Author Topic: 1980/1981 Yamaha YZ250G/H New Build CDI. Expressions of Interest.  (Read 8433 times)

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Offline Devondan

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #20 on: October 21, 2018, 08:37:38 AM »
That was quick Bill!
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Offline DynoTronix

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #21 on: October 21, 2018, 11:30:29 AM »
That was quick Bill!

Yes, it's weird.  Sometimes international shipments take about 7 days, and sometimes they take two weeks or more.

Offline DynoTronix

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #22 on: November 18, 2018, 07:58:23 AM »
Update,

I started to evaluate the two CDIs Dan donated.  One appears to be working ok, but the other one is messed up.  It has a problem in the trigger circuit and produces about 13 degrees more advance than it should, with the max being around 29 degrees BTDC @ 2000 RPM.  The correct timing appears to be 16 degrees @ 2000 RPM.  This problem is probably caused by a bad solder connection or an open resistor in the SCR gate circuit.  I'll know more once I get it opened, and I'll let you know what I find.     

Bill

Offline Devondan

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #23 on: November 18, 2018, 09:29:22 AM »
Hi Bill,
I thought one was toast!

If it helps the Yamaha manual says
CDI Hitachi TIA01-28
Pulser coil resistance 500 ohm +or- 10% red to white/red
Charge coil resistance
Low speed 1437 ohm +or- 10% red to brown
High speed 500 ohm +or- 10% red to white/red

Ignition timing 10 deg BTDC at 7600 rpm ( 0.024inch)

IGN coil
Primary 0.6 ohm +or- 10%
Secondary 6.2 ohm +or- 20%

But no mention of whether it retards any further at higher rpm or whether it starts higher ie 16?!
Keep up the good work Bill.
IT  400D - Trail riding
74 Montesa Cappra - Racing
YZ250 H - Racing
Norton ES2 500 trials
Norton 250 Jubilee - Road
Norton 350 Navigator (in boxes)
Norton 350 Single M50 (in boxes)

Offline DynoTronix

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #24 on: November 18, 2018, 09:54:36 AM »
It's interesting that the manual calls for a Hitachi TIAO1-28.  The CDIs Dan sent me are marked TIAO1-35, and the same goes for the pictures Dave posted earlier.  It's been my experience that the dash numbers denote a Hitachi revision level.  For example, the 3R3-10 CDI is stamped TIA01-34. 

Bill

Offline Devondan

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #25 on: November 19, 2018, 01:47:02 AM »
Interesting, looking at eBay, the 79 appears to be -28, the 80/81 -35 and the 82 -40, although the parts fiches all list the CDI as being common across the 79, 80 and 81 Yz250h model years. So perhaps it was an update or the manual is wrong. Makes you wonder about the timing. The 250 H was supposed to be different from the G because it had a broader spread of power and needed only 5 instead of 6 gears.

Parts Search Results
Assemblies where 3R4-85500-11-00 is used
1979 YZ250F - C - D - I - Magneto
1980 YZ250G - Cdi Magneto Yz250g
1980 YZ250G - Cdi Magneto Yz250h
1981 YZ250H - Cdi Magneto Yz250g
1981 YZ250H - Cdi Magneto Yz250h
IT  400D - Trail riding
74 Montesa Cappra - Racing
YZ250 H - Racing
Norton ES2 500 trials
Norton 250 Jubilee - Road
Norton 350 Navigator (in boxes)
Norton 350 Single M50 (in boxes)

Offline DynoTronix

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #26 on: November 21, 2018, 04:30:58 AM »
Update:

I was wondering what the Black/Red wire does that just loops back into the CDI.  Perhaps this is common knowledge to some, but I couldn't find any information on it.  Now that I have reverse engineered the circuit, I know it's a rev limiter.  Apparently you can cut the Black/Red wire to disable it.  I don't know the RPM where this thing is supposed to trip, but I'm guessing between 8,000 to 10,000.  Does anyone know?  Is this something that you guys would even want in a replacement CDI? 

This CDI (3R4) is a very close cousin to the 2X6, which does NOT have a rev limiter.  In fact, both ignition systems use the same stator coils.

Please give me your thoughts on the Rev limiter, yes or no. 

Regards,

Bill

Offline Martin I Henry

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #27 on: November 21, 2018, 09:19:33 AM »

I seem to remember one of the US magazine tests suggesting disconnecting the rev limiter.

..... But as time goes on,  the memory becomes less reliable!

Cheers,
Dave.

Offline Devondan

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #28 on: November 21, 2018, 09:50:04 AM »
Prob not a bad idea to keep it, they are not exactly low revving engines! Could you make it so it was disconnectable? That would serve both worlds!
IT  400D - Trail riding
74 Montesa Cappra - Racing
YZ250 H - Racing
Norton ES2 500 trials
Norton 250 Jubilee - Road
Norton 350 Navigator (in boxes)
Norton 350 Single M50 (in boxes)

Offline DynoTronix

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Re: 1981 Yamaha YZ250H CDI. Expressions of Interest.
« Reply #29 on: November 21, 2018, 10:18:39 AM »
Yes, I can make it the same as the oem.  Unfortunately, there are 19 additional parts associated with the rev limiter, and I don't think I will be able to fit everything inside my standard size box.  This will also drive the cost up a bit.  I was looking at the replacement that HPI makes, and it looks like they omitted the black/red wire loop, so I'm thinking they may have eliminated the rev limiter feature.

So if I keep the rev limiter, what RPM should I use?

Let me know if you have any other thoughts. 

Bill