R80 lost top end speed. Head scratcher.

Within the past week or so, my '81 R80G/S has lost it's top end speed. On a flat run it will hit 90 at 6K RPM, but that's it. Coming over my mountain pass
commute, best it will make is 80. It will hit red through 3rd gear, and the tach needle looks like the tach is "clipping" under acceleration (gets it's input from the coil), but just for a bit. Every where else the bike runs like a clock. No ping, knock, or oil consumption. Plugs are a nice tan. Fuel consumption is up, but I think it's because I am screwing with it. It pulls all the other hills fine and it used to pull the pass at 90+ (it's a nail biter on the WA freeways close to 100, so never got it past 101. The roads here have gone to crap since the shutdown.)

It has been converted to points with a dyna booster.

Been through the carbs, clean. Changed the diaphragms, no help.
Points are set. Carbs balanced.
Top ends/pistons done two years ago and valves are adjusted properly.
New spark plugs and the wires are good.
Fuel flow is around 400cc/min./side.

Really it acts like it just isn't getting enough gas, or has a major vacuum leak. The carb boots look good. Can't find any thing wrong with the fuel system.

So, I'm going to change the condenser thinking that my be causing the tach to clip, and maybe be my problem. If that doesn't help, pull the tank and ohm out the coil. I haven't done a compression check yet.

Am I headed in the right direction thinking it's electrical? Or is there some thing I'm missing? Any one have this problem?

Open the throttle fully and see if you can pull/push on the cables just before they connect to the carbs.
This will prove whether or not your cables/throttle handpiece are in order and fully opening the butterfly.

yeah..you can also just reach down doing 80 at WFO and haul on one of the throttle cable housings and see if there some more there you aren't getting.

I would check timing and clutch adjustment. Especially check point gap. it is theoretically possible to run out of dwell at high RPM, but unlikely. If the booster uses a condenser (confirm it) then change that and clean it's grounding point.

Look for loose connections at the coil low side, clean the spark plug cables both ends and the coil sockets, silicone lube in both.

Test the coil for good sparks leaving the plugs installed and putting a brand spanking new plug on the cable end, and grounding it.


Slow the fuck down. Getting killed is your business. Not leaving enough of a wreck for someone else to build back up is every bodies business.

Well I did start typing 'reach down with your left hand and'...................but then I also thought about batoutoflahonda not leaving enough parts for us.

As it is pulling redline in third, I would first suspect yo butterflies not fully opening.

You could have a pinhole in one of your diaphragms, your timing may be off, float levels low causing lean condition, tank vent blockage causing lean condition. Check your coil wires. I had a similar thing on my RD and I found the coil wires were corroded where the wires went into the coil. It ran great except at the top of the rev range under WOT. Even then it wasn't bucking like you'd expect, it would just surge a little, and not make the kind of power it should.

The dyna booster I used did not require a condenser - but the condenser could be left connected to the points. The points act as a digital switch for the dyna booster (DC voltage) and the condenser is there for converting back to standard points use (when the dyna booster fails).

I would check the float bowl levels and the ignition timing. I would also consider running a can of fuel system cleaner through the engine - for no other reason than it will help clean carbon off the valves. If the ignition system works fine in third gear at 7k rpm, no more electrical energy is needed to operate in fifth gear at 7k. But, being thorough and meticulous in checking the coils can't hurt. Good luck!

Just trying to help but that is patently not right. It does take more energy to fire the plug at the same rpm in a higher gear for the same reasons it takes more energy to fire higher compression. Higher brake mean effective pressure. It takes more energy to fire a plug at the same rpm in the same gear going up a hill. Why? Again, BMEP.

It could be a lot of things BAOLA. Just to save time, whenever I am working on a bike with points and it isn't running right, the first thing I check is the points. Chances are there's your trouble. There are a lot of good reasons why even lawn mowers no longer use points.

Check your air filter.

Interesting. I have never heard nor read any documents or experienced that higher cylinder pressures require more spark plug energy. Heat, on the other hand, will. The two are interrelated because of the gas in the cylinder. But, at 80 mph, heat is not a big problem.

Regardless (or irregardless), the primary ignition circuit is in no way affected by the transmission gear or engine temperature. So, looking for gremlins in the dyna booster will not be productive, IMO. Good luck!

The problem may be present, but less noticeable in the lower gears. I wonder if you were in third gear going up a really steep hill with the throttle pinned if you'd get the symptom. I bet you would.

Irregardless is not a word. The prefix and suffix are redundant, or even negating one another

Isn't it funny what some people hear and read? I have heard and read what I posted up above all over the place. I have experienced it all over the place too. It should be a common fact: The more pressure in a cylinder, the more energy it takes to get a good spark across the spark plug gap. It makes perfect sense in my mind. Especially since I run into this fact all the time working on bikes.

The primary ignition circuit can be very much effected by heat and vibration. That is in part controlled by engine temp and load (what gear it's in). The secondary circuit is very much effected by BMEP as well which is very much effected by load/temp/pressure.

Irrespective of our best intentions, the English language continues to evolve -

http://www.mtpioneer.com/2012-June-Irregardless.html

As long as confusion is avoided, I guess it doesn't matter. Airhead enthusiasts seem to take extra care in conveying their thoughts but sometimes a few errors creep in. Maybe someone should start a thread. My pet peeves -

• pore vs. pour
• damp vs. dampen
• inflammable vs. flammable
• sleight vs. slight

But then again, what do I know? I missed out on inventing 'twerking'.

Irregardless - not a made up word (by me at least):

http://www.oxforddictionaries.com/us/definition/american_english/irregardless

http://dictionary.reference.com/browse/irregardless

http://www.merriam-webster.com/dictionary/irregardless

and yes, irregardless is similar to infammable:

http://www.merriam-webster.com/dictionary/inflammable

The point of using the word Irregardless - was to add emphasis. I will let the reader determine the content for emphasis.

The most common failure in the old Lucas K2F Magnetos (used on British built twins like Norton Atlas, Royal Enfield Interceptor, Matchless...) is for a short to develop within the armature coil.
The bike will idle, but dies when you try to apply any power at all.
A static test with a spark plug shorted out against the cylinder head will always show a nice blue spark, but when the plugs are screwed back into the engine and you put the bike in gear and let out the clutch, it dies.
I've had this happen to two different magnetos in my Enfields over the years.

You have a bike with ignition points. Therefor the first thing to check for most performance complaints is the ignition dwell and timing. This particular complaint is often a small hole in diaphragm tho.

If points are right and diaphragms are right there may still be an ignition problem. I don't ever see may other riders report this but when a Dyna Booster went out on my bike almost ten years ago it got weaker and weaker in a couple of stages. It did not die all together at one time. I got some miles with poorer performance before it was completely dead. Then when I went back to stock points the bike was fine again. So if everything else looks and tests fine revert ignition back to points only to test if there is a problem with the Booster.

When my airhead failed to get pass 5K rpm, it was because of a broken ring in one of the cylinders.

I belong to the "no irregardless" camp. The "ir" is redundant.

Rather a large clue right there.

Do gas stations in your area change to winter formula gas right about now?

I'd CAREfully check the diaphragms. Sometimes you need to gently stretch them a bit and hold them up to the light to see smaller tears in them. It doesn't take much of a hole to make a big drop in power.

it also takes little stretching and poking to turn a perfectly good diaphragm into junk. At which point you get to replace it, think you found the problem and find out you haven't.

If it is running lean at high RPM due to a diaphragm problem, it won't be on both sides. So a look at the plugs or quickly check head temps with a cheap IR thermometer to reveal the condition. Then you go looking for a cause. If you find no evidence of it running lean, go looking for something else.

OP stated plugs were normal. But he didn't state if he did a high speed chop when the power was down.

No AW. I think it's winter mix gasoline. Slightly lowering gasoline's boil point always slows my bike down at least 20mph.