December 17th, 2014, 02:26 PM | #1 |
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Name: Tez
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Strange high idle issue.
Hi guys,
I have a 1987 GPX250 and have a very strange high idle issue. I have a very similar problem to what most people experience with the high idle ( the one that sometimes is up around 2000 or 3000 rpm and then can idle fine at 1200rpm) but mine can be pulled down by engine braking (whilst underway) or by bringing the clutch out (in gear) past the friction point near stalling while at a stand still. The engine does not idle below the set point or stall. The bike is a little tender to move off from a stop start (easily stalled on the friction point without increasing throttle) but once underway the thing rockets and can not be faulted... until you come to a stop again. 9 times out of 10 the idle will remain high until engine braked, where it will remain on the set point... till you blip the throttle again. I also found that if I choke the left carby (with a rag with the filter removed) nothing happens, if I choke the right carby the engine stalls. Carbs are coming off this weekend for a clean out. I am wondering in the mean time, would a blocked carby (as in the left one) cause the high idle being able to be pulled down by loading up the engine? I have checked and double checked all the usual "choke stuck on" and "throttle cable sticking" avenues, nothing. Any help or comments before I pull the carbies would be appreciated. |
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December 17th, 2014, 02:31 PM | #2 |
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Sounds like the usual suspects to me;
Airbox Air filter Spritz carb cleaner around to check for vac leaks Clean carbs (check floats, slides and diaphragm while you got it out and opened up) Carb sync Good luck, hope it's an easy fix.
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December 17th, 2014, 02:47 PM | #3 |
wat
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the fact that choking the left carb does nothing makes it sound like the left cylinder isn't firing and its only firing on the right cylinder and that one has the idle turned way up to compensate for only running one cylinder?
but aside from that it sounds like maybe a vacuum leak, or a partially clogged pilot jet in the left with the idle up high to compensate but it might also be a sticky float valve
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December 17th, 2014, 03:30 PM | #4 |
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Name: Tez
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I am quite the car mechanic so I have checked for vacuum leaks and found nothing, I was going to double check today both cylinders are still firing firing before I pull the tank.
Both carbs seem to drain the same amount of fuel. One thing I did notice is that the air box boots (not the manifold side) are not seated correctly on the carbies. I doubt this is causing my problem but it is a clear indication, along with a few others, that someone has had a play around with the carbies. Also has new plugs. Another thing I noticed is that the inlet boots are swollen somewhat and that the clamps were closing right up. In the mean time I have cut plastic strips and installed allen heads to get them tight. Are these boots still available replacements? A little history, I purchased the bike which has basically sat around for the last 5 years so I am primarily thinking it is a blocked pilot system in the left carby possibly due to E10 fuel sitting for so long. Tank and filter are clean, I have had a good look as I had to repair the tank where the faring screw had driven into the tank causing the common leak there. I am just finding it extremely strange that loading the idling engine will bring the idle back down to the set point when it is hanging high. It looks like the sync screw is screwed all the way one way, would an out of sync carb cause these problems? Thank you for the comments. |
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December 17th, 2014, 03:50 PM | #5 | |
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Quote:
Out of sync is not the cause of what is happening. Have you considered or verified an electric (spark) problem?
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December 17th, 2014, 04:19 PM | #7 | |
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Quote:
There certainly may be other things involved, but getting the carbs synced correctly is a good start. Comparing the plugs could give you more info. |
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December 17th, 2014, 04:29 PM | #8 |
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December 17th, 2014, 06:02 PM | #9 |
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Welcome, Tez!
Are the left and right exhaust pipes really close to the same temperature when the bike has been running for a while? |
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December 17th, 2014, 10:47 PM | #10 |
ninjette.org member
Name: Tez
Location: Sydney
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Ok so more straws to grab at... I chucked the timing light on just to get an indication if both leads are sparking and the right flashes it's head off while the left is stone motherless dead.
Left pipe is cooler than the right. Tomorrow will be checking for bad connections and ohm test the coils etc... if I find the correct values but leaning towards a coil. I will also pull the plugs and have a sniff. Would the later models be the same? Say upto 2000 or 2008? I met a guy around the corner local trading who has been good for a few parts but he has the later zzr type bikes so not all parts are the same. Looks like atleast the left coil is coming off before the carbies now. |
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December 17th, 2014, 10:52 PM | #11 |
The Corner Whisperer
Name: Chris (aka Reactor)
Location: Northern KY
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Sounds like you already found the main issue?
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December 17th, 2014, 10:58 PM | #12 |
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Name: Tez
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December 18th, 2014, 09:51 PM | #13 |
ninjette.org member
Name: Tez
Location: Sydney
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Both primary winding measure 3.2ohm.
The right coil (the side that was firing) secondary winding reads nothing while the left side reads 44.2k which I believe is way over spec. |
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December 18th, 2014, 11:43 PM | #14 | |
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Quote:
These things are simple voltage transformers. No ohms is a sign of an open coil. IMHO, there is no reason for the ohms to be higher than spec and even in that case, it cannot be bad: inductance is what matters. Click on the ignition circuit schematic: http://faq.ninja250.org/wiki/Wiring_...s_%26_diagrams
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December 19th, 2014, 01:41 AM | #15 |
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I lost my bird today so not real into it atm.
I will test if the left side is getting power before replacing coil later. |
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December 19th, 2014, 01:44 AM | #16 |
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Name: Tez
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December 19th, 2014, 01:55 AM | #17 |
ninjette.org member
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Ok it got the better of me, I stuck the volt meter on the LT wires and got battery voltage continually on the left on ignition and cranking (pulling down to just below 10V cranking) and 0 on ignition and 0 to 3V on cranking on the right side.
Did someone say CDI? |
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December 19th, 2014, 08:34 AM | #18 | |
Rev Limiter
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Quote:
You can get all sorts of odd problems if the battery isn't good. Just something to check before going in deeper. As Moto suggested, I would switch the coils to see if the problem changes sides. |
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December 19th, 2014, 01:56 PM | #19 |
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Name: Tez
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12.4v sitting, pulling down to 10.4v on cranking directly at the battery (that is after sitting for a day.) so I am not seeing true battery voltage at the left side LT coil plugs.
I'm going to have a hard look at the CDI. I notice that the tach also sticks on zero when first started (the gauge needs a wake up tap) and if there is any relevance being connected to the same side that is not firing/triggering? |
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December 19th, 2014, 02:02 PM | #20 |
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Don't forget to clean all connections. Have you clean the plug caps? Renew the ignition wire ends?
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December 19th, 2014, 04:05 PM | #21 |
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Name: Tez
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Well I got the left side to run on the right coil only, seemed real lean, no idle without choke (no coil on right at this stage), swamped it for the left coil only and it fired again (still no right side coil).
Installed the right coil and now no start. Right side not firing I think due to wet plug from all the left side testing. Atleast the left side fired. Aaaarrrrrghhhh!!!! |
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December 19th, 2014, 06:05 PM | #22 |
Rev Limiter
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12.4V is 80% charged, cranking at 10.4V isn't great.
After some more cranking it's certain to be too low. Charge it overnight at a low rate or on a smart charger, and test it again after sitting off the charger. You should see 12.7V if it's holding a full charge. Also check all of the connections. |
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December 20th, 2014, 11:18 AM | #23 | |
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Quote:
Would the left coil, connected to the right side harness, keep the right cylinder working? If so, the left coil is OK. You can leave the opposite plug out to test one cylinder and even to adjust one carb at once: that eliminates the compression work from the opposite cylinder and keeps the plug dry. I agree on the battery strength and the cleaning of all contacts. Could you use a full car battery for your tests? The pick up coil has an optimum gap for producing the strongest spark.
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Motofool .................................Never ride faster than your guardian angel can fly "Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí |
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January 5th, 2015, 10:21 PM | #24 |
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Name: Tez
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Well I repowered the coils as per wierdgeorge and the spark is just great, motor runs of first starter bump every time.
Rule out spark. When I got the air box rubbers out of the way I noticed when I choke the left carb (with a rag) it floods but no change in idle RPM. Choke the right carb (with a rag) and the bike dies, so no real change from ruling out and improving the sparks. Way easier to remove the carbies that way, save pulling half the bike apart. Now just trying to figure out how to test the slides before I pull the carbies apart. Anything else I can check while the carbs are still in one piece? |
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January 6th, 2015, 04:45 PM | #25 |
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Maybe the vac lines had been re routed when someone had their play with the carbies previously?
Where would I find info to double check if the vac lines on the carbies are in the correct places? |
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January 6th, 2015, 05:36 PM | #26 |
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http://faq.ninja250.org/wiki/Hose_routing_for_California_emissions/3_line_fuel_tanks
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January 6th, 2015, 05:45 PM | #27 |
in your machine
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http://faq.ninja250.org/wiki/Hose_routing_for_California_emissions/3_line_fuel_tanks
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January 6th, 2015, 09:50 PM | #28 |
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Mine only has the one vent to the tank, it is a 87 jap bike.
From what I can see on their web site the hoses all look in the right spots. When I get to test the slides I will start to pull them apart. |
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January 7th, 2015, 07:13 AM | #29 | |
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Quote:
Also double, then triple check the assembly of the rest of the carburetors, paying extra special attention to order of assembly.
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January 7th, 2015, 05:24 PM | #30 |
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Cheers, I have that diagram printed.
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January 14th, 2015, 01:44 PM | #31 |
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Well I had the pilots out this morning and they looked blocked so I stoked them and now you can see thru them.
All else looks good. Will do the valves before I refit the carbs so stay tuned. |
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January 14th, 2015, 02:16 PM | #32 |
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I would still run a soft wire through them while spraying with carb cleaner and spinning. I've seen jets that you can see light through that still aren't completely open.
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February 25th, 2015, 11:27 PM | #33 |
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I wanted to compression test this before putting the carbies back on but have not as yet come across one, hesitant to buy another one as I already have 3 for the cars I work on and none fit damn it anyway stuck a finger down each plug hole for shits and giggles and found number one with barely a puff and number 2 pumps hard.
Hoping it's valve related. With a month left of rego, fixing the tank, rewiring the coils, fixing the brakes, cleaning the chain, replacing the tyres etc and the bike still half apart i'm not happy. Lesson here is to do a quick comp test with a finger down the plug hole next time I suspect carby problems before buying... |
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March 2nd, 2015, 09:44 PM | #34 |
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Name: Tez
Location: Sydney
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Everyone's seem to have gone quiet on this one, over it?
Should have sorted it by now? For more shitts and giggles today I dribbled some oil down the plug hole and stuffed a wad of paper on the plug hole and cranked it, What is this hole in the side of the cylinder head and why am I losing compression out of it? |
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March 3rd, 2015, 03:26 AM | #35 |
ninjette.org guru
Name: harry
Location: Central Florida
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Drain hole
That is a drain hole for the spark plug cavity, normally intended to drain water out. If any of the oil you dribbled into the plug hole missed the mark, that is the oil draining out.
It can also leak oil there if you reinstall the valve cover with the gasket improperly installed, and it leaks into the spark plug cavity.
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March 3rd, 2015, 01:59 PM | #36 |
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So angry with myself, I see what's happened here, the wad of paper I have stuffed down the plug hole has only managed to seal the cavity in the rocker cover and not the actual plug hole.
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March 3rd, 2015, 02:10 PM | #37 |
in your machine
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Okay, so to bring us, me especially up to speed here, what have you done so far?, and not?And what your still doing?
Have you serviced the carburetors? If so DoD you set the float height? Idle needle screws? Check for vacuum leaks, checked the condition of vacuum hoses? check to make sure they are all hooked up properly? Check Petcock for proper operation? Etc...... And lastly have there been ANY MODIFICATIONS done to the bike??? Jet kit? Airbox? Etc...... Anything different from the OEM set-up?????
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March 3rd, 2015, 10:07 PM | #38 |
ninjette.org member
Name: Tez
Location: Sydney
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Bike is dead standard.
To summarize, I am stuck, short on time. My next move is to either correctly compression test and diagnose loss of compression on cylinder no1 or remove the rocker cover to see if it is something like a broken rocker or valve adjustment. I really am leaning towards a piston problem seeing as the cylinder built enough pressure up to blow the test oil out the drain hole. Reasons being, no legible compression felt with finger on dry test (as opposed to cyl no2) and the wad of paper and oil building enough pressure on a wet test to not blow any out the inlet port. Thirdly, when the motor is running the cylinder no1 exhaust pipe is cooler that cylinder no2 exhaust pipe. Lastly, there is no indication that there is any back fire thru the carby when it is running. The bike will run/ride fine on cylinder no2 flat out. Sure, the idle will hang around 3000rpm at times and the bike will stall if you try take off on the friction point at idle but all these are easily overcome to ride the bike, without fault from a full tank to empty. No over heating, no problem, not a noise nor a sound, I would not feel there would be anything to stop me riding a 500km round trip somewhere. I am afraid, without the correct fitting compression tester and without the time yet to remove the rocker cover I am only guessing. |
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March 3rd, 2015, 10:11 PM | #39 | |
in your machine
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What have you done about checking the fuel system?
Quote:
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March 9th, 2015, 01:49 AM | #40 |
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