Yamaha DT2 or DT3 engine and/or parts

[ChrisACT]

The DT400 manifold seller replied and the measurements are 70mm x 52mm bolt spacing (which fits my reed block) but the carby spigot is only 39mm.  I need 45mm for my carb.

So that one's a dead end.

[jimson]

Chris how big a difference would it be if you but the carbie against the intake and put a sleeve over the connection  jimson

[ChrisACT]

To be honest, I'd never considered it.  I'd have thought that would give no advantage over running a 34mm carby.  Would it not be better to run a 34mm carb rather than running a 36mm carb through a 34mm manifold.

[tony27]

Its a very common mod on modern trials bikes when fitting larger keihin flatslides

[ChrisACT]

Has anyone ever dyno'd it to see how it compares with running the right sized carb for the manifold?  My engine sim seems to think it would not be such a great idea.  Running the 36mm carb through a 34mm manifold results in at least a 1HP loss over most of the curve compared with running a 34mm carb.  At no point in the RPM range is it better.  So, it'd be easier and better to run the 34mm.

Bear in mind that's not real world data, just a MOTA simulation so it could be wrong.