SL125 carb issue

[husaberg]

According to this i am doing it wrong?

i always brought it around another 45 degrees to the clockwise.....
Edit Grrr

okay i relented here is the original honda service manual which is how i was taught.

click it three times.
that bit on top is the bellmouth end.

[husaberg]

Is not an airleak, I sprayed start ya bastard about to check, is not a choked up air filter, is not ignition, I have spent 3 hrs on it today and got nowhere. Unbelievable. I am just going to buy another chinese carb, although I will interchange with the one I got just to check…but it ran and rode perfectly with it(chinese) the other day…does my fucking head in this kind of shit
I have bent the float tab so many times now trying different levels, it must be suffering from fatigue!
I have an older shittier Mikuni that I could quickly clean up and put on just to try but I might be just wasting more time

I am pretty sure there is/was a decent one at my Mums
that protruding gasket could have been holding the float open or closed or both.

[Laava]

I am pretty sure there is/was a decent one at my Mums
that protruding gasket could have been holding the float open or closed or both.

I wondered about the protruding gasket thing too but it did the same with the old fibre one in. Funnily enough, I think BlackKnight has made an interesting observation about the idle screw replacement simply being too short for the job, which is something I never would have thought of and also a rookie mistake at the same time!😁😁😁
the link you posted earlier Husa showed the carb simply being upside down. But the initial contact method you are talking about is sometimes a thing too. All the utube vids show the carbs as just upside down. In any event, I think my problem hasn't fully been float level. I am going to check the chinese one to see it's float height. Assuming it has the same or similar internals. The outside is identical.

[husaberg]

I wondered about the protruding gasket thing too but it did the same with the old fibre one in. Funnily enough, I think BlackKnight has made an interesting observation about the idle screw replacement simply being too short for the job, which is something I never would have thought of and also a rookie mistake at the same time!������
the link you posted earlier Husa showed the carb simply being upside down. But the initial contact method you are talking about is sometimes a thing too. All the utube vids show the carbs as just upside down. In any event, I think my problem hasn't fully been float level. I am going to check the chinese one to see it's float height. Assuming it has the same or similar internals. The outside is identical.

some what people refer to as idle screws are a tapered screw that only move the slide up. Too short and it will not move anything
Others are a pilot air bleed.
Some are a fuel screw.
if any are wrong they will not work.
i can remember a bike that would only run for a few minutes then stop it was the fuel tank breather blocked.
another that would not rev past half throttle all of a sudden.... that was the main jet falling out.
make sure you have the choke set properly too. i have seen them set off for on. Or flapping in the breeze.

[Laava]

Yeah, well I went and checked the idle speed adjustment screw and as BlackKnight said, it seems short and is only 26mm long and not moving the slide up by much at all when fully in. I have a couple or three spare carbs in a box so I will sort thru and see if I can find one, or when my covid has gone, go for a ride to visit Chris up north!😁
Thanks everyone for all your input, I am still hopeful that I get to keep my 50yr old original carb!

[Laava]

Just again, wrt to float measurement, I am sure I remember my 450 honda manual stating that the measurement is taken from the notched area in the skirt around the gasket mating surface. Which is the same on this carb as well. Am I right about that?

[Black Knight]

Just a thought Al,seeing your throttle screw is wrong size,maybe also the air screw is incorrect-should be 18mm long and I would think the taper might be important,I have a spare air jet here.-The correct adjustment of the air jet is critical to smooth running once the idle speed is sorted,the slightest turn in or out will effect the running, so pretty delicate.

[Laava]

Thanks Chris, but after some careful investigation, involving inspection of the identical chinese carb, here is what I found,
1, The float height is as Husa described. ie. put the carb upside down and then revolve until the float starts to swing away from the needle. Right at that point, touching but not compressed the needle valve spring, measure the float height. And it is to the apparent notches, not the gasket surface. So, at 24mm, when you then invert the carb, it compresses a further 3mm or so which is a lot and very misleading if you try to adjust from this position
2, the throttle screw is only short by 1 mm or so and in any case would in theory still work. I have 5 of them including the new one from kit. And they are mostly 27mm.
3, on the chinese carb, which is running fine, the gap under the throttle slide on the front is only about 1 mm.
4, it is apparent I need a new float bowl gasket as I can't be arsed trying to make one and the replacement is not a petrol grade material

so, I have not test run this setup so can't comment as I now need a new float bowl gasket!
thank fuck I still have a bike I can ride and now I need to do that!

[Black Knight]

Fair enough-I often wonder about float clearances and how accurate these need to be-after all you are trying to achieve (a) sufficient fuel in the bowl to reach the jets and (b) adequate shut off at the float valve to ensure bowl does not flood,or too much where the float needle jambs in the valve-maybe that is where some form of accuracy comes in.
Years ago I saw a simple metal gauge that had "shoulders" cut into a piece of flat steel,the distance from the top of the gauge down to the top of the shoulders was the required mm,you simply held the carb upright,placed the shoulders under the floats and the top of the gauge under the carb where the bowl gasket sits then bend the tab until the seated height of the floats is even with the shoulders on the gauge.Would be pretty easy to make one and would save a shitload of farting about.
I buy a lot Honda spares from Malcolm at Anaconda (was Econohonda) in Te Aroha.If he does not have the item in stock he places fairly regular orders with CML and as a result you do not get stung with the high freight cost on an individual item from CML.

[Black Knight]

Actually that pic that Husa posted looks very much like the gauge I referred to but it appears to be adjustable to suit varying float heights-I am now wondering if the local Honda dealers workshop would have one of these,might be worth an ask.

[Laava]

I think I did myself a disservice watching videos on youtube. Without exception they showed the carbs being inverted, which still makes the most sense to me, and the difference from there to recommended is considerable. Anyway, I just need to track down a good quality gasket to make it stop weeping but I can test it all without that…got to go for a good blowout yesterday afternoon on the monster so is allgood!

[Laava]

Right, so I am going to buy another chinese carb. I just cannot get this one to work anywhere near properly. Put the chinese carb on the good bike, I was hoping to keep original, and went for a big, if slightly illegal ride.

[husaberg]

I think I did myself a disservice watching videos on youtube. Without exception they showed the carbs being inverted, which still makes the most sense to me, and the difference from there to recommended is considerable. Anyway, I just need to track down a good quality gasket to make it stop weeping but I can test it all without that…got to go for a good blowout yesterday afternoon on the monster so is allgood!

Mikuni show it needing to be inverted as well
http://www.mikuni.com/pdf/vmmanual.pdf

The Keihin manual describes it quite well
https://www.keihin-na.com/assets/1/7/slide_valve.pdf
the pic is a little misleading as its a Downdraft looking FCR
but it shows it on a 45 degree.

[Laava]

Yep, so I have set it so it is just contacting the valve stem. I rechecked it after removing it and it is still exactly on spec. So is the chinese carb and it runs fine.

[husaberg]

Yep, so I have set it so it is just contacting the valve stem. I rechecked it after removing it and it is still exactly on spec. So is the chinese carb and it runs fine.

Is the o ring on the carb throat and the gaskets on the intake i good nick?