1972 GT 550 Engine Swap

[Smokeman]

Hi,

I am in the process of rebuilding the engine in my 1972 GT550...it is taking a lot longer than anticipated. Does anyone know if other years of GT550s are a direct swap? I know that all years look similar but I want to know what I am getting into before I jump. Am looking at buying a used '76 engine to drop in and get to ride the bike while the original engine is being gone through. Any direct knowledge of the swap process would be greatly appreciated.

Thanks!

[petead23]

Hi I have a 72 550 and when i bought it it had a GT550A engine in it which i replaced with a J later. There were no issues at all as they are the same size roughly.

[Alan H]

They are all similar externally, but some markets changed ratios on later gearboxes, and carburettors changed over the years. Engine mounts are the same as far as I know for all models.
If you fit later carbs, you'll need a later tank as the tap is in a different place. Generators could be one of two types but work similarly, one is better than the other. There are differences in the barrels and head rear finning and the ram air cowl is different too. The J points and genny cover are prettier than the later models as they are embossed rather than having stickers.
Just fit it and check carb mixtures - they shouldn't be far out.
If you would like a copy of an early service book with all early specifications, PM me your email addy and I'll send it FOC.

Alan

[Smokeman]

Thanks for the replies! I knew I could count on this forum to come through. Thanks for the offer on the repair manual...I have one on hand already.

[Coyote]

One more thing to add to Alan's list. Be sure to hang on to the 'J' mufflers. The 76 mufflers won't fit the 72 frame. The rear mounting points changed beginning with the 74. And of course the throttle cables are totally different for the 76 motor as all three carbs work off a single pulley.