Author Topic: Jetting change or bad reeds? (Read 6962 times)

Deebo · « **on:** May 31, 2014, 03:17:40 pm »

My 500 was running fairly well, jetted during 60-65 degree weather. Now it's pushing 80-85 and it's starting to bog really bad at 3/4 thottle to full throttle. I went down 5 main jet sizes from 410 to 360 and raised my needle one clip and it's barely cleared up the 3/4 - full throttle range. I've never had to go down that many sizes before when changing jetting due to weather.

I pulled the reeds to see if they are giving me the symptoms I'm experiencing, but I can't really tell. All the reeds seemed to have tension on them, but they were some areas of question. I'm attaching a few pics.

Any suggestions are appreciated.

MotorGeek - Jerry Hall · « **Reply #1 on:** May 31, 2014, 06:15:57 pm »

Remove the main jet access nut in the float bowl and turn the fuel on. May sure there is enough constant flow to keep the float bowl full.

A 20 degree change in intake temperature should require about one main jet leaner. Has your fuel been setting for a month or so and all of the good stuff as evaporated and is trying to run on an abnormally high mixture of premix oil.

My definition of a bog is when the engine is lazy or does not make power and does not sputter. If you have a bog it is usually lean. If it sputters at 3/4 to full throttle it is rich or has an ignition problem.

Deebo · « **Reply #2 on:** May 31, 2014, 06:32:24 pm »

Fuel is fresh, just not a lot in the tank... Just a week old. It's definitely a sputter. At 3/4 throttle to full throttle, it just cuts out intermittently, definitely rich. I put a 350 main in it just to see if that would clean it up any and it didn't.

I'll double check the fuel flow...

Toydoc · « **Reply #3 on:** June 01, 2014, 05:49:54 am »

IMO, stop dropping jet size. Try fuel from another station. Switch plugs and close the gap some. Pop the cover and check flywheel. Had ignition issues with the same symptoms.

Deebo · « **Reply #4 on:** June 01, 2014, 10:55:49 am »

Pulled the stator cover, adjust the pick up down some to about .030. Fresh fuel, still experiencing the same symptoms.

MotorGeek - Jerry Hall · « **Reply #5 on:** June 01, 2014, 04:09:31 pm »

Quote from: Deebo on June 01, 2014, 10:55:49 am

Pulled the stator cover, adjust the pick up down some to about .030. Fresh fuel, still experiencing the same symptoms.

A wide air gap on the trigger coil will not cause the problem you are having.

Do like toydoc recommended. Install a new spark plug and set the spark plug gap to about .018". If you have consistent spark but weak spark, reducing the spark plug gap will help diagnose a weak spark problem.

If you have a weak spark (voltage to the spark plug) reducing the spark plug gap will often make the engine seem to run normal for a few minutes.

If you have a peak voltage tester the voltage to the coil from the CDI box should be over 100 volts. If the voltage is lower than 100v check the resistances of the ignition coil, stator source coil, reluctor (pick up coil on stator) and wires in the wiring harness.

Check all of the bullet connectors under the fuel tank. They have a habit of getting dirty and or loose.

A bad ground could also cause the problem you are having as well as a wire in the wiring harness may only have one or two strands of wire out of twenty strands that is not broken.

I have had one LT500 flywheel that caused the engine to misfire any time the RPM was over about 4000 RPM and full throttle. I could not detect a broken magnet, weak magnetism or any other measurable difference between the bad flywheel and the one that made the engine run perfect.

Deebo · « **Reply #6 on:** June 01, 2014, 05:37:20 pm »

Quote from: MotorGeek on June 01, 2014, 04:09:31 pm

Quote from: Deebo on June 01, 2014, 10:55:49 am
Pulled the stator cover, adjust the pick up down some to about .030. Fresh fuel, still experiencing the same symptoms.

A wide air gap on the trigger coil will not cause the problem you are having.

Do like toydoc recommended. Install a new spark plug and set the spark plug gap to about .018". If you have consistent spark but weak spark, reducing the spark plug gap will help diagnose a weak spark problem.

If you have a weak spark (voltage to the spark plug) reducing the spark plug gap will often make the engine seem to run normal for a few minutes.

If you have a peak voltage tester the voltage to the coil from the CDI box should be over 100 volts. If the voltage is lower than 100v check the resistances of the ignition coil, stator source coil, reluctor (pick up coil on stator) and wires in the wiring harness.

Check all of the bullet connectors under the fuel tank. They have a habit of getting dirty and or loose.

A bad ground could also cause the problem you are having as well as a wire in the wiring harness may only have one or two strands of wire out of twenty strands that is not broken.

I have had one LT500 flywheel that caused the engine to misfire any time the RPM was over about 4000 RPM and full throttle. I could not detect a broken magnet, weak magnetism or any other measurable difference between the bad flywheel and the one that made the engine run perfect.

Thanks for the advice, I'll start checking through the wiring tomorrow.

Glamisrider · « **Reply #7 on:** June 01, 2014, 06:10:20 pm »

Just keep eliminating things by switch them out.

Do you have an extra set of reeds you can try?

Deebo · « **Reply #8 on:** June 02, 2014, 09:33:30 am »

No extra reeds. Was thinking about getting a set though. Anyone know if V2s are available for small reed cylinders?

Q2W · « **Reply #9 on:** June 02, 2014, 01:05:35 pm »

I believe all reeds are available just not the cages.

Your reeds looked decent, do they sit flush on the cage? or are warped/flare out at the end?

I'm willing to bet your problem is with the electrical though.

Deebo · « **Reply #10 on:** June 02, 2014, 01:17:08 pm »

Quote from: Q2W on June 02, 2014, 01:05:35 pm

I believe all reeds are available just not the cages.

Your reeds looked decent, do they sit flush on the cage? or are warped/flare out at the end?

I'm willing to bet your problem is with the electrical though.

Id say you're correct. I put a new harness on it a couple months ago. Gonna try to go through it this afternoon

Iceracer · « **Reply #11 on:** June 02, 2014, 07:56:44 pm »

99 percent of the jetting problems I see are Ignition and electrical. Usually guys try to jet out an electrical issue, resulting in a seizure when it suddenly runs rite just long enough to screw them.

Toydoc · « **Reply #12 on:** June 03, 2014, 01:13:41 am »

Best thing you did Deebo was take a step back and talk about it. Sometimes you just have to set the tools down and sleep on it.

LT250RWV · « **Reply #13 on:** June 03, 2014, 09:11:29 am »

Let me know what you find. Ive been chasing this around for last 8 months with no luck.

Deebo · « **Reply #14 on:** June 03, 2014, 05:19:55 pm »

Some testing. Pick up and power source coil test within spec. Primary ignition coil resistance is .4 (within spec). However, secondary ignition coil resistance (between pos on coil and spark plug cap) is testing at 8.76 kilo-ohms. Manual says 3-5 is within spec. Could this factor being out of spec cause the issues I'm having?

Bad cap? Bad coil?

MotorGeek - Jerry Hall · « **Reply #15 on:** June 03, 2014, 09:56:59 pm »

Quote from: Deebo on June 03, 2014, 05:19:55 pm

Some testing. Pick up and power source coil test within spec. Primary ignition coil resistance is .4 (within spec). However, secondary ignition coil resistance (between pos on coil and spark plug cap) is testing at 8.76 kilo-ohms. Manual says 3-5 is within spec. Could this factor being out of spec cause the issues I'm having?

Bad cap? Bad coil?

Remove the cap and then test the coil and plug cap independently. If you were checking the coil with the plug cap installed on the coil wire you are probably ok.

8.76K - 5k = 3.76K

Deebo · « **Reply #16 on:** June 04, 2014, 03:37:41 am »

Electrical work isn't one of my attributes

Deebo · « **Reply #17 on:** June 04, 2014, 01:34:41 pm »

Anyone ever use this stuff on electrical connections? I've used it in other electrical applications...

Deebo · « **Reply #18 on:** June 04, 2014, 02:45:50 pm »

Quote from: Deebo on June 04, 2014, 03:37:41 am

Electrical work isn't one of my attributes

4.24 without the cap...

Deebo · « **Reply #19 on:** June 04, 2014, 03:04:20 pm »

CDI is bad according to the specs in the manual. WTB!!

250 & 500 CDI the same?

Glamisrider · « **Reply #20 on:** June 04, 2014, 03:59:34 pm »

Quote from: Deebo on June 04, 2014, 03:04:20 pm

250 & 500 CDI the same?

Yes.

I also think it is ok to run all years but please verify that with someone.

Not 100% if they have different timing curves for 88-90?

LTman · « **Reply #21 on:** June 04, 2014, 04:55:12 pm »

it maybe a good ideal to jet your carb back to your prevous seting before runing it with new cdi

Deebo · « **Reply #22 on:** June 04, 2014, 05:05:16 pm »

Quote from: LTman on June 04, 2014, 04:55:12 pm

it maybe a good ideal to jet your carb back to your prevous seting before runing it with new cdi

Thanks for the heads up LTman... already done.

Q2W · « **Reply #23 on:** June 05, 2014, 06:09:59 am »

damn. Hate when the cdi goes out.

Deebo · « **Reply #24 on:** June 17, 2014, 10:17:09 am »

Replaced the CDI, still experiencing the same issues... Only other thing it could be is the reeds? I think... Anyone know where to find some 88-90 V2 reeds?

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Author Topic: Jetting change or bad reeds? (Read 6962 times)

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