SL125 carb issue

[Laava]

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

Yep and spraying ether around there confirmed it. Have just given up now. Have spent more on fixing this carb than a new chinese one costs…

[husaberg]

Yep and spraying ether around there confirmed it. Have just given up now. Have spent more on fixing this carb than a new chinese one costs…

Fair enough......

[Black Knight]

Float height sanity check-Turn on fuel cock to fill bowl then turn off-Drain fuel from carb into a container-Remove bowl and tip the drained fuel into it-should be close to half way up the bowl-adjust tab if required.
Install Chinese carb

[Laava]

Taiwanese carb ordered, end of issues in theory…

[Laava]

Ok, update time. I bought and fitted a chinese carb. It instantly started and idled but when you open the throttle it dies instantly. The float height is exact the pilot screw is at 1.5 turns out. If you feather the throttle carefully the revs get up and you can ride it but at idle you just cant crack the throttle.
I have a mate who is an old school mechanic and told me he could fix it but no, he had no success either. He tried putting the original, reconditioned carb back on, which is so much worse again. Timing is spot on and has been rechecked so many times, I have tried several spark plugs, have had the coil, condensor and the current spark plug tested professionally as the spark seems weak. The compression is high. The battery is fully charged and short circuiting the bikes wiring loom makes no difference.
So, back to the idle thing. It will sit there idling away ok but does a funny little spit/hiccup thing every now and then. And the instant stalling thing when the throttle is cracked is the main problem. Does that mean it is too rich? Adjusting the pilot screw has not seemed to affect this. Is the fuel level too high?
I just feel like I have to buy another carburetor but it shouldn't be that hard. My mechanic mate is totally stumped as he has spent 2 days trying to get it to work.

[F5 Dave]

So can you swap the carb from your good bike?

I'd be thinking lean.

old needle in good carb?

Bit of spray engine start just as you crack the throttle. Would replicate a throttle pump bigger engine often have.

Spray around manifold as well, looking for airleak or small split.

[Laava]

So can you swap the carb from your good bike?
Only have this one now.

I'd be thinking lean.

old needle in good carb?
Is all brand new, and I don't want to go down the track of swapping chinese needles and jets with the japanese one

Bit of spray engine start just as you crack the throttle. Would replicate a throttle pump bigger engine often have.
Might be worth a crack, have already done the inlet leak check…

Spray around manifold as well, looking for airleak or small split.

To be fair the only thing I havent done is check the airbox and filter since it was installed. But it was all new so…

[F5 Dave]

Soap spray while leakdown testing my 2 strokes regularly found Reed manifold leaks. Inlet valve closed, carb blocked introduced air could be interesting. But spray if engine start all around would achieve same.

[husaberg]

Earlier i posted about the oring on the carb throat but on early Hondas depending on if it is the alloy manifold or the rubber they have another oring's pluss a gasket or two soft gaskets. Plus that plastic heat isolator..

[Laava]

I have sprayed ether around there when it is running. Also, once above idle the engine pulls ok, just not entirely cleanly and this off idle death is doing my head in. I am just going to have to buy another carb and gift it to the new owner if it actually sells on trademe,
Of course, all this endless tinkering has resulted in some paint damage which now needs a careful touch up in one place and some inconsequential scratches to the frame where the seat and tank mount up. More little touch ups…

[HenryDorsetCase]

Heres a stupid question. Is the float needle round in section, and does it have the correct taper - and is it the same as the seat it goes into? Is there some sort of cam somewhere that pulls more cable at the beginning of the stroke than the end - assuming not a CV carb i.e. the throttle cable pulls the slide up.

[Grumph]

Years back I had the same problem on a SL125 I'd converted to a trials bike for a mate. Corrected by checking and adjusting ignition timing - and freeing the sticky
centrifugal advance mechanism. Hesitation was slow ignition advance. Got a timing light ?

[Laava]

Heres a stupid question. Is the float needle round in section, and does it have the correct taper - and is it the same as the seat it goes into? Is there some sort of cam somewhere that pulls more cable at the beginning of the stroke than the end - assuming not a CV carb i.e. the throttle cable pulls the slide up.

All new and cable is directly onto the carb slide.

Years back I had the same problem on a SL125 I'd converted to a trials bike for a mate. Corrected by checking and adjusting ignition timing - and freeing the sticky
centrifugal advance mechanism. Hesitation was slow ignition advance. Got a timing light ?

Yep I have a timing light and hooked it all up to check it and dropped it breaking the flash tube. I didn't want to just "buy" another timing light as I always try and fix but you guessed it, I can buy a new timing light cheaper than I can buy a new flash tube!….
Ignition advance mechanism is new and quite free. So do you think it might be too retarded?

[Grumph]

Ignition is one possibility. Have you richened it up on the airscrew ?

[Laava]

Yep adjusting the airscrew makes little difference. I am back to endlessly faffinfg about with the float bowl trying to stop it leaking. The chineses carb gasket turns the petrol in the bowl a horrible brown colour so I waiting for nzpost to drop my new one in the mailbox. The float is set to 24mm as per the handbook and although that is where it runs best, it seems to just end up leaking and fucking the paint on the crankcases. Another thing to fix. I am going to try going to 24.5 mm to see if that makes it better. My mate who worked at forbes and davies all those years ago reckons the needle valve spring seems weak although new so we shall see. I have had to replace the brand new fuel tap I brought with a brand new fuel tap to stop it seeping, contributing to the endless overflowing dramas.