Under load - rough performance

[jjs1234]

Hey everyone. Long time no see!


Had to garage the bike for that ridiculous North-Cal winter we just had. Some 60ft of snow fell!




Well now that its warmer and the snow is gone, I am back into riding! But I have an issue. As some of you might know, I completely re-built my bike last year. All new rubber, paint, K1100 front end + rims, spark plugs, 4-hole injectors, fuel-filter. The works. However I am having an issue.


The bike runs rough, under load. It almost and I mean almost sounds like a v2. However I have no issues revving it up (not under load).


When I am riding, it accelerates faster at 50% throttle than 100%. In-fact 100% throttle practically does nothing at all. It also needs the idle adjusted because it basically dies if the choke (throttle adv.) isnt on.


I am trying to figure out the likely culprits. I do not have a altitude plug (currently at 5,800ft) and wondering if that would help?




In my mind I am thinking of a:


- Throttle Sync
- Airbox Sync
- Valve Adj.
(I have no idea when they were last done- if ever).


I did do the "Propane test" to check for leaks. No issues found.

1st pic: I disconnected this when running (I forget what it does) and nothing changed.


Thanks!


85' K100 2v

[Motorhobo]

Sounds like you might be dropping a cylinder at high revs. Did you check to see if any of the plugs is wet with unburnt fuel? When you changed all your rubbers, did that also include the spark plug wires?


If one if the spark plug leads is bad, the spark will arc off onto the block, the plug won't fire, the cylinder will flood. The more gas you give, the more unburnt fuel will be pumped into the flooded cylinder and your power output will drop. At least that's the way I remember it happening when one of my wires failed.


To test, wait till the sun goes down, pull the spark plug cover off, throw a blanket over the headlight, start the bike and look for a spark at the plugs. If you can see the spark then you have a bad wire, or more than one bad wire.

[wally.fisher]

Hey everyone. Long time no see!


Had to garage the bike for that ridiculous North-Cal winter we just had. Some 60ft of snow fell!




Well now that its warmer and the snow is gone, I am back into riding! But I have an issue. As some of you might know, I completely re-built my bike last year. All new rubber, paint, K1100 front end + rims, spark plugs, 4-hole injectors, fuel-filter. The works. However I am having an issue.


The bike runs rough, under load. It almost and I mean almost sounds like a v2. However I have no issues revving it up (not under load).


When I am riding, it accelerates faster at 50% throttle than 100%. In-fact 100% throttle practically does nothing at all. It also needs the idle adjusted because it basically dies if the choke (throttle adv.) isnt on.


I am trying to figure out the likely culprits. I do not have a altitude plug (currently at 5,800ft) and wondering if that would help?




In my mind I am thinking of a:


- Throttle Sync
- Airbox Sync
- Valve Adj.
(I have no idea when they were last done- if ever).


I did do the "Propane test" to check for leaks. No issues found.

1st pic: I disconnected this when running (I forget what it does) and nothing changed.


Thanks!


85' K100 2v

That is the Throttle position sensor, on the 100 it sensors throttle open or closed, some of us disconnect it, though it can cause the bike to backfire on deceleration.


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[jjs1234]

Sounds like you might be dropping a cylinder at high revs. Did you check to see if any of the plugs is wet with unburnt fuel? When you changed all your rubbers, did that also include the spark plug wires?


If one if the spark plug leads is bad, the spark will arc off onto the block, the plug won't fire, the cylinder will flood. The more gas you give, the more unburnt fuel will be pumped into the flooded cylinder and your power output will drop. At least that's the way I remember it happening when one of my wires failed.


To test, wait till the sun goes down, pull the spark plug cover off, throw a blanket over the headlight, start the bike and look for a spark at the plugs. If you can see the spark then you have a bad wire, or more than one bad wire.

By the looks of it, I did not replace the spark plug cables...

I will try that night trick!

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[jjs1234]

Sounds like you might be dropping a cylinder at high revs. Did you check to see if any of the plugs is wet with unburnt fuel? When you changed all your rubbers, did that also include the spark plug wires?


If one if the spark plug leads is bad, the spark will arc off onto the block, the plug won't fire, the cylinder will flood. The more gas you give, the more unburnt fuel will be pumped into the flooded cylinder and your power output will drop. At least that's the way I remember it happening when one of my wires failed.


To test, wait till the sun goes down, pull the spark plug cover off, throw a blanket over the headlight, start the bike and look for a spark at the plugs. If you can see the spark then you have a bad wire, or more than one bad wire.

The Oiliest one is #3 Cyl.




 They are Bosch. Also there was a Dielectric grease on the contacts. Would that affect anything? (I Learned that Dielectric grease is NOT Conductive). So maybe that is the cause...? Should check it out!

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[Motorhobo]

Well...I'm no K-bike genius but if it were me I'd be trying to find out whether all the cylinders are firing like they're supposed to be, and to do that you need to start from square 1 -- clean plugs. So if it were me, I'd probably get a bit of gasoline and a wire brush and gently remove any oil or residue from those plugs, dry them off with hot air then put them back in, start the bike, let it run until the problem you describe occurs, then shut the bike off immediately and inspect the plugs again. If there is unburnt fuel on one of them, then it is not firing. Your plugs are currently so fouled it's hard to tell anything from them, at least it appears that way to me.


You didn't mention in your first post whether the battery was one of the things you replaced. Where I'm going with this is that once I had a battery that was on its way out and didn't have enough juice to adequately start the bike. One of the cylinders was consistently flooding out because it wasn't getting enough spark to ignite the fuel in the cylinder. Long story short, new battery -- problem solved. That might not be your problem but if I were you I'd be wondering why that one plug looks so wet and what it's wet with...


Hoping someone smarter than me will chime in here...

[jjs1234]

Well...I'm no K-bike genius but if it were me I'd be trying to find out whether all the cylinders are firing like they're supposed to be, and to do that you need to start from square 1 -- clean plugs. So if it were me, I'd probably get a bit of gasoline and a wire brush and gently remove any oil or residue from those plugs, dry them off with hot air then put them back in, start the bike, let it run until the problem you describe occurs, then shut the bike off immediately and inspect the plugs again. If there is unburnt fuel on one of them, then it is not firing. Your plugs are currently so fouled it's hard to tell anything from them, at least it appears that way to me.


You didn't mention in your first post whether the battery was one of the things you replaced. Where I'm going with this is that once I had a battery that was on its way out and didn't have enough juice to adequately start the bike. One of the cylinders was consistently flooding out because it wasn't getting enough spark to ignite the fuel in the cylinder. Long story short, new battery -- problem solved. That might not be your problem but if I were you I'd be wondering why that one plug looks so wet and what it's wet with...


Hoping someone smarter than me will chime in here...

I cleaned them. Including the grease. All spark, but as the bike was running #3 exhaust pipe was not getting hot. Shut her off...

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[Motorhobo]

BTW those wires in the bottom pic appear to be the brass-capped OEM ones. If they are, either the PO had a lot of money to throw away on sick overpriced OEM cables or they're the originals, which means they're probably on their last leg. I don't know anyone who has bought OEM spark plug wires for over a decade.

[jjs1234]

Well...I'm no K-bike genius but if it were me I'd be trying to find out whether all the cylinders are firing like they're supposed to be, and to do that you need to start from square 1 -- clean plugs. So if it were me, I'd probably get a bit of gasoline and a wire brush and gently remove any oil or residue from those plugs, dry them off with hot air then put them back in, start the bike, let it run until the problem you describe occurs, then shut the bike off immediately and inspect the plugs again. If there is unburnt fuel on one of them, then it is not firing. Your plugs are currently so fouled it's hard to tell anything from them, at least it appears that way to me.


You didn't mention in your first post whether the battery was one of the things you replaced. Where I'm going with this is that once I had a battery that was on its way out and didn't have enough juice to adequately start the bike. One of the cylinders was consistently flooding out because it wasn't getting enough spark to ignite the fuel in the cylinder. Long story short, new battery -- problem solved. That might not be your problem but if I were you I'd be wondering why that one plug looks so wet and what it's wet with...


Hoping someone smarter than me will chime in here...

Not meaning to double post, but don't these plugs get that fouled by Design? Because the oil seeps into the cylinder right? Also I had replaced the battery. The lithium-ion did not work so I replaced it with a standard Duralast Gold AGM.

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[Motorhobo]

I cleaned them. Including the grease. All spark, but as the bike was running #3 exhaust pipe was not getting hot. Shut her off...

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Well, now maybe you could swap #3 wire to another cylinder? If that one doesn't fire, then you've got a bad wire. Or wait till dark  :2thumbup:

[Motorhobo]

I personally don't remember having plugs that ever looked all wet and oily like that. I remember them being wet if the cylinder isn't firing...don't remember the oily part.

[jjs1234]

I personally don't remember having plugs that ever looked all wet and oily like that. I remember them being wet if the cylinder isn't firing...don't remember the oily part.

So as I recall the cylinders spark in pairs right? So since the number 3 cylinder isn't working I swap the plug with the number one cylinder. It is still not firing. Hmm...

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[Martin]

Read up how to do a plug chop and do it. Sorry about to go to work. I can explain more tonight.
Regards Martin.

[Motorhobo]

Maybe it just needs to dry out for a while...sounds like you're not giving it much rest between tries. Usually when a car floods out aren't you supposed to wait 10 minutes before recranking the engine?


I don't think it matters which wire you swap where, does it? As long as the wire reaches its destination....


BTW you wrote above 'All spark but as the bike as running #3 exhaust wasn't getting hot...'  What do you mean 'All spark...' Where were you testing for spark?

[Motorhobo]

Read up how to do a plug chop and do it. Sorry about to go to work. I can explain more tonight.
Regards Martin.

Plug chop -- that's what it'd called...thanks Martin, good advice.

[jjs1234]

Maybe it just needs to dry out for a while...sounds like you're not giving it much rest between tries. Usually when a car floods out aren't you supposed to wait 10 minutes before recranking the engine?


I don't think it matters which wire you swap where, does it? As long as the wire reaches its destination....


BTW you wrote above 'All spark but as the bike as running #3 exhaust wasn't getting hot...'  What do you mean 'All spark...' Where were you testing for spark?

I had attached all the spark plugs to each cable and ran the starter looking for a spark.

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[Motorhobo]

I don't think it matters which wire you swap where, does it? As long as the wire reaches its destination....

BTW lest someone rap my knuckles for saying stupid s**t, when I say swap cables I mean the whole cable from coil to plug, not just slap any end on any plug. I know that goes without saying but I said it anyway.

[jjs1234]

So I fixed the issue. I was putz-ing around with the spark-plug 3# and decided to widen the clearance on it.


That apparently fixed the problem. Not quite sure how it happened. Maybe I need to check all of them. I can remember not setting the clearance when I bought the plugs though... :yow  I think they should be 0.035 ?


Still the issue of Idling at 480-520 rpm, and having the valves, AF, and throttles synced.

[Laitch]

plugs though... :yow  I think they should be 0.035 ?

.024–.028

[jjs1234]

.024–.028

Hmm. Saw the .035 on the k100 forum. Set it to that... 😱

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[Laitch]

Hmm. Saw the .035 on the k100 forum. Set it to that... 😱

I got my numbers from an ancient K100 Rider's Manual unearthed along with a pile of rune stones at an archeological dig deep within the foggy vails of the WWW. Here's a copy for you.

[jjs1234]

I got my numbers from an ancient K100 Rider's Manual unearthed along with a pile of rune stones at an archeological dig deep within the foggy vails of the WWW. Here's a copy for you.

Much appreciated :)

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[Laitch]

Much appreciated :)

Much appreciated :)

Buy and install the altitude plug aka contact ring 61 13 1 459 504. Then adjust the valves. Then, if your air filter is clean, balance the throttle bodies and set the idle according to specs in manuals that you should already have but that you can download for the Repair Guidance section's Master list if you don't. Then, hit the road, Jack.

[jjs1234]

Buy and install the altitude plug aka contact ring 61 13 1 459 504. Then adjust the valves. Then, if your air filter is clean, balance the throttle bodies and set the idle according to specs in manuals that you should already have but that you can download for the Repair Guidance section's Master list if you don't. Then, hit the road, Jack.

Am I correct to assume that the altitude plug plugs into here? I remember removing some sort of cigarette lighter plug in my rebuild.

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