Several weeks ago I obtained an '89R100RT. Well maintained with records. I've been riding airheads for 50 years but this is the only one other than my long departed R80ST (big mistake) that has electronic ignition. After running great for a couple of weeks, it suddenly cuts out badly above 4000 rpm. This happened overnight. Fuel is flowing fine, inline filters, tank very clean. I suspect coil breakdown but my only experience has been with points and 6 volt coils. I could use the collective knowledge of the group to suggest what to check. Thanks!
Cutting out above 4000 sounds like a carb/ intake issue to me because that's right where the main jet kicks in. It's also where the ignition breaks down. 1989 is a single-sided rear shock with the newer electrical layout and dual output coil. Those early (blue ?) dual coils would crack their plastic cases and act up.
It could be so many things. I'd be checking things in this order...
1. Check the simple stuff first. Is the air filter clean/ clear ? Has the Exhaust Gas Recirculation system been properly removed and blocked off ? Are both intake hose spigots tightly screwed into the cyl head ? Are you running only name-brand high octane fuel ?
2. Fit a paper "kitchen towel" into a funnel. Pour the contents of both float bowls individually through the funnel. Any water in the fuel will "bead up" on the paper towel. Are the main jets loose in the bottom of the float bowl ? Are both needles protruding the same amount from the slide ?
3. Is the L-to-R cross-over fuel hose crimped or blocked ? Does gasoline flow equally out of both petcocks ? Equally out of both fuel filters ? This diagram shows a better routing system that doesn't pinch the cross-over hose...
4. Have you set the ignition timing using a strobe timing lamp ? (5000 RPM should bring the high speed flywheel mark to the center of the timing window.)
5. What plugs are you running ? Are the coil wires zero resistance "metal core" wires ? Have you fitted "resistor style" plugs ? Are the spark plug caps "resistor style".
6. Have the carb diaphragms been checked for leaks/ tares.
7. Have you adjusted the valve clearances lately ? Airhead valves always tighten during use.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Thanks for your reply! I have checked the fuel system and checked for water in the fuel. Fuel is flowing properly from both sides. Float bowls are clean. Power loss is on BOTH cylinders and occurred suddenly. Just riding down the road and started missing and losing power. Connections to the head are tight. I remember having to replace the coil on my R80ST for cracking but I thought the newer ones were a little better and I'm not sure how to rule out the electronic ignition. I may know where I can get another coil from a parts bike. Perhaps I'll try that.
Sincere apologies, my friend. There was something I couldn't remember until I started looking at my old photos.
Remove the engine front cover, as if you were going to repair the alternator. Unplug the connector coming out of the "bean can" for the ignition module. One of the connectors is ivory/white, the other is black. If the 3-wire ivory connector is cracked, split, or even gets a small chipped area, then the ignition will become intermittent. I can't explain it, but it's true.
That ivory colored 3-wire connector MUST be replaced ! It cannot be glued or repaired. The only reliable repair is to replace the connector, which means replacing the entire connector+wire assembly (aka "the pigtail").
The only supplier that I know of is Rick James at Motorrad Elektrik, who sells the complete "pigtail" (connector pre-installed on the wire). This means the ignition "bean can" has to come off the bike. (This is easy, since the can is mounted to the front of the engine with a quick-detach method that only allows one-way mounting.) You can then work on the bean can on the bench. Some disassembly of the can is required to get to the circuit boards where the wires are soldered to the circuit board.
This is NOT a job for a typical tattooed "motorcycle mechanic", nor is this a job for a person who solders once a year. You want someone who 1) solders ALL THE TIME and 2) owns a temp-controlled soldering iron and 3) who knows how to solder at the component level. If too much heat gets applied, the traces on the circuit board will lift and you'll be buying a whole new circuit board. If too little heat gets applied you'll end up with a "cold solder joint" and the wire will vibrate off sometime in the future.
When the can is repaired it can be offered back onto the engine. As far as physical placement, the can only fits one way. However, the angular position of the can determines the engine timing. At this point you will need an ignition strobe light. The "Fast" timing mark should be centered in the flywheel's strobe window at 5000 RPM. (Ignore the old manuals. The position of any marks at idle or any mid-point mean exactly nothing. Exact ignition timing at Full Advance is all that matters.)
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Wow, thanks Richard! The two replies give me a path to diagnose the issue. Fortunately I have an 88 R100Rt that I bought at an auction a couple of years ago that had an oil pressure problem among other issues (many miles) but actually ran quite good. It's pretty much a parts bike now. If the connector is bad I will likely just switch it out.
Fortunately I have an 88 R100Rt that I bought at an auction a couple of years ago that had an oil pressure problem among other issues (many miles) but actually ran quite good.
On both bikes... remove the oil filter and look deep down into the oil filter "well" at the bottom. There you will see a screw head at the 3 o'clock position.
Using only a "hollow ground" screwdriver tip (never a hardware store variety wedge tip screwdriver blade), and remove that 'screw'. Then use a stick magnet to pull out pieces of a spring and ball.
What you will most likely pull out is bits of a broken spring (like the piece on the Left). Only when compared to the new spring (like the one on the Right) will you see what's going on.
1) These parts are merely pennies compared to other Airhead parts, and 2) If you bugger up the screwdriver slot in the aluminum screw head you'll never get the parts apart. So I highly suggest you order a new spring and new screw BEFORE you start. In this way you can be assured you have a perfect fit of the screwdriver bit into the screw head.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
I will check that out !
I will check that out !
You can test the spring before disassembly with anything ~8 inches long and skinny (like a bicycle spoke). Push on the ball through the hole. If it springs back, then you're OK.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
The mystery deepens! swapped out coil, bean can (checked plug closely), set timing correctly, new spark plugs, drained all gas and replaced with fresh. Still cuts out at 3500-4000 rpm! If I accelerate through to higher rpms, it pulls great and runs great. Unfortunately, cruising (and legal speeds around here) are all right in the 3500-4000 range. I am at a loss! The stumble is on both cylinders or I would suspect a bad carb diaphragm. Stock mufflers and jets and nothing was changed. It was running great and this started suddenly. I appreciate any suggestions!
Sounds like you are having fun. My bike is a ‘78, so I don’t have your version of the ignition. So, I’m just thinking out loud. From your description, it seems to me that the problem would definitely be with the ignition. Since you swapped the bean can, which is the trigger device portion of the system, then that leaves the ignition module - which is the brains of the operation. It receives the crank position pulse from the bean can, determines electronically the advance, and pulses the 12v power to the coil to fire the plugs. Seeing as the fault is so rpm specific, and it affects both cylinders, seems like the module almost has to be the culprit. I’ve had an aftermarket electronic ignition in my bike that suffered a module failure, and it started with a stumble at cruising speeds. I don’t know about doing any maintenance or repairs to the module - I know certain editions used a heat transfer paste between the electronics and the aluminum heat sink that folks would reapply - but I don’t know if that applies to yours. I also see that EME has a replacement module at a seemingly incredibly low price - but it’s out of stock. MAX BMW also shows one. Not sure, but it looks like installing a replacement module may involve moving it to a new mounting location?? Apparently, BMW no longer offers the oem module.
Well, already need to correct myself. According to google, BMW still used a centrifugal advance mechanism inside the bean can. Only the K bikes had a fully electronic control, including the advance.
But still, I would suspect the module, since you swapped the bean can.
a) "The devil is in the details." Sorry, not enough information...
> "Swapped out coil" Did the new coil include new wires and plug caps ? Are these wires metal core ? Fully describe the brand and age of the plug caps.
> "Set timing correctly" Per me, or the instruction manual ?
> "New plugs" What brand? What number?
> Did you adjust the valves ?
> Have you replaced the Needles and/or Needle Jets. These should be replaced as a set every 10 years due to physical wear.
b) I somewhat doubt this is part of your issue, but the ignition control module sits on top of the frame under the tank. 1) It is mounted to the frame with heat sink paste. The old paste should be removed from both surfaces and should be renewed with a high-end PC-grade paste, such as Arctic Silver. 2) The multi-pin electrical connector to this module should be treated with a very thin coat of an anti-oxidation compound, such as NO-OX-ID.
c) A side note...
From 1976 on the US-DOT was mandating leaner and leaner carb settings... which eventually led to the need for liquid cooling. This is why they stopped making the Airhead. The extra heat caused by running lean also exacerbates the exhaust valve and ex valve seat issues. You've also got to remember that around 1990 not only were the jets getting leaner, but they also changed the gasoline formulations. A HUGE double whammy to all older engines !!
Thus when ordering Main Jets or Needle Jets I highly suggest you go to the next higher jet number (by 1 step) on both. This should result in the spark plug gaining back some of its color. The spark plug center electrode should not be white, but have some gray or (hopefully) take on a tannish wood-tone. Burning an extremely small bit more fuel will result in cooler engine temps and somewhat of a return to 1970's performance. (Not a full return because we can no longer buy 100 octane leaded fuel, but better.)
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
The coil that I swapped in is a stock coil that appears to be in good condition. The wires appear to be quite new NGK copper. Replaced plugs with BP7ES NGK. Valves were checked several weeks ago when bike was brought home (10mm intake-20mm ex). Timing was set with my Sun timing light at full advance. The carburetors appear to be recently rebuilt. Floats and float needle show no wear and look like new. Pulled the top off of one and diaphragm and needle look perfect. This bike ran perfectly for two weeks and just started this while riding down the road at about 55-60. missed just a little, then got worse. Still runs fine at low speed and higher rpms. Accelerates well after passing through the stumble but the missing is right at normal riding speed.
These things are so simple - it has to be an interruption in fuel or spark - yet sometimes they can be so challenging. For me, when that aftermarket ignition module started acting up, my “seat-of-pants” sense told me it was ignition. Because it was so abrupt and a complete power loss. Very brief, but I could tell. Like a flickering light bulb, all or nothing. Carb issues don’t usually present like that.
Hey, what about your kill switch? I’ve heard of those giving problems. And that kills 12v power to the coil. Maybe a vibration at 3500-4000 is affecting the kill switch. Crazy thought, perhaps.
i jumpered out my kill switch years ago, in the headlight shell. Because I kept inadvertently flipping it with the handlebar contacting my tank bag. I had never intentionally used it in 40 years, so didn’t figure I’d miss it.
The coil that I swapped in is a stock coil that appears to be in good condition. The wires appear to be quite new NGK copper. Replaced plugs with BP7ES NGK.
* But what about the Plug Caps ? Plug Caps can/will crack (often invisible) and allow arcing to the cyl head... which shorts out the HT. Remember that the energy is looking for the absolute shortest path back home. Try a new set of 5K Ohm caps, like THESE.
* Speaking of cracks, the porcelain of the spark plug can also get broken and leak the HT energy in the same way. (My brother once had a Harley and the prospective buyer was "hovering" so he told him to install the spark plugs. The engine developed an ignition miss and the buyer backed out. The next 2 months were spent looking for the cause... which turned out to be a cracked spark plug.)
Valves were checked several weeks ago when bike was brought home (10mm intake-20mm ex). Timing was set with my Sun timing light at full advance. The carburetors appear to be recently rebuilt. Floats and float needle show no wear and look like new. Pulled the top off of one and diaphragm and needle look perfect.
* You cannot "see" the wear on the Needle or the Needle Jet. You simply have to replace them.
* Any Needle or Jet wear would make the engine run slightly richer. (Usually a good thing, as previously explained.) You'd be able to see this result on the plugs if you looked at the plug colors exactly at the RPM of the issue.
* To inspect a diaphragm you'll need to pull the slide out, then go around the rubber part stretching every segment to look for splits, tears and cracks, no matter how tiny. Diaphragm cracking is common on older bikes because the original diaphragm material (like that of the floats and float needles) was not rated for Ethanol fuel. It doesn't matter that all the internal parts "look new", if they are pre-Ethanol then they must be replaced.
Remember: Your 1989 bike pre-dates the fuel change. So anyone working on an older vehicle has to have a "sense of history". There's a certain historical context that must be kept in mind when looking at these issues which demands more than a cursory glance. Each piece must get looked at under a microscope.
>> 1989 also came with the Exhaust Gas Recirculation system. Is your system intact or removed ?
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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