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Thread: 1986 Yamaha 225 Tri Moto

  1. #46
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    Quote Originally Posted by Eberanth View Post
    Was hoping to get some feed back on my question about bogging on WOT just above
    I went back to the beginning of this short thread, second post was some member using Carl from ATHF as an avatar, I got lost ATHF randomness for a minute, then came back to this post.

    Your bogging issue is no load versus load on the engine. A weak ignition can act like that. A higher engine load creates higher cylinder pressures. This isn't the same as compression ratio or compression PSI, and it takes a more energetic spark the higher the cylinder pressure is. If the ignition is borderline, it may idle OK and run alright at light throttle or in neutral, but put a load on it, and you're getting poor combustion from a weak spark.

    It's also probable the fueling system is off, as in incorrect jetting, but in gear versus not is still an engine load difference. Kind of like on a old carbureted car, you really have to rev the engine high to get vacuum secondaries to open on a four barrel carb if it's in park, but under load, they'll begin to open at a lower RPM because the load is demanding more power from the engine.
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  2. #47
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    I don't know the Yamaha models super great, but generally bogging is carb related. If you're stabbing the throttle fast and it bogs, that might be normal, I doubt there's an accelerator pump in the carb so there's a brief moment the engine is to lean. Under normal riding you shouldn't notice bogging though. WOT suggests to me the main jet/needle circuit needs cleaned. Here's a chart to get an idea what effects what range of the throttle generally speaking. Not a whole lot to look at for above 3/4 throttle. This ignores things like fuel supply, like if you're running the machine hard and it starts to run poorly, it's likely fuel delivery, but if you're just starting the engine, letting it warm up some and reving it up and it doesn't run right, I'd be taking the carb apart for cleaning. If you want you could get a "rebuild" kit for the carb, new gaskets, jets and such, but you still have to clean the circuits (holes in the carb body) so that they free flow fluids. Using carb clean and the straw against the hole should shoot out the carb clean in another location if not completely blocked off.



    It also sounds like you've adjusted the pilot jet, this could also be a sign the slow/pilot jet is dirty if you had to open it up more. It's always possible someone fiddled with the settings though. I would give what the factory "base line" setting is, but sadly the Clymer manual seemed to have forgotten to include it... this is why I'm not much of a fan for the Clymer manuals compared to the manufacture manuals. It says to see table 8...



    I don't see the spec, maybe I'm blind?



    Sadly, I don't have the actual Yamaha manual to reference. I have Honda and Kawasaki spec manuals, but haven't expanded to the other brands yet.

  3. #48
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    Great feed back guys! Its a brand new carb so.its in good shape. I ordered the carb it's for a timber Wolf and the fuel line is a little smaller than what was on there so I'm not sure if that could be an issue. I may be a bit stabbing hard on the throttle so I'm going to be more conscience of that It's also backfiring a lot though. If it is an ignition issue any suggestions on how to improve or test?

  4. #49
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    Simplest for ignition system would be a timing light and check the timing. There's also the mechanical timing (crank vs cam) which can cause somewhat similar issues. The service manual should cover the process pretty well on how to test both.

  5. #50
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    Quote Originally Posted by Eberanth View Post
    If it is an ignition issue any suggestions on how to improve or test?
    Yamaha has a spark energy test. There is a 'tool' the OE shops may of had, but there's also something you can buy that's more or less like that, at a very reasonable cost.

    Give me a bit and I'll give you some numbers from the tool I have.

    If you bought a Chinese carb and put it straight on with the jets it came with, it's very likely the jetting is wrong. I've already been down that road on my YTM200K. Check the 'Moved to the Yellow Side' thread for what I went through with one of those carbs.
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  6. #51
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    For the spark energy test, I suspect it's a roundabout way to test the voltage of the ignition coil output. There's an automotive tool to actually read the kv reading, but I don't think those are cheap. In the small engines world, I've only seen a spark gap test tool which does a less accurate version of the same test, about a 6-7mm gap. Here's a random google page on it, not sure if the numbers are right but 6mm gap is 0.6cm * 30,000v = 18kv, seems about right.

    https://sciencing.com/calculate-volt...s-8776030.html

    This tool is a little different than I've seen before, but a proper shop might have a similar tool.

    https://www.youtube.com/watch?v=OHU01046xgU

    For the at home repair job, grab a PET-4000, they are reasonable priced and not a random Chinese no name company. Here's a video of a guy using one on a chain saw, same process applies to 3 wheelers an basically any other engine with spark plug wires. The test tool doesn't need to say echo or any special brand, it's all made in the same place and rebranded for different resellers.

    https://www.youtube.com/watch?v=dipmevU5cjU

    Do NOT use the test light style spark testers, they only show there's *something* there, not that the something is good or bad. The non-adjustable spark testers can work, they generally are cheaper and are built with a 6mm gap.

    I don't know what the Yamaha OE tool is, but I suspect it's something similar to the above. Also you can slightly tell voltage based on spark color with the plug against the head, but it only works for low/weak spark and not when it's closer to boarder line. Aka, if spark is yellow or orange, it's weak spark, if it's white or blue, well it's better than yellow or orange, but doesn't mean it's actually good. If I'm thinking right, the color of the spark is more of a visual of the temp of the spark than the actual voltage.

    Compression comes into play on the open in the wind spark test, the air we breath is effectively around 14.7psi from a complete vacuum, inside the engine the spark plug sees ~150-180 psi (plus the initial 14.7 we don't count for normally) with something like 200mph winds. That means the air is over 10 times more dense which makes it harder for the spark to jump. Don't forget to add in a mist of fuel with those winds =).



    I'd be interested to see what the Yamaha tool is. I also agree, the Chinese carbs seem to have poor jetting out of the box, sometimes you're a winner, sometimes not. I think replacing the jets with quality ones starting at the stock jetting numbers for the machine is a solid starting point, but it should be fine tuned for best results.

  7. #52
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    This is what El Manual says about the spark gap for a YTM200K (presuming a 225 is similar):

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    This is what I got at idle for spark energy:

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    About 4kV at idle. Whether or not that's completely accurate, IDK. It's at least a baseline for my machine if it acts up in the future. The tester ps2fixer mentioned will work good for this application. I like the Snap-On tool because it's an inductive pickup, and nothing is disturbed during it's use.
    Last edited by ATC King; 10-26-2020 at 09:58 PM.
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  8. #53
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    4kv seems quite low, 6mm gap in open air should be around 18kv. That's based on the math of 1cm gap = 30kv at sea level unless that googled number is invalid which is very possible.

    It's interesting the manual shows to use the gap tester inline with the spark plug, so you have the plug gap + the 6mm spec overall. I've never used that tool, maybe that's more of a normal reading for it due to the inductive style pickup?

  9. #54
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    Yes, the inductive pickup is the difference, because it's not testing the system for maximum energy like the 6mm spec the Yamaha gives. The tool I used is just detecting the kV produced during operation of an intact system.

    Try that math again, with a gap of 0.6-0.7mm, which is the spark plug gap for the engine.

    The kV can also be lower because of a rich mixture. There's several things to take into consideration, but I wanted to give the Yamaha test spec and what I found with a inductive test tool. The gap tool you suggested is great for the Yamaha spec, because it's affordable, readily available new, and seems to be what was built into the Yamaha OE tool.

    The kV does read higher on the Snap-On tool if I rev the engine or put it under load, like in gear and dragging the rear brake. I chose idle for simplicity, but I can record the other numbers and find maximum if someone else has a similar tool and would like something to compare.
    Last edited by ATC King; 10-27-2020 at 10:13 AM.
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  10. #55
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    The problem with using the math on the spark plug gap size is out in normal air pressure it will be ~1.8-2.1kv, but when you throw it in the engine, there's a lot more resistance for the spark to jump. That's why at normal air pressure the spec is 6mm, but in the engine it's 0.6-0.7mm for most engines.

    The kv should more or less be determinate on the ignition coil and it's power source. With a tool picking up the voltage, maybe the numbers work a bit different since it's indirectly reading the flow and the spark plug is in the engine so maybe it's only using 4kv (it sparks before a higher voltage is built up?) and not the system's maximum capacity.

    I'd be interested if you could repeat the test with another atv, maybe a good running Honda to see if the figure changes. Also do you happen to have a gap spark tester? It would be really interesting to fire the engine up on that and indirectly read the kv and make the gap larger and see what happens to the reading.

    I googled around a bit and any site that mentions kv about small engines is either hacked or the page diesn't exist any more, really weird. In the summary on google I saw around 12-15kv being the min for lawn mowers and some motorcycle. I know the automotive world with EFI runs at much higher voltages

    Finally found a source I can link, not the greatest site in the world to use for fact checking or anything but that's the 3rd mention for small engines in the 12-15kv range. I know car ignition systems can be very high voltage, I've seen the spark jump atleast 1/2 inch before which would calc to 76kv with the 1cm = 30kv math.

    https://en.wikipedia.org/wiki/Ignition_coil
    A large ignition coil puts out about 40 kV, and a small one such as from a lawn mower puts out about 15 kV.
    Anyway, not exactly trying to argue or anything, I think the kv tester provides a different measurement than the spark gap test. My guess would be effectively working kv vs max kv (you increase the gap till the engine misfires or dies).

    This video supports what you said on the air fuel ratio and such, interesting tester to have around, that's for sure.



    I wonder if different plug types give different readings too, like standard vs iridium.

  11. #56
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    I was going to add some things to my last post, but didn't get around to it early enough.

    The first section in this article sums it up pretty quickly: https://www.agriculture.com/machiner...gnition-system

    I think paragraph five is what's important for this thread:

    "If the engine was still idled and a load was gently applied (engaging a PTO, for example), the voltage required to arc the plug would increase dramatically. Due to this, the engine may run fine under a given operating state and then buck, pop, and misfire when faced with different operating conditions."

    The ignition only puts out what energy is needed to create a spark, and that demand is different from idle on up and under different conditions. A 40kV coil does not produce that all the time, that's only the maximum it can deliver.

    It's like engine horsepower ratings. A 300hp engine only makes that much power when called for. At idle or just cruising down the highway, it's not making anything near that.

    Also, it's why installing a high powered coil on an engine that never needs it, is a waste of money. Most engines have all they need from the factory, but if increasing the power output, they'll probably benefit from a more powerful coil, especially if adding a turbo or supercharger. Higher cylinder pressures requires more energy for a spark to jump the plug gap and higher power engines will have higher cylinder pressures under load.

    The test in the Yamaha manual, where a huge gap is used, is like putting the ignition system under load. It'll test what's the maximum power it can produce, but it's only a basic test for the ignition. If the voltage was measured with another tool while the gap was increased and decreased, it'd be seen increasing and decreasing the same. Whatever energy is needed to jump the gap, is all the ignition will produce. That's also why bad wires and plugs can damage the ignition coil, it's acting like a full load all the time and burning up.

    When using an inductive type tool, the actual kV needed during running conditions is being seen. This will include all the variables, which is why it's a more useful diagnostic tool and why using something like an oscilloscope to watch ignition waveforms can pretty much give an experienced user a direct look into what is actually happening inside the cylinder during ignition.

    Touching on the first sentence of your post, that' why it's ~4kV with the inductive tool at idle and not 2.1kV. Inside the engine, it's taking more energy than it would in open air, like you mentioned.

    Edit: I found a good video on YouTube of stock versus aftermarket 'performance' coils on a stock car, with dyno results. They're all so close to the stock coil performance that even dyno acuraacy isn't close enough to say there's any difference. If they done internal engine modifications or added a turbo, then the performance coils may have made more power over stock.
    https://www.youtube.com/watch?v=NQOApqmq7oE
    Last edited by ATC King; 10-27-2020 at 08:48 PM.
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  12. #57
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    Yea all that makes sense to me, the only thing I don't 100% perfectly understand the physics of is the ignition coil, the whole creating a feild then it collapsing to create the high voltage. I get how transformers work, but ignition coils are.

    The only thing I'd question on the above is the amps, like a high output coil that is capable of 40kv but it only uses 10kv, wouldn't it effectively be putting out 4x the amps, aka 4x the energy, joules, watt, or whatever measurement you'd want to do. I'd think the spark voltage would be the same, but the spark thickness would be thicker.

    I've personally experienced ignition problems related to changing load. 1990 Grand Am with the 2.5L 4cyl, just bought the car so my typical thing is a basic tune up, plugs, and wires for that car (cap + rotor if it had them). I noticed while driving 55mph if I gave it just a tiny bit more gas, it would start missing. It was back when I was a teen, so I asked my dad and the first thing he said was to swap spark plug wires out to see if the problem follows, if not swap plugs around. Wires had no change, when I pulled the spark plugs, the porcelain broke on one when it came out of the socket, it was together good enough to pull the spark plug wire, but was broken new from the box. Replaced the bad plug and it ran fine after that. I suspect the spark must have been jumping from the center electrode to the base of the spark plug through the crack when the engine needed high enough voltage to run and that was the path of least resistance for the electricity to go.

    Like I said, I think both tests measure different things. I bet your spark tester would have picked up the problem on the Grand Am example above, but the gap based test wouldn't because the problem wasn't with the ignition coil. I think both test methods would be valuable to have for anyone serious about reparing engines, one to effectively load test the ignition coil to validate it works even under the worst case situations which I assume the 6mm gap is the spec for, and the kv tester to read how much voltage is needed for the ignition as a whole system test (plugs, coil, wire, fuel mix, compression, oil blow by, etc).

    I didn't know the two testers would give different results, and I think I understand pretty well why that is and when to use each tool. I have the PET-4000 tester, but not a KV tester. I haven't had a chance to try it yet, but I'd like to play around a bit more with the ignition coil readings with different CDI's for the 350x. Generally speaking the low ohms stator with an aftermarket CDI the engine runs ok at low rpm, but mid to high rpm it runs like complete garbage, like the ignition system isn't getting spark above a certain rpm, but it's not a rev limiter. The later model 350x stator seems to not have the problem at all from what I've heard from Mike and people's experience with his aftermarket CDI's. I think it would be interesting to work out a way to read the capacitor's capacitance inside the CDI to see how wildly off the aftermarket ones are vs the stock one.

    Speaking of the CDI, I came across a diagram in a service manual showing AC vs DC powered CDI's, it made a lot of sense why the DC CDI actually performs better, basically it gave consistent output but I'd like to find the page again. The AC CDI's all are powered by an exciter coil, and it seems like each machine has a differnet design of coil, so the CDI is built different, and the ignition coil probably has slightly different specs because of that. The DC CDI in theory should have standardized parts more, atleast within the same brand.



    I think we went a little deeper on this subject than the OP expected, hopefully we haven't lost everyone else xD.

    Just finished reading that page, pretty good write up. I don't really agree with the spark issues first then fuel, atleast in the context of small engines, even more so with ATV's that tend to sit for long periods of time. Now if it's in the context of a car, then yea, ignition first, fuel second since the machine is used atleast once a week most likely.
    Last edited by ps2fixer; 10-27-2020 at 09:31 PM.

  13. #58
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    ps2fixer, I think the big takeaway from what we've discussed is the PET4000 tool you mentioned (available on Amazon & EBay) and the Yamaha test specs.

    I don't think Honda ever mentions any king of spark energy test in their manuals. Probably Kawasaki too and to a lesser extent, Suzuki (barely even made trikes).

    The other thing is your willingness to invest in parts to test them, which is very much appreciated, as others have said.

    It would be nice to start a thread just for various ignitions and their recorded energies using different tools. Spark or no spark doesn't cut it when trying to diagnose poor engine performance, or even for a non running engine with a weak spark.

    Knowing what a good ignition system actually measures at would help tremendously. People have been getting by for decades without that knowledge, but for anyone that doesn't want to guess or doesn't have years of experience, buying a relatively inexpensive tool and having the information, may let them keep most of their hair and possibly, their trike.

    Although I like to go more in depth on some things, there's not much need for going nuts with the ignition stuff on low power, small engines. New parts availability and testing information are more than enough.
    Last edited by ATC King; 10-27-2020 at 09:45 PM.
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  14. #59
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    That's a really neat idea, wouldn't hurt to throw something like that as a community powered database on my site. I don't have any user entered data on the site yet, but there's no way I'd ever be able to test all machines myself, but 1000's of people could pull it off easily. Of course engines will have different readings, but a generic target would be nice to know.

    For the ignition coil, of my understanding, the 6mm gap test is pretty universal, effectively every engine should pass the 6mm spec, but somewhere I'm pretty sure I some performance models spec to 7mm as the min, I'm thinking it was Kawasaki but I can't seem to find it again. Guess I have too many books lol.

    I think we both process things similarly. I like to try to understand things fully, no mystery black boxes and such. I'm better with computers than engines, this is kind of my secondary passion lol.

  15. #60
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    same issue here....although, i never did get my oil plug out.. tried like hell, about the only thing i didn't try was a drill! lol sooo, now i use one of them sucker drain things to get the old oil out lol... dont know how it got in so tightly without snapping or stripping in the first place...

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