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Buell Motorcycle Forum » Quick Board Archives » Archive through March 31, 2008 » Common Concerns: 1981 KZ750Ltd? No spark « Previous Next »

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Thumper74
Posted on Wednesday, March 26, 2008 - 08:26 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

My girlfriend is currently looking for a bike. She's looking for a cruiser while I steer her towards a standard.

She took me to look at a wine colored 1981 Kz750, shaft drive and pretty clean. The guy wants $1250, however he called before we go there and told us that it 'fired right up' for the person before us. They had shut it off and now it won't start...

We still decided to check it out. the plugs are fresh, though he said they were three years old. They didn't even have any surface rust on them so I suspect that they weren't replaced three years ago and most likely were replaced more recently. The bike is cranking fast and I couldn't find any trace of spark on any cylinder.

Are there any common issues?
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Natexlh1000
Posted on Wednesday, March 26, 2008 - 08:33 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Cranking fast as in no compression to slow it down?
Does it sound like the valves are doing anything?
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Thumper74
Posted on Wednesday, March 26, 2008 - 08:42 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

It's hard to tell. Mostly I hear a starter, but that's it. I pulled a plug and there's compression. The guy didn't have many tools and I wasn't able to get a compression guage on the bike for an actual measurement.

I've had ignition modules go bad on Fords and they always seem to crank a little bit faster or sound different.
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Mbsween
Posted on Wednesday, March 26, 2008 - 08:50 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

The 81 should be cdi, so you need to check the igniter (under the right side cover by the fuse area). The coil leads are under the tank towards the front of the bike, if one of those is off, you will have spark on 2 cylinders or if both are off no spark. Did you check more than one plug?

I have an 83 kz750 I've put over 100,000 on. I've hard charging issues, but never spark issues.

I have the service manual and wiring diagrams for 81 - 84 750s on my site that will give you a trouble shooting procedure

Those bikes are generally very reliable and parts are a dime a dozen (the engine didn't change much from 81 - 85 and was actually reintroduced in 2004) on ebay. 1250 would be steep for a non-runner though.

Good luck

matt
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Thumper74
Posted on Wednesday, March 26, 2008 - 09:14 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

The two outer cylinders aren't sparking. I really wasn't into diagnosing someone elses bike too thoroughly.

I offered $500 and he said he wouldn't take less than $750. We walked, but I explained the logic not know what it needed, I couldn't realistically offer more than I can part it out for...
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Mbsween
Posted on Wednesday, March 26, 2008 - 04:46 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Thats a dead coil (or missing lead) 1 and 4 are together as are two and there (inner cylinders)

Sounds like you did the right thing
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Brumbear
Posted on Wednesday, March 26, 2008 - 05:53 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I just bought a 77 kz1000 running with akerker and upgrades from points to EI for $700.00 they are out there don't get discoureged or jump at the first one is all I can say
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