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Thread: Big red HELP !!!! Stuck..

  1. #1
    Join Date
    Jan 2020
    Location
    Atlanta In
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    4

    Angry Big red HELP !!!! Stuck..

    Hello my name is Cory and I'm at a loss for words on this thing. I recently got this 84 Big Red non-running as a project. Things I've done ,
    1. Remove and clean carburetor
    2. Made sure timing is correct everything lines up from the flywheel to the top,
    3. Clean and replaced pulse generator with right spacing,
    4. Checked the valve the exhaust valve with a little tight so I have them set right now I believe,
    5. New spark plug! (Ngk from honda)
    6. Checked all my connections with a multimeter have connection everywhere !.
    The only thing I'm down to because of process of elimination would be the CDI box would be bad? Ive tried testing the did box but not sure how exactly should I just get a new cdi box and go from there? I have videos and pictures if that will help troubleshoot

  2. #2
    Join Date
    May 2006
    Location
    My underwater lair
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    4,287
    Do you have a good spark?

    There are fake NGK plugs out there and they are junk so be careful with that

    What's your compression? Engines with low compression may have good spark and fuel but won't fire. Must have good compression (thumb over spark plug hole is not a good way to check for sufficient compression... Use a guage)

    My sister's 84 200ES wouldn't start because of low compression. Felt ok at the plug hole but was too low on the guage

    Sent from my Z958 using Tapatalk

  3. #3
    Join Date
    Jan 2020
    Location
    Atlanta In
    --
    4
    I will get a compressions Gage and let you know what it reads . is there a way to get better compression , I watched a video on a guy adjusting his valves and he got compression back when I checked my valves they were tight do I loosen them a tad but as of right now I don't have a compression gauge

  4. #4
    Join Date
    May 2006
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    My underwater lair
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    4,287
    Cory when the valves are fully closed, the rocker arm should be able to wiggle a little... About .003-.004 (the thickness of a sheet of paper) loose on the valve stem tip between it and the rocker arm. If your rockers are not loose where you have that .003 gap between the valve stem tip and the top of the rocker arm, then you're losing compression....too tight and the valves won't close all the way and you will leak your compression thru the valves.

    Rockers get too tight in older machines as the valve face and the seat both wear and the valve sits deeper in the head over time putting the other end up into the rocker enough that it no longer closes tightly

    Do you have a manual? There are free downloadable manuals available if not. I'll try to find you the link if you need it

    Sent from my Z958 using Tapatalk

  5. #5
    Join Date
    Jan 2020
    Location
    Atlanta In
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    Okay so I have them set to the manual will be picking up a compression gauge tomorrow and will post the readings, with the gauge and adjusting the valves should give me between 80-140 psi and go from there

  6. #6
    Join Date
    Apr 2014
    Location
    Edmond, KS
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    Be sure to hold the throttle all the way open when you do the compression check.

  7. #7
    ATCKevin's Avatar
    ATCKevin is offline At The Back Of The Pack Arm chair racerFirst time rider
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    Apr 2018
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    Be sure to purchase the proper compression tester meaning it has the right hose for your spark plug thread. Most of your common spark plug sizes for auto are larger. You need one for 12mm thread diameter. As mentioned above, do you have a nice blue spark? You mentioned you installed a new new plug and pulse generator but never said you in fact have spark. Good luck!

  8. #8
    Join Date
    Apr 2012
    Location
    MI, USA
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    3,645
    For the compression spec you *should* have 142-171 psi. It isn't a low compression lawnmower engine. Below 142psi it will still run but be out of spec. Most engines can run on around 100psi, maybe a bit less but won't have as much power. Compression is lost in 3 main ways, head gaskets are pretty rare to go bad on Honda engines, so most likely that's not the cause, most common I'd guess is the piston rings being worn out due to 30+ years of use, but the last one is also fairly common where the valves are too tight and compression bleeds through the valves (not fully shut) as mentioned above.

    https://atvmanual.com/honda/atc200es/1984-specs


    FYI, you don't have to buy the spark plug directly from Honda, you can go to any parts store and get the exact same plug, just make sure it's the same NGK model number.

    You said you checked the wiring with a multi-meter, did you test each part for the ohms spec, or were you just checking if you had any connection, or was it just testing the main harness for the two points most wires go (like CDI connector to pulse generator connector, blue/yellow wire).

    Since you're doing a lot that involves spark/timing, it sounds like you think there's an electrical issue with your machine. You can do a basic check for spark by pulling the spark plug out of the engine, leave the coil wire hooked to it, and set the spark plug against the head where you can see the electrode of the plug. Weak spark is signaled by a orange or thin spark while "normal" is thick white/blue spark. White/blue doesn't always mean good spark, but you can't validate with out a special tester (it measures how far the spark can jump, spec is generally 6mm or 1/4 in min).

    If you have spark, your electronics should be fine and I'd focus more on ignition timing, mechanical issues (like compression), or a fuel delivery/carb issue (most common).

    If your harness has been messed with, like clear signs of mods, or is in poor shape, you can follow the tests in the service manual for the ignition system, but instead of testing at the parts, test them at the CDI connector, and use the green wire for ground. This tests the part through the harness, so if there is a harness problem, the ohm spec will be off while direct at the part it will be correct. FYI, the harness adds a tiny bit of resistance to the readings, but shouldn't be much, something like 1-3 ohms at the high end.

  9. #9
    Join Date
    Jan 2020
    Location
    Atlanta In
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    4
    I got good connections . red and black wire 200 oms , yellow/black .3 -.5 , all grounds .2-.4
    Blue/ yellow 29.0-31.0 oms spark at spark plug yes the wiring harness was all hacked up so I rewired it myself . I have a CDI box order that will be here by tomorrow before 9 p.m. I'm going to plug it in and see what it does cuz my CDI box looks really nasty and Dad if no luck there where we going for a compression tester

  10. #10
    Join Date
    Apr 2012
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    Generally speaking, CDI boxes are a part that either works or doesn't work. Sometimes with age the capacitor(s) inside can get weak and cause weak spark, but it seems it's more common for them to fail where the connector solder joints break on the circuit board.

    An OEM replacement CDI box isn't cheap but they are available yet. Careful of the no name/aftermarket CDI boxes, some will work, some won't, ignition timing of the CDI box is very critical for how well it will run. The OEM one does little to no advancement since most/all of the advancement is done physically at the pulse generator (pickup coil).

    https://www.partzilla.com/product/ho...fe4b7bf33bf6dc

    The actual CDI box really doesn't matter what it looks like, it's a circuit board that's encased in epoxy to make it water and weather proof, unless it's physically damaged I wouldn't worry much about it, that or if the connector is loose, corroded, etc.

    Assuming spark is a check, the next step I'd go is either check the ignition timing with a timing light, or tear into the carb and make sure it's clean inside, no plugged jets and such. Also while working on the carb, put the hose in a container to catch the gas and open the gas tank valve to make sure it comes out as a steady stream.

    It's possible to make the engine run on an LP portable torch (unlit) but backfiring etc could be problematic and is a do at your own risk type of test. The concept is that it pre mixes the fuel (LP) for the engine and is enough to start/idle on and can help rule out if the carb is the cause of no start or not. You could also try starting fluid as an alternative.

    If spark, timing, and fuel all check good, then it comes down to mechanical issues like low compression.


    Also FYI, just replacing parts blindly is a bad practice, it introduces more variables into the mix because new/aftermarket parts can be bad. If you replace a part and it doesn't solve the issue, I'd suggest putting the OEM part back on unless it's known 100% the part was bad. The pulse generator rotor is possible to be installed 180 degrees off timing, so be sure the cam vs pulse generator timing is right, for mechanical timing you'd be checking crank timing (F mark on flywheel) to the cam timing (on cam sprocket, not pulse generator).

    If you don't have a manual yet, grab one off this site.

    http://www.oscarmayer.net/atc/manuals/

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