They need to transmit sufficient energy for efficient combustion of fuel.

Those spark plugs don't smell of fuel and smoke is not emitted from the exhaust pipe during operation?

Laitch wrote:Those spark plugs don't smell of fuel and smoke is not emitted from the exhaust pipe during operation?

When operation it's not smoking.
I've check the spark plugs, 1 and 2 are like the previous picture, a little oily, little smell of fuel and the head is black.

But it's not for the 3 and 4 :

You seem to have located the site of the problem—cylinders #1 and #2. You indicate their cylinders' compression is within allowable variance with #3 and #4 and all cylinders are within the Good compression range. You indicate their coil pack resistance numbers are within specifications found here and are in agreement. You don't know the resistance of the #1 and #2 plug wires as compared with #3 and #4 wires. Are the plug wire terminals within the #1/#4 and #2/3 coil packs clean?

You also don't know what is creating oil deposits and fouling the plugs so they couldn't fire efficiently. Usually oil leaking into the combustion chamber caused by worn valve seals will emit some smoke with the exhaust while it is fouling the plugs ad increased oil consumption will be likely., but you indicate neither is happening. Are you certain the sludge on the plugs is from oil and not soot mixed with coolant or fuel? Is the coolant level stable in the coolant reservoir during all this?

If the plugs aren't firing, there will be no smoke but there will be a strong smell of fuel somewhere and a distinct loss of engine power, yet you indicate power is acceptable. If you rode this moto before doing the latest work, is there less power now? What is your ground speed at 5000rpm in fifth gear?

Believe it or not, you are getting close to resolving this.

Laitch wrote:You seem to have located the site of the problem—cylinders #1 and #2. You indicate their cylinders' compression is within allowable variance with #3 and #4 and all cylinders are within the Good compression range. You indicate their coil pack resistance numbers are within specifications found here and agree with the #3/#4 pack numbers. You don't know the resistance of the #1 and #2 plug wires as compared with #3 and #4 wires. Are the plug wire terminals within the #1/#2 coil pack clean?

You also don't know what is creating oil deposits and fouling the plugs so they couldn't fire efficiently. Usually oil leaking into the combustion chamber caused by worn valve seals will emit some smoke with the exhaust while it is fouling the plugs ad increased oil consumption will be likely., but you indicate neither is happening. Are you certain the sludge on the plugs is from oil and not soot mixed with coolant or fuel? Is the coolant level stable in the coolant reservoir during all this?

If the plugs aren't firing, there will be no smoke but there will be a strong smell of fuel somewhere and a distinct loss of engine power, yet you indicate power is acceptable. If you rode this moto before doing the latest work, is there less power now? What is your ground speed at 5000rpm in fifth gear?

Believe it or not, you are getting close to resolving this.

Thank you for your detail feedback, as always.

I check the resistance of all wire
#1 4,89k
#2 5,03k
#3 4,85k
#4 5.25k

They are all clean.
Maybe it's not oil indeed, but the coolant is at the same level..
It doesn't seems to have less power, and I don't have any smoke..
Tomorrow i will check the 5000rpm on 5th if the weather is good.

Replace the fouled spark plugs, ride out again, compare your rides and also determine if the plugs are fouling quickly or are resisting fouling.

If you have fouled plugs on #1 and #2 which fire off different coils then the problem will be down stream. If your temp sensor or maf were reading incorrectly then all cylinders would be affected.
Check your HT leads for correct resistance and even your spark plugs (they should be <0.3Ω). As they develop resistance the spark degrades.

Have you checked the coil resistance on those injectors? Should be 16.2Ω

Another possibility to consider is that you have #1 and #2 leads swapped around. That would certainly give you abnormally high fuel consumption and fouled plugs but I think you'd probably notice the decrease in power. Just a thought.

Laitch wrote:Replace the fouled spark plugs, ride out again, compare your rides and also determine if the plugs are fouling quickly or are resisting fouling.

Hum I have to check if I still got the previous ones

Holister wrote:If you have fouled plugs on #1 and #2 which fire off different coils then the problem will be down stream. If your temp sensor or maf were reading incorrectly then all cylinders would be affected.
Check your HT leads for correct resistance and even your spark plugs (they should be <0.3Ω). As they develop resistance the spark degrades.

Have you checked the coil resistance on those injectors? Should be 16.2Ω

Another possibility to consider is that you have #1 and #2 leads swapped around. That would certainly give you abnormally high fuel consumption and fouled plugs but I think you'd probably notice the decrease in power. Just a thought.

I have to check the resistance of the spark plugs, but they are news?
And i'll check the resistance of the injectors...

The swapp you guess for the cables for the injectors? Or the spark plugs wires?

ouafnico wrote:The swapp you guess for . . . the spark plugs wires?

Verify that the front coil has the wires from spark plugs #1 and #4 and the rear coil has the wires from plugs #2 and #3. Replace the blackened spark plugs #1 and #2 with clean spark plugs of the correct type and test the moto. Fifth gear speed at 5000rpm might be illegal; record second, third and, maybe, fourth gear speeds.

You are close to finding the problem.

It's good I have the good spark plugs wires at good places 

5000rpm at 5th might be high indeed, I may able to check only some gears

ouafnico wrote:It's good I have the good spark plugs wires at good places 

5000rpm at 5th might be high indeed, I may able to check only some gears

I checked my old spark plugs, but they are all black, so I can't use them to compare.

This morning I drive a little but on the city, can't test the speed at 5000rpm (I will see tonight), but I can show you 
https://www.youtube.com/watch?v=oXmi55JHM8E (in optimisation so better quality can come later)

(the rear brake make some noise :p)

Globally the motor seems fine, it got a lot of torque, don't have to run higher than 3000rpm, and I can drive at 50 km/h at 5th without any issue

I try again in the next post.

If your observations are correct, the engine appears to be operating correctly. 

According to your original post, the air/fuel ratio your engine is running on is about 7:1, the lowest air fuel ratio a gasoline engine will run on is approximately 9:1.  The amount of fuel you claim to be using is not possible in a running engine, and if indeed you could make it run, the engine would be having major problems with idle, acceleration, fouled spark plugs and large amounts of unburnt fuel in the exhaust.

I would suggest that you use the bike as normal and keep an accurate record of the actual distance traveled and the amount of fuel you use and recalculate the usage.

Rather than use the odometer, I would take a round trip over a known distance of at least 100km total and check the fuel used.  You should have a number around 5-5.5 liters/100 km at normal speeds.  At constant speeds above 140km/hr usage may rise to as high as 6.5 liters/100km.

ouafnico wrote:I checked my old spark plugs, but they are all black, so I can't use them to compare.

Globally the motor seems fine, . . . and I can drive at 50 km/h at 5th without any issue

Short trips at low revs will create carbon deposits that affect performance. Poking around city streets like in the video won't bring good fuel economy but will foul plugs.

When I'm in town, I keep the revs higher than you do; the spark plugs are less likely to foul and engine braking helps with maneuvering. Also, quick stops in traffic like the one done in the video at the crosswalk are more likely to have the vehicle behind trying to ride pillion, where I live anyway. 

I'm using a comparison table based on 5Krpm, so your riding at 3Krpm doesn't isn't help me compare performance from a few thousand miles distance without my exercising math skills beyond my depth. Going with Point-Seven-five's suggestion is simpler but it is unlikely to answer why two plugs foul and two don't.  For my amusement, clean the plugs from #1 and #2, verify their electrode gaps are correct, then swap them into cylinders #3 and #4, use those plugs in cylinders #1 and #2, ride and record speed again. Then verify if the plugs are becoming fouled.

Regarding your driving without any issue: I am not convinced you understand how a Brick engine in good tuning runs if you are satisfied with its performance when the spark plugs in #1 and #2 cylinders are fouled with goo. Maybe they are powerful spark plugs. Nevertheless, you are close to understanding what is actually happening rather than what seems to be happening, if you stay on the path.

Maybe I'll understand, too.

I will do whar you both says.
I will run the most I can on a highway to see the actual consumption.

And i will clean and inverse the spark plugs on #1#2 with #3#4.

For my home-work travels I can't use speeder roads... City only. Maybe I need indeed to use higher rpm (I was doing this to lower my consumption and see).

In 5th gear, i'm at 90km/h at 3000rpm, above 110km/h at 4000. Can't go higher on the speedway I used.

Sorry Laitch, I didn't understand perfectly what you said in your last sentence ...
I don't know actually how runs a good tuning brick, I don't have a good one to compare, and my daily bike (xsr900) is sooo different to compare

I'm checking tonight.

First i have removee the 4 spark plugs.
As you will see below, it's like only the #2 is very black.





Then, i used my little camera to check on the cylinders.
It's seems the is some liquid on the second.
The third seems very dry.

https://youtu.be/zoONPZkAKz8

Hum .. spark #2 is dead. But i don't know since when.

That's interesting, isn't it? Replacement is the next step. Verify the electrode gaps before installing the replacements and be certain that the spark plugs are tightened down sufficiently for successful heat transfer.

The 900 looks fun.   

Here is the crux of the matter. Before you remodeled it, your LT Brick was manufactured as a touring machine designed to thrive on long distance travel at high speeds. It isn't surprising that your Brick is now drinking more after chugging around town. It is probably depressed because it doesn't enjoy being treated like a Bichon Frise with a short haircut. Although a periodic Italian tuneup might help, it won't respond well to long periods of idleness while the XSR gets the action.

Maybe you should trade it for a Gas Gas or a Tuk Tuk, as soon as it is running well.

Laitch wrote:That's interesting, isn't it? Replacement is the next step. Verify the electrode gap before installing the replacements and be certain that the spark plugs are tightened down sufficiently for successful heat transfer.

The 900 looks fun.   

Here is the crux of the matter. Before you remodeled it, your LT Brick was manufactured as a touring machine designed to thrive on long distance travel at high speeds. It isn't surprising that your Brick is now drinking more after chugging around town. It is probably depressed because it doesn't enjoy being treated like a Bichon Frise with a short haircut. Although a periodic Italian tuneup might help, it won't respond well to long periods of idleness while the XSR gets the action.

Maybe you should trade it for a Gas Gas or a Tuk Tuk, as soon as it is running well.

I cleaned the 3 and took an old one for temporary replacement. The gap is not perfect... I will order the same model as the 3 others. This one is a ngk d7ea.

You are right, this bike is not supposed to ride in city.. but this one was sleeping in a garage, waiting for destruction.. a second life.. trying to give her a second (I know the look will not be like by all). I'm not a pro, but it did take all my work on YouTube for some people on the same project. You can check on my yt, but it's in french 🤭

You made my day about the tuktuk

I keep you in touch for the next road trip and results 
Thanks for all your help, even at thousand kilometers away

It could be that you should change the color of one of the front brake calipers to white and the rear one to blue— or maybe the reverse —to determine if doing that improves fuel economy.    Anyway, the machine looks good and getting that particular aftermarket speedometer/tachometer to work correctly is a stellar achievement in itself, judging from the hand-wringing displayed in previous threads about it here.    Also, I foresee whistling mechanics trending on Tik Tok after this.

Have you accidentally reversed the injector leads for cylinders 3 and 4?

Also, NGK plugs need bobbins, to go on the threaded part and the bobbins do not come with the plugs when you buy them.

Laitch wrote:It could be that you should change the color of one of the front brake calipers to white and the rear one to blue— or maybe the reverse —to determine if doing that improves fuel economy. 

I made them red to go faster, like Ferrari's. You think it will work?

92KK 84WW Olaf wrote:Have you accidentally reversed the injector leads for cylinders 3 and 4?

Also, NGK plugs need bobbins, to go on the threaded part and the bobbins do not come with the plugs when you buy them.

No they can't be reversed, the size is specific I can't mismatch them.

The NGK are the spark plugs I got with this bike when buying it.

ouafnico wrote:I made them red to go faster, like Ferrari's. You think it will work?

No. Then your brake callipers will arrive at your destination before the rest of the bike does. Bad social form.

Point-Seven-five wrote:If your observations are correct, the engine appears to be operating correctly. 

According to your original post, the air/fuel ratio your engine is running on is about 7:1, the lowest air fuel ratio a gasoline engine will run on is approximately 9:1.  The amount of fuel you claim to be using is not possible in a running engine, and if indeed you could make it run, the engine would be having major problems with idle, acceleration, fouled spark plugs and large amounts of unburnt fuel in the exhaust.

I would suggest that you use the bike as normal and keep an accurate record of the actual distance traveled and the amount of fuel you use and recalculate the usage.

Rather than use the odometer, I would take a round trip over a known distance of at least 100km total and check the fuel used.  You should have a number around 5-5.5 liters/100 km at normal speeds.  At constant speeds above 140km/hr usage may rise to as high as 6.5 liters/100km.

This is the key right here. If Ouafnico's mixture was that far off, or if he wasn't getting ignition on some cylinders (eg swapped plug leads), the bike would be running terribly. He has repeatedly said the engine is running great. Yeah, his plugs are fouling a bit but he's saying it's running smoothly, not smoking, no gas smell. Though it might not be perfect, this is a bike that's at least running pretty well.

I totally agree with point-seven-five. Test the mileage with a measured distance ride rather than the odometer. 

One other thing that comes to mind is that, since you're trying to track down an issue, you're likely spending a lot of time scratching your head while staring at an idling bike. It won't burn a ton of gas while idling, but it will burn some. Once, during a road trip, I was stopped for about half an hour for a construction delay with my bike idling the whole time. I keep track of my mileage with a phone app and at the next gas stop I was shocked at how bad my consumption had been for that stretch until I remembered the half hour stop. It makes a difference.

Also, in your response to my last suggestion about a slipping clutch you said the clutch was new, adjusted, and "seemed to be working fine". Did you try the test that Laitch suggested? K-bikes definitely have enough power to mask a problem like a slipping clutch. It could seem fine but still have issues.

Finally, check to make sure you aren't missing some silly, tiny error in your experimentation. All of this headache could be a math error (Not calling you bad at math, everyone makes small errors sometimes). A friend with a K75 was confused about fluctuating fuel consumption until I noticed that he sometimes uses the center stand while filling his bike and sometimes the side stand. Threw all his calculations way off. Are you 100% sure that your odometer is giving you kilometers, not miles? Bottom line is recheck all of your assumptions.

Bikesmith wrote:

Point-Seven-five wrote:If your observations are correct, the engine appears to be operating correctly. 

According to your original post, the air/fuel ratio your engine is running on is about 7:1, the lowest air fuel ratio a gasoline engine will run on is approximately 9:1.  The amount of fuel you claim to be using is not possible in a running engine, and if indeed you could make it run, the engine would be having major problems with idle, acceleration, fouled spark plugs and large amounts of unburnt fuel in the exhaust.

I would suggest that you use the bike as normal and keep an accurate record of the actual distance traveled and the amount of fuel you use and recalculate the usage.

Rather than use the odometer, I would take a round trip over a known distance of at least 100km total and check the fuel used.  You should have a number around 5-5.5 liters/100 km at normal speeds.  At constant speeds above 140km/hr usage may rise to as high as 6.5 liters/100km.

This is the key right here. If Ouafnico's mixture was that far off, or if he wasn't getting ignition on some cylinders (eg swapped plug leads), the bike would be running terribly. He has repeatedly said the engine is running great. Yeah, his plugs are fouling a bit but he's saying it's running smoothly, not smoking, no gas smell. Though it might not be perfect, this is a bike that's at least running pretty well.

I totally agree with point-seven-five. Test the mileage with a measured distance ride rather than the odometer. 

One other thing that comes to mind is that, since you're trying to track down an issue, you're likely spending a lot of time scratching your head while staring at an idling bike. It won't burn a ton of gas while idling, but it will burn some. Once, during a road trip, I was stopped for about half an hour for a construction delay with my bike idling the whole time. I keep track of my mileage with a phone app and at the next gas stop I was shocked at how bad my consumption had been for that stretch until I remembered the half hour stop. It makes a difference.

Also, in your response to my last suggestion about a slipping clutch you said the clutch was new, adjusted, and "seemed to be working fine". Did you try the test that Laitch suggested? K-bikes definitely have enough power to mask a problem like a slipping clutch. It could seem fine but still have issues.

Finally, check to make sure you aren't missing some silly, tiny error in your experimentation. All of this headache could be a math error (Not calling you bad at math, everyone makes small errors sometimes). A friend with a K75 was confused about fluctuating fuel consumption until I noticed that he sometimes uses the center stand while filling his bike and sometimes the side stand. Threw all his calculations way off. Are you 100% sure that your odometer is giving you kilometers, not miles? Bottom line is recheck all of your assumptions.

Thank you.

It's what I'm going to do, ride a good distance and see.

I've checked the clutch according to the Laitch post, it's good now. I didn't test his method to twist the throttle firmly to see if the clutch is slipping, not yet.

Im' sure it's not in miles

Hey guys

The last month, I did some road with the K, and I got my consumption checked at the end of the tank.

Seems I don't have a problem anymore, I was running only on the city (for the work), and I got a consumption of 6.5L/100km.

That's seems quite good for the city.

Engine is running smoothly, I can push it easy to 7000rpm (didn't do more, too fast/noisy on city).

Just, sometimes while waiting on traffic lights, got some missed fires I think on one cylinder, but it happens only 4 or 5 times.

Anyway, thanks for all your help for this problem !

Thanks for getting back to us! 

Good to hear that your bike is running properly.  Now you can go out and just enjoy riding it.