Finally got an airhead..

[hadabadachada]

Hello all.
I was referred to this forum by a good guy from another forum, said this is where the REAL DEAL information is regarding airheads.

I talk a lot and may not get what I’m saying across well, but that’s just me, I try my best.

Sorry this is going to be a long one as I try and lay out where I am.

I got a steal of a deal (starting to rethink that) on a 1978 R100/7 with 24,000km on it, it is apparently a Canadian bike so it’s in KM, as the previous owner bought it up there and now lives in south Florida. Who wasn’t a “real” rider, so to say.
Bike hadn’t run in over 10 years, and of course, had a half tank of fuel in it. He just set it up and left it since he couldn’t ride anymore. Wasn’t able to get the cap off to visualize it and try and get the price lower but I got it a bit lower regardless. Cap just clicked and clicked.

Finally got the cap off the can and man, varnish like a mofo! Cleaned the tank over a week with vinegar and baking soda and all that and it actually turned out s lot better than I thought. Put a screw in the cap as those things new are EXPENSIVE!
Took the carbs apart and soaked them and cleaned everything up pretty good imo. I’m starting to question that now..still think I did good, I took my time. Replaced the gaskets and seals but left the original diaphragms, they look and feel good still. Have a spare set.

I put new plugs in and doing that I checked compression which was at like 130-140 on each side, that seems good to me.
So at this point I have gotten the bike started and idling pretty good it seems. Fires right up. Choke cables are new and kinda a pain to get them tightened to the right spot where it’s all off and all on, gonna have to mess with that more. With the choke on half or full it seems kinda wonky running. but that might be related to something else.
Don’t really need the choke in Miami anyway imo.

Main issue this post is about is, I crank up the bike, get it warm to try and balance the carbs. Make sure the choke levers on each carb is fully off. Set the carbs at 1 turn out on the idle fuel screw as bing recommends, I tried doing the pull one wire off the plug and adjust each side but upon further research (since I’ve been non stop searching for information) I’ve now found I shouldn’t do that because the bike has that dynatek electric ignition. And I’m wondering if I messed that up now by doing that pull the plug wire balance thing. You all can tell me based on the info.

Either way I’m still going. Made another tube manometer as I haven’t sprung to get a nice pricey one. I’ve used these in the past on my R1100S and they worked for me there.
I feel I’ve gotten the idle balanced with the butterfly adjustment screws, I haven’t messed with the idle mixture screws, have left them at 1 turn out.

Issue I’m having now which will be the most revealing for finding an answer is, when I go to adjust the throttle cables which are brand new, as well as new seal kits in the carbs, when I turn the throttle to about 1500-2000ish, low revs, it will sit then give a little “poof”, a little misfire every 10 seconds or so give or take. Gets me thinking, damn, did I mess up the electronic ignition??
Then when I get up to 3000rpm it’s a hard vibration to about 4000rpm when it goes away.

So I’m thinking there’s something else wrong with this engine.
I’m wondering if maybe the throttle needles could maybe cause this? As they were pretty dirty, all the carb parts were super gummy with that lacquer fuel. I thought I did a good job cleaning all the passages and jets and everything. I didn’t use anything harsh to scrub through holes or anything. I did use some scotch brite lightly on the needles to smooth them out, but maybe they need replaced.

I’m hoping it’s just carb related or else it’ll start to NOT be such a good deal on the bike.
I mean I knew everything needs to be redone being such an old bike, that was granted going into this. I knew it was going to be a project for me. So I’ll soon be a regular here.

Thanks for your time.

[hadabadachada]

Shoot, forgot to mention, I took the head covers off and adjusted the valves. .15 intake and .20 exhaust. Also torqued the bolts to 25ft lb, as some were a little loose. Haven’t checked timing, I’ve never done anything like that nor do I have the tools. I’d hope the electric ignition is mounted right and I didn’t mess it up.

[gspd]

The very first thing you need is a timing light, a cheap one will do, just to confirm that you are in the ballpark timing-wise. S mark at idle, F mark at 3000 rpm and up.

Next, while idling, pull up on the left throttle cable, release it, then pull up on the right throttle cable, and release it. From this point on, act like you have two single cylinder engines, a left and a right. Are both ‘engines’ reacting the same when you open their throttle? They should. Turning the mixture screw (lightly) all the way ‘in’ should stop that side. Does it? You’ll know the mixture screw is pretty well spot on if turning it in or out 1/4 turn noticeably slows the engine down.

If you can’t figure it out, you can switch parts (plugs, HT wires, coils, carbs) from the good side to the bad side until you find the problem component by process of elimination.

The left and right ’choke’ assemblies are internally different. A very common error with people not familiar with these carbs is to mix the chokes up when they rebuild their carbs. Another very common thing is not properly positioning the inner and outer notches on the diaphragms. I’ve also seen seemingly perfect-looking diaphragms that were riddled with tiny pinholes that were only apparent when held up to a light and stretched a bit.

[hadabadachada]

So I got a timing light. At idle I see the S in the middle, however at 3000rpm the F is just low of the window.

I did find an air leak in the RH air tube. Gonna have to order a new one of those it looks like. Was able to patch it for now.

Pulling on each of the cables does the same thing. I’m thinking the air leak was causing most of the roughness tho some is still there from about 2250,2500 to 3000 then smooths out. Maybe still getting air with the patch, or maybe the timing is slightly out?

Also the choke mechanisms are correct as I worked on rebuilding one carb at a time, I think that was all air leak issues.

Turning the idle mixture screws in a quarter turn does affect cylinders, turning them out doesn’t affect much until about a half turn.

Gonna wait till I get that new air tube in and try it all again. Probably should get some new plug wires too, I mean shoot, should get everything new being 47 years old, but I didn’t want it to make it all crispy, just want it to work.
I know things are going to need replaced sooner or later.

[gspd]

I didn’t want it to make it all crispy, just want it to work.

You sound like you know what you're doing.
Have you been riding the bike or just trying to tune it in the garage?
Put a few miles on the bike. If you fall in love with it and decide to keep it, you can make it 'all crispy' a bit at a time. Airheads are an acquired taste. Don't expect GoldWing smoothness throughout the entire rpm range but when properly tuned and in their 'sweet' zone, these old relics become quite enamoring.
The timing over 3000 rpm should be on the line or dot adjacent to the actual letter F on the flywheel so it sounds like it’s about right. A degree or two off either way isn’t the end of the world but it’s best to get it dead on if you can, just on principal.
Installing new needles and needle jets (the hole the needle goes into) always makes them run better, especially at small throttle openings. The fact that you had to 'smooth out' the needles indicates wear.

For the mixture, carefully adjust in and out for max rpm at idle. If it's too fast, slow it down with the throttle stop screw. Synchronization wise, what matters is that both come off the throttle stops smoothly, with none of the shuddering you feel like when you pull a bit on just one cable. Trying to sync the carbs at higher rpms by killing one cylinder and then the other is a waste of time (and total lunacy). If the cables are good the carbs will remain in sync at larger openings. Your final carb tweaking should be done after a good run, like 10 miles or more, when the carbs are up to full operating temperature.

[hadabadachada]

I have not ridden it around much at all. First and only ride I saw how vibey it was and figured I need to get these carbs right. And that the front brake may need a rebuild, it’s sticking.
But I have ridden on a 1994 R1100RS, 2004 R1100S and a 2013 R1200R currently. So I like BMW because of the boxer. I’m somewhat familiar with the feeling. I’ve done some work on those bikes with the throttle bodies, rebuilds and stuff, as much as I can anyway. I’m no mechanic but my brain works good, and I can follow instructions but I do overthink things.
But we always want reassurance!

This IS my first carbureted vehicle so that’s all new to me, lots of wonder there.
I’ve always wanted an old airhead for the simplicity and “bulletproof ness” so to say. And to just have an old classic. That I SHOULD be able to do everything myself on, with help to learn. It doesn’t have to look the prettiest I just need the engine brakes and suspension to be good.
Which is all going to need work!
Front fork job is involved! Lots of parts in them forks! Makes me like the telelever front end even more!

Oh an edit, I was going to say with the F being below the window checking timing that, the dot was in the middle.
F was low but dot was in the middle so that sounds good.
I do think maybe I should order some new needles. And you suggest the jets if I do that or not totally necessary? Everything seemed to clean up good in the Chem dip carb cleaner air pressure job, there was just lacquered fuel all over the needles.that I took some scotch brite to. Maybe I should have used bronze wool or something, smoother is smoother right?

[gspd]

Maybe you should put some test miles on it before doing anything else.

Front brake sticking? A very common cause is a blocked (or partially blocked) return hole in the master cylinder. If you open the bleeders and the brake frees up right away, that's your problem. It's also good to pump the pistons part way out of the calipers and check them for corrosion. Either way, a full brake fluid change is highly recommended.

Keep us posted.