cold running prob

[banditv]

my wee 250v runs like a hairy dog when its cold.
it starts alright, needs a bit of choke for maybe 10 seconds and holding the revs at bout 6k until it gets some heat in the plugs and will rev reasonably cleanly.
the thing is it sounds like its only on 3 holes unless you crack the throttle to get it off the idle and progression ports and onto the mains.
also, until its running at an indicated 50 degrees C (trail tech vapor digital dash) it misses abit at cruise and 6k revs.
bare in mind, this is at air temps of less than 5 degrees C and when AT is below 0, it runs like a real bastard.
the engine temp wont get to 45 degrees on my 5 mile commute.
it might just be because its cold and not getting any heat into it, but even my older 91 gj73a ran better than this gj77a in same conditions.
and the gj73a used less gas. 260 km to reserve vs 220km.
mind the 73 was standard where the 77 has an aftermarket rear can.
any ideas?

[Chris H]

Sounds like one of the pilot jets may be slightly blocked, if you touch the exhaust down pipes with a damp cloth are they all steaming when on tick over?

[banditv]

well last night i pulled the carbs off so i could take them to work and give them a good clean out. pulled the tops off them and found one has had the diaphram caught up in the top and is all crushed in one spot, bout 1/2 inch long. that wont help the running and would prob explain why it sounds like its missing slightly at times.
also found that the o rings under the balancing ports were missing on 2 carbs.
i dont know where the factory  setting for the needles are , but they are all in the middle slot out of 5. is that stock position?
also, the idle screws were 2 turns out from lightly seated. am guessing thats about stock.
should have a new diaphram this week and have some o rings at work that are the right size.
was a little bit of crap in the float bowls that could have blocked an idle port a bit.
does anyone know the float level for these bikes?

[canyonbreeze]

On the 400 at least the stock needles don't have slots, so there is no stock setting.  The slotted needles in mine are from a carb kit.

I set my floats at 15mm.  Rule of thumb is that they are aligned with the bowl mating edge.

[banditv]

after cleaning the carbs so well, they are better than new and reassembling them, i have found that the only slide that moves smoothly from rest to top and back to rest, is the one i've just put a new diaphram  in. looks as the original ones have gone stiff over 16 years and am going to have to replace the other 3. but at $53 a pop at suzuki, it'll take me 2 months of fuel savings to pay for the bloody things. am thinking the old diaphrams wouldnt have helped the running probs.
the temp of the carbs would have been well below 0 with the weather i've been riding lately which would have made things worse.
and the float levels are a bit high, bout 12 to 13 mm. will reset to 14-15mm before i put them back on.
will keep informed.

[canyonbreeze]

I bought a complete set of 4 carbs off ebay a while back for $60.  Had one rusted butterfly valve but all other parts were good.  When I rebuilt my carbs I used parts from those.  Worth looking into.

[banditv]

second hand carbs for theses things are few and far between down here eh, otherwise i would look for a spare set.
decided that since i've put one new diaphram in, i may as well do the lot of them to keep them all the same.
on the plus side, i asked a bike mag a question bout fitting rgv forks and rear shock, they said not to bother but to revalve what i have.
was abit disappointed bout the reply, but won  4 liters of silkolene pro 4 10w40 race fully synthetic oil, a can of silkolene chain lube and some silkolene penetrating spray. not bad for asking a question eh!
am still keeping an eye out for some gixxer or rgv suspension tho

[banditv]

well, got all the diaphrams in, floats set and carbs back on the bike and think i found the cause of the miss at cruise.
at some time in its life i think some one has put on a new choke cable which is to short, so the choke is always bout 1/4 to 1/3 on, rich mixture miss fire anyone?
with a bit of tweaking of the linkage i,ve got them all to shut off properly.
tomorrow night will be the acid test when i see how she runs.

[banditv]

well after having to take the carbs off again to replace the leaking float bowl gaskets , i finally went for a wee ride tonight.
starts well and revs pretty cleanly apart from a bit of a hiccup around 7k then it cleans up and pulls well to 16500rpm.
heats up far quicker now its not rich as all hell.
am thinking the hiccup is just due to brand new soft diaphrams causing the slides to open a bit to fast and its getting to rich for a wee moment until the airflow catches up with it.
will take it for a longer ride tomorrow and see how it is at cruise and how it is in the high revs in taller gears

[canyonbreeze]

16500?

[banditv]

yeah 16500, is only a 250, although they redline at 15000 they still pull pretty well past that.
they still have the older gj73 250 bottom end, which was a 17000 redline, just have a different head for the variable valve timing.
put gsxr 250 cams in the earlier, non vvt motor and they are good for 19000.
have miss shifted the 1 - 2 shift and got neutral and hit 18500 with no ill effects.
but anyhoo, just got back from quick 15km squirt and apart from seeming to be a bit rich at cruise but still pulls clean as when you crack the throttle.
i did give the idle mixture screws an extra 1/8 turn out which would prob cause that.
but then again, the bike wasnt running right when i bought it so it might just be running right now
starts from cold first touch of the starter and runs spot on apart from being a bit lumpy( sounds like its on 3 holes still) and blowing just the slightest whiff of black smoke when giving it a rev at standstill.
from 60kmh in top, open the tube to bout 1/2 throttle and the back end drops and it just keeps on pulling til lose the license speeds

[banditv]

just found out some interesting info on the 95 and later 250's
in 95 the jap govt said screw the 40 hp limit and they all went back to 45hp.
and the rev limiter is at 18,000 rpm.

[banditv]

well after much screwing around and replacing carb bits, i think i have finally got the bandit running right.
after i replaced the diaphrams, set the float levels right, put new float bowl gaskets in and put it all back together, it developed a cold start problem.
it would cough and die with full choke/part choke and no choke with no throttle.
wouldnt even think bout starting with any throttle at all, even a whiff.
after bout 2 minutes of trying, it would start to run roughly on 2 cylinders and then the rest would catch up and it would run ok until it warmed up when it would run great.
so, i went to my dealership and ran through everything with the head mechanic and decided to replace the last seals left, the wee o rings under the carb tops and while i was in there i lifted the needles 1 slot.
put it back together tonight after 3 days of not running, gave it full choke, thumbed the starter and she hooked up straight away on all 4 and revd up nice and smoothly.
after 15 seconds of choke, let the choke out and it idled nice and even ( for a suzuki ) straight off.
went for a ride.
it is a new bike! pulls nice and smooth even from 4k in 6th gear, no flat spots at all, has better mid range pull ( 5k to 10k rpm ) and screams right to 15000rpm .
no hunting or missing at a steady 35mph in 6th
the true test for the cold start prob will be in the morning since we are forecast for 3 degrees C

[banditv]

had a win on the cold start prob. starts like a dream.
but a fail on the coldweather running prob.
have decided that the 250 didnt like me raising the needles and it started to foul the plugs this morning.
have put it down to the morning being to cold and it just got to rich, since at the same engine temp but higher air temp it ran just fine.
have put the needles back to the middle position so will try it again tomorrow.
after talking to the suzuki mechanic, the cold start problem is a fairly common issue in the more southern parts of new zealand . he has put entire new sets of carbs, complete new ignition systems on some of these and it hasnt fixed the problem.

[interfuse]

It also gets pretty cold here. When it's below freezing the bike can take a while to warm up. Sometimes I have to let it idle with the choke on for 5 mins and then drive with the choke for another bit before the bike is warm enough to run.