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1968 YG5T Timing Question - may apply to other bikes too..

  • amsbstn
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Hello!  I just rehabbed a basket case YG5T.  It actually runs really nicely, but maybe some folks have input on this timing question:

I've set max gap .3mm (.012) and timing at full advance at 1.8mm BTDC (using a dial indicator) and a meter to determine points "break" at this crank angle.

All is good!  But, the points plate is almost at one end of its travel (i.e. screws essentially at end of slots) when set as described above.  The plate (which is on left side of engine) is swung almost fully counter-clockwise (engine runs counter-clockwise).  If I'm thinking about this right, if I wanted less advance angle, I couldn't do it because I couldn't move the timing plate much more counterclockwise.

Anyway, I have the setting done, but it's surprising that it's not in the middle of the plate's adjustment range.  Has anyone run into this?  Does it suggest I did something wrong with the setup?  Incidentally, the 1.8mm is from the factory manual, so I'm assuming that's correct.  There are typos all over the place in there though!

Thanks for the input!
- Adam
26 May 2022 16:57 #1

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Hi, all the YG5T's down here in NZ had magneto ignition but the 100 farm model YL2CA had elecric start like yours. Anyway--sounds like you have the timing right @ 1.8btdc on advance? & held the advance weights full open to set it. If you gave the points 15 sounds like you'd be running right out of slot as that would advance it more & need moving even further towards the end--as you sort of said. So i don't know [if its electric start which i guess it must be] not sure if severe points heal wear would need to do that. First thought is crank key is half shorn off & armature's moved but very unlikely. Secondly is something ammis with location of the advance unit in the armature. I'll leave it there or i'll get into an essay of my G5T & all the warranty clains we had on new ones breaking the inner crankcase from big hairy farmers kick starting like you'd kick a 360 Yam. Yamaha sent us stronger right side crank case half in the end. Was a long time ago haha.
26 May 2022 20:44 #2

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Aftermarket points or original Yamaha part?
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
27 May 2022 07:39 #3

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  • amsbstn
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I think they are OEM.  This bike has points mounted permanently on the advance plate - a fairly complex single assembly and I'm not sure if there are aftermarkets out there (just guessing though).  Also, it was crashed and left to rust early in its life so little was ever changed from factory - 800 miles on the clock.  Old 60s oil and water was in every possible thing.  Even the exhaust was filled with oil (full to the top of black liquid in the pipe-dip from the cylinder to the high exhaust) - kind of like a sink trap.

I do have another oem breaker plate with points, so I might try swapping at some point.  Thanks!
Last edit: 27 May 2022 08:30 by amsbstn.
27 May 2022 08:25 #4

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RT325 - Thanks for the info. and good to know about the weak case.  As far as I can tell, mine isn't cracked.  I'll take it easy on the kick, though. This does have the starter-generator with electric start and it starts almost instantly even when cold, so should be okay.
Last edit: 27 May 2022 08:31 by amsbstn.
27 May 2022 08:27 #5

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Here's a picture of MDScott's YG5T ignition from his excellent restoration thread.

yamaha-enduros.com/index.php/forums/attachment/34784

Looks centered...  you haven't shown us what you are looking at or enough info to know for sure what might be going on.  My first thought was maybe advance wasn't wedged open when setting timing.  Or you might have mismatched parts or something like aftermarket points which do exist. 

That said if you're sure timing is correct then just run it. 
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
The following user(s) Liked this Post: RT325, Ht1kid
27 May 2022 20:10 #6

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  • amsbstn
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That pic does look more centered than mine.  (I had to add www. to the front of the URL for the pic to work - just as a tip for someone checking this thread). 
I will take a photo of mine - but going away for a week, so it will be a after that. I did have the weights pushed out fully when I adjusted - I made holders out of 12 gauge wire that I bent up to fully drive the weights open.  The "matchstick" method in the manual did not get the weights fully apart for me.

One thing that I think is a typo in the official manual - maybe someone can confirm this instruction to be wrong??  The official manual lists these procedure steps (instructions abbreviated here):

1. Screw dial indicator in plug hole
2. Find TDC using indicator
3. Move crank/piston to 1.8mm BTDC
4.*** Set point gap to .3 - .35mm ***
5. Expand governor weights and use multi-meter to set points break at this crank position (i.e. 1.8 mm btdc).

The point gap instruction (4 above) seems wrong to me in terms of where the manual is stating to do this:  I.e. I don't think that 1.8mm btdc crank position - even without the advance mechanism engaged - would be anywhere near full points opening (i.e. top of cam lobe).  Does this imply that .3 to .35mm is NOT the intended max gap (i.e. The gap would get larger somewhere else in the rotation), or is this instruction just incorrectly placed in the series of steps? 

I assumed it was just a wrong instruction and found the largest opening and set the .3 to .35mm gap at that point.  Then I set the timing after that using the procedure above.

Also, (just for the sake of correctness), the manual states in its specs section: Timing: 21 degrees BTDC (1.8mm) then a spec for Advance: 15.5 degrees.  This doesn't make sense to me because advance should always be a greater number of degrees BTDC than the idle spec.  Since the procedure states, set the weights to full advance and time at 1.8mm (i.e. 21 degrees), I'm assuming the spec. section is a typo.  Meaning idle timing is actually 15.5 degrees and advance is 21 degrees.  Just some things to mull over.

Thanks again for the help and all the input.
28 May 2022 16:08 #7

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I'll read later but i'm sure ya know what ya doing so ignore any dodgy yamaha guff. So long as you've got a reasonable full open gap like no more than 15 & have them breaking at 1.8 on advance then can't go wrong. I might've said somewhere [maybe on a flywheel type] that sometimes the cam can take on an odd shape, be it wear or whatever, i don't know-- & climb wider just before closing. If that's the case i'd not quite go that far & call that max gap. Once open it should stay pretty constant for a time before closing or as i say get slightly wider then close. Been a long time since being anywhere near a battery ignition generator model though, so happy to be corrected & stood in the naughty boy corner.
28 May 2022 20:55 #8

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Again, not looking at the manual you're reading so can't comment too much on its correctness without the full context.

That said, point gap is generally set at "maximum"...  points rubbing block on the high spot on the cam. 

As far as timing, it will be fully advanced to 21 degrees at idle or perhaps a very few rpm higher...  retard is for starting only...  once engine is running it should be fully advanced.  The 15.5 degree spec means to me that the timing is set at 5.5 degrees BTDC at zero RPM for easy starting and advances 15.5 degrees to 21 degrees once the engine starts.
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
28 May 2022 21:07 #9

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