78 SR500 No Spark

[socalyamaha]

ok i'm at my wits end.

new spark plug, no spark

new coil, no spark

new CDI, no spark

new wiring harness, no spark

battery is getting juice so it's not the stater.

if the battery is low will i not get a spark?

ingnition?

kill switch?

pulsar coil?

rectifier?

is there a ground connection i'm not seeing?

i followed the clymer manual.

and the manual says to check the head bolts???

please, anyone, it been 2 months.

[bralkan]

...

[jeepurz]

can you bypass the kill switch? those are sweet bikes had a 78 back in 78. are all the wires plugged correctly in headlight shell & power to coil. did you try another plug, gezz thats bout all I could think of sounds like you tried it all. good luck.

[drewpy]

maybe ask these guys

http://www.yamaha-xt500.co.uk/portal.php

there may be a particular fault to this particullar model. Its frustrating for us ,as its hard to diagnose from a distance. I would get my multimeter out and check all parameters of the electrical system.

[socalyamaha]

maybe ask these guys

http://www.yamaha-xt500.co.uk/portal.php

there may be a particular fault to this particullar model. Its frustrating for us ,as its hard to diagnose from a distance. I would get my multimeter out and check all parameters of the electrical system.

thanks drewpy, i'll try to get in contact with them.

[drewpy]

thanks drewpy, i'll try to get in contact with them.

lets us know how how you get on?

[fosdyke]

Drewpy's right I'm afraid - this is a multimeter and a ton of spaghetti job - no short cut, you're just going to have to trace an test all the ignition wiring. I had a similar fault on an old RS - turned out the be LT wire from ignition to the coil, but took me ages to find it!

Good luck

[jeepurz]

heres a wiring diag if it will help. double check it to be sure, this is US version dont know if there all the same, and I also tend to mix em up from time to time.

[socalyamaha]

lets us know how how you get on?

ok, checked the stator this afternoon.

charging coil

red to brown read 5ohms: good

brown to black read nothing: not good

pulser coil

wht/green to black read 87 ohms: good

wht/red to black read 16 ohms: good

now what?

[JoeSchmo]

Some fundamental on the SR500 ignition

The red-engine-cut-off switch does not disconnect the power to the CD. It grounds out a part of the CDI and acts to inhibit the ignition.

The battery and rest of the charging system are never involved with starting the SR. The SR can start and run fine without a battery. But it must have a specific working coil in the stator. 'Battery eliminators’ are just large capacitors to smooth out the electrical pulses (mostly so you don’t stress the lights with too high a voltage which will shorten the bulb life).

The CDI unit is powered by two coils on the stator. These are not battery charging coils, they make voltage just for the CDI. The coils are: the-low-speed coil, and the high-speed coil. To start you need the low speed coil to work. This is usually the problem with unmodified SRs that do not run. The CDI box itself is rarely bad. But given the vibrations the bike puts out anything could fall apart.

The low speed coil is wired directly to the CDI with the Brown and Black wires that come from the stator. (There are two plugs from the stator, the plug with the white wires is for the charging system and the other plug --with Black, Brown, Red, White/Red, & White/Green wires-- goes to the CDI..) The low speed CDI coil (Brown to Black) resistance should be 330 ohms +/- 30%. If you look at the stator (its under the flywheel) it has one coil about half again as large as the others; this is the low-speed coil. The high speed CDI-charge-coil in the stator (Red to Brown) should be 335 ohms +/- 30%.

Before removing the stator (a chore, you will need a flywheel puller -the standard Yamaha/Suzuki/Honda 27mm Left Hand puller--, and NEVER put anything in the flywheel holes) be sure to scribe reference alignment marks where the stator mounts because it has rotational adjustment that need to be realiged when you put it back, and also scribe the part that goes in the the stator.

If the stator CDI-low-speed-charge-coil is diagnosed as bad, this is very bad news as the stators are epoxy sealed complete units. The list price for a stator from Yamaha (before they stopped making them) was about $850 USD.

The options for a stator with a bad CDI coil are several:

Buy the German conversion for about $500 to $800 USD, it removes the flywheel and replaces the entire stator-flywheel-CDI everything. (I could not find this on-line) SRs are very popular in Germany and Japan up to about 1999 or 2004 when emission laws caught up to most air-cooled motorcycles.

Have the stator repaired. RMSTATOR (www.rmstator.com) in Canada does good business repairing your old stator. This was $150 to $200 USD last time I checked. You need to actually pick up the phone and call them. They have nothing but praise on the internet for repairing all kinds of motorsports discontinued stators. There are other companies in Germany and the USA that do this too for about the same price.

Convert the ignition to TT/XT points. This is a project that requires you to drill into a boss under the clutch cover to accept a TT/XT points drive gear (about 2-inch diameter, and its affixed 9mm shaft), then you add the gear (and the smaller crank gear) replace the SR aluminum clutch cover with the TT/XT magnesium unit (that holds the points), and finally add the advance weights, points-plate, points, and cover and fire it up. (There are some washers that go in there too.) With points you can then either run the TT/XT coil powered by the battery, or convert it to an automotive MSD ignition unit. The points give you the advance curve to advance the timing. The stock CDI has an all-electronic advice. With the MSD you get 20 sparks in the combustion chamber per single points opening. If you’re over 50 years old, starting the SR is a great way to hurt yourself, so the MSD is a one-kick guarantee to start. Rather than watching the kick indicator, or feeling the kickstart on compression, you can actually hear the chirp of those powerful 20 purple arcs from the spark plug inside the cylinder, and there you are at TDC, let go the compression release, and easily swing your fist-kick start up.

If you convert it to points, you (generally) can’t use the early model (most all TT/XT’s are these early models) TT/XT’s ‘generator’ without converting the entire bike to the XT’s 6 volts. And the TT/XT’s ‘generator' also has an ignition system that is electrically separate from the charging system. The XT will also start and run without a battery. The TT has no battery! The TT & XT have identical ignition systems. The XT generator has two simple coils, one for the magneto-points, the other to charge the 6 volt battery, which provides for the lights and horn. On the TT the ‘charging coil’ is a ‘lighting coil’ and is only used to power the (optional) headlamp.

The points-holding XT clutch cover on the right-hand side is easily spotted by its ‘extra bump’, which is the points cover. (Look for pictures on the internet) You can get the two gears on ebay for about $20 to $40. The advance weights and points plate for about $15 to $30. The (painted-black-only, magnesium) clutch covers run about $20 to $50. Or some other combination for less, or more. The MSD ‘5xxx’ or ‘6xxx’ ignitions go for about $50 to $100. All used on ebay.

The XT engine was combined with SR into a single identical engine type with CDI/full 3-phase stator for the 1980 model year. These identical SR and XT engines were sold in the 1980 and 1981 model years in the USA. The SR was not sold in the USA after the 1981 model year. However these two years where they shared the same engine (1980 & 1981), the XTs are 6 volts, and the SR’s 12 volts. They may only differ in the voltage regulator, or the stators may be different, I do not know. So if you buy a used stator it could be a '6 volt stator' if there is such a thing. (the 1980 SR stator P/N is 3H1-81400-50. The XT's P/N is 3H6-85500-50 or 4R9-85500-50) The TT's were all sold in the USA with the ultra simple magneto-points up to 1981, the last year offer in the USA.

One last bit of advice: Never attempt to kick-start a Yamaha SR or TT or XT while ‘bump’ starting it at the same time.(or probably any other motorcycle – but definitely not the SR). You can kick it, or you can bump it but not at the same time. If you are rolling it down the hill to start it and feel somehow you can add some more oomph with the kick lever, this is an error. It will catapult your knee right into the handlebars, and break the kick gear, and the clutch cover, and maybe even the engine cases. And this has no possibility of starting your bike.

Joe Schmo...

[DT400SUPERMOTO]

Some fundamental on the SR500 ignition

The low speed coil is wired directly to the CDI with the Brown and Black wires that come from the stator. (There are two plugs from the stator, the plug with the white wires is for the charging system and the other plug --with Black, Brown, Red, White/Red, & White/Green wires-- goes to the CDI..) The low speed CDI coil (Brown to Black) resistance should be 330 ohms +/- 30%. If you look at the stator (its under the flywheel) it has one coil about half again as large as the others; this is the low-speed coil. The high speed CDI-charge-coil in the stator (Red to Brown) should be 335 ohms +/- 30%.

...............

Joe Schmo...

Mr. Schmo...

I tested the Low and High coils on a SR I am working on and all checkout well but the Charge coil resistance High Speed.

I measured between the Brown and Red wires from the stator outlet plug and get 5.7. But when I connect the Red with

the Black lead it reads 326.8 ohms. FYI- the reading for the Low Speed(Brown-Black) is 321.5 ohms.

Any help would be awesome. I am getting no spark and am waiting for the shop book to get shipped.

Thank you.

Clay

[JoeSchmo]

I am not real newsgroup contributor, as you can tell by the lateness of my response...

You said...

I tested the Low and High coils on a SR I am working on and all checkout well but the Charge coil resistance High Speed.

I measured between the Brown and Red wires from the stator outlet plug and get 5.7. But when I connect the Red with

the Black lead it reads 326.8 ohms. FYI- the reading for the Low Speed(Brown-Black) is 321.5 ohms. ...

These look good, so the CDI is probably getting it's charge.

The stator has two more coils the trigger/pulse coils. One of these is the coil outside the flywheel. It is small, about 10mm diameter. It triggers the CDI where TDC is; where/when to fire. The advance for the ingnition is in the CDI probably uses both coils to figure out how far to advance the timeing at a given engine speed. The pulse coils should be:

High-speed: White/Red to Black: 16 ohms +/- 30%

Low-speed: White/Green to Black: 87 ohms +/- 30% (I think this is the coil outside the flywheel. )

If the color stripes have faded from the wires, these are the two white wires in the same plug with the brown, black, and red wires, not the plug with the 3 white (battery charge current) wires. The White/Red is the wire near the center of the plug. The White/Green is the wire next to the empty connector on the 6-connector plug. Again this wire goes to the pulse coil outside of the flywheel. This part used to be available from Yamaha separately from the rest of the alternator. P/N 2J2-81416-50-00 is the pulser coil. (often you need to drop the last two zeros when looking up Yamaha part numbers.)

If these two additional coils are good, then you are down to the CDI or the coil.

To check the coil the primary resistance should be .98 ohms (1 ohm) and the secondary should be 12,000 ohms. You can also jumper the coil to charge it directly from the battery by starting with the both the grounds connected properly, and the plug wire connected to a removed (but grounded) plug, then remove the low voltage positive wire from the coil and touch it directly to the battery. When you break this connection the, the low voltage electricity stops flowing, this causes the magnetic field to collapse and this causes the spark on the high voltage side. The coil should spark. (Just take an alligator clip wire and connect it to the coil low “+” side of the coil and tap the other end on the battery “+”. You should see sparks at the spark plug.) --old school test. You should also check the coil for cross-resistance between the high and low positive sides of the coil. If there is a short in the coil it can be from low to high, and from each of the low and high sides to ground.

If you are down to the CDI, the only way I have ever heard to test electronics when all other parts check out OK, is by replacing with known good units. “RPWKGU” as it is sometimes referred to. The SR500 CDI is not used on any other bike, and used units on ebay go for 50 to 150 USD.

Joe.

[JoeSchmo]

I just re-read your post, you said: "measured between the Brown and Red wires from the stator outlet plug and get 5.7."

To clarify the specs for the CDI charge coils are:

High Speed: Red to Brown = 3.5 to 6.5 ohms; Red to Black = 334 ohms +/- 30%

Low Speed: Brown to Black = 329 ohms +/- 30%

-Joe.

[Speedshop]

Well I build and sell SR 500 CDi units for £79.95 (UK). They come with a year's warranty.

To purchase e-mail me: [email protected]

I also have specialised shop equipment that was built by myself during the research stage to run the cdi 'off bike' to obtain its operating perameters. Its handy as you can test to see if a unit is faulty too.

So far we've run the SR500 to 117mph (timed) on Speed Shop cdi units!