Early GT550 carb underside shape difference

[Gr8uncleal]

Does anyone know why the underside of the casting, and therefore the shape of the float bowls, is different on some early GT550s? A photo is attached to show what I mean.

Also, is there a reference guide for the numbers stamped on the carbs? I have a set stamped 340 and a set stamped 346.

Many thanks.

Alan

[Harrymail]

The parts book gives all the carb numbers for each model year. In the main the carb numbers refer to the factory jetting for the year.

[Gr8uncleal]

Thanks for coming back so quickly Harry, I appreciate it.

What I don't understand is why my 2 sets of high top early carbs from the same era have different shaped bases and bowls.

Regards.

Alan

[barney01]

Image from OJB

[Gr8uncleal]

That's brilliant Barney, thanks.

I'm still left with the query over the shape though, as I have a set of 346s with the straight edged carb base and a brand new 346 with the curved edge base.

[teazer]

72 was the 340 model number and came with curved sides to the float bowls. At some later stage the model was changed to 346 model code and it appears that there was a change at that point to straight sides.

At about that same time, T500 also changed from rounded sides to straight.

From my rather limited notes, I see 340 on early US models, 341 also on US models but linked and 346 on UK models. Maybe Ian Sandy at OldJapaneseBikes.com might know more about those differences.

[barney01]

Look here for the later 'low Hat' carbs that have the rounded bowl shape
https://www.oldjapanesebikes.com/mraxl_ ... les/page-7

[Gr8uncleal]

Thanks very much for the replies everyone, I am very grateful.

[teazer]

Look here for the later 'low Hat' carbs that have the rounded bowl shape
https://www.oldjapanesebikes.com/mraxl_ ... les/page-7

BArney, that's back to front I think. Late carbs flat sides. Early carbs round sides.

The low top shown on Ian's site has straight sides.