Reviving A -99 Tdm 850

[anda3243]

<!--sizeo:4--><!--/sizeo-->Intake manifolds<!--sizec--><!--/sizec-->

As it was mentioned earlier, the center-center distances for the carbs are the same on the 900 and. This is good because the carbs and air filter can bee fitted without modifications.
I also think that the distance between cylinders is the same, since the 900 barrels should fit the 850 engine. The crankshaft has a different article number in the parts catalog, but is weary similar on later 850 and 900 engines. The balancer shafts, bearings and some other parts near the shaft are the same.

The intake manifolds.
The 850 intake manifolds are on the left, and the 900 on the right. One can see that the 900 ones are shorter and that the bolt pattern is a little different. Also the diameter of the 900 "carbs" that goes into the rubber boot is bigger.


My plan is to make a adapter from the shorter 900 manifolds to the 850 rubber boots. I should also get the right "height" of the inlet manifold by doing so.
The 900 inlet manifold on the left top in the picture. Then the aluminum rod for the adapters. And the original 850 inlet.


The ready adapters, it took some hours. The inside of the adapters has a rounded conical shape, since the 900 inlet manifolds has a somewhat bigger diameter.


Fits perfect


With the 850 rubber boot it has the same height as the 850 inlet. The 850 original inlet on the left.


Between the boots there is enough space for a vacuum tube connection. It will be used for synchronizing the cylinders.
The connection is made of copper car brake tube. It is pressed down in a tight fitting hole and glued.


Since the 900 inlets does not have a cylindrical shape, some grinding was necessary. I used a dremel like tool to remove some of the vulcanised rubber from the 900 inlet manifold. Metal was exposed in some places.




By doing so the cross section area was not constant trough the inlet manifold. It increased when near the 900 inlet and aluminium adapter mating. It is not good, but I do not know if it is critical for this engine. There are no sharp edges tho.
It is better to make the inner diameter of the aluminium adapter cylindrical, and then grind it to fit the shape of the 900 inlet.