[jp_prat]

Thanks for your help! Here is log from starting attempt where it barely run on starter motor. https://gofile.io/d/C4th4r
So these logs are now taken with 12-3 trigger wheel and older but same model hall sensor. Same setup i used earlier this summer. It seems something has changed because bike used to be driveable with this setup. I have no idea what has changed everything should be the same.

Fueling should be good and all exhaust runners are getting warm when it tries to run. It seems like when cylinders start to fire, sync loss cames in and ruins everything.

Somehow this is so sensitive for this kind of thing. Can you take a look of my logs? And get any ideas what might be good idea to try to fix this.

Here is log: https://gofile.io/d/C4th4r
and attachments have tooth log and scope pic

[LAV1000]

I see you did find the DC settings on your scope
Voltage reading makes more sense now.

Datalog:
MAP sensor doesn't do much ?
Vacuum leak ?
Sync losses at up.
Ignition advance is now at 12 for starting rpm.
Might be a bit to much try 8-5 for now, to see if helps on starting up.
Did you chance settings for starting rpm ?

[PSIG]

It looks like some of those teeth opposite the missing tooth are going slow, perhaps > 1.5x duration of the other teeth.

@jp_prat - I still think @jonbill is on a possible track, looking at your new 'scope traces. Note in the image below the tooth-time using Falling Edge. It appears that the spacing is close, but less than 1.5T, on this one trace. However, if you look at the Rising edges, it's definitely beyond 1.5T and would lose sync.

So, if you are set for Rising Edge, try Falling Edge. The Trigger Angle will have to be changed, of course, for correct timing. If you're already on Falling, then your compression is possibly taking timing beyond 1.5T with the low tooth-count wheel. More teeth with compression cycling would have more gradual changes between teeth. I'm not saying this is it, and possibly the T requirement could be altered for this application, but it may be worth looking-at.

updated with both Falling and Rising edges
Compression T read as gap.jpg (199.29 KiB) Viewed 5400 times

[jp_prat]

I see you did find the DC settings on your scope
Voltage reading makes more sense now.

Datalog:
MAP sensor doesn't do much ?
Vacuum leak ?
Sync losses at up.
Ignition advance is now at 12 for starting rpm.
Might be a bit to much try 8-5 for now, to see if helps on starting up.
Did you chance settings for starting rpm ?

Hi
Map sensor is actually fine. That engine just doesnt pull much vacuum at all, probably because it has aggressive cams and low compression maybe. Also plenum is HUGE because it has air to water intercooler in it, and it uses single 60mm throttle body. When it opens, it quickly flows more than engine sucks on starter.

That advantage i forget to 12, when i was using timing light to check that timing comes in right time. I have used 5 degrees on starting before, and 12 on idle. 12 might not be optimal for starting, but it did want to start, and it really fell on its face when it starts to having sync loss.

I haven't changed starting rpm in long time. I think it just is what it was set on spring when i did some troubleshooting.

[jp_prat]

It looks like some of those teeth opposite the missing tooth are going slow, perhaps > 1.5x duration of the other teeth.

@jp_prat - I still think @jonbill is on a possible track, looking at your new 'scope traces. Note in the image below the tooth-time using Falling Edge. It appears that the spacing is close, but less than 1.5T, on this one trace. However, if you look at the Rising edges, it's definitely beyond 1.5T and would lose sync.

So, if you are set for Rising Edge, try Falling Edge. The Trigger Angle will have to be changed, of course, for correct timing. If you're already on Falling, then your compression is possibly taking timing beyond 1.5T with the low tooth-count wheel. More teeth with compression cycling would have more gradual changes between teeth. I'm not saying this is it, and possibly the T requirement could be altered for this application, but it may be worth looking-at.

Compression T read as gap.jpg

Hi
Okay, this is good. I have actually it set on falling edge now. I have read on oldscoolsuzukiinfo forum that people are using 24-2 wheel with similar engines on megasquirt. Someone used 36-1 and some had problems with, that were fixed going 24-1, or 2.. i dont remember for sure.

I am building trigger wheel cutter machine and i have all the parts already. Then i can make pretty much what ever tooth count trigger wheels i want. Hopefully pretty accurately and cheap.

What do you guys think, 24-1 or 2 trigger wheel would be worth trying? I would like try that before changing T requirement.

[LAV1000]

Go for the 24-1 type and since you have the tools also make 24-2.
Set it up in such a way that it is mechanically set for missing tooth at about 90 dgr BTDC.
Because at that point crank speed is smooth.
Due to compression before and combustion after TDC it is slowing down or accelerating .
On a 4 inline engine it happens 720/4 every 180 dgr.
And the lesser the crank weights the more it noticeable.

If you put the missing tooth detection at TDC you could run into sync losses at start up due to effect mentioned above.
And then a 24-2 could be the answer.
Or if it has a lot of kickback on starting up, even if ignition timing is setup spot on for the engine.

Now to make things more difficult.
On Tuner Studio ignition set up Speeduino uses a ATDC, yes AfterTDC.
So it would be then 270 dgr, don't ask me why, I am getting a headache when trying to figure out
And if I am wrong on this last part please feel free to correct me

[jp_prat]

Hi, thanks for the ideas! I have made and tested 24 tooth trigger wheel now. I am not sure about the design, is it good?
I did put it on the crank so that the missing tooth was about 90 degrees before tdc. When i started to crank it, it gave sync loss and was a mess. I then started to look it on oscilloscope and it looked like its hard to spot where missing tooth is because engine is slowing down because of compression.

So i already did cut it to 24-2 and tried again. It didnt give sync loss anymore when cranking, but when i stared to check ignition timing, i noticed that it is impossible because of the timing jumps around like crazy. Like if i crank it, it might show for example 10 degrees BTDC and stay there, but when i stop cranking, and crank over again, it can show 20 degrees ABDC. It jumps like that now randomly, but not during cranking, only when i stop and start cranking again. Almost like it can't latch to same spot every time.

What could cause this kind of issue to happen?

I put tooth log there cranking it with this 24-2.

[theonewithin]

Make it a 12-1 wheel.

[jp_prat]

Make it a 12-1 wheel.

I have tried it first. The reason i went now with 24-2 was to get rid of some issues that i had with 12-1.

[LAV1000]

Check ignition timing settings in fixed timing and cranking advance.
Might be the cause of 10-20 dgr. issue.

Since it is a motorcycle engine converted to turbo and lowered on compression.
I Think it is strange that starter can't turn the engine more smoothly.
Check on these points, weak battery, worn out starter relay, carbon brushes starter, weak or corroded connection somewhere between battery and starter.
Also check ground connection.

Question, why such deep cut between teeth ?
5-10 mm (about 0.2-0.5 inch) would be more then sufficient.
And less trouble to get the balance sorted out due to missing mass of those 2 teeth.