yamaha slider idles fine needs 1cm of choke to run

i have a yamaha slider idles fine all day but when accelerating it bogs down after 30 seconds, if i leave 1cm of manual choke open it runs but progressively richer. If im going 30 mph straight and i turn choke off it slowly dies, but comming to a stop it will idle perfectly. Dont know if the bogging is too much rich mixture or lean.

 

previous owner had left gas in for 3 months, i prob should have to strip it down, the choke lever is on the handle bar but i cant see how it effects the carb or where it goes in

 

ok so.

if bike runs only with choke on theres a number of spots to check.

carb inlet hose leading to engine, check its sealed and tight and has no rips / cuts/tears
Blocked airfilter, remove air filter cover and check the state of the foam inner if its thick with dirt and crap its causing a rich fuel flow.
blocked main jet.

have you fitted a new filter foam ? if so its possible old owner had a problem and adjusted idle needle to get it to hold idle. if you replaced the foam filter its possible the idle screw is adjusted to far out.

another area is mixture screw possible your running way to lean/rich so check this is set correctly to.

 

Thanks for reply

I've taken filter out a few times it's pretty clean and has been oiled

I bought some carb intake spray and shot some into the snorkel while reving

This did make acceleration more responsive

I noticed that on long stretch I can close choke and at full throttle will not bog but if close throttle it bogs

Presumably the idle needle only has jab to do at idle as it does idle and idle screw does allow it to go up and down

The air mix is something I'm testing but doesn't make much difference

Seems idle needle is good and exhaust manifold tight as doesn't change revs when spraying

Just seems odd the small extra fuel from choke makes all the difference must be from the point the idle part hands over to the jets

 

have you had the throttle slide out and unasembled. it could be your slide needle setting wants a tiny bit of adjustment .

yes idle screw goes through throttle body and rests in a little space in the slide area on carb, the throttle slide has a ramped area, when the screw is tightened up this pushes against the ramp on the slide pushing the slide up, screw out the needle the throttle slide slips down.

 

I started from assuming nothing so screwed the fuel screw all the way in, I had turned it five times out thinking it needed more air the the mix, then screwed out two turns ran bike on long stretch turning choke off seems the full throttle main jet is ok so turned the screw in half a turn and now it can pull off without choke but will need to fine tune for mid range. When running with choke it was prob flooding spark after running at main and I was thinking it needed more air so was turning fuel screw out. Now it also doesn't belch 2 stroke smoke at the lights

 

go careful buddy dont wanna run her to lean.
a bit of smoke is a good thing on a twostroke.

from a 1/4 to 3/4 throttle range your going to need to pull out the throttle slide this is where we tune mid range from.

so first off its best to set the needle to its richest position , remove the slide from the cable and you will see inside the slide a little clip holding the needle in place, pop out this clip and extract the needle. now on some carbs the needle is a fixed point ie non adjustable. but most needles will have either three or four grooved rings around the top of it and a little C clip

Bottom grooved ring is max richness
middle grooved ring is medium richness
top grove is lean richness.

your going to set the needle to its most richest so the very bottom grooved ring. having the scooter so its back wheel is well off the floor your going to start the bike and listen to the motors tune and throttle response. if it splutters a lot and/or struggles to gain rpm and has a flat tone or dull tone its to rich. if it boggs down with a funny like bwaahhhh sound your to lean if you started out in the richest position you may need to swap out to a different needle. keep adjusting this needle setting till you have no spulttering / bogging down or hanging of rpms.

your not done yet though !! , now you need to find a place where you can test this tune , do not ride the roads keep yourself safe so pop to a carpark area have a ride around using 1/4 to 3/4 throttle range and listen to the motor tone and any symtoms from running to rich or lean as above. roll onto the throttle and also hold it at certain areas and see how the motor reacts , if your happy your not finished just yet !! ( remember running a little rich is a good thing.

once the aboves done you need to set the idle again you may need to adjust the idle and the mixture setting to for that low down below 1/4 throttle setting ( below 1/4 throttle is the mixture and idle screws on carb )

a little spluttering is ok on a twostroke it shows its running a little rich and thats always good , better that melting the piston crown or running super hot on the motor , on a fourstroke there should be NO SPLUTTERING

 

fixed needle mod ( richen only you cannot lean out a fixed needle )

some needles have just one ring where the C clip fits so its not adjustable but you can adjust it using a couple of added extras at a very small cost.
first off you need a Oring that will fit over the needles upper top section the widest part and a couple thin small ID washers.

remove the fixed needle and slide on a small washer onto the bottom of the needle and slide it upto the C-clip, next slide on the rubber o ring to hold this extra washer in place. you can now insert the needle back into the carb slider and re-assemble the throttle into the carb body.
you have adjusted the needle to now be a little more richer between 1/4 and 3/4 throttle range.
if you find the setting still a little to lean you can add a second washer under the first washer remembering to keep them inplace with the rubber Oring .

if your doing this mod its best to test scooter/bike NOT ON a populated road, somewhere like a disused/closed road or a carpark, you need to be sure this mod does not hinder throttle closing off when you roll of the throttle. so it needs to be tested all the way through the throttle range a good few times to be sure the throttle will not jam wide open and you have a runnaway on your hands.

The above mod is AT YOUR OWN RISK, and myself or scooter shack cannot be held at fault for any damage to yourself or your machine

 

thanks for the info found this vid showing variable settings

 

yeah buddy thats an adjustable needle . when you get into race tuning and likes you change the whole needle out, but for just making 1/3-3/4 throttle a bit richer you can just move that C-clip down to the bottom ring.