hello

[troposcuba]

Hello everyone. i am new to the forum, but have owned my '77 r100/7 for about 5 years. anyway a couple questions. I have read a lot about dual plugging these bikes and wondered how much difference it makes. the other mod i wondered about is the conversion to electronic ignition (forgot the name of the product) versus points. Just recently rebuilt my carbs and petcocks (i am an aircraft mechanic and was surprised how simple this was!). also wondered what kind of common suspension upgrades are out there for me. bike runs great, just looking at anything that will improve the already great machine. It's gettin pretty cold around here, so i will have some "off time" to tinker with things.

thanks

[lkchris]

Dual plugging arrived on the Airhead scene in the late '70s/early '80s as a "fix" for the fact premium fuels became unavailable. Until that time, all (most) Airheads did require premium fuel, and it was a big problem. Beginning 1980, Airheads arrived in the USA with lower compression and able to use reqular fuel.

It does apparently change the way the motor runs a bit, and folks say they like it.

Also, on the later R100s, valve sizes got overly large to the point the head could warp, and dual plugging is claimed to even out heat distribution and fight the warping problem.

I think both "plusses" mentioned as beyond the basic "use regular fuel" benefit are highly theoretical at best, and that your satisfaction with the dollars spent will be mostly psychological rather than noticeable. I think it will take some time to recover the cost of the conversion through buying cheaper fuel.

Others can better comment on retrofit electronic ignitions.

[srb]

Let me preface this by saying that I am not the expert, my mechanic is. So this info is second hand. Dual-plugging is benificial, but may fall under the category of more trouble than it is worth. You have to change/modify the coil setup, and more than a few of the added plugs have been problematic. Tapping an old head is not going to be as good as when it was done way back in W. Germany.

Electronic Ignition (EI) is one of those 'modern' amenities that I have been allowed and it is great. Performance is improved, reliability is improved, and tune-ups are now limited to valves (every 1500-2000 mi. whether they need it or not) and the rare carb synch. I have the Boyer setup.

Suspension/braking can be improved by getting a post '81 front end setup with the Brembo brakes. I have the old setup '79 but augmented it with a Telefix fork brace which greatly reduces any real or perceived fork walking/flex.

Enjoy your airhead,
steve

[Braddog]

I have a fairly early '77 R100RS that has:
-telefix fork brace
- Koni rear shocks
- new valve guides, pistons, rings, etc.
Standard ignition, standard air filter, single-plugged heads. Standard brakes. I don't know that I've seen an airhead of this vintage without a fork brace. The suspension is almost a "must" as well. I've owned this bike for 3 1/2 years, and put maybe 12,000 miles on it. I love it dearly.

I also just picked up a '77 R100S that previous owner(s) did the following:
- dual-plugged heads
- lighter flywheel
- updated pistons/valves/rods
- K&N air filter
- electronic ignition
- rejetted carbs
- Progressive front, Koni rear suspension
- braided steel front brake lines and EBC pads
- deep oil pan

The "S" feels "tighter" on the road than my RS, but that's due to suspension set up, I suspect. I haven't had the "S" all that long, so really haven't had a chance to sort it out much yet. I really haven't noted any major performance differences at this point, or reliability differences, but time will tell.

My suggestion is to for sure update the rear suspension to Koni (now known as IKON) or Works or Progressive, and possibly the front to Progressive. This will make a huge difference. I would also consider the electronic ignition upgrade, although I've read where some people have actually "de-converted" their airheads back to the standard points configuration.

Welcome to the board, and good luck with your mods. Let us know how it all works out. :thumb

[troposcuba]

thanks fellas. good info. :thumb

[Pheonix]

Hi I am new to this forum but I have had an R100 RT for 24years. I had it double plugged back in '85 I had no trouble with the install or the plugs for all these years. I have logged over 200,000 miles on her.

[campari]

"Dual plugging arrived on the Airhead scene in the late '70s/early '80s as a "fix" for the fact premium fuels became unavailable. Until that time, all (most) Airheads did require premium fuel, and it was a big problem. Beginning 1980, Airheads arrived in the USA with lower compression and able to use reqular fuel."

i have a 1974 r90/6 with no major mods. is this is a fact about having to use premium gas? i just took her on a 6000 mile trip into mexico and used cheap gas basically all the way. are all you bmw gearheads cringing when you read this?

[pmdave]

I had a '78 R100 that cost me some additional money. I listened to the aftermarket guys at a rally, and forked over my plastic card for dual plugs and electronic ignition. Then I had to start futzing around with ignition timing to get it to run better. I agree that it's mostly a psychological upgrade. Doesn't hurt--just doesn't help much.

The biggest advantage of electronic ignition with the pre-'80 engines is that the tiny points are very difficult to access. With electronic ignition, you set the pickups as accurately as possible, and you'll probably never have to get down there again. Well, with the exception of the Dyna pickup plate, which is thinnish circuit board and tends to warp with heat. I had to build a "bridge" from thin stainless steel to keep the circuit board in shape.

The 1980 (and possibly some 1979) engine used a points-in-a-can that meshed with the front of the camshaft with a slot. You can unbolt the "can" and adjust the points on the bench, then install it (like a distributor) and time just by turning the can in it's mount. Piece of cake. And the 1980 points were about twice the size of the older ones--so they hold their clearance better.

So, for the 76 - 79 engines, I think it makes more sense to spend your bucks on a good valve job with late model valves, seats, and guides, but install an electronic ignition and coils to get more stable timing. I don't think dual plugging accomplishes much on an airhead, and it adds the risk that the thinnish threads on the lower plug will strip out.

Perhaps someone else knows whether a later model cylinder head will drop compression on an early engine, or if it's a matter of pistons only.

pmdave :brow

[troposcuba]

cool, good info. I am kinda old school, so i think i will stick with the points. i have 2 cars that also have points, so it doesn't really bother me that much to have to set them. i found a good trick for access to the points on the bike. i just bent a feeler gage over 90* on the end to reach the points easily. I don't hear any detonation when the bike is running, so i am gonna assume that i am ok. there is also no evindence on my plugs of detonation, so i think i will roll as is for now.

thanks again for the info. :thumb

[lkchris]

"Dual plugging arrived on the Airhead scene in the late '70s/early '80s as a "fix" for the fact premium fuels became unavailable. Until that time, all (most) Airheads did require premium fuel, and it was a big problem. Beginning 1980, Airheads arrived in the USA with lower compression and able to use reqular fuel."

i have a 1974 r90/6 with no major mods. is this is a fact about having to use premium gas? i just took her on a 6000 mile trip into mexico and used cheap gas basically all the way. are all you bmw gearheads cringing when you read this?

Be careful if you hear pinging. Otherwise, don't worry about it.

[donkey doctor]

Hello; I have a 77 R100/7 which had 75,000 miles on it, it has teh twin plug mod and Dyna electronic ignition. It has progressive springs in teh forks and progressive shocks, I have a Corbin seat on it too. The bike is so close to perfect that I can't think of anything to do to it to improve it. I use regular unleaded gas in it and get 50 miles per gallon, about the only part about it that can be improved is the brakes, but they are pretty good too.

I like the twin plug setup, the difference in cost between regular and premium gas is about 10 cents a litre. Over the years the cost of fuel is the biggest expense in running this motorcycle. If I can go the same distance at a lower cost that will put more money into my pocket.

The Corbin seat is an acquired taste, I hated the thing until I had to sit on it for three straight days, since then I love it.

[troposcuba]

hey Donkey Doc, fill me in about the springs and shocks that you upgraded on your bike. I need to rebuild my forks anyway, and my rear springs are all rusty, so i would like to replace them for aesthetic value if nothing else. So what did you upgrade to and would ya do it any different if you had the chance to do it again?

thanks.

[donkey doctor]

hello; I bought the bike from a Dutch immigrant, a sailor, who did all those stated improvements before I bought the bike from him. He was at sea for 10 months a year, so He pretty much just sent money, and allowed his Dutch guru to do whatever he thought was best. I did see teh reciepts, but my Dutch is really dusty no rusty but I can make out the word Progressive Suspension on the bill.

Sorry I can't tell you more about it.

[troposcuba]

cool story, thanks anyway. :thumb

[PeoriaMac]

Tropo said: "also wondered what kind of common suspension upgrades are out there for me. bike runs great, just looking at anything that will improve the already great machine. It's gettin pretty cold around here, so i will have some "off time" to tinker with things".

Progressive springs up front are the common upgrade, ($70.00) and will make a difference -- ESPECIALLY -- if you take the time to make sure everything in in the proper allignment up front. Back in the day, a lot of folks installed fork braces ($130.00) , and a good upper triple tree ($119) , as it was said the stock aluminum one could flex. Proper alignment is still the key for 95-percent of airhead riders ((OK, that's just a guess)) who don't try and drag their heads in the corners.
Rear end...Koni shocks were the go-to thing until they quit manufacturing them. The specs were bought by an Australian company which now produces them as "IKON"s. $335.00 at Bob's BMW, or Progressive has their own line of rear shocks-about $250.00, or there's Hagon shocks, made in England, which currently sell for 100 British Pounds -- plus shipping.
Motobins in England ( www.motobins.co.uk ) sells the Hagons, Ikons, Progressives, and some models of shocks not usually seen over here, as well as the OEM stockers and the "Nivomat" self-leveling shocks.
San Jose BMW used to sell a swingarm brace - yeah, I bought one - so as to cure swingarm flex. Maybe EBay or the IBMRA sites has some used....

[GlobalRider]

I have read a lot about dual plugging these bikes and wondered how much difference it makes.

Well the person I work with got 10 mpg more with dual plugging as well as a better running engine.

Just remember that you have to modify the ignition advance (easy to do on a mechanical advance) so that you limit the maximum amount of advance. We did it by slipping on a few layers of heat shrink to the "stop" posts. The bike ran beautifully. Adjusting the timing by itself will not do the trick. Note, you also have to adjust that as well. You'll have to experiment.

[pmdave]

The upper triple clamp on airheads is a steel stamping, not aluminum. It's very strong perpendicular to the fork tubes, but not very resistant to torque loads. (when the two fork tubes are twisted by say, the front wheel being pushed sideways) The aftermarket upper triple clamps I've seen are machined aluminum, and thick enough to incorporate a clamp bolt on each side that helps prevent torquing the tubes. The lower clamp is aluminum (forged, I think) and quite strong.

Telescopic forkes are notoriously flexible, primarily because there must always be some clearance (read: slop) between the tubes and the slider bushings. Secondarily, the two sliders can move independently, and what helps prevent that is some sort of connector between the two sliders. The axle serves as a connector, but the older axles were somewhat small in diameter, and therefore can flex slightly. One fix is to install a fork brace that bridges across the tops of the sliders. What's important when installing a fork brace is to get the tubes aligned well before adding any reinforcement.

It may be possible to loosen all the clamp bolts and bounce up and down on the front end to allow things to self-align, but it's better to remove the wheel and fork springs and feel the sliders as you raise and lower them on the tubes. If there is any binding, you can adjust the position of the axle slightly, or raise or lower one fork tube in the clamps. They should slide freely up and down with as little "stiction" as possible. After checking alignment, you can install the fork brace, assuring that you don't alter the alignment. If necessary, do a little filing on the holes in the brace so it goes on straight.

Reinforcing the rear swing arm is somewhat more involved. You have to remove the swing arm and have a reinforcing loop welded to the swing arm. Of course welding always causes some change in shape, so it's important to keep the swing arm beams aligned as the welds cool. There used to be kits for this.

Naturally, as you beef up the front end and rear swing arm, the flexible frame becomes more obvious. The airhead were called "rubber cows" for good reason. So the next fix is a tube braced between the horn mounts and the rear frame tubes (just above the pivot bosses) on both sides. OK, now the frame is getting tighter, and it may be obvious that the wheels are bending a little. Time for heavier guage spokes, or stronger rims, perhaps? Don't forget to have a machinist install steel inserts in the hubs to better support the wheel bearings.

Or, you can just ride it as is, knowing you're on a vintage machine with character of the age in which it was built. Technology has moved on, and the aftermarket suppliers with it.

pmdave :brow

[jhelming]

Be careful if you hear pinging. Otherwise, don't worry about it.
My trusty ride is a '91 R100RT with 52K -- runs like a top in all respects, but I started noticing some pinging on hills on the slab last summer, although I always use premium gas (93 RON). When checking the timing at full advance (3000+ rpm), the timing mark moves slowly back and forth by several degrees in rythmic cycles of approx. 1 sec. Does this sound like worn timing chain, worn ignition trigger unit, or . . . ?

Also would welcome advice on top end work. I gotta pull the heads this winter to replace pushrod tube seals, and am wondering whether to do a complete top end while it's apart, i.e., send the heads out for reconditioning, replace rings, etc. As mentioned, the bike starts and runs perfect (except for the new pinging problem), and uses a quart of oil approx. every 2000 mi. Oil/filter are changed every 2500 - 3000 mi (Golden Spectro 20W-50 synth/dino blend). Compression is 140 psi left, 145 psi right. Valve clearance is stable - only slight adjustment is required at normal intervals. Plug tips always look good, tho' the base of each plug is always black and shiney.

Any and all advice welcome! TIA . . .

[pmdave]

Yes, do take the heads apart, check the valves and seats for wear, and decarbon everything. Carbon on the valve stems can cause sticking that can quickly lead to burning. And carbon in the combustion chamber will raise the compression ratio, making it more susceptible to pinging.

If you don't see any valve wear, it's still worthwhile to have someone touch up the valves. A fresh cut on the seats will help preserve compression for another 40,000 miles or so.

Based on the mileage and compression results, it doesn't appear that you'll need a ring job. Those late model cylinders seem to go for years with little wear. You can disconnect the rod lowers and pull the piston out with the jug to avoid having to stuff the rings back in place. Clean the block and jug mating surfaces well (I use clutch and brake cleaner) lubricate the new rubber seals, and put it back together. I like to coat the sealing surfaces with gray silicone-base gasket sealer (but don't put anything on the pushrod seals or O rings--they need to flex)

Pay attention to the various O rings. Different years used different styles. Replace all O rings with new ones. Pay attention to the head gaskets, too. An upside down head gasket allows the pushrods to rub.

Use a stethescope to listen to the engine before taking it apart. Especially listen to the timing chain box as you roll gently on/off the throttle. If you hear rattling from that area, you might want to take it apart and check the timing chain. No rattle--don't do anything.

The varying timing? I'd check the pickup and advance carefully. Depending on the model, you could have advance springs stretched, or a sticking advance mechanism. It's also possible that the pickup coils could be loose, but I'd expect the engine to run really terrible if that were the case. Clean and lubricate everything, replace springs and O rings, and retime. Should cure the problem.

pmdave:thumb

[pmdave]

BTW, I trust all the airheads know to disconnect the negative battery cable at the transmission before attempting to remove the front engine cover. If the battery is still connected, it's very easy to short the cover to a hot side of the diode board and fry everything. You don't have to disconnect the hot + side of the battery, just the ground - side.

The reason for disconnecting the ground side is that if you goof up and touch the wrench to the frame and battery terminal at the same time, the ground side doesn't do anything. The hot side would instantly arc across the wrench and perhaps even weld the wrench to the frame.

So, when disconnecting the battery cables, remove the negative first, and when connecting a battery, connect the negative last.

pmdave :brow

[jhelming]

Thanks for the top end advice, Dave.

One further question: If I'm not going to touch the rings, wouldn't it be easier to ease the wrist pins out and remove the pistons with the jugs, rather than disturbing the lower ends? I'm told a little evenly-applied heat from a hair drier on the pistons is all it takes to push the wrist pins out by hand.

[pmdave]

Hey, I've never had one of those "modern" airheads apart!

There isn't a lot of space down there, and while you're jiggling the pistons to get the pin out, you may pull the rings out, too. But it's do-able. Be sure to install the circlips correctly when you put the pins in again--the sharp side of the circlips (unless they are wire springs) go away from the pin.

be prepared with a piece of soft wood to support the rod so it doesn't bang down on the edge of the block.

Some people use a rubber band around the two lower studs to support the rod, but that can be a trap. It's easy to forget the rubber band and try to install the jug, cracking the cylinder. Go ahead, ask me how I know.

If you happen to pop the piston rings out, don't worry. When re-assembling, position the rings so the gaps are 1/3 around from each other. I usually position the oil ring gap facing up. I've used a large hose clamp as a ring compressor.

Removing the pistons would give you the opportunity to check ring end gap, which can be contributing to your oil consumption. Of course, one thing leads to another, and you need to know where curiosity needs to take a rest.

pmdave ;)