Hi all,
I am working on a '73 DT3 play bike project. I am planning to keep it very simple and run a carb with no air box. The DT3 has a diamond-shaped cylinder mount and the carb I have for it is round. I see there are adapters available but I have some concerns. I am thinking that 32mm carb is kinda heavy and may put a lot of stress on the rubber adapter without the support of the airbox connection.

I will be bashing around in the desert with this bike and I need it to be pretty solid.

Anyone have experience with this type of carb setup?

Thanks

so if you have an engine with no reed valve intake you must have a dt1 the 71 model. I believe in 72 and 73 they had reed intakes. My experience is the way to go is with the stock airbox if your going to ride in a lot of dust. Just my opinion of course
Doug

Hi Doug, Thanks for the reply. It has reeds. The intake is not round but diamond shaped, The OE carb that came on this bike is is totally seized inside and is not serviceable. I cannot find a replacement or OE carb anywhere that will fit on that manifold. I have a beautiful Sudco 32mm Mikuni that I could use but it would need and adapter to fit it on the bike. It is round. I would need to run it without an airbox; only a sock filter. If I run a 26mm (OE size) round carb with the adapter, I think it would not fix with the airbox assembly.
IF I could find an OE carb or suitable replacement it would be no problem to run with no AB. That manifold is stout aluminium with bolts and would support the carb with no issues I'm sure. I would run a Uni filter and change out often.

I've had carbs pop out of the rubber manifold adapter without an airbox... kinda rare but it can happen. Make sure the groove in the carb locks into the bump in the manifold... I've had to trim the carb a little so it goes in far enough. If that bump locks in and the clamp is snug, you should be fine. Those rubber adapters are tough and will support the carb without tearing or anything.

Measure the bolt spacing carefully... I think there is only one rubber adapter that fits the stock Yamaha reed adapter... I think I have one here I can get the number from...

Buying a couple of filters is not a bad idea... without an airbox they tend to get dirty fast in the desert. Easy to swap for a fresh one when needed. I used to have four spare filters and would swap them during fuel stops when I raced desert with open filters.

Dang, Advice from a desert racer from back in the day. Does not get more reliable than that. I feel better about this now and will definitely heed your advice about mounting the carb. I have a '75 DT250 motor with a 4 bolt manifold that the carb is in now that may fit onto the DT3 engine. I will have to check it out.

Thank you!!

The picture is the type of bike I am planing to build only I will be running a stock pipe. The blue bike is what is the project machine.

I would use the short adapter manifold over the full rubber one they used on later models.

If you have some sheet metal and basic fabrication skills you can box in the frame area around the filter to provide some basic protection. If you're really getting after it and churning up some roost you could completely foul a filter in a half hour or less. First they get dirty, then they dry out, then they merely sift the grains of sand as they are sucked into your engine.

An air box is a pretty big advantage for dirt riding.

I agree that protecting the air filter element can be of benefit in wet or dirty conditions. On one machine I used a Tupperware container to do the job. Cheap, durable and waterproof except where I cut holes for air inlet and output. At the time I couldn't find a stock airbox and was too much in a hurry to wait to find one. Hopefully not too silly. When they are installed, the side covers hide it. Nobody ever missed the Tupperware from the kitchen!