Post by: kenrams on October 20, 2019, 01:18:32 PM
Working my way through a recent K75 purchase that the PO had lost interest in getting properly running. It was his fathers and was parked up in his garage 6 or 7 years ago. 50,000 miles. Symptoms are that it starts fine but once the throttle is opened it runs really rough and has no pull at all.
So I systematically went through the bike and found the Z pipe and the big 90 pipe to the airbox split. I also replaced the plugs, air filter, fuel filter, and adjusted two tight exhaust valves. Adjusted TPS switch. The PO had also replaced the fuel injectors. The compression test is good. Fuel pressure was measured using an inline meter, at 32 psi.
Still runs rubbish.
So while thinking about next logical step, I noticed that the idle stop screw was maybe 1/8 - 1/4 inch away from the stop. I removed and freed the throttle cable from the perch to eliminate binding, routing and throttle cable adjustment as the culprit.
I then looked at the "choke" cable adjustment to see if that was adjusted incorrectly. I backed the knurled knob until I could see the cable slacken. No change was detected to the idle stop "gap". Weirdly, when I engage the choke lever it has zero effect on the idle stop gap. ( the mechanism at the throttle body rotates fine)
Even screwing the idle stop out fully didn't make contact with the stop.
Anyone got an explanation or suggestion as to what to do next?
Post by: kenrams on October 20, 2019, 01:28:22 PM
Post by: Laitch on October 20, 2019, 01:49:15 PM
Post by: kenrams on October 20, 2019, 01:54:46 PM
Post by: kenrams on October 20, 2019, 02:52:44 PM
Ok on to TB synching. I'll be buying some analyzers( any recommendations ?) today
Post by: johnny on October 20, 2019, 03:39:07 PM
Post by: kenrams on October 27, 2019, 03:12:47 PM
Post by: johnny on October 27, 2019, 05:07:31 PM
you gotts to start engine and let it run until fan cycles on... turn it off and hook up hoses...
then follow the instructions posted here at the world famous motobrick.com... where to start at what rpm and what to turn and not what to turn...
carbtune search returned this in less than a second...
http://www.motobrick.com/index.php/topic,7964.msg58423.html#msg58423
j o
Post by: kenrams on October 28, 2019, 01:23:40 PM
Post by: johnny on October 28, 2019, 03:10:33 PM
you mean with hoses outta the bottom like this...
download.jpeg (9.52 kB . 168x299 - viewed 722 times)poast up some photos so we can see what you see...
j o
Post by: kenrams on October 28, 2019, 04:10:35 PM
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And here it is with the engine running at idle (fourth input not used obviously)
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It looks not bad but unfortunately, the bike still revs very poorly. Poor response, poor pickup, occassional backfires. I have searched the site and carried out everything that might be causing the issue and I am now considering taking it to the shop but I really want to fix it myself.
Post by: Martin on October 28, 2019, 04:27:04 PM
1/ Correctly adjust the TPS.
2/ Check for air leaks at the throttle bodies and "Z" hose and eliminate.
3/ Check for exhaust leaks especially header to muffler and eliminate.
4/ Correctly adjust the mixture and balance the throttle bodies.
5/ Have the injectors cleaned and checked for the correct spray pattern.
6/ Do not have the throttle partially open on overrun down hills or when slowing fully close it.
The only time mine backfires now is if I don't follow 6/.
Regards Martin.
Post by: johnny on October 28, 2019, 04:33:47 PM
needs miles and snake earl...
1st tank 1 bottle of marvel mystery oil...
2nd tank 1 bottle of marvel mystery oil...
3rd tank 1 bottle of techron...
4th tank 1 bottle of techron...
5th tank straight no corn ethyl...
do this in 1 day or 2 continous days...
redo the carbtune...
ride it... wants miles...
j o
Post by: Laitch on October 28, 2019, 04:46:07 PM
A recent complainant with a sluggish engine claims to have discovered the voltage regulator was providing inconsistent output. Replacing it seemed to remedy poor running, so determining its output at various revs using a multimeter might be useful. Avoid replacing parts without determining first if they are malfunctioning.
Post by: kenrams on October 28, 2019, 05:08:33 PM
I've already replaced the usual rotting hoses (Zhoses and 90deg plenum) and sprayed WD40 around to check for other leaks around the TBs.
I've not done the coolant sensor check so I'll do that later. Also, I'll check the coils and run the bike in the dark. Voltage output is good rises to about 13,4v after startup and revvin around 3000rpm.
Post by: stokester on October 28, 2019, 05:17:17 PM
So I just got the Carbtune Pro 4 delivered. I cut 4 inches off each hose and inserted the restrictors and connected the carbtune to the throttle bodies - restrictor end to the engine. I warmed up the bike first. Here's the funny thing - the pipes inside the carbtune barely move at all - no matter what the revs ! Do I have a bad tool or is there anything else I could have done ?I use a Carbtune Pro also and do not have this problem. Did you T the hose to the FPR?
Using carb, brake cleaner or propane is much better than WD-40.
Should be able to send a pic of my setup tomorrow.
Post by: The Mighty Gryphon on October 28, 2019, 05:18:18 PM
Does the bike have OEM wires?
Can you post some photos of the spark plugs? Both the sparky part and connector end.
Post by: daveson on October 28, 2019, 07:22:54 PM
Plus a full service, clean the earth's, plugs and ICU.
I'm surprised about 75's backfiring, mine was (and is) poorly maintained, but I couldn't get it to backfire if I tried.
Post by: Martin on October 28, 2019, 09:54:09 PM
Regards Martin.
Post by: daveson on October 29, 2019, 12:22:31 AM
(Actually, I have to admit that I used to love the sound of a loud and rough overrun on my old cruiser)
Post by: alabrew on October 29, 2019, 11:44:40 AM
Post by: stokester on October 29, 2019, 03:00:32 PM
The attached pictures show my '93 K75S at approx 1000 rpm idle (on the high end) and then at 3500 rpm.
Should be able to send a pic of my setup tomorrow.
Post by: johnny on October 29, 2019, 03:42:28 PM
check your radiator... may be clogged up with buggs and dert...
j o
Post by: Kramsay on October 30, 2019, 09:45:59 PM
I removed the coils, cleaned up the ground, checked primary resistance.
Just to reiterate, the plugs are new NGK, all have sparks and the fuel injectors are also new. When it was parked up years ago it was due to the main oil seal failure.
Post by: Laitch on October 30, 2019, 10:45:38 PM
Don’t expect it to be the cause of my problem. Radiator was flushed and looks new.What do you expect to be the cause? Years of neglect can cause deterioration of many components, especially rubber and electrical components.
When it was parked up years ago it was due to the main oil seal failure.
Post by: stokester on October 31, 2019, 12:30:09 AM
I start with basics, it sounds like too much or not enough fuel or a weak spark which may be caused by multiple problems. Knowing the basic problem will help guide the diagnosis.
Although the plugs are new, what do they look like after it bogs down?
Post by: volador on October 31, 2019, 02:23:39 AM
If so may have a blocked tank vent http://www.motobrick.com/index.php/topic,12374.msg109410.html#msg109410
There is also a grounding point on left side under the tank
"The PO had also replaced the fuel injectors."
Verified fuel injectors are working properly?
Verified ignition timing? Hall Effect Sensor?
Post by: The Mighty Gryphon on October 31, 2019, 08:05:15 AM
Post by: volador on October 31, 2019, 11:50:21 AM
Do the spark plugs have terminal nuts??? NGK plugs don't come with them. That's why I asked for photos, to confirm that you have them. The bike won't run for shiite without them if you still have the original wires.
You dab any green threadlock on those sparkplug caps?
Ever have one loosen up on the road?
Any change in moto performance?
Post by: kenrams on November 02, 2019, 05:12:40 PM
Thank you, everyone, for your comments and help. It was a great learning exercise for me to go through the bike in what I thought was a logical step by step procedure. I hate it when threads just end with no solution, so I will eat a bit of humble pie and reveal the actual problem. https://www.motobrick.com/Smileys/default/donkey.gif
I pulled the spark plugs and checked for a nice big spark and sure enough, I had that on all three. They were all sooty and a little bit wet - not good but I moved on to the next thing. I should have dug a bit deeper when I had them out the first time. Like a few of you suggested I went back to the start this morning after I fitted the radiator back on and that's when I found it - HT leads for 1 & 3 were swapped !! Not sure when that happened but maybe I got it that way or I did it during my investigation. Just took it out for a short spin and it feels great.
Thanks a lot everyone
Post by: caveman on November 03, 2019, 06:50:34 AM
Post by: The Mighty Gryphon on November 03, 2019, 12:51:38 PM
Post by: stokester on November 03, 2019, 01:04:04 PM
Post by: beemuker on November 03, 2019, 02:24:24 PM
Thanks for running this thread to conclusion.Good for you. Some threads are never concluded. My flashers are acting up again. good grief! I'm just using hand signals till it gets too cold to ride, then I'll revisit the whack.
Post by: daveson on November 03, 2019, 03:06:43 PM
Post by: volador on November 05, 2019, 10:06:09 AM
(https://www.motobrick.com/index.php?action=dlattach;topic=7825.0;attach=13497;image)