I remember a few scenes from a vaguely scary children's movie I saw as
a kid. It's in colour and probably about 80s, I thought it was called
"The Quest" but must have remembered wrong. I could possibly be
remembering these scenes from different movies.

1) In first scene, boy in small town attaches his bike to train
railroad and bikes to school, but almost hits a train and jumps off.
This takes place within a forest.
2) By a small lake with a windmill, somebody dead is found. 
3) The boy from (1) believes there is a monster in the lake. 
4) Boy sees his fish tank decoration move, and has a theory. He gets
the adults to drain the lake, and they find an encrusted pneumatic
shovel which was moving around when gas bubbled up.

Help?

---

Clarification of Question by astrophil-ga on 26 Oct 2005 20:32 PDT

I should say hydraulic shovel. Also it may have been a BC film or not.

The movie you're remembering is known under the titles "Frog
Dreaming," "The Go-Kids," and -- as you have recalled -- "The Quest."
The plot contains the elements you've mentioned, notably the
rail-biking and the "monster" in the lake that turns out to be heavy
construction equipment. I really like this movie, so I recognized it
instantly from your description.

You'll find the cast and crew listed here:

Internet Movie Database
http://imdb.com/title/tt0091810/

A few online mentions of the film:

"Some years ago I saw a film, made in Australia, called 'Frog
Dreaming' In it was that kid who starred in "ET" (Henry Thomas was
it). The film contained scenes of a bicycle converted for running on a
railway."

RailPage: Railbiking
http://www.railpage.org.au/ausrail/97july/0080.html

"The Quest (again!!!)(1986) aka Frog Dreaming starring Henry Thomas...

A group of boys (dont remember if there were any girls) are trying to
find out about a monster that lives in a lake. They find some old man
lives in the backwoods in a shack, claims he has seen the monster rise
out of the lake. To sum it up it turns out that this lake is in an old
quarry, turns out the monster is some old machinery like a bulldozer
that occasionally moves in the water and the shovel comes out and
looks like a monster's head."

The Internet Movie Critic: Found That Film!
http://www.datafriend.com/timc/found.html

This film was released on VHS quite a while ago. It's out of print
now, but used VHS tapes are not difficult to obtain:

Half.com: The Quest
http://product.half.ebay.com/The-Quest_W0QQtgZinfoQQprZ3119465

Half.com: The Quest
http://product.half.ebay.com/The-Quest_W0QQprZ3122960QQtgZinfo

Half.com: The Quest
http://product.half.ebay.com/The-Quest_W0QQprZ3342035QQtgZinfo

Amazon: The Quest
http://www.amazon.com/exec/obidos/tg/detail/-/B00004U9Q3

Google search strategy:

Google Web Search: "frog dreaming" "henry thomas"
://www.google.com/search?hl=en&q=%22frog+dreaming%22+%22henry+thomas%22

I hope this is the correct film! If it is not, or if anything is
unclear or incomplete, please request clarification; I'll be glad to
offer further assistance before you rate my answer.

Best regards,
pinkfreud

Thank you very much for the five stars and the nice tip!

~pinkfreud