Lance Duke Touring 250 cooling By billg (Read 5,475 times)

[billg]

I have a 2008 Duke Touring 250 that I'm pleased with but concerned with temp pegging when run on the freeway full out with speedo pegged.  I have removed the radiator and checked for obstructions without finding any.  Coolant level is burped and maxed.  Plug reads perfect light brown.  Radiator fan is working properly.  I had it out today in cold weather and the cooling system still can't keep up.  Once pegged on hot, it will not cool down at any speed.  To anyone's knowledge, is this a common problem with the Duke Touring 250?  Is the radiator undersized?

When I replaced the head gasket I looked up a YouTube video of the operation on this engine in another scooter.



That video directed setting the timing chain differently than the manual. I followed the manual. Valves are adjusted in accordance with the manual, snug and backed off 1/2 mark.

When I replaced the head gasket recently, I noticed that the coolant holes in the head gasket are not as large as the coolant holes in the head and sleeve.  I purposely did not alter the head gasket, figuring the reason for its coolant hole sizes were there for a reason.  This is the Honda Helix engine which has a reputation for running all day at speed.  What's wrong?

[cyborg]

I would think the undersized gasket holes are part of the problem , I would inspect the coolant galleys and also I would check your thermostat

[Bashan]

I never had any trouble with mine overheating. I'd do as Pete suggested and check the thermostat. I'd pull it and see if you run hot without it.

[billg]

The thermostat is brand new as I suspected that in the first place.  The one I took out functioned correctly, as it turned out.  I'll check it out, but I doubt that's the problem.  If it was the thermostat, there would be little or no circulation at all and the fan would never turn on as the fan switch is located at the bottom of the radiatior.

When I had the thing apart to change the head gasket, which was exactly the same as the original one as to the size of coolant holes, I checked the coolant ports and found no obstructions.

I'm beginning to think there are some plugged radiator tubes even though I ran a wide open garden hose through the radiator with no problem.

I'm running out of things to check.

[Bashan]

Are you sure the gauge is correct? Does it run funny when it's pegged? How about installing an analog gauge?

[adamhoyer]

Scooter looks like its still keeping it's "head up" and not giving up yet. I hope you find the problem.

[cyborg]

A member had a very similar problem with a sym not two weeks ago,,, turned out to be Not " burped" correctly

[billg]

It runs fine when pegged, just pegged hot. It acts like a volume problem. Per another post, I'm gonna recheck burping the coolant. I saw something somewhere on how to do it correctly but can't find it now. Any suggestions?

[billg]

Boy am I gonna feel dumb if that's it. How do I do it 'correctly'?

[Bashan]

.
Post by JR:

Now here's how I (burp) or get the air out of the system after replacing the coolant;

Now to get started;

(1) Put scooter on center stand and remove carb/radiator plastic cover under the seat.
(2) Place catch pan under the drain bolt location, remove allen head bolt, then remove radiator cap. [DO NOT LOSE COPPER WASHER ON BOLT]
(3) After coolant is drained take water hose and flush radiator well with clean running water, can even do it two or three times. If you have an air compressor you can even blow out all water completely
(4) Replace allen head drain bolt with the copper washer , a little silicone gasket maker is good to use too, secure tightly.
(5) Fill radiator completely with coolant, a long funnel is nice and doesn't make a mess. [USE ONLY COOLANT FREE OF NITRATES, BORATES, SILICATES & SPECIFIED FOR ALUMINUM BLOCK ENGINES] One can mix their own coolant on a 50/50 ratio but it is a lot easier to use a 50/50 premix (I use Prestone)
(6) Start scooter and let run until thermostat opens and you see coolant start to circulate (this only takes a few minutes) Re-fill until full as the coolant will generally go down, immediately put on radiator cap securely after re-filling
(7) Fill radiator plastic reservoir tank to about 3/4 full with same coolant after putting on the radiator cap
(8) Let idle until the temp gauge comes up to about the 1/2 way mark and then shut off scooter (the fan may or may not come on, doesn't matter)
(9) Go watch TV, read a book, but let scooter sit until it's bone cold.
(10) Remove radiator cap and re-fill with coolant, start engine, let circulate, fill again if needed, put radiator cap back on.
(11) Fill plastic reservoir tank again to about 3/4 full, put on rubber cap and watch temp gauge and see if fan cycles on and off.
(12) DONE!

If for some reason it seems to want to get warm and fan not cycle on and off then repeat steps number 9,10 and 11 again.
You can even run the scooter around the block and see if the fan comes on and off and how the temp gauge reads.

This has always worked for me first time and every time.




Read more: thescooterprofessor.proboards.com/thread/24/250a-coolant-drain-location-radiator#ixzz3NyYcU9dq

[billg]

It's a bonkers scooter. Took a while to find out that low tire pressure costs 10 mpg. It will get out on the freeway and run flat out with the speedo pegged at about 90, which I figure is about 70. Once I drilled the clutch bell, the clutch shudder disappeared and everything is smooth. Great machine - for a mechanic.

[billg]

Will reburp tomorrow. It just seems to me that if it's a burp problem, it would not maintain correct temp when just tooling around town. It's after about 10 min. of flat out on the freeway that the temp pegs. I noticed that slowing down a little resulted in a little temp reduction, but then reduction to street speeds does not return temp to normal street temps. To me, that points to a radiator capacity problem. That make any sense?

[jct842]

I own a harbor freight infrared thermomitor. Its a no contact type. you might try one or borrow one and take the scooter temps in a few places. The in and out of the radiator should be quite a bit different showing the radiator is working. Its late now but the gasket with its restriction isn't helping either.

[Bashan]

I still think the gauge is faulty. If that thing was truly as hot as pegged on the red it would be wheezing and losing power. Here's an idea, run it until it's pegged. Pull over and stick an oven thermometer down in the oil. If it's stratospheric then it is actually running hot. What should the oil on a water cooled be boys? Hotter than the water, so I'm guessing 200 maybe....just spit balling.

[jct842]

Like the doc says, "take its temp"!