I'm putting an 85 engine into an 84

[Winger Ed]

Howdy,
I'm putting an 85 engine into my 84, both are Interstates. The 85 has a pulse generator....what is a pulse generator? It looks like something for the tachometer or timing. I took the heads off and there is virtually no wear in the cylinders. The odometer of the 85 reads 20985 miles. I think the previous owner flopped it a couple times as the rear view mirrors are broken. The PO apparently didn't know the value of using the front brake as the rear disk is really worn and probably is way under specs for reuse. I guess a further question about the pulse generator is: If I use it, will I need to use the electronic control for the 85. This may sound like a stupid question but I was hoping to use either the 84 or 85 electronic control as a spare for the other. I've found that the low gear is a little lower and the OD is a little higher on the 85, which is okay with me. I also plan to use the 85 final drive, shaft, and U-joint.

[Guest]

Interesting project. The pulse generators are the pickup coils. Wiring schematic shows the same wire colors. The only difference is the pulse generators are at the rear of the '84 engine, and under the timing belts on the '85. As long as you keep the wiring colors straight, you should only have to lengthen the cord to reach the connector on the '84. Suggestion. If you can find an old subharness for the saddlebags, they have a four pin plug that should work. The connectors and wiring colors for the '84 and the '85 are the same. But because the gearing is different, I'd recommend using the control unit out of the '85 in the event there is a timing curve change. One thing I did run into when I put an '85 in an '86, is that the subframe was different. But if I remember right, the subframe for the '86 accepted the motor on the '86 frame, so I don't think that will be an issue for you. I'd recommend a dry fit of the motor before spending a lot of time on the wiring. You never know what little surprizes Mother Honda has in store. Be attentive to the clearance around and near the fuel tank. Good luck!

[Winger Ed]

Thank you for your voice of experience. I do have the plug you are talking about and I will use the 85 ECM. I hope the frames are the same. These are all good tips. I haven't ridden in about 2 weeks and I am ready to go. It's been 65 to 70 degrees here in Bakersfield, Ca and I have been missing out. I should have the engine out tomorrow and be going for the install soon.

[Winger Ed]

Well, I got it in and am riding it. I've just been riding around town in the evenings getting my confidence in it back again. The engine is very smooth and runs good. When I had the heads off the cylinder walls were in great shape! The only problem I have is the 85 timing belt covers are different. That's really not a problem except I polished the wrong ones and they wouldn't fit right. The engine sat for ten years and only had 21k on the clock. The gear shift is stiff but seems to be loosening with more use. When I first started it one of the cylinders wasn't getting fuel but it eventually smoothed out. This weekend several of us from the Pashnit website are headed to Death Valley for an overnite ride and campout. That will be the test.