GT750 'Split Head' Models
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Contributed by Gunnar Forsgren
In Japan there were several models of GT750 that were not released elsewhere; the "split head" engine used in some of these is one example. While it appears split head engines never "officially" made it out of Japan, it is clear that at least some other GT750 design features were released in Japan a full year before being seen else where.
The GT750 was first shown at the Tokyo Motorcycle Show in October 1970, and the 1971 model year is referred to as being the "R" model year which is when the GT750 was first released into the Japanese market only, as a B1 model which closely resembled the "J" model released globally in 1972. Following that, for the Japanese market, local GT750 variants identified by the frame numbering GT750B2 in 1972 which looked much like a 1973 K, B3 which looked much like a 1974 L and a B4 which looked much like a 1975 M model.
In the Japanese parts catalogue pages below, the 1971 model is named "1". The 1971 model did not have the same cylinder block, head, carburettors and exhaust pipe flanges as on the model later exported as the GT750J. The model we know as the GT750K (the 1973 GT750) existed as the 1972 year model on the Japanese market, where it was named the GT750B1. All B1's have the split head. There was also a B3 model produced with this head. See the parts list below. All of these were only sold on the Japanese home market. What remains to be answered regarding the split head is WHY this type of head was produced and put into serial production compared to the type of head that was used on all exported GT750's.
Below is a photo of the two piece head:
This is the gasket to join them:
Side view of the head:
Here's a photo of a 1973 split head B3 owned by a GT750 owner in the U.K
Evidently, this is a model for the Japanese market which was never put into serial production and no parts catalogue exists for this model (see pages below). Apart from the split head this is looks exactly like what became the 1974 GT750L export model.
Parts Catalogue Pages for Split Head Model
These scans show pages from a Japanese market GT750 parts catalogue which have been scanned and magnified them a few times for better readability. The pages list the models "1" (1971), "B1" (1972), "B3" and "B4". Based on the scans, it seems that the split head was "officially" used on the B1 and B3 only.
