Loss of power at 4,000 and up.

DennisDarrow said:

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Learn to read ….Sorry they don't teach that any more. Anyway, not to be RUDE, as the "YOUNG TIMER" is......Having gone through slides and vacuum carbs those are not suggested. Instead what is advised is to find out loss of vacuum and starvation of fuel that would imitate what happens with a vacuum type carb to cause the condition that is being experienced at 4K RPM...……Ever even put your palm over the intake of a lawn mower back when you were in the 4th grade and felt the vacuum??????…..LEARN TO READ and keep your rude comments under your hat...…….

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I apologize if I had come off rude, not my intention. I am not always the most eloquent when it comes to non verbal communication.

So the consensus is a fueling issue? Would we be suspecting too lean or too rich, its a super easy adjustment so I suppose I can give it a whirl either way.

I just wanted to may sure I have all my ducks in a row for timing as well since I can fiddle with a carb for hours and never fix anything if its an ignition problem. Being that the concern isnt present until the bike would be at max advance. Considering the max advance is now adjustable for me, it introduces variables that I am not quite certain of the best way to navigate.

Am I understanding correctly that with no load, it sort-of spins up, but with a load, it just won't?
And is the "load" actually on the street, or maybe a stationary stand? Just being picky for troubleshooting ideas here.
That's an odd one, and I doubt that the wrong resistance of the spark lines are a factor in that.
A maybe - plugged exhaust... Also, recall that many Evo Harleys got hit with leaky intake manifolds, cheap rubber (Jerry Branch made a few bucks on replacements).

Lectrons aren't new tech; they've been used (with varying degrees of success) on Harleys and in-line Japanese fours (including at Bonneville). Carbs don't much care what they're mounted up to; it's us silly humans that want them set up and tuned for the specific application. As simple as they are, some have said "They're what Amals wish they could be."

DD - Thanks for that! I'm over 65...

Paul S

Pauls1150 said:

Am I understanding correctly that with no load, it sort-of spins up, but with a load, it just won't?
And is the "load" actually on the street, or maybe a stationary stand? Just being picky for troubleshooting ideas here.
That's an odd one, and I doubt that the wrong resistance of the spark lines are a factor in that.

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I did the typical "spray it with brake clean and see if the idle changes" for the intake boots, no change there. Wouldnt hurt to get a newer set though.

As far as the exhaust system, its the stock headers and essentially a gutted slip on with very minor baffling, only been on the bike for about 500 miles.

No load, on the center stand in neutral, it revs normal until 4k till 4500, then winds out aggressively (as it should considering the aggressive cam in it)

Loaded is riding in essentially any gear. Just gets worse the higher the gear I'm in but, at no time while riding does it "pick up" and rev like it does in neutral.

It sounds more fuel related to me. What have you done as far as carb tuning? It sounds either slightly lean, or extremely rich on the mid to high RPM. Lean would be my guess. Have you adjusted the power jet?

Certainly the Bings are not for performance, but they are surprisingly versatile. Typically there are three regions of use with the Bings and which jets are primarily being used - idle jet, needle jet, main jet. In the Bing book they show the range over which each jet is operating based upon throttle position, and of course, there are overlapping areas. In troubleshooting Bings, you basically figure out which region you're in and make some adjustments.

I think you should get something like that for the Lectron carbs. Could be useful in trying to figure out which jets need to change in order to blend better as throttle is added.

I think the earlier R100s were 9.0:1 to 9.5:1 compression ratio. But after 1980, I'm pretty sure the ratio dropped to something like 8.2:1. So, I suspect you've really changed the way the engine wants to run - with the bigger jugs and cam coupled with the non OEM carbs - I think it does really suggest that you'll need to do some performance tests with small changes until you hit on something.

As for rich/lean, you can use the old fashioned plug-chop method to see how the bike is running. Find a safe spot to do it, but run at a certain speed that you want to test at for a mile or so. Chop the throttle and quickly shut the engine down. In that safe place, look at the plugs...all white would be lean, blackish would be rich. You could also consider where the float level is if the Lectron has that. You get to the bogging situation...quickly shut the bike down and see what the fuel levels are.

Reference post #16 - I've been looking for the timing spec and can't find it, so... Can you see the timing marks in the window with a strobe light? That will get you easily within the ballpark.
Also - try entering SITE:forums.bmwmoa.org "ignition timing" into Google.

One thing I am not seeing mentioned here is gas cap vent. Try popping the gas cap open see if that fixes your problem. If the vent is plugged all looks good until you get to max fuel usage.
Gator