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Makotosun

['78 SR500] I'm back! New bike, no spark.

  • 19stuberd
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Hello again everyone! You may remember some months ago helping me achieve my dream of fixing my 1973 DT3 when nobody else could and you may also remember that it was stolen from me in September of last year. I made it my sole goal to get a new one before the start of the 2024 semester, initially my goal was to buy a 1978 DT400 that was nine or so hours away. I managed to get very lucky though because it just so happened that my friend's dad was looking to sell his motorcycle and by some incredible odds it happened to be a vintage Yamaha as well! I talked to him and got a great price for it and now it's all mine! I put about 125 miles on it after owning it for a week or two, and the clutch blew. I'd never worked on a clutch but I bought the new parts and learned as I went along. The oil smelled like barbecue ribs and so did the clutch plates, the friction disks were nearly nonexistant. New ones went in and new oil added and everything's back to normal! 

Now comes the current issue. With 175 miles on the bike I rode it two days ago and put it away for the evening and then took it back out the next morning and it wouldn't start. I grounded the plug against the engine and kicked it and sure enough no spark. I took the bus to an autozone and bought two new BP7ES plugs for it (one for later) as the service manual says but I popped it in the boot and still no spark. Both times, though, I took one for the team and stuck my finger in the spark gap to see if it would shock me and sure enough in both cases I DID feel a weak shock, which probably means something.

I'm used to my DT3 with its caveman banging-rocks-together level ignition system and I believe this bike has a CDI which I am entirely unfamiliar with. I was wondering if any of you have any experience with working on this type of bike and how I might be able to troubleshoot this issue. I am looking in the service manual and online but you guys have been so helpful in the past I thought I would ask you as well. I'll keep you posted and look forward to talking to everyone again!

Thanks, 
Daniel

Pictures in case the attachments don't work:
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08 Feb 2024 16:04 #1

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Replied by darinm on topic ['78 SR500] I'm back! New bike, no spark.

I like to start basic, first thing I'd do is replace the wire and boot if they look old. Not too expensive or time consuming to do. Also is that plug a true BP7ES not a BPR7ES with the R for resistor in the name?
1972 Yamaha CT2 175
1972 Suzuki TS185 Sierra
2000 Suzuki RM100
2003 BMW F650GS
2009 Yamaha WR250R
2013 Yamaha XT250
08 Feb 2024 16:58 #2

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Replied by RT325 on topic ['78 SR500] I'm back! New bike, no spark.

By memory--long term memory--these have 12volt TCI ignition not flywheel generated CDI.
They 'do' have a flywheel alternator charging system for the battery.
Also they'll have a pulser coil external of the flywheel.
So first is there a chance the kill switch on left or right of the bars has been 'killed'.
After that i'm a bit lost at the moment.
I'll now go partzilla to see if i'm talking rubbish.

Ok Edit--think i 'was' talking rubbish. looks like there's a coil on the alternator windings for the CDI ignition but i'll keep looking.
Hope your issue is a simple fix or could get expensive.

Here's a pic of a Ricks Stator one showing the cdi winding plus the pulser coil sticking out.
photos.app.goo.gl/YsMo9bb1EjYdWs4n9
photos.app.goo.gl/YDREAWdoZpJQtHBy8
I now see two cdi looking coils within the Ricks Stator so two cdi coils, which would acount for the red wire & a brown wire in the diagram from the stator "i think".
White-Red & White-Green from the pulser in the diagram sound like start then advance wire colors going back to what those colors represent in say a DT360A type ignition & Yamaha don't vary colors without good reason--so me thinks that's what they mean. Wouldn't want a 500 kicking back anyway anyway lol.
Not helping am i.
Last edit: 08 Feb 2024 19:48 by RT325.
08 Feb 2024 19:09 #3

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Replied by Tinkicker on topic ['78 SR500] I'm back! New bike, no spark.

In general terms, most often a bad HT side will cause misfires.  A bad LT side will cause no spark.

Getting a jolt from the HT side is one you can usually feel right up to the elbow.  Yup been there... So you have low voltage from the coil.

You say you have no spark at all.

Low voltage from the HT side of the coil can be caused by low voltage from the low tension system.

Look to the low tension system. 
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Last edit: 09 Feb 2024 05:06 by Tinkicker.
09 Feb 2024 05:04 #4

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Replied by MarkT on topic ['78 SR500] I'm back! New bike, no spark.

I did some searching on the SR500 forums and it sounds like a stator coil going bad is a fairly common thing and symptoms sound just like yours.  There was also some discussions on adjusting the pick up coil gap, not sure that would be your issue though. 

I found a couple of posts that even tell you how to rewind your own coil.  Here's one of them:  sr500forum.boards.net/thread/2551/diy-stator-rewind

The SR500 system is different than what the Enduros had as far as I can tell...  reminds me of a more modern CDI magneto design like the Powerdynamo or Honda ones I've seen with multiple "phase" charging coils and a solid state regulator and rectifier.
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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09 Feb 2024 10:29 #5

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Replied by LongStride on topic ['78 SR500] I'm back! New bike, no spark.

Stator coils are known for failing, SR's can be challenging to troubleshoot, they are known to read within tolerance but still not make spark with new CDI , these year model CDI have an issue with solder on the PC board, they are incased in silicone, as the silicone dries and shrinks it loosens components on the PC board and will loose spark, pressing on the CDI box sometimes will push components back and will work, once used a hose clamp to hold pressure on the CDI box on the YFM 80 and it worked for years, it would stop sparking, tighten the clamp and off again, did same thing on the RZ , as.said above .cover your basics, , plug cap, engine kill circuit, etc. 
2ET703 Central Texas
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09 Feb 2024 11:04 #6

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  • 19stuberd
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Replied by 19stuberd on topic ['78 SR500] I'm back! New bike, no spark.

Hello everyone!
Update- I checked out the diagnostic sheet from Rex's Speed Shop ( drive.google.com/file/d/1ds48JON5ZCEoU92-dm269MFteAf1Pj-t/view ) which seemed to be a good guide in diagnosing issues. I have filled it out, the tests are as follows:

Test 1, "ignition/kill switches": didn't do it, there is some current flow so I don't think it's a killswitch
Test 2, "HT coil": didn't do it because I couldn't find the plugs, might try it again later
Test 3, "low speed pick up": expected 87 ohms +-5%, measured 94.6
Test 4, "high speed pickup": expected 16 ohms +-5%, measured 17.3
Test 5, "source coil" pt.1: expected 330 ohms, measured OVERLOAD
Test 6, "source coil" pt.2: expected 4-6 ohms, measured 6.3
Test 7, "source coil" pt.3 expected 334 ohms, measured OVERLOAD

So this says to me that the issue is with one or some of the source coils, right? Are those under the flywheel like before (god forbid)? Anyone know which ones or would I have to figure it out? Would this make sense with the rest of the symptoms? Please let me know. 

Also here's a video I took with some observations with some oil covering everything including the stator wires, feel free to watch and let me know if that's normal, causing issues, or if it's just an entirely separate issue. Thanks for reading and I look forward to hearing from you guys!

photos.app.goo.gl/WvcFqVE8SqV2nMfU9

-Daniel
 
09 Feb 2024 12:24 #7

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Replied by MarkT on topic ['78 SR500] I'm back! New bike, no spark.

The same puller you used for your DT (27mm x 1 LH Thread) should work on your SR flywheel.  Source coils are under the flywheel.

When you say "overload" on the two source coils, is that the same reading you see on the meter with the leads not connected to anything?  If so, your theory about the oily wires could be the problem...  The source coils could be bad or there could be broken wires to the source coils.
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
10 Feb 2024 10:30 #8

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Replied by RT325 on topic ['78 SR500] I'm back! New bike, no spark.

Kick it over & see what voltage you get from the various wires stator ignition related wires.
I'm not sure how to do it but if you have ohms readings & there's a 'brown & a red' i'd try testing individualy to earth on ac volts.
Only guessing what you should expect but i'm thinking 80 ac on the brown & a lot less on the red.
If i used my peak meter it'd show double those voltages.
Then on the pulser i'm not sure but think i'd expect about 10+ ac volts.
But guessing again you'd need to earth one wire, green-red or green-white then test from whichever wire to earth, then do same to other wire.
Lotta guesses there haha & happy to be corrected.
Also just unplug everything ignition related & spray the connections with whatever you use & plug them in--she might spark!!.
10 Feb 2024 15:14 #9

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  • 19stuberd
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Replied by 19stuberd on topic ['78 SR500] I'm back! New bike, no spark.

Update for everyone!
So I was getting some funky numbers on my resistance readings with my $20 multimeter so I pulled the stator off and brought it in to school to use one of the six digit multimeters they have there. I got two things out of this, easiest one first: It seems that the pickup coil is only reading the right value if it's in the right position and it's rattling, which I assume is not normal. I'll probably tighten that down or maybe buy a new one? It does read the right resistance when I hold it right. Here's a video on that. photos.app.goo.gl/ScTAm6xTV5ivGnrL6

Additionally, it seems that the low speed source coil is not working (open circuit, no flow) and upon testing the actual coil itself it seems it's broken and in an attempt to get the caked on elephant snot off of it I definitely broke it (it was already no good anyway). Unfortunately for me this means I'm going to have to rewind FOUR THOUSAND turns of wire so I have to see if I can manage that or find some other way to do it. It looks like there's a service that can do it for you for about $200 which is not terribly unfair but I am terribly broke and terribly impatient so I might just try and do it myself.

Let me know if any of you have any input and also id still like to know what the deal is with the oil thing in the previous video i.e. is that a normal part of the bike. Thanks for reading and I look forward to hearing from you whether you have helpful input or not.

Daniel
15 Feb 2024 16:36 #10

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