Stumpy re-engined
This normally only happens after
a mid-life refurbishment, however after three months of trying to persuade the
Kohler Magnum M8 engine in Stumpy to run reliably, I gave up!
Approximately 6 months ago I had
bought through Ebay (where else!) a Kubota GS300 with electric start. It
history was that is used to be paired with a compressor on the back of a mobile
tyre repair truck. The seller (of the engine) had bought the compressor,
but converted it to electric drive.
The engine ran, but needed a new
air filter and an exhaust muffler. A quick search on the web led me to
Hurley Engine Services of Bath as
a local Kubota dealer. They were most helpful and after a bit of to-ing
and fro-ing the parts were ready for collection.
The parts were soon assembled on
the engine and it was started. A result. That just left a minor
problem that whilst the engine was electric start, the key-switch was broken and
according to Hurley, none of their books showed a wiring diagram for an electric
start. As it turned out it wasn't that difficult to identify the parts and
guess the wiring. However to be sure I contacted
Kubota UK and a very nice
gentleman (Eddie Wright) very kindly e-mailed me the relevant pages from the
manual so that I could identify the parts and confirm the electrical operation
of the key-switch.
That just left the installation.
I had tried to be careful in the design of Stumpy, but like most things that
evolve, it's not always perfect. When the engine was out I took the time
to review the chain tensioner between the Eaton unit and the wheels, I also
decide that there was no need to sit the engine low between the frames. It
doesn't make that much difference to the stability and I can build the engine up
on a cradle and just bolt the cradle in. I'd also learnt last time that I
had too much flexibility in the resilient mounts, this time I'd looked for a
simpler solution and following a suggestion from my local metal merchants (Avery
Knight & Bowler) it was simple - two 3/4" tap washers between the cradle and
chassis at each of the four mounting positions.
A number of late nights over the
last 7 days and Stumpy is in the garage awaiting a ride to Coate Water at
Swindon tomorrow to see how Stumpy handles. My concern is that this engine revs
a lot lower than the Kohler and that the gearing will be too low. Whilst
going too fast is bad, going too slow is almost as bad. Anyway, I'll find
out tomorrow and let you all know!
Following are some pictures of
the re-engining, I'll add some from the day out at Coate Water later.
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The starting point. The Kohler
engine, alternator and electric start has been removed, everything else is
to stay.
Note the two engine mounts (square bar)
lying in place to allow me to temporarily sit the new engine in and judge
the fit.
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The cradle is in place (well OK, it's just
two pieces of square section tube. The alternator has been trial
fitted and a bracket is about to be welded on.
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And the second bracket is about to be
welded
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The new tensioner. A spring one side
counterbalancing the chain the other with the whole lot able to slide
horizontally in a slot. Will it work? I'll find out!
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Another view of the tensioner. The
spring is behind the screw on the right hand side.
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The engine in situ on its new cradle that
just simply bolts across the frames. Resilient mounts are created
from 3/4" tap washers between the cradle and chassis in four places.
The only other change was the need to get
another drive belt between the engine and alternator. Supplied very
efficiently (as ever) by JA Crew
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A view of the throttle servo. Another
slight change to the previous arrangement. On this engine the servo is
mounted on the cradle so there is no relative movement between the servo and
engine. It also means that if I ever have to take the whole engine
out, all I do is disconnect the servo at its plug/socket and out it comes. |
