Recently bought a 1970 RT1 360 and a 1971 DT 250 both resto jobs. Started with the RT first by buying a seat from Dave at KDI ,which I must say is wonderfull . When the seat was fitted it would not close because the air filter box is to high. Both bikes have same air box, . Is the lid different for each bike, should it be lower and flatter for the RT. Bike did not have a seat when it was bought so had nothing to go from. Thanks Alan.

Someone will correct me if I'm wrong... but I don't think the RT and DT had the same airbox case... shared parts lists confuse things but I see a 275 prefix (RT1) and a 285 prefix (DT1) for the air cleaner case.

Hopefully one of the experts on those models will comment.

Air cleaner cap and filter elements may be different too going by parts list.

If you post pictures I can compare with my RT1

RT1 uses a 275 case , while the DT1 uses a 214 case . ( 285 case is DT1 MX / RT1 MX ) .
Obviously , there is some difference there , perhaps air volume . They both use the
same filter element , so height might be the same .

Maybe someone swapped an RT2 box and lid. The RT1 should be zinc coated with a flat lid. The RT2 box would be black with a humped up lid. Pictures of the box and lid will confirm what's going on.

Well, SOMEBODY needs to post up some pictures !?!

When I can get my 9 year old granddaughter to post the pics for me I will , until then this old dinosaur will continue to blunder along. Thanks for your patience.

Thank You for falling on that sword ,KKman. From another old dinosaur who can't do it either.

Eventually got photos of both bikes. Black one is 1970 RT360 and orange one is 1971 DT250. Both have same airbox and lid. The seat on the Dt is different base to the new RT one which is the correct one for the year.
With the lid removed the seat closes on the RT. Putting plastercine on top of box without the lid and closing the seat you have a 9 mm gap so what I am thinking is making a lid from a piece of 2 mm plate to use as a lid.
Any ideas from anyone much appreciated.
In the UK
Alan