T500 carb question

[87m6chris]

The early T500's produced 47 hp and then about 1973 or there abouts they detuned them to 43hp.
I have a 1975 43hp bike, is it just a matter of installing a restored set of early carbs to get the
extra 4 hp?
Thanks,
Chris

[Frank T]

The later cylinders have a different porting arrangement which may account for the rating difference. Also the Cobra carbs were 34mm and are difficult to find these days.

[H2RICK]

Frank +1.
I believe they also changed the internal baffling setup in the mufflers and the actual end baffles themselves. They changed the airbox too, which would also have an effect on the power output.

[parksie]

I believe you will find that the main diff is that the 73 and later models have a smaller "more restrictive" intake port due to the larger "bridge" in the port. They then used different jetting in the carbs to match the port.

[husson73]

The later cylinders have a different porting arrangement which may account for the rating difference. Also the Cobra carbs were 34mm and are difficult to find these days.

but NOS modern VM 34 are easy to find, just need to be rejetting for the T 500

[tz375]

To add to that last post, I just had the opportunity to examine a pile of Mikuni carbs including a 34mm from a Cobra and I have to say that OEM Zinc carbs are not really suitable for much - other than a stock resto that is.

If you want more performance I'd recommend lighter aluminum bodies VM34 carbs and jet them to suit.

[H2RICK]

Yep, those old zinc bodied VM's ARE heavy.....
You could probably make TWO modern carb bodies out an old zinc 34....

[tz375]

Rick,

Stock Cobra carb with anodized slide 1165gms
Vm34 Aluminum body brass slide 692 gms
Adjust for difference in slide weight and yes it's a twofer - or very close!

That's ridiculous.

[H2RICK]

Ah, yes, TZ....but those old VM's were made back in the day when carbs were made of zinc
and men were made of iron.