Newsgroup: it.hobby.motociclismo.scooter
Titolo: surriscaldamento motore HondaSH

 
Ciao Oggi ho fatto il passo della Futa con il mio Honda SH 150 (il
modello pre iniezione) , durante la salita, tutto perfetto, indicatore
della temperatura spaccato sulla meta della scala. Arrivato in cima ,
mi fermo con il motore al minimo. Vedo la temperatura salire
e lambire la zona rossa , senza pero' che la ventola di raffreddamento
iniziasse a girare. Premetto che lo scooter l'ho appena comprato
usato e non so quale sia il comportamento normale della ventola
ma credo che raggiunta la zona rossa dovrebbe iniziare a girare.
Riparto e subito la temperatura scende di nuovo a meta' scala.
Ritornato a casa smonto la copertura anteriore e verifico
che il livello del liquido di raffreddamento e' perfetto.
Vedo che l'elettroventola ha un filo che si inserisce
su quello che credo sia un interruttore termostatico alla
base del radiatore sulla sinistra. Stacco quel filo dall'interruttore
e lo cortocircuito a massa e la ventola inizia a girare.
Mi viene il sospetto che l'interruttore sia fottuto, ma prima di
comprarlo nuovo, mi chiedevo se la ventola parte subito
quando l'indicatore raggiunge la zona rossa o solo quando
la supera abbondantemente. 
Qualcuno sa quanto costa l'interruttore termostatico?
Andrea,38, Firenze.
_______________________________
Fiat 500F 1968
Fiat X1/9 1300 1973
Lancia Fulvia Coupe Safari 1976
Alfa Romeo GT 1300 Junior 1969
Nissan 200SX S13 1990
www.fiat500.it
________________________________

I have an SH 125, and it used to behave exactly in the same way. It's
an error Honda made, and won't accept it's an error.
When you see the temperature going up, past where it should be,
accelerate a bit, and the fan will start.
I'm not yet sure about this, but I suspect that a slightly high rpm
idle speed might help with this.
If you search Google groups, you'll find threads there discussing this
problem - in Italian, mostly! Sorry, I can read, but I can't write
Italian.
Good luck,
jbr
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Ride your 2 wheels, but in order to ride them yet another day!
bbb

I will replace the thermo-switch as my fan does not blows at all

I will replace the thermo-switch as my fan does not blows at all
If you are refering to the part in the radiator where the wires and
plug from the fan connect, you might not get any better results, as I
have already replaced that part, and the situation did not change!
I felt stupid, as the mechanic told me before that they had other
bikes like mine behaving exactly in the same way, and the part I
insisted on replacing was not considered malfunctioning...  I suppose
it's  matter of how much water *pressure* reaches this part in a high
position.
When you see the temperature going up, closer to the red area,
accelerate, as you would when starting your bike, and the fan should
most likely start working.  Try this before you spend any money on a
part that may not change anything in your bike's behaviour.
Read here 
http://tinyurl.com/yqy826
  what Alescar writes (in Italian)
about this situation, on 25/Jun/2002.
I suggest you also check the bike's idle rpm speed. Too low makes this
problem worse; a bit higher might avoid you having to accelerate to
make the fan start working.
Talk to other owners of SH bikes, or to mechanics, as this is a know
issue, at least in the carburetor model. (I don't know if Honda fixed
it in inject model, released in 2006, if I'm not mistaken.)
So far, I've gotten around the problem by using 100% synthetic (car)
oil, which keeps your engine cooler than mineral or semi-sinthetic
oils, and adding as much heat sinks/dissipators to the radiator as I
could.  (I can explain this one better, if you're interested).
So far, with environment temperatures around 25 degrees, the temp.
needle only reaches halfway of the meter after I've ridden hard on
nacional roads (non-highways), and right after I have to go through a
town/city traffic.  Otherwise, it doesn't go past the 1st quarter of
the meter indicator.
Let's and wait andd how it behaves when temperatures reach 35 degrees
:-( ...
Good luck!
bbb

I dismantled the front grill and i have found that the water level in
the radiator was extremely low (just 2 cm) instead of top level of
radiator. As i got this SH used and "serviced" as i have been told
from the previous owner, i supposed water was ok.
The water in expansion tank was at right level instead.
Now is much better as water temp arrives at maximum to half scale when
stopping after run and while driving i see the needle between the
first quarter and half , but i am still in doubt about the fan ...
when is supposed to start? three quarter ? redline?
as i still cannot hear it running. Maybe my problem was water level
too low. When i was with low water levei i also found that if i
accelerate from idle the temp goes down, i suppose because the water
pump at idle does not work well. My idle is quite low.

pump at idle does not work well. My idle is quite low.
Even at idle speed, the pump is working, and the water is circulating,
as long as it is hot enough to make the thermostat open.  If the idle
rpm is too low, the liquid won't circulate fast enough, therefore
engine temperature will increase when the bike is stoped, with engine
idling. 
Pay attention to battery condition also, as too low an idle rpm, may
be too low to (re)charge the battery.
If now you don't see  the temp going past the middle in the indicator,
I guess you'll have to wait untill Summer time for a more severe
test... such as I am waiting, in confidence, though.
Did you hapen to read the thread I indicated you, in Italian, on
google groups? It describes the problem, and how to deal with it -
although it was a disapointment to me, how Honda did not recognize
this mistake, and did not provide a proper solution for it.
I guess there are no good and bad brands, just good and bad models,
from every brand.  (Having tried, and loved (!), the Sh 300, I'm
waiting to see if the model has any serious mistakes, and how Honda
possibly deals with them, while saving money to buy the bike ;-)   )
Good luck! (and let (us) know how your bike is going)
bbb