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Post by 17again on Jun 1, 2022 17:42:12 GMT 1
Just noticed on my new purchase that there is two stroke oil coming out of the airscrews on my carbs. the left is worse than the right. would i have a air leak because of this or weaker mixture the clutch arm is weit from it too  |
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Post by Tobyjugs on Jun 1, 2022 21:06:10 GMT 1
Looks like a chinese version, i notice that the carb rubber is also perished. Also in your other post it looked like no coolant in the expansion bottle . Be very carefull and check everything before you start it.
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Post by headcoats on Jun 1, 2022 21:22:03 GMT 1
I get that too on my genuine Keihin PWKs and they don't have a little 0 ring on the air screw like a lot of other carbs
I run premix too and I think it's down to more unburnt oil gobbing about at low revs
Remember seeing PWK air screws with the 0 ring machined in but were aftermarket
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Post by 17again on Jun 1, 2022 22:38:26 GMT 1
Looks like a chinese version, i notice that the carb rubber is also perished. Also in your other post it looked like no coolant in the expansion bottle . Be very carefull and check everything before you start it. con you tell me how to tell the difference, yes you are right header is low o empty. the radiator is full, my other lc doesn't even have a coolant tank which i found strange. |
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Post by 17again on Jun 1, 2022 22:39:55 GMT 1
I get that too on my genuine Keihin PWKs and they don't have a little 0 ring on the air screw like a lot of other carbs I run premix too and I think it's down to more unburnt oil gobbing about at low revs Remember seeing PWK air screws with the 0 ring machined in but were aftermarket thank you, you know when something is new to you are not sure if its normal. last time i ran premix i was 16 FS1e days |
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Post by 4l04ever on Jun 2, 2022 11:35:47 GMT 1
I never fill my overflow bottle. If any fluid gets into it, there is a problem I need to know about... :-)
It is not an expansion tank, as it is isolated by the radiator cap valve.
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Post by arrow on Jun 2, 2022 11:41:17 GMT 1
I never fill my overflow bottle. If any fluid gets into it, there is a problem I need to know about... :-) It is not an expansion tank, as it is isolated by the radiator cap valve. Why do you do that? Before all the air is expelled on every warm up its free to get round the system. Plus a fresh dose of Oxygen each time. The radiator is designed to be full of coolant. |
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Post by 4l04ever on Jun 2, 2022 11:45:18 GMT 1
The pipe to the overflow bottle is blocked by the radiator cap unless there is more than 0.9bar pressure in the coolant system, so no coolant can move up the pipe to the overflow bottle under normal conditions.
The default state for the radiator cap means that the overflow pipe is blocked from cold.
Any air in the system generally stays at the high point of the cooling system, i.e. the top of my radiator.
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Post by tony2stroke on Jun 2, 2022 12:07:28 GMT 1
I never fill my overflow bottle. If any fluid gets into it, there is a problem I need to know about... :-) It is not an expansion tank, as it is isolated by the radiator cap valve. Forgive me if I am wrong here, I agree its not an expansion tank, if it were it would have a cap like the radiator cap and be made of a much harder compound, it is a reservoir, same as on a lot of cars, its my understanding that the radiator sucks fluid from that tank when needed, the manual (gen Yam) says to fill it to top level, you would do this with any car too, every manual I can recall says to fill to top level and keep toped up, I am confused by your not putting any fluid in it, I would have thought at least some, as Gary said, it would suck air in at the point it wanted to suck in water. Or am I completely over thinking this and have the wrong end of the stick. |
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Post by arrow on Jun 2, 2022 12:11:25 GMT 1
The rad cap correctly releives itself every heat cycle, in normal use. That's why the level of the expansion bottle changes, every heat cycle. Its also why the level is correctly checked - cold.
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Post by tony2stroke on Jun 2, 2022 13:07:32 GMT 1
The rad cap correctly releives itself every heat cycle, in normal use. That's why the level of the expansion bottle changes, every heat cycle. Its also why the level is correctly checked - cold. That was my understanding too, its not an expansion tank though, its a reservoir in this case, its not under pressure, and I was under the impression water was drawn from that tank in a similar fashion as an expansion tank, hence the wording being reservoir, and reservoir being a device with an amount of fluid to draw from. I am not having a go at anyone, I am intrigued at Rob's post not putting any fluid in the tank though and his reasoning for that. If no fluid in that tank it will draw in air, won't it ? |
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Post by arrow on Jun 2, 2022 13:32:19 GMT 1
Yes it will. The other valve in the rad cap, the low pressure one opens up on cool down to allow water back in. You can tell on a faulty rad cap if that valve is not working, the hoses will be partially collapsed when the motor is cold.
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Post by Tobyjugs on Jun 2, 2022 14:24:03 GMT 1
Looks like a chinese version, i notice that the carb rubber is also perished. Also in your other post it looked like no coolant in the expansion bottle . Be very carefull and check everything before you start it. con you tell me how to tell the difference, yes you are right header is low o empty. the radiator is full, my other lc doesn't even have a coolant tank which i found strange. The original PWK's have serial numbers and couloured markings on different parts of the carbs. But these are also being copied now as well. i think it is all explained on the Keihin website about forgeries etc. |
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Post by Tobyjugs on Jun 2, 2022 14:31:32 GMT 1
Both types mentioned are expansion tanks.
I'm with Gary on this one
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Post by midlifecrisisrd on Jun 2, 2022 14:52:24 GMT 1
I'd say expansion too as the water expands into it
Everything expands when heated so the water is let out into the tank
When cool it contracts and is sucked back in so there is never air in the system
In an ideal world the exact amount let out will be sucked back in so no extra fluid required but life is rary ideal
Air will always rise to the high point of the rad. As it expands more than the fluid it will self purge
Every time it cools it will suck water back in to replace the air
Steve
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Post by JonW on Jun 3, 2022 1:16:40 GMT 1
I was sure it was a blow/suck expansion, thats why there is a level to fill to on it. If it was just a catch tank that wouldnt be needed.
The cap isnt a pressure cap as there is no need, any air would just be expelled as air rises up and out of the fluid in the tank, the lines and tank being 'full' of fluid.
Interesting discussion tho as I hadnt considered how the sucking back in would work since the cap looks only like it would lock off and then lift when pressure exceeds the stated value (pushes against the spring), not draw back in... whats the system to do that in the cap?
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Post by JonW on Jun 3, 2022 1:19:14 GMT 1
This the is underside (pic form CMS obvs lol) I can see how the pressure pushes the seal up to let pressure out, but i dont see a secondary drawing in device? Happy to be educated if anyone knows?  |
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Post by arrow on Jun 3, 2022 1:48:05 GMT 1
Hi Jon, the cap is a pressure cap, with two, one way valves that work in the opposite direction to each other. Pressure needs to be (as spec) to push the pressure valve of its seat. The other valve, much weaker by design opens up and releives the negative pressure on cool down.
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Post by arrow on Jun 3, 2022 1:49:35 GMT 1
In your photo, the silver bit (center) pulls out, on quite a weak spring. That's the relief bit.
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Post by arrow on Jun 3, 2022 1:54:10 GMT 1
Also, most coolant systems are pressurised. Raises the boiling point of the coolant.
Boyle? or Pascal? Sorted that law many years ago.
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Post by JonW on Jun 3, 2022 2:22:21 GMT 1
super info Gary, thanks m8!
So you need fluid in the overflow bottle to complete the system as has been stated. Running without means youre likely not running with 100% coolant and some air will get in to the top of the rad.
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Post by reedpete on Jun 3, 2022 5:53:35 GMT 1
In summary, the cap is the ‘unmarried type’… sucks and blows, and it’s beers all round on Rob !
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Post by 4l04ever on Jun 3, 2022 9:16:29 GMT 1
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Post by 4l04ever on Jun 3, 2022 9:34:57 GMT 1
I just checked my 2 LCs. They have both been running with empty catch tanks for approx 500 to 1000 miles each and both catch tanks are still empty and both radiators are still full.
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Post by JonW on Jun 3, 2022 9:52:56 GMT 1
What a great thread. This is what forums are about. Great discussion and learning about something you already know a bit about. Good stuff!
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Post by midlifecrisisrd on Jun 3, 2022 10:31:19 GMT 1
But is the expansion bottle not there as a system checker
If you fill it to the centre of the min/max it in normal use should stay there and should be part of your usual routine checks
If the head is starting to leak the level will be higher as the excess pressure in the cooling system and the introduction of air will make the level rise
If you have a coolant leak that is not excessive the level will drop
Nearly every vehicle has them, there must be a reason for them
Running with it empty is another thing, that's a choice for whatever reason you have
Steve
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Post by rich on Jun 3, 2022 10:33:17 GMT 1
My PWKs get oily here too, never really caused any issues
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Post by chrisg on Jun 3, 2022 10:40:43 GMT 1
Hi Jon, the cap is a pressure cap, with two, one way valves that work in the opposite direction to each other. Pressure needs to be (as spec) to push the pressure valve of its seat. The other valve, much weaker by design opens up and releives the negative pressure on cool down. That was the bit that was throwing me. How did the rad suck fluid back when cooling ie negative pressure. Keep saying it, every days a school day. |
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Post by 4l04ever on Jun 3, 2022 11:15:19 GMT 1
But is the expansion bottle not there as a system checker If you fill it to the centre of the min/max it in normal use should stay there and should be part of your usual routine checks If the head is starting to leak the level will be higher as the excess pressure in the cooling system and the introduction of air will make the level rise If you have a coolant leak that is not excessive the level will drop Nearly every vehicle has them, there must be a reason for them Running with it empty is another thing, that's a choice for whatever reason you have Steve You can do the equivalent checks with the bottle empty. I just have to check my radiator coolant level. If it is down, I can then check the overflow...if there is coolant in the bottle, my system is over pressurising, and if there is not I have a leak. :-) |
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Post by midlifecrisisrd on Jun 3, 2022 11:17:23 GMT 1
Each to their own 👍
And before anybody says it I know a Tesla does not have an exp tank 🤣
Steve
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