Low coolant temperature on GT200
Post Reply    Forum -> General Discussion
Author Message
Enthusiast
Vespa GT 200 L
Joined: 09 Jan 2015
Posts: 53
Location: Lviv, Ukraine
Sat May 11, 2019 2:42 am quote
Hello gentlemen
Before servicing, arrow of the gauge was always in the middle while riding.
I did a valve adjustment (intake was overtightened - now it's 0.10mm, exhaust was 0.20mm instead of 0.15mm).
Also, I have replaced a leaking thermostat and its cover.

Now, arrow always looks like this, is it a good temperature?
I did 20km in "full throttle" mode, after that I was able to see it pointing to the middle after few minutes of idling.

Thank You very much for help and participation!

P90510-212303.jpg

Lurker
2006 GT200L
Joined: 11 May 2019
Posts: 1
Location: North Port FL
Sat May 11, 2019 5:20 am quote
I've wondered about that, too. My 06 GT200 with 10k miles always reads low.
Enthusiast
Vespa GT 200 L
Joined: 09 Jan 2015
Posts: 53
Location: Lviv, Ukraine
Sat May 11, 2019 6:00 am quote
Well, at least we are not lonely now)
Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 36949
Location: Pleasant Hill, CA
Sat May 11, 2019 7:31 am quote
Mine does that too. Not fussed by it.
Addicted
2, aprillia scarabeo light. 500. 2007 2009
Joined: 29 Apr 2018
Posts: 575
Location: North central florida.
Sat May 11, 2019 8:58 am quote
Too high wouldbe bad, but too low can cause problems also. I think one of the early 500 cc aprilia scooters had the wrong thermostats znd it somehow caused engine lroblems because the motor never warmed up properly or it could be this old fart is having a brain lapse.
Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1143
Location: Hamilton, NZ
Sat May 11, 2019 7:01 pm quote
Mine has run low occasionally and in particular on a longer run low load generally downhill section. I talked to the local dealer and he was unconcerned. Like most, he said high temperatures are a bigger problem, particularly if the fan doesn't kick in. I know that bit works okay and the scooter runs really well so I relax and enjoy the ride.
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1788
Location: Not really sure but I think somewhere in the engineering dept at Starfleet's UK HQ
Sun May 12, 2019 2:27 am quote
Did you get all the air out of your cooling sytem. If not that can give a lower temperature reading. Most air finds it's way to the thermostat housing where it can interfere with the function of the thermostat. Often this can cause it to stick partially open causing the engine to run cooler. Not good! Try re-bleeding the air from your system. You may find that suddenly it reads correctly again. If you run it for a long period with air in the system it can cause the thermostat to stick partially open, permanently.
Addicted
2007 GT200, 2008 Yamaha C3
Joined: 27 Jul 2012
Posts: 504
Location: Denver
Sun May 12, 2019 3:26 am quote
GT200 has a self bleeding system. Air in there wouldn't cause it to run cool anyway. Could be running cooler now that the valves are adjusted correctly. Mine never made it above 3/8 even in the dead of summer.
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1788
Location: Not really sure but I think somewhere in the engineering dept at Starfleet's UK HQ
Sun May 12, 2019 11:48 pm quote
The self bleed system doesn't work very well on the GT's. In the workshop we are wary of them. That's why they don't use the self bleed on the GTS's. If air is in the thermostat housing it can cause the stat to run partially dry leading to the stat not closing properly because of the build up of deposits on the slider. If it doesn't close properly this means the motor never or rarely reaches full normal working temperature. Stats regulate the engine temperature even when the motor is hot, and if it's defective you can find your motor running cooler than it should. I've had to replace the stat on a GT and GTS due to this very thing. Of course, it may not be that for the op but I'm suspicious due to the fact the temp guage was working just fine before he replaced the stat housing & gasket. So, assuming it's the right stat, the next thing is checking for air. It's what we would do in the workshop. If that's ok we would check the connections are clean to the temp sender unit and measure the resistance. Just saying it's something to check.

The engine valves were not out of adjustment anywhere near enough to make a difference to engine temp before or after adjustment. Valves have to be out of adjustment very significantly for that to happen. Notice also the op says it was only the INTAKE valves that were tight. This would not make a difference to engine temp anyway, but if out by alot the engine would have been running very erratically indeed.
Enthusiast
Vespa GT 200 L
Joined: 09 Jan 2015
Posts: 53
Location: Lviv, Ukraine
Mon May 13, 2019 1:02 am quote
Stromrider wrote:
Did you get all the air out of your cooling sytem. If not that can give a lower temperature reading. Most air finds it's way to the thermostat housing where it can interfere with the function of the thermostat. Often this can cause it to stick partially open causing the engine to run cooler. Not good! Try re-bleeding the air from your system. You may find that suddenly it reads correctly again. If you run it for a long period with air in the system it can cause the thermostat to stick partially open, permanently.
GT200 doesn't have a bleeder screw on the cover, what would be the best method to bleed the system there?
The only idea I get, is to loosen thermostat cover or disconnect the hose to carburetor.

Thank You!
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1788
Location: Not really sure but I think somewhere in the engineering dept at Starfleet's UK HQ
Mon May 13, 2019 1:40 am quote
The hose near the carb is the only way if it doesn't self bleed. About one in 5 GT's don't seem to bleed themselves fully.
Your Rally Here   vespa scooterwest scooter west Motorsport Scooters   AF1 Racing Vespa Austin
Post Reply    Forum -> General Discussion
[ Time: 0.3279s ][ Queries: 25 (0.0545s) ][ Debug on ]