250 Roketa 244cc cooling issue By mxmatt (Read 7,481 times)

[mxmatt]

Mar 5, 2015 0:57:39 GMT -6 Guitarman said:

Lets solve this once and for all.
Get some black light dye and add it to your system. Run the thing around the block a few times till it overheats and then shine a black light in there and see where the frickin leak is coming from.

Once we know that, we can decode why it's leaking.

Where do I get said black light dye?

I'm going to be outta the country for a week so I'll respond if I get wifi service where I'm at.

[mxmatt]

Mar 6, 2015 1:38:15 GMT -6 Guitarman said:

Ok, it's over heating. We are guessing that it's over heating because it's losing fluid.
Do we know 100% FOR SURE where the fluid is escaping from? If not, then run the dye test and find out.

If we do know 100% for sure where it's leaking at, then we need to know that.

So.... Because this thread has gone so long and back and forth, please do the following;

1. Stop any guessing. *Sounds good*

2. Run the dye test (if we don't know 100%) *where do I get this stuff*

3. Give us the specs on the Rad cap. Rating #'s and the like. *16 lbs*

4. Give us an updated run down on what's been done. *replaced thermostat, tested old and new thermostats, both working, removed radiator and all hoses, flushed them and used compressed air to blow them clean/dry, burped the thing silly a million times, I can not detect any coolant escaping other than from the reservoir cap, scoot stayed cool for 3400 miles, even in brutal AZ heat but during a freeway ride last fall in cooler temps it started overheating and blowing coolant out of the reservoir cap, seems to do this when traveling at higher speeds on highway, around town under 45mph it doesn't heat up that I can detect, fan is completely operational, comes on at quarter reading and is on during overheating*

5. Post some pix so we can see what is going on. *I will when I get back*

6. Bypass the carb heater lines and eliminate it from the equation. *instructions please*

There is too many ideas floating around and you've tried to check them in a fashion, but lets just do it once from the get go and diag this thing correctly. It's just possible it's a hunk of road debris keeping the fan from running. So, let's start at the top.

Replies in your text above.

[Guitarman]

BLACK LIGHT INK CLICK HERE

[rks]

Mar 5, 2015 2:44:42 GMT -6 jct842 said:

head gaskets do that

I'm with you jct842.... OP states he's burped the system a million times, yet still sees a steady stream of bubbles....building enough pressure to bypass the two different 16# pressure caps he's tried, water temp would have to be over 268* to boil at that pressure. Considering the parts that have been checked out.. (thermostat, water pump impeller, hoses and radiator flush plus 2 pressure caps) .... Sure sounds like a bad headgasket is pressurizing his cooling system to me.

[jct842]

Could also be a bad casting. When you keep doing the same thing expecting different results.............well you know how that goes.

[cyborg]

yes or a crack in the cylinder,,,freeze damage perhaps,,,

[Alleyoop]

Cheapest Leak dye and Light Kit I could find.
www.ebay.com/itm/like/230754744531?item=230754744531&lgeo=1&vectorid=229466&rmvSB=true

[billg]

If you have fluid coming out of the radiator cap at any pressure, you have not screwed it on all the way.  Make sure of this before going any further.

[Alleyoop]

If coming out of by the radiator cap then maybe a bad cap not enough pressure.

[gooter]

Rev up the engine with the over flow bottle clearly seen...if you see any bubbles in the reservoir bottle...your head gasket is blown...if you replace it....very carefully check the machined mating surfaces of the head for pits...and replace the head of any are found.

[mxmatt]

I just replaced the head gasket on my scoot. I'll put it all back together as soon as I can and give an update. *crossing my fingers*

[mxmatt]

Final Post!!!

Sorry for the bump guys. It's been a while. A huge thank you to all of those who helped me with this. At long last I believe I found and have fixed the overheating problem on my 250 Roketa 244cc.

I am posting this because in my attempt to find the solution to this problem I found almost no information about what fixed it.

After burping it for days, replacing a fully functioning thermostat and radiator cap, adjusting the idle, testing the electrical system, fan, temp gauge, water pump impeller, hoses and every other suggestion purposed on this thread, it turns out it was the head gasket. I suspected this early on but really didn't want to believe it was because I couldn't believe a four month old scooter that was babied and serviced to perfection (I have the records) could have a bad head gasket. Nevertheless it was. I replaced it over a month ago, but do to my busy schedule did not get the scooter back together until this week. I have now put 200+ miles on it and at least 100 on the freeway at 95% throttle. It never even came close to heating up and there are no more air bubbles in the cooling system. The following is what I experienced.

1) At 3500 miles. It was a cool AZ November night 2014. I rode it for 20 miles on the freeway (65mph) to buy some tickets to a game. On the return ride home, for the first time ever, I noticed my foot was covered in coolant and then saw the temp gauge redlined. I pulled over and let it cool down, added some water and then limped home. It kept heating up.

2) I drained and replaced coolant and proceeded to burp it. (Ultimately I did this a hundred times) It seemed to be ok, but if I got on the highway it would overheat. If I kept it under 45mph it would stay cool for 5-10 miles but eventually overheat. I would repeatedly refill and burp and try everything suggested on this thread to fix the problem. It did not work.

3) Symptoms include never being able to get all the air out of the system. Bubbles in the coolant tank and in the radiator cap cup. Coolant coming out of the overflow bottle. Repeated overheating no matter what you replace, adjust or test. There was no coolant in the oil and no oil in the coolant. *I don't know it it is related, but my muffler turned into a terrible rattletrap a month earlier and I'm wondering if some loose baffling plugged or restricted the exhaust causing back pressure.

4) This is not an easy fix! If you have no experience with engine repair, have someone who does do this for you. I don't recommend doing it without a manual. Form start to finish (body removal, disassembled, replace gasket and install, reassembly) over several days I'd estimate it took me 10-15 hours. I am not a professional, but I have rebuilt a 150 GY6 in the past. If you have an older bike with high miles, I'd replace at least the rings too. My piston and rings looked amazing (maintenance does a motor good).

5) I ordered the gasket on eBay for around $10.

I hope this post serves someone useful. Message me if you want more information or have questions.

I'm so excited to be back on the road. I should be back on this site more now as well. I've missed you guys!

[Alleyoop]

From the way you describe what is happening I think its a bad THERMOSTAT so I would FIRST put in a new thermostat, it appears to me that sometimes it opens at the right temp and other times not so when it does not you get overflow.
Alleyoop

[mxmatt]

Apr 30, 2016 12:55:24 GMT -6 Alleyoop said:

From the way you describe what is happening I think its a bad THERMOSTAT so I would FIRST put in a new thermostat, it appears to me that sometimes it opens at the right temp and other times not so when it does not you get overflow.
Alleyoop

Did you mean to respond to s different thread here?

[Alleyoop]

Don't know what happened but NO when I opened the thead it only showed the 1st page and I responded to that page. It did not show that it was novel and it had 5 more pages.