High RPM miss

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Johnny Boy

Member
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Mar 5, 2018
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Location
Crossville, Tn.
Hello fellow Wingers. I have a 1980 1100i. I got it a couple of months ago. It starts, idles, revs clean to 5500 rpm, shifts, brakes and generally runs well. 27,000 miles on the clock. However when running hard through the gears it has a miss right at 5500 rpm.

I checked the fuel flow from the petcock and installed a new Napa fuel filter. I pulled the carbs and checked the float heights. They were right on at 15.5mm. Jets and related bits were removed and checked for blockage of the tiny side holes, all clean. Float needles and seats sealing well, not leaky. Mixture screws were set to 3.5 turns out. I reset them to 2.25 turns out. The slides on the top move clean and smooth up and down.

I put the carbs back on and did a carb sync. I have the Twinmax carb sync tool. Nothing changed, I still have the same miss.

I then went after the spark. I removed the coils and wires. One coil ohm tested bad, one tested good. I ordered a set of Caltric (?) coils off Amazon. They came with new wires. I am not running a radio or intercom so I removed the 5k ohm resister in the plug caps. I had some thick solid copper wire and cut pieces the same length as the small 5k ohm resisters. I put the wire pieces in place of the resisters. I then confirmed continuity through the wires and caps. The plugs are new NGKs.

I then took it for a test ride expecting no miss considering it had a bad coil and now has 2 new coils and non-resister caps. No luck, still a miss at 5500 rpm.

I then read about the vacuum ignition advance. I pulled the hose off carb #3 and applied vacuum to the hose (to the advance). I didn't hold the vacuum forever but it took a very long time for the needle to move a small amount. That looks like pretty good vacuum, right? Well, I tried running without that vacuum line attached. I capped the nipple on carb #3. Right from the start it missed bad and ran terrible. I pulled over and re-attached the vacuum advance hose to carb #3. It then ran good but with the original problem (5500 rpm miss).

Air filter is a new Emgo. The exhaust is not collapsed. Non-ethanol (not old) gas.

I'm stumped fellas. Can anybody help?
 
Three things to check or do. First mixture screws should not all be the same. Adjust procedure is in the book. I do not use the idle drop. Second mechanical advance may be rusted and not functioning. Third Fuel pump may be getting too weak to flow enough supply for the higher rpm.
 
I am leaning toward the mechanical advance being stuck. My 81 revs to 8k on pretty much every ride I take on it. When the mechanical advance is stuck then your base timing can be set incorrectly.
 
Perhaps the voltage supply to the coils is not quite up to snuff. Several here have wired the coils with a relay, direct from the battery, to eliminate the ignition switch causing problems. Just a thought. :yes:
 
Well I checked the vacuum hose, good. I don't think the mixture screws being set the same (2.25 turns out) would cause a misfire at 5.5k.
I'll try running a hot to the coils first, sounds the easiest.

Do I use a standard 12v relay from the auto parts store? So hot from the battery to the 12v relay then to the hot wire that feeds 12v to the coils? I haven't ever run a relay so just 12v in then 12v out right?

Thanks fellas.
 
The voltage at the black/white coil feed is down more than 1 volt from battery voltage. I cleaned up the stop/run switch on the bars. I cleaned up all the connectors and grounds and glass fuses. I didn't remove the ignition switch but I cleaned the connector from the switch to the harness with contact cleaner. After all that cleaning I still had the 1+ volt drop at the coils. 13v at the battery, 11.8v at the coils feed wire.

I initially thought the miss was electrical now I'm not too sure. I mean I found a bad coil and replaced both, new wires, removed the resisters in the caps. Still got the miss. I still plan to try the direct feed with a relay to the coils. But it looks like I'm dropping just 1.2 volts from the battery to the coils.

Do all the bikes in Classic Goldwing land have full battery voltage at the coils? If they do then it looks like my ignition switch is robbing too much voltage. If 1.2v +/- drop at the coil feed is typical then my miss is caused by something else.

Anybody feel like checking their battery volts and their coil feed volts?
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=203305#p203305:2wus8h53 said:
Johnny Boy » Wed Jun 06, 2018 8:32 pm[/url]":2wus8h53]
The voltage at the black/white coil feed is down more than 1 volt from battery voltage. I cleaned up the stop/run switch on the bars. I cleaned up all the connectors and grounds and glass fuses. I didn't remove the ignition switch but I cleaned the connector from the switch to the harness with contact cleaner. After all that cleaning I still had the 1+ volt drop at the coils. 13v at the battery, 11.8v at the coils feed wire.

I initially thought the miss was electrical now I'm not too sure. I mean I found a bad coil and replaced both, new wires, removed the resisters in the caps. Still got the miss. I still plan to try the direct feed with a relay to the coils. But it looks like I'm dropping just 1.2 volts from the battery to the coils.

Do all the bikes in Classic Goldwing land have full battery voltage at the coils? If they do then it looks like my ignition switch is robbing too much voltage. If 1.2v +/- drop at the coil feed is typical then my miss is caused by something else.

Anybody feel like checking their battery volts and their coil feed volts?
That voltage drop is the reason for this suggestion. viewtopic.php?p=203023#p203023
 
As I said, I do plan to try that. A few posts back I asked for a "how to" to hook up the relay, thinking someone here might have done it, seeing it was suggested. But if you want to keep it a secret and not help a brother out, so be it.

In my last post I was inquiring if a small voltage drop could cause the miss. And if a forum member was familiar with the typical voltage drop from the battery to the coil feed....if in fact any voltage drop is typical.

I'm a long time member of other (model) motorcycle boards and am only happy to help when someone runs into a problem that I'm familiar with...still hoping someone here has been down this "high RPM miss" road.
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=203314#p203314:lshohevi said:
Johnny Boy » Thu Jun 07, 2018 3:04 pm[/url]":lshohevi]
As I said, I do plan to try that. A few posts back I asked for a "how to" to hook up the relay, thinking someone here might have done it, seeing it was suggested. But if you want to keep it a secret and not help a brother out, so be it.

In my last post I was inquiring if a small voltage drop could cause the miss. And if a forum member was familiar with the typical voltage drop from the battery to the coil feed....if in fact any voltage drop is typical.

I'm a long time member of other (model) motorcycle boards and am only happy to help when someone runs into a problem that I'm familiar with...still hoping someone here has been down this "high RPM miss" road.
There are many previous post here about installing relays and their wiring schematics. I honestly believe that you would do well to google a YouTube video about relay installs. I have just done one on a CB750 k6 but it may not help because I only took some pictures at the end
 
My thought... and this isn't coming from any particular flat-four incidence, but rather, just an engine in general thing... is that you might have one valve spring that's just a wee bit weak, and a little crud on a stem, such that it's not closing up quite soon enough...

I dunno these engines like I know my CX-D... can the valve lash be opened up a bit to 'earlier' the on-seat time for a short term test? If so, giving it about twice as much valve lash, one valve at a time, then spinning it above the miss point, MIGHT give you an audible indication of which valve, which spring...
 
Well I tried the hot w/relay to the coils. Positioned it where the radio face was. Didn't solve the miss. This has got me stumped. I think I'll check the valve clearances then sync the carbs next. I'll get this sooner or later. Wish me luck.
 

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Valve Spring PRESSURES... not just clearance... PRESSURE.

See, the valve has inertia. When you push it open, you take it from sitting still, to motion... and then to close it, the SPRING must push it back... but if there's a spring that's a little weak... the mass of the valve will resist the springs force, causing it to not close fast enough... and that causes compression and vacuum to go to pot.

Faster the engine is spinning, the more spring tension is required to keep them from 'floating'.
 
I know how to check clearances but are you suggesting I remove the heads, disassemble them and check the valve spring pressure? There are only 27,700 miles on the bike.
 
The 'Formal' way to test springs, is to release the keepers, take the spring out, and put it on a test tool... but on an OHV, it doesn't require removing the heads. Turn the crank 'till piston is at TDC, then push in on the spring holder... valve will open 'till it touches the piston, a little more push, and the keepers will be exposed, take 'em out (I use hemostats), then the spring holder will slip back over the stem, you can then take the valve spring out and test it...

But that's not what I do. I make sure the crank is not in a position for the cam to partially open a spring... then I push on the valve with my hand, and feel the pressure. A soft spring will, if your hands and brain are sensitive, be pretty noticeable. Pop the valve covers, and push on each valve with the palm of your hand... right on the back of the rocker. If one moves easier than the rest, pull and test them ALL, and replace any that are weak.

Some types of valve spring pressure tools will work in-situ, however, I have no clue if there's one that'll work on a GL motor.

Low miles guarantees absolutely nothing. Matter of fact, long years and LESS miles, means there's a higher likelyhood of sacked-out spring.

Why?

Because the engine sat in one position... with one valve open... for a decade or more.

I frequently revive engines that have been 'asleep' for half-a-century, and folks bring me engines that they THINK are 'shot'. When I'm faced with one that's been sitting for a long time, I pretty much assume that it'll need at least a COUPLE springs. If it's a flathead, I pull the head, lift out all the valves, clean the ports and seats, wire-brush the valves, clean out the guides with solvent, check spring pressures, use some lapping compound and a sucker-stick to bed the valves into the seats, then put the springs and keepers back in. Amazing how it helps out an engine... but I've pulled apart an engine that had 22 hours' runtime after a rebuild in 1947... and sat 'till 2006, and it started and idled fine, but would NOT make it past 1100rpm, on account of one intake, and one exhaust valve spring (on two different cylinders) that were totally shot... developing about 12lbs on a 60-lb spec...

But high speed miss... if it's not ignition triggering, it's a lean mixture, plugged up exhaust, or floating valve.
 
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