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Old 04-10-2006, 10:24 PM   #1
Andrew2 OP
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Overheating Aprilia Pegaso

Howdy all,
I'm hoping some one out there can figure this one out.I have an 2000 Pegaso which runs the 650 Rotax motor.After a ride the overflow bottle fills up about 2" above the max mark causing the bike to run warmer than normal ( about 65C on the hwy-normal 60C- and hot enough for the fan to run constantly at low speed work ) and does not return to the radiator when it cools down.I have replaced the overflow return hose in case I had a hole in it causing vacum lose.I also removed the thermostat which I thought was the problem.But on todays ride,with the thermostat still out it did it again.
Any ideas guys.
Cheers
Andrew
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Old 04-10-2006, 11:57 PM   #2
GTinAus
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Removing the thermostat can actually make the motor run hotter, in hot weather, because the water is moving through the radiator too fast to cool properly.

Sounds like a faulty radiator cap, it is pushing water out into the overflow when it heats up, but when it cools, it sucks air around the radiator cap, rather liquid from the overflow bottle.
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Old 04-11-2006, 12:05 AM   #3
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Quote:
Originally Posted by GTinAus
Removing the thermostat can actually make the motor run hotter, in hot weather, because the water is moving through the radiator too fast to cool properly.

Sounds like a faulty radiator cap, it is pushing water out into the overflow when it heats up, but when it cools, it sucks air around the radiator cap, rather liquid from the overflow bottle.
Yep GT solution has my vote . . .
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Old 04-11-2006, 01:24 AM   #4
Andrew2 OP
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Is this normal to be pushing liquid into the overflow bottle all the time.I can't say I've noticed it before.My other theory was a blown head gasket .
Andrew
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Old 04-11-2006, 02:21 AM   #5
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Andrew

Did yah ever work out what that petrol smell was?

How many K's on the peg now?

I know the bmw 650s have water pump trouble - seen it and heard about it.

A lot of the KTM 950 crew upgrade rad caps - could be a cheap first step?

Good luck with the fix.
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Old 04-11-2006, 02:30 AM   #6
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Quote:
Originally Posted by davorallyfan
Andrew

Did yah ever work out what that petrol smell was?

How many K's on the peg now?

I know the bmw 650s have water pump trouble - seen it and heard about it.

A lot of the KTM 950 crew upgrade rad caps - could be a cheap first step?

Good luck with the fix.
The cap is probably my next try although I would'nt call $50 for a cap cheap.
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Old 04-11-2006, 02:32 AM   #7
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Any of you U.S. guys had a similar problem with any other brand of bike,BMW,KTM etc?
Andrew
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Old 04-11-2006, 05:08 AM   #8
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Quote:
Originally Posted by GTinAus
Removing the thermostat can actually make the motor run hotter, in hot weather, because the water is moving through the radiator too fast to cool properly.

Sounds like a faulty radiator cap, it is pushing water out into the overflow when it heats up, but when it cools, it sucks air around the radiator cap, rather liquid from the overflow bottle.
GT took the words right outta my mouth. Thermostat back in, new cap for Radiator.
Cheers
Craig
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Old 04-11-2006, 06:17 AM   #9
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Yep, I'd start with a cap and T-stat.

You can start it with the rad cap off, if there are a lot of bubles in the coolant you probably have a bad head gasket.

It is normal for a bike (or cage) to push coolant out into the bottle as it warms up. This is simply due to the coolant expanding - it shoud suck the coolant back into the rad from the bottle as it cools though. The movement from room tempature to operating temp on my TLS is about 20% of the total coolant overflow bottle capacity or about 5/8" of verticle movement.

good luck
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Old 04-11-2006, 06:51 PM   #10
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Probably not the thermostat i'm thinking, if it's stuck closed the engine will boil, stuck open you may not notice 'til winter. As bikepilot says look in the raditor for bubbles and a film of oil, maybe foam too, also check your oil in case it's going white, which means head gasket (+ the fact that it's running hotter). No bubbles then it's proly radiator cap. The head gasket shouldn't be too hard to change if that's the problem.
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Old 04-11-2006, 09:24 PM   #11
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Quote:
Originally Posted by OldDog
Probably not the thermostat i'm thinking, if it's stuck closed the engine will boil, stuck open you may not notice 'til winter. As bikepilot says look in the raditor for bubbles and a film of oil, maybe foam too, also check your oil in case it's going white, which means head gasket (+ the fact that it's running hotter). No bubbles then it's proly radiator cap. The head gasket shouldn't be too hard to change if that's the problem.
G'day Bill,
the thermostat is already out and it is running cooler on cold days.I thought it was the thermo as it has'nt played up for a couple of rides but it did it again yesterday.The oil looks ok as does the coolant.To change the head gasket I gotta drop the motor.
One thing I did do when I pulled the thermo out was run som high temp grease around the base of the rad cap.Was wondering if that could have provided a better seal for a short time.
Andrew
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Old 04-12-2006, 01:57 AM   #12
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Had the same problem with a previous LC4 KTM(99 model).
Didn't have a overflow/catch tank , just an overflow hose.
Spat coolant all over the front of the bike, where the hose was routed to.

New radiator cap fixed it.
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Old 04-12-2006, 02:35 AM   #13
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Quote:
Originally Posted by scottmoto16
Had the same problem with a previous LC4 KTM(99 model).
Didn't have a overflow/catch tank , just an overflow hose.
Spat coolant all over the front of the bike, where the hose was routed to.

New radiator cap fixed it.
If it's normal to expand and contract why did'nt your KTM have an expansion bottle?.
Anyway,I removed the tank this afternoon and ran the motor after topping up the coolant in the radiator from the over flow bottle.There was no bubbles,foam or discolourization of the coolant and the oil was fine also.I had the cap off and as the motor warmed the coolant started to expand as it should.
I should say that this has been happening only since I did a coolant change.Could I be using the wrong coolant ( doubtful ) or maybe the cap had'nt been off for a while and got damaged when removed.Also took about 300kms between the last time it did it and this time.When I replaced the cap last time I put some high temp grease on the base of the cap,maybe this kept the caps seal for a while?.
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Old 04-12-2006, 02:52 AM   #14
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Quote:
Originally Posted by Andrew2
If it's normal to expand and contract why did'nt your KTM have an expansion bottle?.


2005 model LC4, that I own now, is the same.
Overflow tube runs down near the bottom of the steering head , and is just an open tube.

Maybe KTM allows for expansion inside the radiators.
KTM say to only cover the inside core of the radiator, with coolant, by 10 mm.
That leaves a lot of room for expansion into the rest, of the top of the radiator.

Does that make sense
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Old 04-12-2006, 03:44 AM   #15
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Quote:
Originally Posted by scottmoto16


2005 model LC4, that I own now, is the same.
Overflow tube runs down near the bottom of the steering head , and is just an open tube.

Maybe KTM allows for expansion inside the radiators.
KTM say to only cover the inside core of the radiator, with coolant, by 10 mm.
That leaves a lot of room for expansion into the rest, of the top of the radiator.

Does that make sense
It does if your radiator capacity is big enough. If it's the same as Lego's 660 rallye i assume.
Andrew, looks like it is the radiator cap then, and that bit of grease may well have sealed it for a short time. Time for a new one. Did you say that you'd removed the thermostat? That can be a bad idea as it can actually cause the bike to overheat, but anyway, go and buy a new radiator cap already!
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