs fall below a level to get reasonable output from the generator.

The handlebar seems to be cocked with respect to the forks. It seems to pointed slightly to the left when going straight down the road.

On the front brakes, they really can be good when set up right. Check out this page for the /5, a lot of which transfers to the /2:

https://brook.reams.me/bmw-motorcycle-r ... nt-brakes/

As for loss of power, it might be that the jet needle is in the wrong position or maybe some of the jets are wrong sized or need more cleaning. Or maybe just downshift!

Kurt

[6bikegarage]

I've started to review your video I found on youtube. One recommendation I have regards starting. I would not stand on the footpeg in order to reach the kicker. Over time, you will damage the support structure for the center stand which lets the rear tire touch the ground when on the stand. Currently you have some room under the rear tire as seen in the video. But standing on the center stand is something I wouldn't do. I start my R69S on the center stand, but my left foot is on the ground. I guess maybe I'm tall enough to reach the kicker that way.

Another thing I noticed was looking through the throat of the carb. That center section, which the needle goes through, has worked it's way up. That will restrict the lower movement of the slide. Duane Ausherman has suggested that this item needs to be pushed back down to more flush with the throat of the carb. It's just pressed in on a spline with the body of the carb.

A battery is not needed to run the bike. It is just a reserve to power the lights when the RPMs fall below a level to get reasonable output from the generator.

The handlebar seems to be cocked with respect to the forks. It seems to pointed slightly to the left when going straight down the road.

On the front brakes, they really can be good when set up right. Check out this page for the /5, a lot of which transfers to the /2:

https://brook.reams.me/bmw-motorcycle-r ... nt-brakes/

As for loss of power, it might be that the jet needle is in the wrong position or maybe some of the jets are wrong sized or need more cleaning. Or maybe just downshift!

Kurt

Thanks for all the great info. I found some other posts about suggestions for starting that I'm going to try and will stop standing on the peg when doing so.

Very good to know about the needle slot on the carbs. I'll pull the carbs back off and see what I can do about pressing the needle guides back in.

Regarding the battery, yeah, I realized after I recorded that part of the video that it would run on the magneto alone and that the battery was just for the lighting. Glad the battery is holding a charge though and now the lighting and horn are working. I will follow that link for setting up the brakes. I think I have them better now, but can't really check.

Carb jets are very clean and definitely not just a downshift issue. It was losing all power like it was out of gas. What it was doing on the uphill in the video is similar to what it's doing in the garage now.

I think the handlebar is a trick of perspective with the wide angle on the camera. They don't appear cocked at all in real life. I'm going to take another whack at a couple things over the next day or so and will be back with an update.

Cheers,
jason in Seattle

[Kurt in S.A.]

When the bike loses power again, quickly (and safely) reach down and loosen the gas cap. You could be developing a vacuum in the tank under high demand.

Kurt

[6bikegarage]

When the bike loses power again, quickly (and safely) reach down and loosen the gas cap. You could be developing a vacuum in the tank under high demand.

Kurt

I'll keep this in mind and if other things don't work, I'll give it a shot, but the fuel level is so low that I can't imagine it would create enough vacuum to do this. Especially considering it was coming back on song so quickly when I got back to level. Also, I had a look at the slide needle guide and I don't think it is sticking up at all. I found Ausherman's site that you refereneced, but the pic links are dead so I didn't have anything to compare to, but I don't see any splines on Frank's (pic attached). The other side looked the same.

I'm going to try an experiment with a small zip tie tight to the underside of the float and see if that helps keep them in position, but not sure how soon I will be able to try another test ride. Forecast is showing a fair amount of rain.

Cheers,
jason in Seattle

[Kurt in S.A.]

If the slide guide sits too tall, your slide won't be able to hit the bottom...you'll have trouble balancing the carbs.

You may have to find Ausherman's site on the Wayback Machine.

Kurt