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Discussion in 'Suzuki 250cc In-line 4's' started by Alibongobingo, Mar 18, 2018.
Does the mixture screw affect the engine at WOT?
I had wondered, being a 'pilot' jet adjustment, what it would do at WOT.
So. The erratic idle is fixed. I had clip on the carb rubber come loose. I've replaced them all with new hose clips and have a good seal now. Idle is steady.
I've set the pilots to 1.25 turns out each and it seems to like it. It's smooth up through the revs and at WOT. (Probably because i fixed any air leaks)
Still. I'd like it if it just felt a bit more pokey. A go on a known 'good' example might set any fears to rest but on looking at the figures for the model, I feel some ponies have fled the stable. Perhaps not.. When the bike is registered and tested and road legal I'll run some timings and perhaps we can decide.
My gpx250 definitely felt livelier in the mid range though and that was only a twin. Very light though and admittedly i was somewhat lighter and a novice rider back then. Anything feels quick to a novice. Heck, my ZZR600 daily donkey feels slow to me some days and that's a 100bhp bike.
Are the front and rear sprocket teeth count stock? if so maybe drop the front a tooth or raise the rear by 2
Its all totally stock.
This bike actually belongs to my house mate. She's decided not to take up bike riding and just wants it sold. To that end I'm trying to get it running as best as it can stock to sell.
I would buy it off her myself and keep it as I am quiet fond of it, especially the smile factor chuckability, but I have to concede that it's just physically too small for 188cm, 100kg me.
Chug mode has returned. :/
Float height seems to only stop it from doing it as often, if i go too low it starves it of fuel altogether.
To recap. On acceleration it will suddenly die and drop to 2000rpm WOT. Letting the throttle off will stall it. It stays like this until the fuel is shut off and then after 30 secs or so it comes good.
I am still at a loss. The carbies are totally cleaned thoroughly. Needles and tubes all show no wear. I cannot fathom how this is possible. The float valves are not leaking etc...etc....etc ...!
Also the R/R has probably **** itself now as the light dims on revving and all the connections/earth etc are good.
I'm ready to throw the bike in the bin.
Beware of the assumption of the needles and tubes all show no wear at all - that misreading when I first encountered the same problem - the clearances are minuscule.
My needles didn't display any wear at all and it was impossible to discern emulsion tube wear
It is cases like this that are my incentive to do complete seal kits for carbs including throttle shaft seals. I have zero patience for chasing my tail. Rebuild the carbs once and once only. If you do part of the job you might get lucky and if you don't then you will never fix the bike because you think you have already done the carbs. Not aiming this at you specifically @Alibongobingo you are stuck between a rock and a hard place because it is not your bike and you are not free to spend the money you need to get it done. A 250cc four is a high strung complex machine and they are so old now that it is only those who love them that are willing to give them the attention they need. The learning to ride group are much better off buying a newer commuter model.
Sound's like it's flooding or the float height/fuel level is still to high, then when you turn the fuel off it come's good (when the float height / fuel level drop's)
I got a very similar thing happening to my 250 bandit @ WOT. Revs to 5-6k bogs out then drops & most of the time stalls.
Had my float heights at 12mm, 13mm & 14mm made very little difference. Brand new needles & had a full kit put through it. I've pulled the carbs at least 10/12 (lost track) times & about to run the bike into the wall. Doing my head in.
All up prob pulled the carbs at least 12 times.
Pretty sure it was a combination of a few things.
Wrong size jets. Pulled them all including the emulsion tubes & soaked then overnight.
Underneath the float valve needle on two of the carbs there is a little filter attached to a copper tube. There was very small stick like things actually underneath the filter blocking the flow of fuel. How the hell did they get there only god knows.
Anyway here are my current settings that have the bike purring like a kitten. ZERO hesitation all the way to redline 18k.
Float height 12mm exactly all 4 floats
1.75 turns out on air fuel mix all 4
Bench syncd eyeballed it & feels almost perfect. No hanging at all.
Pretty stoked at the moment.
Good work! That is one Bandit fixed. I think Mr Grey has a maxim that states something about carbs and 4 bangers.
I think its the first Bandit here ever to run 100%
I had the same thing with my Bandit. pulled carbs off, cleaned, adjusted, balanced.
Ended up being the fuel tap!
'For now' is the best you can get... tis the nature of the Mikuni BDST carb
Hahahaa, well it took me a month or probably more. Like having a second full time job.
Put some new plugs in today with exactly .7mm gap & took her for a 4hr ride. Pulled one to check the color & it was in the Perfect color air/fuel mix zone.
Boy what a pleasure these bikes are to ride when they actually run really well.
I strongly suggest changing the needles as well very important. I eyeballed the needles on the motorcyclespareswarehouse at identified these as the correct needles.
These guy's have just added "GSF250 Bandit 1990" to the list because I told them to.
I made up a makeshift seat leak checker for the carbs as well. I should probably start a thread with all this info that may help someone in the future.
Some of the Keyster needle's (needle and seat's) have a heavier rate spring in them i found, much harder than the original's