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Post by jonatan on Jun 18, 2018 11:33:05 GMT -5
I´m 160 miles in to my break in of the new 51mm bbk with 20/23 bvh. Still the stock carb but with a 95 main.
(20mm carb, Naraku intake and spacer to match the intake port on it‘s way)
After the bbk instal (I went from a 47mm) the scooter is running really hot.
I´m using a lambda, and I´m jetted on the rich side throughout the register. I‘m also using an oil temp gauge.
I used to reach about 220 F at WOT, but the othe day I reached 250 F before I pulled over. Not WOT at all!
The air temp was 68 F.
Valves set at 0.10mm (0.04) intake and 0.12mm (0.047) exhaust and only using premium 98.
1. Is this normal? Read that 50-52mm bbk could get really hot during the break in, but never saw any numbers.
2. Is this dangerous? Could I mess things up?
3. What can I do?
2017 Kymco Agility City 50.
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Post by GrumpyUnk on Jun 18, 2018 12:21:44 GMT -5
I would think you have some pretty tight piston rings, which would cause more friction and hence higher temperatures. How does it crank over when hot? If the effort is increased, you might want to consider doing more part throttle break-in.
Have you looked at the spark plug? You may be jetted properly, but have insufficient fuel flow.
When you installed the cylinder, did it seem that the rings slid into place without problem, or were they difficult?
Did you check 'end gap'? If you did not, your rings may be jamming together at operating temperature, and trying to expand past the diameter of the cylinder. Not good.
tom
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Post by jonatan on Jun 18, 2018 13:13:55 GMT -5
I forgot to say, english is not my first language. I'll do my best answering though! The engine cranks over just fine I guess. Never any problems with the starter nor by hand (turning it to TDC using the fan). What does "part throttle break-in" mean? Haven´t looked at the plug yet, I´ll be doing that first thing tomorrow! The rings came pre-installed. I just set them up according to this picture. I notised the end gap on the compression rings, but I didn´t mesure it. Seemed huge, 3-5mm when holding the piston in my hand. Installing the piston in the cylinder went easy though. If the answer is tight piston rings, what can I do? Buy a new set? Will the current ones wear down and "set in"? Haven´t seen these oil temperatures in any forum yet..  |
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jun 18, 2018 13:26:19 GMT -5
I´m 160 miles in to my break in of the new 51mm bbk with 20/23 bvh. Still the stock carb but with a 95 main. (20mm carb, Naraku intake and spacer to match the intake port on it‘s way) After the bbk instal (I went from a 47mm) the scooter is running really hot. I´m using a lambda, and I´m jetted on the rich side throughout the register. I‘m also using an oil temp gauge. I used to reach about 220 F at WOT, but the othe day I reached 250 F before I pulled over. Not WOT at all! The air temp was 68 F. Valves set at 0.10mm (0.04) intake and 0.12mm (0.047) exhaust and only using premium 98. 1. Is this normal? Read that 50-52mm bbk could get really hot during the break in, but never saw any numbers. 2. Is this dangerous? Could I mess things up? 3. What can I do? 2017 Kymco Agility City 50. I really hope you did not set your valves to 40 thousandths and 47 thousandths. I think you meant .004" and .0047". Hopefully you went by the MM measurements which seem large if it were a GY6 but may be correct for a Kymco...I have never worked on a Kymco...wouldn't cause it to overheat anyway. Bill |
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Post by jonatan on Jun 18, 2018 14:18:07 GMT -5
My bad, I meant what you said mr!
So the valve clearance is to big for a gy6 you say?
The engine is called KL10B and is basically a 139qma/b (but 16" wheels) down to the actual gears. Head, cylinder, crank, cvt and so on, is identical.
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jun 18, 2018 15:43:31 GMT -5
My bad, I meant what you said mr! So the valve clearance is to big for a gy6 you say? The engine is called KL10B and is basically a 139qma/b (but 16" wheels) down to the actual gears. Head, cylinder, crank, cvt and so on, is identical. I figured it was just an error. On my 49cc gy6 I set both valves to .0025", so, you are not really all that much higher. Mine start to make a tapping/clicking noise if they get around .005". Bill |
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Post by 90GTVert on Jun 19, 2018 6:42:59 GMT -5
Is this an under plug temp sensor? I use a ring under my plug on my TaoTao, which is mostly stock 49cc, and it will see up to about 400F in the summer. 300s are normal for me. Unfortunately, I've found that CHTs can vary depending how much air flows around the sensor. That makes it so that you may have to use your own readings as a gauge rather than a standard figure.
Also, I have a wideband oxygen sensor on mine. I did not trust it before doing my usual tuning procedure though. I tuned the carb at full throttle as if I had no wideband sensor. I used speed and RPM over a set course as well as my own observations. Once it turned out that the gauge gave readings I'd expect when I chose the jet that I would use without it's input, I was happy enough that it worked. I'd advise that for anyone using them because you don't want to rely on a reading that could be off due to sensor placement or some other issue.
If it gives no other symptoms, I don't know that I'd be terribly concerned. I would definitely check the tune as said above though to be sure.
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Post by jonatan on Jun 19, 2018 8:16:31 GMT -5
Hi I use the Koso Pro 1 with the oil temp sensor/ tachometer and a/f meter.   Went down and took a picture of the plug. I´m using stock filter with the box and a 95 main.  No other symptoms runs great and I really feel the difference from the 47mm. I'm still breaking it in, why I wouldn't wanna do the full throttle test just yet right? If it´s a case of tight piston rings, will they wear down? Is there anything I could do regarding the break in? The bigger, matching, intake manifold and gasket is likely to arrive later today. Hopefully they will improve the cooling effect some. |
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Post by jonatan on Jun 19, 2018 8:20:07 GMT -5
Here is a better picture off the plug (without the top light)  |
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Post by GrumpyUnk on Jun 19, 2018 9:35:59 GMT -5
That plug does not appear to be running 'lean', and looks pretty good. Short bursts of full throttle, while at 'mid-range' rpms, are not a bad thing, and should be tolerated by the engine. Doing so may be helpful to seating the rings. You develop pressure in the cylinder under full throttle which will help push the rings out towards the cylinder wall. You do not want to go to higher rpms, but just 'walk' the engine from a lower road speed to a higher one, using the full throttle, and then allowing the throttle to go closed completely. The engine should accelerate, and the rpms increase, and when you release the throttle the rpms should drop as the vehicle speed drops, not right to idle rpms. You want slower rpm drop so the increased manifold vacuum can work to place high vacuum/suction in the cylinder, keeping more oil on the cylinder walls than normal. Load them and then let them relax with a cool drink of oil... more or less.
Changing the rpm is more important than throttle position, IMO. I will/have used WOT intermittently, and done the above 'coast' for a bit after.
If you place your hand underneath the 'left' side of the cylinder/engine, where the blower air is let out of the shrouding, you can tell readily if the engine is overheating. In general, the blower air should be hot, but not so hot that you cannot keep it blowing on your hand without discomfort. You should be able to keep your hand in the airflow without worrying it will get burned. Early on in the break-in process, the engine may put out a lot of heat, but by 10-20mi/16-32km, it should be close to 'normal'.
tom
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Post by 90GTVert on Jun 19, 2018 12:22:32 GMT -5
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