Non Monster Carb problem

20-03-2005, 10:32 PM

Right, this is totally doing my nut in!

I've got this Honda CB125TD-E, I've stripped and cleaned the carbs, done a few other jobs etc, and after re-assembling everything bar the side covers, turned the fuel tap back to 'on' ready to start her only to see fuel pouring out of the bottom of both carbs!!! Slight panic, turned the tap back to 'off' and it eventually stopped. Fine, checked stuff like the drain screw was fully done up, check, even let out more fuel by undoing it. Dismantled carbs to check float chamber, blew air through fuel line and lifted float, air stopped (got puffy cheeks etc

), re-assembled carbs and remounted, fuel on, more pouring of fuel. Off comes the carbs and again dismantled.

Now, I can find NOTHING wrong with them. I have only cleaned them and dismantled the float assembly (the guy I got the bike from said one was sticking), I haven't touched either the main jet body or the pilot jet. The floats themselves aren't punctured or full of fuel and nothing seems to stick on the assembly. After that there's not much to adjust and I've done a static setup as per the Haynes manual. There's only one bit to attach the fuel pipe too so it's nothing THAT stupid and I've stripped and rebuilt lots of old SU carbs on Mini's over the last 10 years so I'm familar with the mechanics of how they work.

As far as I see it I must be missing something REALLY obvious, I can find nothing of any help in the Haynes manual and have followed it to the letter (ish) with regards to rebuilding it (they're even more basic than SU carbs!). Has anyone got any ideas or suggestions cos I'm at a loss

Cheers

one miffed DJ

gary tompkins · 20-03-2005, 10:43 PM

DJ,
The only thing I can think of that you didn't mention was the actual float height settings. They would need to be a country mile out, but could cause the float bowl(s) to overfill and flood if they are set way too high.

Other than that I'm pretty stumped too

Pedro · 21-03-2005, 06:31 AM

DJ

it could be the float valves not shutting off properly. The little valve thing the float lifts as the carb fills - these tend to wear with age. Have a look at the end of the pin to see if it's worn - it only takes a small amount of wear to cause a leak. I had the same prob with my RD125, took ages to find it as they looked ok.

Ped

21-03-2005, 08:03 AM

The actual floats themselves don't have any kind of adjustment, they're solid plastic

I think I'm gonna have to replace the floats at worse, just seems wierd they were not leaking before and now don't stop.

Ho hum, was supposed to be easier to maintain than the Monster

DJ

21-03-2005, 10:03 AM

I seem to recall many years ago having a similar problem, it turned out that the floats could be fitted upside down which was not immediately obvious

Might be worth checking..........

gary tompkins · 21-03-2005, 03:50 PM

DJ,

You can adjust float height by bending the tab on the mounting bracket, that's the bit which sits against the bottom of the float needle. However if the carbs were not leaking before the strip, it could be (as Dave said) worth checking everythings in the right way up?

24-03-2005, 08:58 AM

I had a CB 125 TDc, same thing on one carb not both. The taper end on the valve seemed to be very delicate and I had to put a new one in because I just couldn't get the damn thing to seat properly.

24-03-2005, 09:24 AM

Well, I've ordered 2 new carb float needles from David Silver spares. See what happens when they arrive

Cheers all

DJ

20-03-2005, 10:32 PM	#1
Dark-Jon Guest Posts: n/a	Non Monster Carb problem Right, this is totally doing my nut in! I've got this Honda CB125TD-E, I've stripped and cleaned the carbs, done a few other jobs etc, and after re-assembling everything bar the side covers, turned the fuel tap back to 'on' ready to start her only to see fuel pouring out of the bottom of both carbs!!! Slight panic, turned the tap back to 'off' and it eventually stopped. Fine, checked stuff like the drain screw was fully done up, check, even let out more fuel by undoing it. Dismantled carbs to check float chamber, blew air through fuel line and lifted float, air stopped (got puffy cheeks etc ), re-assembled carbs and remounted, fuel on, more pouring of fuel. Off comes the carbs and again dismantled. Now, I can find NOTHING wrong with them. I have only cleaned them and dismantled the float assembly (the guy I got the bike from said one was sticking), I haven't touched either the main jet body or the pilot jet. The floats themselves aren't punctured or full of fuel and nothing seems to stick on the assembly. After that there's not much to adjust and I've done a static setup as per the Haynes manual. There's only one bit to attach the fuel pipe too so it's nothing THAT stupid and I've stripped and rebuilt lots of old SU carbs on Mini's over the last 10 years so I'm familar with the mechanics of how they work. As far as I see it I must be missing something REALLY obvious, I can find nothing of any help in the Haynes manual and have followed it to the letter (ish) with regards to rebuilding it (they're even more basic than SU carbs!). Has anyone got any ideas or suggestions cos I'm at a loss Cheers one miffed DJ

20-03-2005, 10:43 PM	#2
gary tompkins 1/2 man - 1/2 pogo-stick Join Date: Aug 2002 Location: Dartford, Kent Bike: M900ie Posts: 7,241	Bit of a long shot - but..... DJ, The only thing I can think of that you didn't mention was the actual float height settings. They would need to be a country mile out, but could cause the float bowl(s) to overfill and flood if they are set way too high. Other than that I'm pretty stumped too __________________ GT Fully paid up member of the S.A.S. (Scottoiler Appreciation Society) 27,000 miles on original chain - and still going strong!

21-03-2005, 06:31 AM	#3
Pedro Ciao, come stai? Join Date: Apr 2003 Location: Somewhere Bike: Multiple Monsters Posts: 4,157	DJ it could be the float valves not shutting off properly. The little valve thing the float lifts as the carb fills - these tend to wear with age. Have a look at the end of the pin to see if it's worn - it only takes a small amount of wear to cause a leak. I had the same prob with my RD125, took ages to find it as they looked ok. Ped __________________ M900 - 1993! Monster 1200R!

21-03-2005, 03:50 PM	#6
gary tompkins 1/2 man - 1/2 pogo-stick Join Date: Aug 2002 Location: Dartford, Kent Bike: M900ie Posts: 7,241	DJ, You can adjust float height by bending the tab on the mounting bracket, that's the bit which sits against the bottom of the float needle. However if the carbs were not leaking before the strip, it could be (as Dave said) worth checking everythings in the right way up? __________________ GT Fully paid up member of the S.A.S. (Scottoiler Appreciation Society) 27,000 miles on original chain - and still going strong!

24-03-2005, 08:58 AM	#7
Miki Guest Posts: n/a	Floats I had a CB 125 TDc, same thing on one carb not both. The taper end on the valve seemed to be very delicate and I had to put a new one in because I just couldn't get the damn thing to seat properly.

21-03-2005, 08:03 AM	#4
Dark-Jon Guest Posts: n/a	The actual floats themselves don't have any kind of adjustment, they're solid plastic I think I'm gonna have to replace the floats at worse, just seems wierd they were not leaking before and now don't stop. Ho hum, was supposed to be easier to maintain than the Monster DJ

21-03-2005, 10:03 AM	#5
Dave Pearson Guest Posts: n/a	I seem to recall many years ago having a similar problem, it turned out that the floats could be fitted upside down which was not immediately obvious Might be worth checking..........

24-03-2005, 09:24 AM	#8
Dark-Jon Guest Posts: n/a	Well, I've ordered 2 new carb float needles from David Silver spares. See what happens when they arrive Cheers all DJ