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750T Motoplat ignition timing

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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2016 at 23:57
If rotor is past the pickup at TDC then it's too advanced. Should be dead on or possibly very slightly before.

I presume yours looks like this?






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GuzziLancs View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2016 at 08:02
Morning Mike, and thanks again for your response.

That is the same unit as mine and I have managed to attached pictures to show the relevant rotor positions at SAM and at TDC (left piston on compression stroke).

Taking it back to fundamentals of a four stroke, 'spark' occurs just before TDC on the compression cycle and I assume this is the point when the rotor should be aligned with the pick up and the Static Advanced Mark is visible in the inspection window.
Hence as the piston continues to TDC the rotor will be just slightly passed the pick up not before it?

ROTOR AT SAM (left cyl)



ROTOR AT TDC mark (left cyl)



As the pictures show the rotor is bob on the pick up at SAM but just slightly passed at TDC.

Regards



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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2016 at 10:28
The only information I have found on setting the motoplat is in the SPIII manual scroll down to page 305.
 
On that the rotation is clockwise, I'm guessing yours is the opposite.
Brian.

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GuzziLancs View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2016 at 18:02
Hello Brian et al,

I have attached the Timing page from the manual I have for the 750 Targa / Nevada, which I believe is the same engine as the 750T and how I have set up the timing.



The crank rotates clockwise and through the internal gear / drive the timing rotor rotates anti-clockwise.

As shown in my earlier photographs the rotor is aligned with the pick up when the Static Advance Mark is in the inspection window and then half way past the pick up at TDC.

Reading the page for the 1000 SPiii, that you sent it also says that engine timing occurs when at TDC the LH side of the ignition rotor flag is positioned near the half of the sensor on the pick up, which for a clockwise rotating rotor I understand this to be halfway past the pick up. Hence is this not the same as my set up just the other way round as its an anti-clockwise rotation?

I can try and advance the ignition as you say such that the rotor is just approaching the pick up at the SAM and see what happens, but this will mean that the reference marks will not be aligned.

Regards
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GuzziLancs View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2016 at 20:07
Ok, so quick update.

I advanced the timing such that the rotor was just on the pick up with the SAM in the inspection window and still nothing. So I reset everything with the timing reference marks aligned and tried again....big backfire, so loads of unburnt fuel. 
I started to check the connections on the coils which looks like a birds nest which made me think that someone had been playing around so I checked the resistances, which are ok (5 Ohms and 13 Kilo Ohms, primary & secondary). I then tried swapping the leads over and with a bit of persuasion it fired but wouldn't run.... but it fired Clap. So now I have to figure out what is going on with all those wires and then get it to run and idle (probably fuel mixture) so that I can adjust the timing with a strobe.

I'll let you know how it comes along, but thanks for all your input and please feel free to offer any further advice / support.

Best regards
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2016 at 20:50
It does sound as if there are some problems with the wiring, maybe just a loose connection. Worth going through it all carefully. Do you have the wiring diagram? it might help to simplify things.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote wuckfitracing Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2016 at 22:16
After having the exact same isues with my targa, I replaced the motoplat units with a second hand pair and swopped out one at a time. Found 1 to be fawlty. Had the back firing issue and the fault was intermittent.
I previously tried new coils, new rotar arm, new pickup. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2016 at 07:28
Thanks for that Brian, that's a real help. I only have dodgy black & white copy in Italian
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2016 at 07:36
Hi Wuckfitracing....(just checking the spelling),
Hope you've got it all sorted now.
I have slowly been through the ignition system checking each component in turn and I am happy that the CDIs and coils are functioning properly.
Next task is to get it running and idling better so that I can set the carbs up and properly check the timing then I can start with the restoration in ernest. 
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iceni View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iceni Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2016 at 12:25
As I also run a 750T, I've been following this out of interest.  Last night, I went on a club run and the bike wasn't running as well as it usually does.  Got home and instead of the usual gentle tick over, it cut out.
Went out this morning, started it and bugger me, it seems to be running on one cylinderAngry
The moral of this tale is, don't read about other people's problems ----- they're bloody infectiousBig smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2016 at 15:47
Hopefully its a simple fix!
 
I'll be posting regular updates and probably asking more tricky questions as I complete the resto, so please feel free to join in the discussions...or maybe not!
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iceni View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iceni Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2016 at 15:58
I went out and had a few words with it, threatened it with a tree branch adding a few choice italianised swear words.
It seems to have worked, but I'm not letting it fool me. I'll be taking it out later for another run to find out if
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2016 at 20:43
That's probably where i've been going wrong...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote red leader one Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2016 at 20:46
You have to shout at them.

It shows you care.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziLancs Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2016 at 11:53
Had the bike running and I have checked the timing with a strobe (only slightly out) but the right cylinder cuts out when the engine warms up even though there is still a spark. 
The mixture is very rich even though I have stripped and cleaned the carbs and backed off the idle mixture.
Carburetor main jet is 112, spec says 100 and atomiser is 268T, spec says 266T, so I suspect P.O. tried to improved performance, but then too much fuel from main jet causes cut out? 
So I have ordered replacement jets etc (EUROCARB) to check if it runs better.
Also rechecked valves and checked compression, which is 175 / 180 psi, which seems a little high, but not sure if this is a problem or why?

Iceni, did you find out why your 750T cut out on one cylinder?


As I also run a 750T, I've been following this out of interest.  Last night, I went on a club run and the bike wasn't running as well as it usually does.  Got home and instead of the usual gentle tick over, it cut out.
Went out this morning, started it and bugger me, it seems to be running on one cylinderAngry
The moral of this tale is, don't read about other people's problems ----- they're bloody infectiousBig smile


Maybe need to learn some Italian profanity...

Regards

Keep calm and carry on fettlin'
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