Yamaha Big Wheel EFI

[dontz125]

Are you sure that inch-long bump is a magnet, and not a long tooth for a VR sensor?

A single tooth CAN be used for ignition - clearly, Yamaha thought so when they designed the bike. A single tooth CAN be used for injection, but it won't be as accurate as a multi-tooth arrangement. Since ignition generally wants more accuracy and precision than batch-fired injectors, this can be made to work. Just bear in mind, your tuning will require the acceptance of a little slop, so you won't be doing any ragged-edge adjustments, either for power, efficiency or emissions.

[BW250]

Thank you dontz! I think you are correct in it being a VR sensor, as that makes more sense (at least in my mind) on how the cdi knows how to change spark timing in relation to engine speed.

I should have been more specific with my plan-- its to make a 36 tooth timing wheel for the camshaft and fit it with two sensors. This would give me relatively precise injection and spark timing correct?

Sorry for the lack of clarity, I have so much to learn...

[dontz125]

Why do you want to use two sensors with a single wheel? A single missing-tooth wheel at cam speed is all that is needed. Also, you don't need to be too fixed on a 36-tooth wheel; this is the most common, but cetainly not the only option. Honda likes its 12-3 wheel for bikes, as it offers excellent resistance to confusion due to variation in cranking speed, something to which a single-cyl engine is quite prone.

Actually, thinking some more, for your application a 12-0 wheel on the crank and a single tooth on the cam might be ideal, and would offer almost bullet-proof sync information.

[BW250]

Now we are getting somewhere. I am hoping to use two sensors on a single cam wheel because fitting a trigger wheel/sensor to the crank would be very difficult in my application (I would say impossible, but, you know) whereas the cam wheel shouldn't be too bad at all. Is there a particular configuration of teeth that would work best for that?

Just to clarify-- I don't want to just use a stock ignition setup for a few reasons. First off I would have to buy a CDI, etc which would add cost to the project and second, if I'm not mistaken a toothed wheel provides more accurate spark timing. Lastly, I want to avoid bulk as much as possible, so not having the factory ignition stuff in conjunction with all of the Microsquirt would be plus.

[dontz125]

As with a crank wheel, you can use a single missing-tooth wheel or a dual non-missing-tooth wheel plus a single tooth at cam speed. This will work for both spark and fuel.

[BW250]

Dontz, I am trying to understand your reply but my lack of knowledge is proving to be a barrier. Can you please elaborate?

[dontz125]

Single sensor and wheel (36-1, 12-3, etc).

Two sensors and wheels, 12-0/1.

[BW250]

Upon further review, it doesn't look like the bike uses a VR sensor for the pulse generator-- its simply a square winding of wire with two leads coming of and so I'm back to thinking the bump (which is actually about 2 inches long) is a magnet, or perhaps something entirely unrelated.

You guys have probably answered my questions 5 times over and I'm just not smart enough to understand , but my goal is to have the injector and the spark plug fire once per cycle of the engine (so not batch injection or wasted spark I believe). It would seem like to me, where the camshaft makes one rotation per cycle of the engine, fitting it with a large tooth number wheel (like a 36-1) would provide both the fuel and spark with good timing input. I am not saying I know this works/is the best, I'm just trying to verbalize my thinking because it sounds like you are saying a 36-1 is overkill.

So I guess my two questions are

1.Can two senors be made to work off of one trigger wheel placed on the camshaft?
2.If yes, what tooth pattern would best serve the purposes of fuel and spark?

Thank you so much for your patience.

[dontz125]

Don't get confused or distracted by the long fancy VR or Hall sensors found on cars - on a bike, a VR sensor IS a little square winding (with a 3-4mm button nose) with two leads coming out. A quick Google for pics, and I found this:

TTR225 Stator and pickup.jpg (18.84 KiB) Viewed 3219 times

Assuming that square thingy on the right is what you're talking about, that IS a VR sensor.

A single wheel works with a single sensor, whether on the cam or crank. A dual sensor arrangement needs a separate tooth. At cam speed, it can be part of the same chunk of metal, but physically offset (stacked). At this point, I'm going to suggest just sticking with a 12-3 wheel on the cam with a single sensor.

If you want a single injection and spark, you need to switch over to the MSExtra code; I think the B&G code supports COP, but not sequential injection. There's a link to the Extra forum at the top of the page. You'll need to register, as it is a separate forum.

[BW250]

You are the man! Yeah that is exactly what I have and you are correct, I did get fooled by the long cylindrical VR sensors... Ok so perhaps single injection and single spark may be asking for a bit much. So what your saying is if I just use a 12-3 wheel on the cam with a single sensor in conjunction with the stock pulse generator (which I guess in actuality is a crank position sensor) I should be able to run my v3 Microsquirt with sufficient accuracy?