GN250 running too rich?

[globe]

OK, I'm getting frustrated now. Its still dripping from the carb overflow, have raised the float height a couple of times now (and tested with the bowl off running fuel from a funnel). I have taken the little fuel needle that is attached to the float apart and "lengthened" the spring as it didn't seem to be that stiff.

Not sure where to from here, I am assuming there are no 'o' rings missing from the fuel needle thingy (there isn't one on there).

Any thoughts/suggestions (before I take to it with a hammer)? Cheers

[Akzle]

OK, I'm getting frustrated now. Its still dripping from the carb overflow, have raised the float height a couple of times now (and tested with the bowl off running fuel from a funnel). I have taken the little fuel needle that is attached to the float apart and "lengthened" the spring as it didn't seem to be that stiff.

Not sure where to from here, I am assuming there are no 'o' rings missing from the fuel needle thingy (there isn't one on there).

Any thoughts/suggestions (before I take to it with a hammer)? Cheers

take your float out and chuck it in a bucket of petrol and see if it does... float

[globe]

take your float out and chuck it in a bucket of petrol and see if it does... float

I’ll give this a go but not convinced it’s the issue, it’s only started doing this following ,me giving the carb a good clean, but hey good suggestion, I’ll check it out

[Akzle]

wait you say raised the float height twice... like letting more fuel in?
or raised as in it sits higher when the carb is upside down

[globe]

wait you say raised the float height twice... like letting more fuel in?
or raised as in it sits higher when the carb is upside down

Yeah sorry that wasn’t very clear. I adjusted th float so that it shuts of the fuel earlier.

[oldiebutagoody]

If your carb leaks at standstill you have either a fuel tap that is not shutting off properly, or a fuel tap that does not shut off properly in combination with a leaking float valve needle. Either way the float needle is the more immediate problem. It will cause too much fuel to be in the system at any given time and make it run rich. Trying to tune this out of the carb will end up with you chasing your tail as nothing will be ideal in all of the operation ranges.

Float needles have a rubber tip (rubber goes hard with age/heat/solvent exposure/time) which is supposed to be pushed up by the floats when fuel fills the bowl. If the float level is not set to (whatever the manual states) ....it will either starve or flood. If in combination with incorrectly set float level you have a float needle that has gone hard, or is binding in its housing then you get heavy fouling of the spark plug.

Simplest and least frustrating remedy is order replacement float jet/needle assembly (buy OEM and forget EBAY/TardMe), reset float level to factory spec, throw away the plug and insert new one. Honestly its not a lot of money, probably less $$$ than you have poured down the drain in fuel wastage.

Ask me how I know this..............

Things wear and need replacing with age (mechanical things also). A GN250 is not a complicated machine, get a manual or download one off t'internet, google search terms like " GN250 running rich, carb leaking fuel"

[globe]

If your carb leaks at standstill you have either a fuel tap that is not shutting off properly, or a fuel tap that does not shut off properly in combination with a leaking float valve needle. Either way the float needle is the more immediate problem. It will cause too much fuel to be in the system at any given time and make it run rich. Trying to tune this out of the carb will end up with you chasing your tail as nothing will be ideal in all of the operation ranges.

Float needles have a rubber tip (rubber goes hard with age/heat/solvent exposure/time) which is supposed to be pushed up by the floats when fuel fills the bowl. If the float level is not set to (whatever the manual states) ....it will either starve or flood. If in combination with incorrectly set float level you have a float needle that has gone hard, or is binding in its housing then you get heavy fouling of the spark plug.

Simplest and least frustrating remedy is order replacement float jet/needle assembly (buy OEM and forget EBAY/TardMe), reset float level to factory spec, throw away the plug and insert new one. Honestly its not a lot of money, probably less $$$ than you have poured down the drain in fuel wastage.

Ask me how I know this..............

Things wear and need replacing with age (mechanical things also). A GN250 is not a complicated machine, get a manual or download one off t'internet, google search terms like " GN250 running rich, carb leaking fuel"

Cheers, did as you suggested and will get replacement needle. As for the float height may be more tricky, it’s a frankenbike so non standard carb. It’s got TK stamped on the side but finding one that matches on the web is proving to be troublesome, but yes new float needle to begin.

Anyone know of any TK carb suppliers in AKL (preferably the shore but not essential) where I might be able to take it in to get it ID’d. Cheers

[oldiebutagoody]

Cheers, did as you suggested and will get replacement needle. As for the float height may be more tricky, it’s a frankenbike so non standard carb. It’s got TK stamped on the side but finding one that matches on the web is proving to be troublesome, but yes new float needle to begin.

Anyone know of any TK carb suppliers in AKL (preferably the shore but not essential) where I might be able to take it in to get it ID’d. Cheers

Here's a thought..........try Bike Busters wreckers in Ngaruawahia to see if there is a GN250 standard carb you can put on it.

My bad, I hadn't read entire thread and jumped in not realizing you have non standard parts.

I ran a GN250 as a courier bike many many years ago when I first started. Hard to think of a more reliable trouble free model

[globe]

So I am going to keep musing on this thread as i am sure at some point in the future some other forum rat will come across the same issue, sharing is caring so I'm told.

Took the carb apart again this morning after watching Andy Mechanics excellent youtube video last night on carb leaks. I had a look at the o ring around the fuel needle housing thingy. It slipped in and out easily suggesting there wasnt a tight fit between the o ring and the casting so i took it off and yes its as brittle as thousand year old toffee. Will replace this week and see if that stops the dripping from the carb.

Doesn't help that I jumped to float level as being the cause of the leak so now it is all over the show so need to reset that. Emailed a supplier of TK carbs in the UK, he tells me the carb is (surprise surprise) non-original and some Chinese version so no float height data (that he has sent me yet). So I will try and set the float level a few mm's below the gasket level (which will be about 7-10mm below the overflow) and see where to from there. I understand using a clear tube off the overflow outlet is the best approach to this, unless there are some other suggestions.

Andy, if you read this forum, that float height video you talked about would be really really useful right about now mate

[Autech]

Good idea, however.....yup......it is no longer in my possession.....bugger

yeah i know dumb move

I don't think its a mikuni, I think the previous owner must've out an aftermarket on it - no ID that I can see from anywhere.
By bogging, I mean it slows down has not guts even with the throttle out - presuming this is the international definition of bogging, then is this an indication of running to rich still?
The odd thing is when it is up on it stand and idling away nothing appears too untoward, still get it stalling every now and again when I twist the throttle but nothing like it was before the clean.

The throttle cable adjustment feels OK but I can loosen it off a bit to see if that makes any difference (why do you think that would affect this, or is it one of those odd things that can't be explained but sometimes do).

Will have a look at the throttle slide over the weekend.

Cheers

Cheers, did as you suggested and will get replacement needle. As for the float height may be more tricky, it’s a frankenbike so non standard carb. It’s got TK stamped on the side but finding one that matches on the web is proving to be troublesome, but yes new float needle to begin.

Anyone know of any TK carb suppliers in AKL (preferably the shore but not essential) where I might be able to take it in to get it ID’d. Cheers

Hey mate I have a few standard carbs in the garage if you want to try them. Located in Otorohanga but I'm up in Auckland from time to time. Also have a stock pipe but with the baffle knocked out.

[globe]

Hey mate I have a few standard carbs in the garage if you want to try them. Located in Otorohanga but I'm up in Auckland from time to time. Also have a stock pipe but with the baffle knocked out.

Cheers mate, I'm going to give the O ring upgrade (LOL) and adjust the float again if not i'll be knocking on your door for sure. I often head through Otorohanga in winter heading backwards and forwards between the mountain so that may work out too, cheers I'll send you a PM

[Akzle]

, sharing is caring so I'm told.

not gonorrhea

[globe]

So after a bit of a break from the mighty GN, back into it.

Did a bit of research and it looked as though the white plastic washer on the needle goes below the e clip accorded to the parts cats. Swapped it over this morning and it ran fine through to half throttle then nothing, No acceleration just sat there. Occasionally it made a low popping sound but generally nothing until i backed off the throttle, then fine again. Did a plug chop (on the stand albeit) at WOT and it came out black so that suggests running rich in the top end. What I don't understand though is that moving the needle up (by swapping over the plastic washer thats about 2-3mm thick) richens it up considerably and this eliminated the flat spot at 1/4 throttle I had before I moved this. Hows that work? Is this suggesting lean out the main needle or jet and get a bigger pilot jet?

HT lead and coil are fine as I have replaced them.



Thinking of getting a new (wrecker) original carb, or sending it to a mechanic, sigh....

[globe]

The really frustrating thing is that it was running fine before I cleaned the carb even if it was stalling now and again at idle when warm.....so the jets mustve been ok at some point, maybe I damaged something when cleaning it?

[globe]

The other odd thing is that I can't make the engine stumble with the a/f screw when turning in (leaning as it is on engine side) but can when I wind it out to about 3 turns