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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: brichbk on April 13, 2018, 10:40:09 PM
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I've been trying to diagnose why my 1993 K75RT will die or hesitate to accelerate RPM's when starting from a stop if it's not above 2k RPM's. I start the bike, let it warm up with full choke, then with full choke or half choke or no choke it will die unless I keep the RPM's over 2,000 and let the clutch out slowly and I mean slllowwwwlllyyyyyy. There is a noticeable hesitation of when the RPM's increase when I quickly roll on the throttle when I slowly roll the throttle the hesitation is not as noticeable.
After about 10 minutes of stop and go traffic it still requires the RPM's to be over 2,000 or it luggs. If I downshift from 3rd to 2nd and go around a sharp corner the RPM's drop to idle (1100) and then when I give it throttle it luggs like I'm in 5th gear going 20mph (even though I'm in 2nd gear).
I'm looking for some advice and suggested items to check first.
When I start it from cold with full choke it idles at 1300
then half choke 1100
and no choke 1000-1100
What I've done so far:
I've replaced the Z-shpaed breather hose on the top of the crankcase. Because it was cracked.
I checked for cracks around the intake boots by spraying carb cleaner around them to see if the RPM's changed, they didn't.
I don't hear a "click" from the TPS at any position, but I'm going to check this with an ohms meter.
I'm pulling the fairings off and the tank to check for any more air leaks.
Next I'll be pulling the gas tank to get to the air filter. Do I really have to pull the gas tank to get to the air filter?
What I haven't checked yet:
Spark Plugs, but it doesn't have any problem starting or running except at launching from a dead stop.
Air Cleaner
Fuel pump, injectors, throttle bottle, fuel filter - although it seems to run fine other than the launch issue
What I found to be weird:
This hose which looks like it's broken and I have no idea what it's supposed to connect to. I checked for vacuum when the bike was running but nothing. It connects to the front of the motor. it is on the right side in front of the air box.
(http://www.motobrick.com/gallery/1/5663-130418203945-11331570.jpeg)
I tried adjusting the TPS by loosening this screw (and the otherside screw) and moved the TPS to the top and bottom and inbetween to try to find the "click".
(http://www.motobrick.com/gallery/1/5663-130418220021-11372109.jpeg)
Here's my crankcase breather hose. The crack was on the end that connects to the airbox.
(http://www.motobrick.com/gallery/1/5663-130418203659-113053.jpeg)
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Do I really have to pull the gas tank to get to the air filter?
No.
https://www.youtube.com/watch?v=QLH7IcFeGKo (https://www.youtube.com/watch?v=QLH7IcFeGKo)
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Took the plug off my TPS and found the center probe and hole covered in green stuff. I’m thinking this might be my problem. Any suggestions on how to clean this? Scrape with a screwdriver?
(http://www.motobrick.com/gallery/1/5663-140418004018-11382285.jpeg)
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Hi Mate - Definitely need to scrape the green shite out of the TPS first and spray with Deoxit. You should check you plugs and leads and fuel filter before messing around with the settings on the TPS. A poor quality plug can cause exactly the problems you're having.
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This hose which looks like it's broken and I have no idea what it's supposed to connect to. I checked for vacuum when the bike was running but nothing. It connects to the front of the motor. it is on the right side in front of the air box.
If it ends up at spigot just behind the cam chain cover at the front right corner of the engine block it's the
breather for the fuel tank.
It was bulletin from BMW that the hose should be removed and the connection at the engine end closed as
it didn't function that good.......then the tank is open to the atmosphere, like the euro models.
Just put a screw with a unthreaded part into the hose to close it off.
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Just want to mention you have done a superb job of posting here brichbk. http://www.motobrick.com/index.php?topic=1522.0 (http://www.motobrick.com/index.php?topic=1522.0)
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I doubt your problem is with the TPS. Have you pulled a spark plug to see if the engine is running lean or rich?
I suspect your engine is running lean and starving for fuel. Possibly a plugged fuel pump or plugged fuel filter, two places you say you still need to check. Another remote possibility is a faulty fuel pressure regulator that is not providing adequate fuel pressure in the rail.
Before chasing anything down, pull a spark plug.
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Just FYI for you Brichbk, the "choke" is not a choke in the sense of cutting off air like one would assume, but it is only a throttle advance, nothing more.
How does the outlet of the exhaust look, black and sooty, or other.
Check to see that you don't have a critter nest in your airbox.
I agree with MG, check your fuel filter as well.
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My K75C started right up after its winter nap but ran roughly and stalled when I let out the clutch in 1st gear. After 42,000 km (16,000 km recommended), one of the Bosch x5dc plugs had somehow died over the winter. New Champion 810s and it is humming once more.
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Pulled my plugs today. Number 3 looks fouled and has some yellow/orangish coloring on the white ceramic part of the plug.
(http://www.motobrick.com/gallery/1/5663-140418173309-1144240.jpeg)
(http://www.motobrick.com/gallery/1/5663-140418173246-11431613.jpeg)
It looks to me like they need replacement. I am planning on using the NGK DR7EB.
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When you get your new plugs, make sure that they have the rounded top on them....... some only come with the threaded stud, and that won't work alone without the proper cap.
Some come with the cap in the box, some don't. A local small engine shop should have them if you need them.
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Hi Mate - Definitely need to scrape the green shite out of the TPS first and spray with Deoxit. You should check you plugs and leads and fuel filter before messing around with the settings on the TPS. A poor quality plug can cause exactly the problems you're having.
Agree...
Have you ever checked your valve clearances?
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It looks to me like they need replacement. I am planning on using the NGK DR7EB.
Their gaps look wider than .9mm for sure although I am viewing them from the other side of the country. :giggles
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+1 Gaps look way to big what are they?
Regards Martin.
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+1 Gaps look way to big what are they?
Regards Martin.
#1 & 2 were ok, but 3 was way off. Replaced them anyways with some Bosch plugs from the local dealer. I haven't got a chance to test it yet got hit with a pretty nasty cold. :musicboohoo: [size=78%] I also checked the air filter, no critters and the filter looked ok.[/size]
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Installed a new Napa Gold 3032 Fuel Filter today, the bike stills hesitates when starting. I let it warm up for a long time and took it for a little ride (less than 5 miles) and at the first stop I pulled in the clutch and the RPM's decreased until it just died (2500RPM -->500RPM and died).
So, far I've replaced the spark plugs and the fuel filter. What's the next step? Test the Fuel Pump or pressure regulator?
Here's a video I took of it idling in the driveway before the ride and I'm rolling and blipping the throttle.
https://www.youtube.com/watch?v=O6IfP64DBoE (https://www.youtube.com/watch?v=O6IfP64DBoE)
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Checked the fuel pump flow by disconnecting the fuel filter and running the fuel back into the tank. It seems like it's pumping it out well enough. I put my finger over the hose and wasn't able to stop the flow.
(http://www.motobrick.com/gallery/1/5663-200418180207-11561761.jpeg)
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Have you checked intake manifolds for leaks with propane? Adjusted your throttle bodies?
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I going with new fuel injectors, that would be my bet. :popcorm
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Sticky barn door in the MAF sensor???
Throttle lag in the Jetronic vs. the relatively instantaneous response of the Motronic is readily apparent to anyone who owns both systems. The barn door is the source of that lag. It relies on the suction of the cylinders to pull the air that opens it. If it isn't opening, no amount of throttle is going to make the engine increase power output.
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Have you checked intake manifolds for leaks with propane? Adjusted your throttle bodies?
I haven't messed with the throttle bodies and tested intake manifolds and found no leaks.
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I haven't messed with the throttle bodies and tested intake manifolds and found no leaks.
Anyone who buys a used bike should do a tuneup on it from the start rather than jumping from one symptom treatment to another.
Part of a tuneup on a used K-bike is to clean the electrical connectors using a high quality cleaner like DeoxIT—the four-pin connector under the tank, the ignition switch connector, the ignition control unit connector, the fuel injection control unit connector. Be sure they fit tightly together. You've already replaced the fuel filter, the Z-hose, checked the air filter and checked for vacuum leaks. After you've cleaned all the connectors, you could balance the throttle bodies.
Or not.
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As per Laitch but also check the mixture. With your engine warmed up and idling at 1000 rpm press the green starter button. If the mixture is correct the revs should stay the same or rise slightly. If the engine dies the mixture is too rich, if the revs increase significantly it is too lean. Adjustment is made by removing the rubber plug on top of the RHF corner of the air box. You need to insert a 5mm allen key. There are a couple of method for determining the mixture, one is the lean drop method, just type in lean drop method. The easiest is by using an exhaust gas analyser, I purchased a Gunson about 20 years ago and it has worked well. If you go the Gunson route patience is the key and follow the instructions. Also it is a light weight piece of equipment and treat it with care do not drop it or lend it out, and always purge it thoroughly after use. TMG has bought one and may want to add to this. I think they can be had for about $250.00 US try Ebay.
Regards Martin.
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Thank you to all those who have chimed in. I greatly appreciate it. I'll work on cleaning all the connections next and might even look at replacing the fuel pump. Although I don't want to just replace parts. This K75 is definitely a bit more complex than my '82 nighthawk.
I took the tank off today to get a better look at what was under it and took a better look at the air filter, which was pretty bad and so I replaced it. I was also cleaning around the fuel injectors today and noticed that the #2 (middle) injector looked like it was leaking where it enters the engine. I didn't use any thing other than a screwdriver and can of air to clean so the wetness didn't come from anything I was doing. Tell me if this picture looks normal or not.
(http://www.motobrick.com/gallery/1/5663-210418181658-11611989.jpeg)
Thanks again for all your help. I'll look into getting a manometer to balance the throttle bodies and my other bike carbs probably could use a little balancing.
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I went back to the start of this thread, and have a question. Please forgive me if you have already answered this. Is this a new to you bike? Did it run properly for you in the past, or did this problem come with the bike?
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Please forgive me if you have already answered this. Is this a new to you bike? Did it run properly for you in the past, or did this problem come with the bike?
The bike was pre-flogged by others before he plopped down cash for it, Gryph. He's had it a few weeks. Some of the sordid details can be found in his first post (http://www.motobrick.com/index.php/topic,10984.msg95531.html#msg95531).
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Is it fair to assume that the bike hasn't ran properly for a long time and that is the reason(among others) for the incredible price?
If so, my recommendation is to go through the entire bike front to back getting everything right before taking it out for a ride. This is a bike with a troubled past and there is nothing you should take for granted.
If the bike has sat unused for an extended time, the old fuel has probably built up a lot of varnish in the injectors. You can take them out and send them to be cleaned, or possibly dump a bottle of Techron fuel system cleaner into the tank. Run the engine for a couple minutes to circulate and mix the Techron throughout the system. Then let it sit for a few days and restart the engine. Depending on how bad the varnish is, it may take a couple weeks of doing this to get things loosened up. If they still don't work after two weeks of circulating the cleaner, you will need to send them out to be professionally cleaned.
If you haven't drained the tank of old fuel, do it now and replace it with two gallons of no corn premium mixed with a bottle of Techron. An easy way to drain most of the fuel out of the tank is to pull the return line hose from it's spigot on the tank and put it into a container so it can't spray and splash all over the place. Start the engine and let it run until all the gas is pumped out and it quits.
Since this is a "new" bike, when you have the tank empty, you should remove it and use the opportunity to do any service that requires the tank to be off the bike. This includes cleaning all the connectors under there, especially the ground connections on the frame backbone. Then you can drain the cooling system and put in new coolant. It will also be a good time to do some improvements like an Eastern Beaver headlight relay harness and a manual fan switch.
Tank removal can be done without removing the main fairing. The hardest part is disconnecting the fuel lines which should be replaced anyway. You don't even need to remove the seat, although it isn't very difficult, and makes tank removal even easier.
Once you've done the under tank stuff, get the tank back on and start circulating the Techron fuel mixture while you address everything else.
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if this was my moto it would be no corn ethyl and 4 bottles of techron till near empty... then 3 bottles of techron then 2 bottles of techron then 1 bottle of techron then just no corn ethyl... that would be 1000 miles and my heap would me spinning like its 420 (http://www.motobrick.com/index.php/topic,11113.0.html)...
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Is it fair to assume that the bike hasn't ran properly for a long time and that is the reason(among others) for the incredible price?
If so, my recommendation is to go through the entire bike front to back getting everything right before taking it out for a ride. This is a bike with a troubled past and there is nothing you should take for granted.
If the bike has sat unused for an extended time, the old fuel has probably built up a lot of varnish in the injectors. You can take them out and send them to be cleaned, or possibly dump a bottle of Techron fuel system cleaner into the tank. Run the engine for a couple minutes to circulate and mix the Techron throughout the system. Then let it sit for a few days and restart the engine. Depending on how bad the varnish is, it may take a couple weeks of doing this to get things loosened up. If they still don't work after two weeks of circulating the cleaner, you will need to send them out to be professionally cleaned.
If you haven't drained the tank of old fuel, do it now and replace it with two gallons of no corn premium mixed with a bottle of Techron. An easy way to drain most of the fuel out of the tank is to pull the return line hose from it's spigot on the tank and put it into a container so it can't spray and splash all over the place. Start the engine and let it run until all the gas is pumped out and it quits.
Since this is a "new" bike, when you have the tank empty, you should remove it and use the opportunity to do any service that requires the tank to be off the bike. This includes cleaning all the connectors under there, especially the ground connections on the frame backbone. Then you can drain the cooling system and put in new coolant. It will also be a good time to do some improvements like an Eastern Beaver headlight relay harness and a manual fan switch.
Tank removal can be done without removing the main fairing. The hardest part is disconnecting the fuel lines which should be replaced anyway. You don't even need to remove the seat, although it isn't very difficult, and makes tank removal even easier.
Once you've done the under tank stuff, get the tank back on and start circulating the Techron fuel mixture while you address everything else.
Thanks Gryphon for the recommendation. I don't have much time to work on it this week so I'll start with the Techron advice. I can take a few minutes to start it once every few days. Dos it matter how much gas is in the tank? The gas light is currently on so it has less than a 1/4 tank of gas. Then I'll move on to removing the tank and cleaning the connections.
Yes you are correct in that I bought the bike with this issue. So I am trying to undo something that might have been a long standing issue.
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Dos it matter how much gas is in the tank? The gas light is currently on so it has less than a 1/4 tank of gas.
Techron isn't engine fuel; it's detergent. It matters. Now if instructions matter—only the weak follow them and besides, Standard Oil is part of a pervasive, profit-driven evil that only Armageddon can eliminate—here's what the manufacturer recommends:
Q: Can I use a full bottle of Techron in smaller fuel tanks? (http://www.techronclean.com/en_us/faq.html#qcaniuseafullbottleoftechroninsmallerfueltanksmiscvalue6)
A: If you use Techron in smaller engines, such as a motorcycle, don’t use the whole bottle. The recommended treatment rate is one ounce per gallon, so in a four-gallon tank, use four ounces of Techron.
Only j o and a select few are able to operate successfully outside these earthly and arbitrary constraints. It's unlikely you are one of them, yet.
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My engines run fine on rich Techron mixtures. 2-3 gallons of gas with half a bottle, a full bottle in a full tank. Or a half bottle in a full tank. How much I put in depends on how much I have and whether or not I want to empty the bottle so I don't have it hanging around.
When I got my K100RS it was running pretty rough so I was hitting the system pretty hard with the Techron for the first 2000 miles until it started to run like my other bricks. My bikes are running pretty good now, so I am dialing it back and just doing it as preventive maintenance.
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greetings...
always follow the mfr directions...
with that being said... the most i have used is 6 bottles... have used 4 bottles a few times... use 2 bottles often...
its bogof at advance auto parts right now...
j o
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Update on my progress. I decided to check the vacuum hose from the throttle body to the fuel regulator. So I took out the air box and cleaned up all the little gravel, dirt, and crud that had accumulated under the air box. The vacuum hose was a little hard and dry so I replaced it. I cleaned the connections for the AFM while I had the air box apart. I put everything back together and decided to ride down to the gas station for a bit more gas to help run more techron through. I felt like the bike ran a little better. I still have to clean the rest of the electrical connections, but so far I think its moving in a good direction but its still not quite there.
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Update part 2: I decided to check my plugs that I just installed and have less than 10 miles on them. I wanted to check #3 since it was the worst when I replaced them. So I pulled #2 and #3 to compare. Here is what they look like. Should I be concerned that 3 looks worst than 2?
(http://www.motobrick.com/gallery/1/5663-270418211536-1197116.jpeg)
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Should I be concerned that 3 looks worst than 2?
#2 looks good. #3 doesn't look good. What about #1? Does it fit into your numerological maintenance scheme?
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Have you done a compression test?
Looks to me like you might have either ::
1, leaking injector on #3, or
2, bad/week coil/wire for #3.
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2, bad/week coil/wire for #3.
+1
Replace all the secondary leads and help the economy. 100K miles was good enough out of the originals.
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#2 looks good. #3 doesn't look good. What about #1? Does it fit into your numerological maintenance scheme?
#1 looks the same as #2.
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Any suggestions on where to get replacement ignition coils? Do I have to replace all of them or can I replace just the one I think is bad? I'd rather replace them all but bikebandit lists the cost at $165 per coil!
Suggestions for replacement spark plug wires?
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I got three ignition coils as spares on eBay for $65. I bought a complete engine with coils for $75. sold those coils for $20.
They're out there...
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Do I have to replace all of them or can I replace just the one I think is bad?
How did you determine the coil was faulty and not its lead?
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How did you determine the coil was faulty and not its lead?
I don't know that it is the coil necessarily. I did the test from the book and using both the #1 and #3 lead all 3 plugs give off a nice blue spark.
Most of the reason why I was thinking of replacing the coils was based on my experience with a similar issue with my '82 nighthawk where it kept dying when I would pull in the clutch (much like my K75 is doing right now). I replaced the coils and it fixed the problem, of course I could buy two coils for $15 for that bike so it wasn't much of a risk.
I am looking into getting new leads since the ones on the bike are OEM and probably original.
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Update: I installed new NGK spark plug wires today. Unfortunately it didn't fix the issue. So now I'm going to get a used set of coils and then hopefully I'll be zooming down the road.
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Before spending money on coils, I would suggest swapping #3 injector with #1 or #2 and see if plug rich symptom transfers. Looks like injector spray pattern poor or leaking.
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I got 3 coils from beemer boneyard today in the mail. I replaced my old ones and the bike is running like a bat out of hell. The throttle is much more responsive, the bike warms up very quickly, and doesn't seem to have the hesitation that it had before. I'll be taking it out tomorrow to get a better feel how it runs but it is running much better. Thanks all.
Before spending money on coils, I would suggest swapping #3 injector with #1 or #2 and see if plug rich symptom transfers. Looks like injector spray pattern poor or leaking.
I might try this in the coming weeks. But for now it seems to be running good.