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-   -   IVJ / 3AJ engine / gearbox parts compatability (http://www.horizonsunlimited.com/hubb/yamaha-tech/ivj-3aj-engine-gearbox-parts-23078)

Alfow 8 Sep 2006 11:45

IVJ / 3AJ engine / gearbox parts compatability
Hi all,

I have an 86 IVJ that i'm going to use RTW in approx 1 years time. I have also bought a 3AJ in pieces. I intend to put the kickstart on the 3AJ engine for backup and completely rebuild and recondition the rest of the engine.

Does anyone have any thoughts on which gearbox to use and are they compatible? Is one stronger than the other?, bearing in mind it will be rebuilt anyway.

I'll definatley use the 3AJ barrel for the better cooling but what about the head and all the other parts.

Any advice or experiences greatly appreciated.



aukeboss 8 Sep 2006 17:12

As far as I know the 3aj engine had the following modifications with respect to the 1VJ:
- Kickstarter was removed. However, the casings and the head have all the right openings etc, so it can be easily taken from the 1vj engine and put in. Certainly a good idea because it enables you to start when all electrics have gone. On this engine you do not need a battery to run.
- Larger oil pump, 30% more capacity. Also good to have.
- Gearbox with some mods to make it more durable. Also good, though not the ultimate answer to the problem. There is none, by the way.
- Carb on 1vj is tuned overrich. For the largest part because of the intake system / airbox. Plug the two silly hoses above the cilinder head and just remove the maintenance cover for the air filter. This way there is more air coming in from a better place, not just above the hot head.


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