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68 DT1 ignition timing

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Replied by DEET on topic 68 DT1 ignition timing

That's a good observation: "If you can't believe the manual, what do you believe?"

The manuals are notorious for mistakes.

So when you are looking for "truth".... there used to be an old saying in journalism:
The first rule is "Who says so?"
The second rule is "Who ELSE says so?"

So the bottom line is: Gather information from many sources. 




 
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Where the Yamaha Enduro is still a current model...
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Last edit: 16 Sep 2021 12:05 by DEET.
16 Sep 2021 11:48 #21

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Replied by Dirtboy on topic 68 DT1 ignition timing

I used your tech guide to set the timing on my motor just yesterday Deet.  

Thanks for taking the time to write that up, it was very helpful!!

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16 Sep 2021 13:34 #22

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Replied by MarkT on topic 68 DT1 ignition timing

Tvrc18,  For what it's worth, from your very first post on, in my opinion you have been 100% correct in your interpretation of the manual and the course of action you have taken.  

You've set the timing and then checked and discovered the maximum gap is outside the specification RANGE given by Yamaha.  You reported it way too wide if i remember correctly.  

You never tried to adjust the gap to be in spec...some people set the timing and then try to adjust the gap to be in spec which now means the timing is off...  you seem to know not to do that...  all you can do in your situation is replace the points.  

Fingers crossed the new points will have the gap in spec with timing set to spec.

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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16 Sep 2021 13:55 #23

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Replied by DEET on topic 68 DT1 ignition timing

Once again, let me state that I not an expert on anything... so my comments are just my opinions.

I will be curious to see how the gap will change with new points. 
Regardless of the new points rubbing block length, they will be set to open when the cam begins to rise.
The cam will lift the new points to the maximum opening, and the maximum gap will be exactly the same as the old points.

In my opinion, the only thing that can change the gap is to change the flywheel cam lobe profile.

But maybe I'm confused as to how this all works.
I don't want to lead anyone astray, so I'll be quiet.
Sorry for any confusion I have caused.
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Where the Yamaha Enduro is still a current model...
16 Sep 2021 14:32 #24

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Replied by RT325 on topic 68 DT1 ignition timing

I'll stir the pot a bit more lol. Could you--if all else fails & points are over 15--slot the plate a little to get gap & point of breaking within spec. I know i'll be told about why magnets etc need to be in the right place at the right time for maximum punch & i'm "keen to learn things i don't fully understand", but i just know what works for me. Only reason i'm tossing this in--is--later 250 mags had a slotted stator plate--'so'!!?. Have a happy dayyy.
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16 Sep 2021 15:13 #25

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Replied by DaveinSC on topic 68 DT1 ignition timing

I agree that the cam only has a certain amount of lift but couldn’t the pivot point position of the stationary plate change the amount of lift, maybe that’s the problem? Think of a seesaw, if the pivot is in the center, the amount you move one end will be the same at the other end. If you move the pivot point off center there’s a certain ratio of movement from one end to the other. 
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16 Sep 2021 15:33 #26

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Replied by apex on topic 68 DT1 ignition timing

After reading 3 pages of this thread, the thing I kept looking for, is, are the points opening where you set them to open, at 3.2 MM BTDC? I know you started the thread with you set them to open there, but the focus has been more on the gap, than are the points opening still at 3.2mm?

Sorry if I'm being too obvious. But, if the points DO open where you set them, as DEET and others have said, the points gap is 100% irrelevant. Everything is the timing of points opening, gap don't matter.
Allrighty Then
16 Sep 2021 21:16 #27

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Replied by RT325 on topic 68 DT1 ignition timing

Ok, lets have discussion & i don't know the answer but like to think i do at times lol. So yes timing is critical but points gap must be important or they wouldn't give a max or min to keep within. Say with points breaking at 3.2 so timing correct, but the max gap ends up at 30. So must be open for longer before touching closed to charge the condenser. So they're closed for less time before opening again, therefore things aren't as fully charged, so a less useful spark at the plug. So if it ends up way too wide, what can cause that besides a cam problem--high lift cam grind--Na, but if the cam was worn at the start would you end up with a wider gap at full lift to get them opening on time due to cam lift starting point wear. Think they wear more at full lift anyway. I'm sure i've seen them at about the right open gap looking in the slot just before disappearing out of view but get wider just before closing if you watch on an angle. I'll leave it there as starting to wander & only trying to sound clever haha--not working. Put me right someone.
17 Sep 2021 02:51 #28

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Replied by tvrc18 on topic 68 DT1 ignition timing

RT325 that is exactly why they give a max gap, when the points are closed things are charging up and if they are open to long then that is a problem. May not cause a big issue but it is not as designed.
17 Sep 2021 04:34 #29

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Replied by RT325 on topic 68 DT1 ignition timing

Thanks above. I started writing before reading your reply.Thought i'd get back on before someone answers & ask what dwell is--well i guess its how long they're open for or is it how long closed for. It's a term i've heard often enough to do with cars which would be battery ignition & i know they read it on a meter. But its something i've never had to know--would be nice to know though. So i'm guessing gap determines 'that' dwell. But you can move the distributor to get the timing '& dwell' correct.?. So how do you do that on a DT1 with a fixed stator plate. Or does a gap of 12--15 get dwell close enough providing timing is at 3.2btdc. Sorry, just doodling but feel free to sort me out.
17 Sep 2021 05:01 #30

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