aprilia RS 125 overheating straight away after top rebuid

leafy1986 · Derestricted Danger Joined: 21 Mar 2016 Karma :

ive just done a top enginge rebuild, changed coolant, transmission oil, and 2stroke and as soon as I start the bike she sounds a bit tight in the cylinder and as soon as I drive to the end of the street and back the temp is like 60 PLSSSS any help?

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

Head gasket? Have you torqued the head down properly? Are you sure there's no air lock in the cooling system?
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

Jmh600 · Nova Slayer Joined: 02 Mar 2016 Karma :

Sounds like a typical airlock to me. Did you run the bike (briefly!) with the radiation cap off to release any trapped air?

How much coolant did you put in?

Joe
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Jmhmotorcycles

leafy1986 · Derestricted Danger Joined: 21 Mar 2016 Karma :

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
rs has a drain bolt for coolant (5mm hex key iirc).
empty it & start again.
mix up your coolant/water & fill it up.
remember to bleed air out, especially at the wee bleed screw where hoses join together (you can see it by lifting fuel tank iirc).

cheers,
GAZ

leafy1986 · Derestricted Danger Joined: 21 Mar 2016 Karma :

leafy1986 · Derestricted Danger Joined: 21 Mar 2016 Karma :

leafy1986 · Derestricted Danger Joined: 21 Mar 2016 Karma :

any more help no?

Pjay · World Chat Champion Joined: 18 Jan 2016 Karma :

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Usual process for filling coolant after draining.

1. Pour in coolant until it stops going down.
2. Open bleed hole. Close it when coolant is coming out with no bubbles. Repeat for all bleed holes.
3. Rinse off any coolant that has splattered on the bike with hose. Coolant attacks paint.
4. With the rad cap open, start the bike and let it warm up on tickover. When the thermostat opens, expect to see the coolant level drop.
5. Turn the engine off. Walk off and have a cup of tea. Let it cool down for at least half an hour.
6. Top up the coolant. Put the rad cap back on. Take it for a short test drive.
7. After a few hours, check/top up the level again.

If it is overheating after this, you have a problem. The thermostat is the most common point of failure, you can test it in a pan of hot water on the stove. It should open around 70-80 degrees, or when the water is first showing some small bubbles.