TZR powered Hovercraft

[David141]

Apologies I meant to get round to this months ago, but life got in the way as now lockdown has pretty much stopped that as well. So here goes:

A bit of back ground about my adventures in TZRs I got my first TZR powered hovercraft in 2004 supposed to be S.S wide profile tune. A couple of years later I got a G.F tuned engine with BDK adjustable CDI & PV.

We do not use the gearbox so make our own adaptors and take the drive straight off the crank. The gearbox casing is then removed.

I first found about the 2xt many years ago, but could never find one (as expected) and then several years ago someone mentioned they had a crankcase so I proposed a swap, a fresh file std top end for them they took it and were very happy at the results of those barrels! About a year after I found out a different person had been sold the barrels, at the time he was by luck would have it my team mate so he was willing to part with them thankfully!

At the time the team was just in first place, but with one weekend left and knowing 2nd place was faster than my craft, so I figured lets just go for it a 2nd is secured if you get a point, 1st is only yours to loose.

The motor went in the craft, turned up at the meeting, It drew a lot of attention, and when I fired it up smoke, thick white smoke and firing oil out the pipes, when I say thick smoke I mean It smoked out probably 15m of an open paddock Lots of noise and no go. Lots of people proposed different theories, tried them all but in the end, ended up putting my original motor back in. Giving up on my 2XT for now. Not sure on barrels or crankcase frankly!

So my crazy idea of this build was conceived.

-   Custom made billet mounting blocks, welded into a 1kt case.
-   RS125 Vforce reeds & Ital RS 125 manifolds for the 34mm carb
-   35mm TMX carbs
-   2XT barrels



Making the manifolds above (Yes I know, the machining is dog ****, I hadn%u2019t done any for about 5 years and the mill had about 5 mm backlash in X and Y).



Case was machined to take the new mounting blocks.



Case was then welded and re-machined to take the mounting blocks. (Welder from work who is brilliant!)



Mounting blocks welded onto the case.



Putting in new case studs (2xt cylinders are reinforced around the mounting area on the intake side of the cylinder, hence why the need for new.. also originally I had another different project planed)

Now I believed that it was the head gasket that was giving me problems with the 2XT. One barrel had been given to me with original gasket on it, the other someone had gone over heavily with scotch brite or some thing%u2026. So

The barrels were lapped, and boy did they need it nothing flat about them! Head was lapped as well as the new mounting blocks. Oh and for good measure gave the bottom of the barrels a once over as well%u2026

Carbs needed sleeving to fit in the manifolds as there meant for dellortos not mikunis as well.

Then cleaned and assembled everything. This is what It looked like in the end:




Started first pull over! Not as powerful as I would have liked but definitely lots of potential.
I still believe that I machined and got the new intakes too far down in the case, If I do another of these ill do it higher and shorter and have some adaptor plates so I can vary volume in the crankcase.

Please excuse the lack of photos/ bad quality of them!

Thanks for reading

[teezer250]

Nice project.
White smoke usually means a head gasket leak,with coolant getting into the combustion chamber.
I had this happen to me many years ago due to a pattern head gasket,lesson learned about cheapo head gaskets.
You might need spacers between the reed valves and the cases,similar to the set-up as standard to get more power.