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Old July 5th, 2023, 06:26 PM   #41
jk3099
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Quote:
Originally Posted by racered View Post
I watched the video's, I read the thread, here are my notes...
Paul
Thanks for taking the time to read this thread and for your great comments and questions! My responses/answers are as follows (questions in italics)

(I think) The petcock is "off" in the video's, not reserve or on. ( OK for the vacuum test but not for a fuel flow test).
Good point. This is very possible, so I'll have to try this again. I believe I switched it to reserve while doing the fuel flow test, but I'm not sure.

I did not hear any "compression events" while you were cranking the engine, are the spark plugs installed in the video's?
Yes, spark plugs are installed. I just changed them, so I'm going to go back and take a look at them again. Maybe I incorrectly installed them?

When you adjusted the intake valve,did you have the cam out to change a shim? or is there an adjuster? Cam timing may not be accurate if you had to remove the cam, resulting in no compression, no vacuum.
Cam was not out, and I wasn't aware of any adjuster. I didn't mess with the engine for the most part other than just measuring the gaps.

For the vacuum test during cranking, the throttle plates need to be "closed" as in "idle" not held open by the adjuster screwed in a bunch. Spark plugs installed, and a charged battery that will spin the motor.
For a "compression" test you hold the throttle open.
No need to crank more than three seconds for vacuum test result.

Good notes; thanks! The adjuster screw comment is interesting. It's opened/screwed all the way right now; should I lower it and then try again? I had better luck firing the engine up when it was a little lower.

On the oil overfill, how much are you pouring in?
I remember my 250 was just a little more than one quart.
How much oil is draining out when you think it is overfull, two quarts?

I probably poured in ~2.3 quarts or so. There was ~1.7 quarts left in the gallon of oil I purchased, so that's how much I added, and it seemed to be perfect per the line on the sight glass.
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Old July 5th, 2023, 07:30 PM   #42
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Originally Posted by jk3099 View Post
No compression test lately! I'll add it to the list of things to do while doing the valve check. Thanks for the suggestion!
You can do that first. It's way quicker than checking the valves clearances.
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Old July 23rd, 2023, 06:14 PM   #43
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Hi all,

Finally got around to working on my bike. I redid the vacuum test because it seemed odd; turns out the battery was dead (go figure), resulting in no vacuum.

Here's a video of the actual results: https://youtube.com/shorts/l_biVnh7M6w

Thoughts?
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Old July 23rd, 2023, 06:15 PM   #44
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Originally Posted by jk3099 View Post
Hi all,

Finally got around to working on my bike. I redid the vacuum test because it seemed odd; turns out the battery was dead (go figure), resulting in no vacuum.

Here's a video of the actual results: https://youtube.com/shorts/l_biVnh7M6w

Thoughts?

Also, the choke was off for this test, and I adjusted the idle screw to be about halfway "screwed."
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Old July 25th, 2023, 07:24 AM   #45
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What a troubleshooting thread! Dead battery is just the cherry on top. Carb woes are black magic sometimes. Hope this gets sorted soon!
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Old August 9th, 2023, 07:21 PM   #46
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Hi all,

It's been a while! I started troubleshooting my bike again. A few findings...

1. I took the carbs. off to look at the rubber boots and took pictures included in the link below. They didn't seem to have any obvious cracks, though there was some deformity in the rubber. Is there a chance this is the culprit for the low vacuum on the carbs? I also verified that there were no obstructions in the spaces connecting the engine/airbox to the carbs.
https://photos.app.goo.gl/BrBkFx6AtDdZ2TH59

2. I began readjusting the valves. The left intake was too tight (from my last valve adjustment), so I adjusted it to the appropriate clearance. The right intake was fine. I'm working on the left exhaust, which seemed just barely loose, so I'm trying to tighten it up a bit. I still have to check the right exhaust.

3. From looking at the video of the low vacuum, does anyone have any other ideas of what I might want to check other than the valves and passages to the carbs?
https://www.youtube.com/shorts/l_biVnh7M6w

4. The air filter isn't terribly dirty, though I did find a hazelnut at the bottom of the airbox. No changes at the moment.

Thanks for everyone's help!
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Old August 9th, 2023, 10:47 PM   #47
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compression test
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Old August 27th, 2023, 01:32 AM   #48
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Originally Posted by DannoXYZ View Post
compression test
Thanks; I finally got around to doing this (been a crazy busy last few weeks, sadly). Here are my results (all in PSI):

Without Oil:
Left Cylinder: 70, 70, 70
Right Cylinder: 70, 70, 70

With Oil:
Left Cylinder: 80, 78, 76
Right Cylinder: 70, 72, 72

I know this is way too low to even get this to run, and I guess I'll be focusing on the engine next. What should I be considering next? Piston rings? My methods are below if you want to check my work (note about valve adjustments at the end).

Methods:
All done with the throttle held fully opened, battery fully charged beforehand, valves adjusted, and cranking for 8-10 seconds while also watching to ensure the max compression value was reached. When testing a cylinder, I left the other spark plug in (ex: if testing the left cylinder, the right spark plug was still in). Each test was done without oil and then with oil three times on each cylinder. I also checked to make sure there were no leaks between the carbs and airbox/engine. I used the "PITTSBURGH AUTOMOTIVEQuick-Connect Compression Tester" from Harbor Freight (is it possible this is what gave me low values?).

Valve Adjustment Note: I triple-checked (after finishing all my adjustments) my valves to ensure that the intake valves were .08 - .13mm and the exhaust valves were .11 - .16mm. Every time I adjusted one, I ended up checking them all, so I'm pretty confident that the valves should be to spec.
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Old August 27th, 2023, 09:51 AM   #49
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Compression should be done with all plugs out. Little change with oil shows rings are fine. Problem is with valve-sealing. Might be fried exhaust valves from lack of maintenance previously.

Boots between airbox and carbs won't affect vacuum levels because it's before throttle-plates. It's restriction of throttle-plates that generates vacuum between throttle and intake-valves when pistons are on intake-stroke.

Did you verify alignment marks on cam-sprockets and that lobes point in proper direction at TDC?


More measurements needed:

1. battery voltage with everything OFF, volts = ??

2. battery voltage during cranking, volts = ?? too low of voltage will kill sparks

3. key ON, kill=RUN, voltage at coils' red terminals, volts1,2=??

4. verify spark. Remove plug-wires & plugs. Insert plugs into wires and ground case of plugs to bare metal on engine. Crank. Do you seen bright blue spark?

5. Now that you have some vacuum, re-measure petcock flow-rate to see if that amount is sufficient to fill carbs. Disconnect fuel hose from fuel-rail and aim into measuring cup. Crank for 10-sec. How much petrol did you collect? cc=???

Extremely difficult when there's little vacuum and low flow to get fuel into carbs if it has to flow uphill. Once things are moving, it's fine. But if you can't even get it moving, nothing's gonna come out. It's like syphoning petrol out of auto's tank. Have to overcome that uphill section by applying external forces. But there's no petrol pump on this bike to get past that any uphill leg of journey. Downhill or horizontal only.



6. isolate tank, petcock and carbs from fuel-delivery. Use squirt-bottle to spray 2-3cc petrol into airbox. Wait 15-sec for it to vapourise. Crank engine. Does it start & run?


Last futzed with by DannoXYZ; August 27th, 2023 at 11:30 AM.
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Old August 30th, 2023, 04:17 PM   #50
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Quote:
Originally Posted by DannoXYZ View Post
Compression should be done with all plugs out. Little change with oil shows rings are fine. Problem is with valve-sealing. Might be fried exhaust valves from lack of maintenance previously.

Boots between airbox and carbs won't affect vacuum levels because it's before throttle-plates. It's restriction of throttle-plates that generates vacuum between throttle and intake-valves when pistons are on intake-stroke.

Did you verify alignment marks on cam-sprockets and that lobes point in proper direction at TDC?


More measurements needed:

1. battery voltage with everything OFF, volts = ??

2. battery voltage during cranking, volts = ?? too low of voltage will kill sparks

3. key ON, kill=RUN, voltage at coils' red terminals, volts1,2=??

4. verify spark. Remove plug-wires & plugs. Insert plugs into wires and ground case of plugs to bare metal on engine. Crank. Do you seen bright blue spark?

5. Now that you have some vacuum, re-measure petcock flow-rate to see if that amount is sufficient to fill carbs. Disconnect fuel hose from fuel-rail and aim into measuring cup. Crank for 10-sec. How much petrol did you collect? cc=???

Extremely difficult when there's little vacuum and low flow to get fuel into carbs if it has to flow uphill. Once things are moving, it's fine. But if you can't even get it moving, nothing's gonna come out. It's like syphoning petrol out of auto's tank. Have to overcome that uphill section by applying external forces. But there's no petrol pump on this bike to get past that any uphill leg of journey. Downhill or horizontal only.



6. isolate tank, petcock and carbs from fuel-delivery. Use squirt-bottle to spray 2-3cc petrol into airbox. Wait 15-sec for it to vapourise. Crank engine. Does it start & run?


Thanks for all of your help! I'm glad that it seems like we're getting closer to the root of the problem

Here is a partial set of results.
1. Voltage with everything off: 13.37, 13.36, 13.36 (fully charged); after cranking, this resting voltage dropped to 12.5 and 12.47

2. Voltage while cranking: 11.5, 11.6, max = 11.64

3. Can you clarify what you mean by this, please? Does this mean I should get the voltage from just one terminal of the battery? If so, where do I place the other lead to close the circuit? Where do I find the coils' red terminal?

4. There is a bright white/blue spark on both spark plugs while cranking and grounding the plugs to the engine. Very consistent results/spark.

5. TBD - going to get a beaker first. Also...

6. Before putting the fuel tank back on for #5, can you clarify this test, please? What am I isolating from one another? In other words, what should I be leaving on the bike/connected vs. what should be taken off? Is the "fuel-delivery" you're referring to just the hose connecting the petcock to the carbs that delivers the fuel (not the vacuum hose)? Just wanting to make sure I do this test correctly.

I did get a new battery last year, and that seemed to be one of the major causes of the bike to start again last year. Not sure how it's held up since, but it's seen very little use since being replaced.

Additionally, I redid the dry compression test with both spark plugs off. Results were consistent with the previous test (left = 70 psi, 70 psi; right = 72 psi, 72 psi).

I also have not formally verified that the cam timing was correct (I wasn't directly looking for it while doing my valve adjustments), but nothing looked out of the ordinary when aligning the valves to TDC.
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Old September 4th, 2023, 01:56 PM   #51
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Quote:
Originally Posted by jk3099 View Post
Thanks for all of your help! I'm glad that it seems like we're getting closer to the root of the problem

Here is a partial set of results.
1. Voltage with everything off: 13.37, 13.36, 13.36 (fully charged); after cranking, this resting voltage dropped to 12.5 and 12.47

2. Voltage while cranking: 11.5, 11.6, max = 11.64

3. Can you clarify what you mean by this, please? Does this mean I should get the voltage from just one terminal of the battery? If so, where do I place the other lead to close the circuit? Where do I find the coils' red terminal?

4. There is a bright white/blue spark on both spark plugs while cranking and grounding the plugs to the engine. Very consistent results/spark.

5. TBD - going to get a beaker first. Also...

6. Before putting the fuel tank back on for #5, can you clarify this test, please? What am I isolating from one another? In other words, what should I be leaving on the bike/connected vs. what should be taken off? Is the "fuel-delivery" you're referring to just the hose connecting the petcock to the carbs that delivers the fuel (not the vacuum hose)? Just wanting to make sure I do this test correctly.

I did get a new battery last year, and that seemed to be one of the major causes of the bike to start again last year. Not sure how it's held up since, but it's seen very little use since being replaced.

Additionally, I redid the dry compression test with both spark plugs off. Results were consistent with the previous test (left = 70 psi, 70 psi; right = 72 psi, 72 psi).

I also have not formally verified that the cam timing was correct (I wasn't directly looking for it while doing my valve adjustments), but nothing looked out of the ordinary when aligning the valves to TDC.
This is awesome work!

1-2. Yay! Shows strong charged battery

3. Voltage measurements shows differential between probes. So leave blk/gnd probe connected to battery -neg terminal.

4. Awesome! This also confirms #3. Poor wiring to coils showing less voltage than at battery will result in weak orange sparks

6. Maybe I should use "bypass" instead of "isolate". You want entire fuel-system re-assembled. We'll bypass its function of fuel-delivery by manually sending petrol directly into engine.

This removes tank, petcock, hose, and carbs from equation. IF engine starts, then we know for sure with 100% certainly that fuel-delivery is problem. Something wrong with tank, petcock, hose or carbs. Then we can ignore everything else and do specific tests to determine which one of those is bottleneck.
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Old September 6th, 2023, 06:15 PM   #52
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Originally Posted by DannoXYZ View Post
This is awesome work!

1-2. Yay! Shows strong charged battery

3. Voltage measurements shows differential between probes. So leave blk/gnd probe connected to battery -neg terminal.

4. Awesome! This also confirms #3. Poor wiring to coils showing less voltage than at battery will result in weak orange sparks

6. Maybe I should use "bypass" instead of "isolate". You want entire fuel-system re-assembled. We'll bypass its function of fuel-delivery by manually sending petrol directly into engine.

This removes tank, petcock, hose, and carbs from equation. IF engine starts, then we know for sure with 100% certainly that fuel-delivery is problem. Something wrong with tank, petcock, hose or carbs. Then we can ignore everything else and do specific tests to determine which one of those is bottleneck.
Thanks for all of your help and for clarifying all my questions! It means a lot

I bypassed the third test since the fourth test showed that it was effective, but I did get results for 5 and 6.

Results:
5. 10 cc of fuel after cranking for 10 seconds. Doing this test twice yielded the same results. There was a fuel filter on, so I began counting as soon as the fuel started flowing out of the hose; the flow was steady and strong for all 10 seconds.

6. Bike didn't start from this test. I tried a few times by putting 2-3 cc of fuel into the airbox (once with the filter on and once with it removed), letting it vaporize for a few seconds, then cranking for about 10 seconds, but it didn't start up. I also tried using a gloved hand and "smearing" it onto the airbox screen (connected to the carb) and tried again, but this also didn't work. While doing the test, the fuel tank, carbs, and petcock were all on the bike, but the fuel and vacuum hose connecting the tank/petcock to the carbs were both disconnected.

So, taking all of this info in, since tests #1-4 showed that the electrical/spark is good, and assuming that #5 is adequate fuel flow/vacuum from the petcock/carbs, does this mean that #6 shows that the low compression is most likely due to an engine issue?

Thanks again!
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Old September 18th, 2023, 09:01 AM   #53
jk3099
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Quick update on the bike: since I’m using a cheap Harbor Freight compression tester, I wanted to see whether it would start up since it could possibly be underestimating the compression levels. I tried charging the battery then starting the bike, but it didn’t start, so it must be low even if the values aren’t accurate. Any thoughts on next steps?
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