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Ignition Timing - 1969 DT1

  • Norcal
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Ignition Timing - 1969 DT1 was created by Norcal

Interested in member thoughts relating to the timing of this machine.

I have spent considerable time studying various service manuals regarding this topic, and would like to share some of my findings as printed in Glen's Yamaha Enduro Series manuals and others.

Previously I was of the mindset that point gap and timing were separate measures each attained via different means - Point gap to spec via feeler gage and point opening via stator plate indexing to engine case.

I now know this is not the case as the stator plate is not slotted and cannot be easily rotated to adjust timing point opening relative to piston position in this manner.

Per the Glen's manual both requirements point gap and timing are to be made via point anchoring screw and adjustment slot. If either condition point gap .012 to .015 in. or point opening 3.2 mm or .080 in. BTDC cannot be achieved it is time for new points. Per Glen's manual small changes in point gap can affect timing considerably.

I am aware that timing of this machine requires cylinder head removal. This is not a problem however I have been having difficulty finding the exact point of breaker point opening with my multimeter. I have recently purchased an Okuda Koki point checker with both visual (LED) and audible indicators to help validate this precise opening.

My machine is currently running pretty good with only minor indications of possible timing woes - kickback in kickstart lever during start up and specifically slight hesitation at all engine speeds when throttle is abruptly opened - maybe a bit too advanced. Plug color is a nice tan with no indication of an overly rich or lean condition.

Will provide update relating to performance after Okuda point checking tool arrives.

Respectfully,

Norcal
01 Dec 2019 07:50 #1

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Replied by MarkT on topic Ignition Timing - 1969 DT1

Welcome!

Yes, you got it right. Set the timing by adjusting point gap and then check to be sure point gap is within specified "range".

Even if you have a slotted stator, it's best to keep the plate in the OEM position. There's more "timing" than getting the points to open when the piston is at the exact position BTDC... The stator coils and magnets need to also be aligned to where the AC voltage generated by the spinning magnets is at or just approaching maximum at the time the points open. Mess that magnet/coil/points opening relationship up too much and you'll get weak or no spark.

(The only exception to moving the stator plate would be if you wanted to significantly change the ignition timing from stock for some reason. Then it would be best to rotate the stator plate the exact amount you want the timing to change rather than changing timing from stock with points gap.)

Yes, digital meters are often hard to use for points opening... a good old fashioned Analog ohmmeter like a Simpson works good on the lowest range... or my favorite is an "aircraft points checker" for magnetos.

Would you mind posting info on the Okuda tester? I don't think I've ever seen one.
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
01 Dec 2019 08:40 #2

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Replied by KennyV on topic Ignition Timing - 1969 DT1

Hi Norcal and welcome! I had the same questions and concerns with timing on my RT2. I was used to my 250A with the stator plate slotted to set timing, same with my 400C that I converted from CDI to points. On my RT2 when the timing was correct my point gap was at .009". Performance was ok but I wasn't really content with the point gap. So I decided to elongate the stator mounting holes to see what difference it would make. I figured if I needed to I could always put it back in the same position it was originally. I elongated the holes 3mm and now my timing is correct with point gap set at .014". It starts easy, ocasionall kick back not as often as before, and runs better in my opinion. Seems to be better across the entire RPM range.
71 Z50 Minitrail
72 RT2
74 250A
20 CB500X Halfrica Twin
01 Dec 2019 09:13 #3

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Replied by MarkT on topic Ignition Timing - 1969 DT1

KennyV wrote: Hi Norcal and welcome! I had the same questions and concerns with timing on my RT2. I was used to my 250A with the stator plate slotted to set timing, same with my 400C that I converted from CDI to points. On my RT2 when the timing was correct my point gap was at .009". Performance was ok but I wasn't really content with the point gap. So I decided to elongate the stator mounting holes to see what difference it would make. I figured if I needed to I could always put it back in the same position it was originally. I elongated the holes 3mm and now my timing is correct with point gap set at .014". It starts easy, ocasionall kick back not as often as before, and runs better in my opinion. Seems to be better across the entire RPM range.


Not arguing with what you did... it worked. If your max point gap was below spec range with timing correct, then the points had too tall a rubbing block. Tight point gap is not good and could cause running issues.

That's an unusual situation. Usually the points gap gets too wide when timing is set because the block is worn. If you have the slotted plate, you can rotate it to get both the points gap and timing in spec. That might work once if all you need is a small movement of the stator plate. If you have to move the plate much to compensate for worn points, you'll eventually get to a weak/no spark issue even though timing is correct and gap is correct.

Some manufacturers with slotted stator plates used to give a coil-to-magnet relationship measurement so you could check to see if the magnets and coils were timed right when the points opened. I've never seen that spec for Yamaha. Yamaha chose to simplify and say if points are not within gap range with timing correct, replace points. Without knowing the rotational position of the flywheel where the voltage created peaks, that's the best practice for these bikes.

I also want to say I don't know exactly how much adjustment of the stator plate is "too much"... obviously 3mm isn't. :)
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
01 Dec 2019 11:11 #4

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Replied by KennyV on topic Ignition Timing - 1969 DT1

Norcal wrote: Interested in member thoughts relating to the timing of this machine.

I have spent considerable time studying various service manuals regarding this topic, and would like to share some of my findings as printed in Glen's Yamaha Enduro Series manuals and others.

Previously I was of the mindset that point gap and timing were separate measures each attained via different means - Point gap to spec via feeler gage and point opening via stator plate indexing to engine case.

I now know this is not the case as the stator plate is not slotted and cannot be easily rotated to adjust timing point opening relative to piston position in this manner.

Per the Glen's manual both requirements point gap and timing are to be made via point anchoring screw and adjustment slot. If either condition point gap .012 to .015 in. or point opening 3.2 mm or .080 in. BTDC cannot be achieved it is time for new points. Per Glen's manual small changes in point gap can affect timing considerably.

I am aware that timing of this machine requires cylinder head removal. This is not a problem however I have been having difficulty finding the exact point of breaker point opening with my multimeter. I have recently purchased an Okuda Koki point checker with both visual (LED) and audible indicators to help validate this precise opening.

My machine is currently running pretty good with only minor indications of possible timing woes - kickback in kickstart lever during start up and specifically slight hesitation at all engine speeds when throttle is abruptly opened - maybe a bit too advanced. Plug color is a nice tan with no indication of an overly rich or lean condition.

Will provide update relating to performance after Okuda point checking tool arrives.

Respectfully,

Norcal


Hi and welcome again, I think the 3.2mm measurement should actually equal 0.126".
71 Z50 Minitrail
72 RT2
74 250A
20 CB500X Halfrica Twin
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01 Dec 2019 12:52 #5

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Replied by Norcal on topic Ignition Timing - 1969 DT1

Thank you. You are correct. .126 in is correct in equivalent to 3.2mm.

Appreciate all the feedback in this thread.


Norcal
01 Dec 2019 13:01 #6

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Replied by Norcal on topic Ignition Timing - 1969 DT1

The model is Okuda Timing Tester TC-2030. I have not yet received, but this tool has been described as being made specifically for the purpose of determining that exact moment of point opening.

Thanks for the feedback.

Norcal
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01 Dec 2019 13:13 #7

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Replied by MarkT on topic Ignition Timing - 1969 DT1

Thanks for posting the Okuda... looks like a NOS unit that should work.

The one I use is more modern.... used for aircraft. Doesn't make it any better than the one you found... the aircraft ones used to be about $40 shipped but price has gone up quite a bit. www.aircraft-tool.com/shop/detail.aspx?id=LED51

Powered test light (dims slightly, does not turn off when points open) can also be used.

Here's a short video showing an old Simpson VOM and the aircraft buzz box being used to detect point opening...






.
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
01 Dec 2019 13:55 #8

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Replied by Norcal on topic Ignition Timing - 1969 DT1

Excellent videos. That is the kind of feedback needed to get timing spot on. Hope the Okuda setup delivers similarly to your setups.

Thanks,

Norcal
01 Dec 2019 17:21 #9

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Replied by RT325 on topic Ignition Timing - 1969 DT1

For the DT1 with the fixed backplate i ony make sure the tab on the stator coil is lining up at 3.2mm then providing no-one else has got at it & bent it, just have the points breaking at that point. No mucking around taking head off except for the first time to get an acurate measurement for the timing tab.. Could if you wanted--mark the flywheel to something stationary with twink [correction fluid] & strobe it. except sometimes it's better not to know what's going on as strobe shows up worn mains & loose points pivots & you'll drive yourself nuts.
Personaly on my DT1 that never fails i just set the points at a tight 15 & ride off into the sunset--umm, no lights come to think. Not recommending my methods though, rough B@#$$d. I'm sulking as my 20 acres is planted in pumpkins & nowhere to ride damn it. Have a happy dayyyyy.
01 Dec 2019 17:43 #10

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