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Post by mikulskn on Jan 20, 2021 22:21:23 GMT -5
Well just after less than two days, there is significant pooling of oil in the carb in my second experiment as can be seen in attached photo. So looks like the relief valve at the oil inlet of the carb is not working properly. And now I can understand while moped is sitting for weeks how oil will eventually flow into carb and then into other hole (I think part of pilot circuit) and go into bowl, and eventually overflowing the contents of the bowl, and thereby coming out the bottom of bowl via overflow tube. So I guess it is time for trying either add-on oil tube relief valve like pinkscoot recommended or after-market carb. I am thinking of a new after-market carb since it is only $23 on ebay and relief valve is $12. I would then do same test with new after-market carb, and hopefully prove to myself that the relief valve on the carb is actually supposed to hold back the oil while scooter and oil pump are not running.  |
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Post by aeroxbud on Jan 21, 2021 6:06:56 GMT -5
A lot of carbs don't have a one way valve in. Unless you can be sure. It will be money wasted, with the same results.
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Post by pinkscoot on Jan 21, 2021 16:14:35 GMT -5
A $23 Ebay carb is exactly that. Can you show us a link to it? I have bought a few of these before and for the price it was alright. They weren't all good but most were. They do need new jets and other parts to tune them to your machine. |
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Post by mikulskn on Jan 22, 2021 0:08:03 GMT -5
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Post by pinkscoot on Jan 22, 2021 10:07:53 GMT -5
If you got the Dellorto one it probably isn't jetted for your needs. The one you picked has the double throttle cables that you need for the Zuma and you should just put your jets in. Be sure to clean it when you get it and make sure your jets are clean.
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Post by aeroxbud on Jan 22, 2021 10:09:46 GMT -5
The jets will probably be different. Just swapping your old jets over might not work. It's hard to say. Not a lot of details about the carb.
It looks quite small though.
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Post by mikulskn on Feb 1, 2021 20:18:33 GMT -5
Well it took 1.5 weeks to receive new aftermarket carb. I did my little test by just hooking up the new carb to the oil feed tube, and letting it sit just to see if oil comes thru the oil inlet by itself. After just one day, I could notice significant oil coming into the body of the carb by the throttle slide and then flow down by the carb opening. See attached pic. So to me, I have verified the oil leaking into carb when not running is not due to the oil pump (tried 3 pumps) or carb inlet itself. There is really nothing else in between oil reservoir and carb. The cause should be able to be found without resorting to putting an additional check valve like suggested in previous posts. So if the leak was happening with stock parts, the only conclusion I can make is that it must be the viscosity of the synthetic oil like previously mentioned as one potential cause. So when I get time, I need to drain all the oil and try some different oil. Any suggestions? If all else fails, I would just need to put in the extra check valve as a work-around.  |
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Post by repherence2 on Feb 4, 2021 16:17:33 GMT -5
You could switch to premix and rejet your carb.
Switching to a thicker oil may work. However most oils for injection pump are on the thinner side.
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Post by aeroxbud on Feb 4, 2021 17:15:01 GMT -5
I tend to stick to a couple of brands of oil. Castrol and rock oil, and years ago yamalube. But they all seem to be of a similar viscosity to me.
Anything made for an oil injection system will be a light oil i'm guessing.
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Post by mikulskn on Mar 10, 2021 22:28:28 GMT -5
Just to kind of finalize this thread... I ended up just pulling the brass oil inlet out of the carb which came out fairly easily. I thought it would be press fit in there so tight that I wouldn't be able to remove it. It had the spring and steel ball in it as suspected. See attached pics. Nothing looked out of the ordinary. But I did end up using the steel ball and a punch as shown in the attached pic to try "peening" the inside hole that the ball fits against, hoping the maybe the ball will fit precisely against the hole when moped is sitting. I just put the carb completely back together and I really could not notice any oil coming into the main passage of the carb like before. I put all the rest together and zuma is running fine now. Not sure if it permanently fixed, and not sure what made it better (just removing the oil inlet and cleaning, the peening, etc.). In any case, if I experience the same problem in the future with too much oil flowing into carb while sitting, I would then just think about a) going to pre-mix, or b) buying the plastic check valve (Zoro 695-2B2b-B 1/8") and putting that inline in the oil hose. I really appreciate the time and comments from everyone on helping me think thru it!     |
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Post by aeroxbud on Mar 11, 2021 6:48:04 GMT -5
That's good you sorted it.
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Post by Zino on Mar 11, 2021 7:04:34 GMT -5
nice work tracking that down and great pictures for the next guy to see
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Post by snaker on Mar 11, 2021 13:09:50 GMT -5
Now that's interesting.
So apparently the spring pushes the ball against the seat to seal.
Then when the pump is running it has to build up enough pressure in the oil to overcome the spring.
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Post by mikulskn on Mar 11, 2021 13:52:25 GMT -5
snaker: yes, it is like a check valve. But what I learned, it is unlike the normal check valve that stops flow in one direction, this one stops flow up to a specified "cracking pressure" based on the spring pressure. The ones I was looking at potentially using for this application had a cracking pressure of 1 or 2 psi. So you are right, the pressure to "overcome" the spring is known as "cracking pressure".
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Post by repherence2 on Mar 11, 2021 20:17:01 GMT -5
snaker: yes, it is like a check valve. But what I learned, it is unlike the normal check valve that stops flow in one direction, this one stops flow up to a specified "cracking pressure" based on the spring pressure. The ones I was looking at potentially using for this application had a cracking pressure of 1 or 2 psi. So you are right, the pressure to "overcome" the spring is known as "cracking pressure". Thanks for sharing what you found in regards to the "guts" of the oil inlet spigot. "Cracking pressure" reminded me of when i worked in the hydraulic shop, overhauling and setting/testing relief valves. In principle, that ball and spring act like a relief valve. Cool stuff. Thank you taking the time to explore the oil spigot and thank you for sharing the info and pics. |
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