1200 Bandit Carb Mod problem

[1340banditpaul]

Hi all, I'm after some more help & advice if anyone can help?? (and sorry for the long post but wanted to get as much info in as I could).

I've got a standard MK1 97 1200 bandit, that I've done the 'Krazy Ed carb mod' on, 127.5 mains, 35 pilots, shimmed needles, pilots 3 turns out, float heights 14.5 & a 2" hole in the airbox. (It had a free flowing race can & K&N panel filter already on it).

I've done a few of these in the past with good results, till now :-(

On the first test ride it was running good everywhere with improved performance over stock, apart from a bad stuttering between 2k to 3k revs and you couldn't ride at 30mph without it stuttering (chugging along), but it was fine when you opened the throttle and gave it some, lifting the front wheel in first and second off the power no problem and reving/pulling all the way upto the red line. I tried everything, different settings on the carbs but couldn't get rid of the low down stutter (I changed float levels, pilot screw turns & even taped the 2" hole back up).

I noticed a couple of the emulsion tubes looked slightly egg shaped (but only slightly) so I changed them anyway for new genuine Suzuki ones and it was a totally different ride. The stutter was more or less gone & you could actually now ride at 30mph when needed without the dreaded stutter, but now I have a new problem that I'm wondering if anyone can help with??

At standstill, in neutral if you rev the bike it now wont rev cleanly past 3k revs without coughing & spluttering upto about 5k revs and then its ok upto the red line, so 3k to 5k it coughs & splutters but everywhere else its fine inc on tick over.

Also when riding it @ full throttle it seems a bit flat/hesitant between 2k to 3k but then takes off and is ok everywhere else.

I've tried going less than 3 turns on the pilot screws to 2 1/2 turns but it then wont tick over properly, with the revs hunting up and down, from 500rpm to 1.5k rpm. (@ 3 turns the revs are steady @ 1k rpm).

When you blip the throttle, the revs don't hang and they don't drop below the tick over either and it doesn't seem to get better or worse as it warms up, the carbs are also spotless inside.

I've checked the plugs and they look OK (a bit rich if anything) and the outlet on the end can is slightly sooty but not really bad. So I'm thinking its running a bit rich if anything but it doesn't like me leaning the mixture and turning the pilot screw in, so that's threw me abit and now I'm lost :-( .

Could it be float heights are wrong or would the needle heights affect this part of the running (thinking needles are more mid range)?

Before I start stripping the carbs and changing things I'm after some of your knowledge and input to maybe point me in the right direction again ..........

Thanks in advance :-)

[wraith]

Carb tuning, we all love it 

One thing at a time, have you still got the extra holes in the air box still block off? 

1-3rpm pilot jets

3-6rpm needles

6+ rpm main jets

Flot height should be 14.5 mm all the time.

Hope this helps but sounds like you have a idea of what your doing.

[TonyGee]

try dropping the needles slightly. 

[1340banditpaul]

9 hours ago, wraith said:

Carb tuning, we all love it 

One thing at a time, have you still got the extra holes in the air box still block off? 

1-3rpm pilot jets

3-6rpm needles

6+ rpm main jets

Flot height should be 14.5 mm all the time.

Hope this helps but sounds like you have a idea of what your doing.

Yes, the 2" hole is still in the box and I've not blanked it off.

The thing that's got me lost is the coughing and spluttering in neutral more than the flat spot when riding.

Think I'll try and tape over the hole and try that, then if no luck, I'll try dropping the needle a notch.

Thanks for the reply and I'll report back if I find the problem.

[wraith]

Check your spark plugs, may of got suted up and not giving a good spark 

[Nick]

1 hour ago, wraith said:

Check your spark plugs, may of got suted up and not giving a good spark 

This.  Try new plugs - not iridium ones, either.  Getting jetting right seems to kill plugs in my experience...

[1340banditpaul]

Right, I've just blocked 1 of the 2" holes up and tried it again. 

It's not coughing and spluttering in neutral when you rev it any more and doesn't seem as bad when riding (i cant quite tell if its 100% right), so I'm taking it that it was too lean.

Now, should I strip it all down again, check float heights, try the bigger standard pilot jets back in it and un block the hole again or just leave it as it is?

I'm thinking even though the 'Krazy Ed' mod says smaller pilot's, could for some reason they be making it too lean?

I'm getting fed up of stripping the carbs and I've never had this problem when doing the carbs on bandits before.

Thanks for all your advice.

[imago]

Just to back this up a touch, how was the bike running before you did the mods? Also, did you give the carbs a go through a heated ultrasonic cleaner before you built them back up?

What I'm getting at is are you chasing a problem after doing the mods that may have been present before but is now much more noticeable with the changes you've made.

[1340banditpaul]

48 minutes ago, imago said:

Just to back this up a touch, how was the bike running before you did the mods? Also, did you give the carbs a go through a heated ultrasonic cleaner before you built them back up?

What I'm getting at is are you chasing a problem after doing the mods that may have been present before but is now much more noticeable with the changes you've made.

The bike was running OK before I started (I know, why touch if its ok) and I haven't got an ultrasonic cleaner at the moment but did give them a thourgh clean.

I've just tried the standard pilot's back in it and un-blocked the hole and it was bad again, so I've blocked the hole back up and it's OK, so gonna leave it like this and just mark this bandit down as a temperamental one and leave it alone.

Thanks everyone for all your help.

[imago]

7 minutes ago, 1340banditpaul said:

The bike was running OK before I started (I know, why touch if its ok) and I haven't got an ultrasonic cleaner at the moment but did give them a thourgh clean.

I've just tried the standard pilot's back in it and un-blocked the hole and it was bad again, so I've blocked the hole back up and it's OK, so gonna leave it like this and just mark this bandit down as a temperamental one and leave it alone.

Thanks everyone for all your help.

The reason I mentioned the ultrasonic cleaning is that with the extra air coming in through the hole the new jets etc are supposed to increase the fuel to suit. If one or more drillings has crap/fuel varnish in it then that will restrict the fuel flow so the new jets aren't making any difference.

 

[Ted M]

Can you confirm the carbs you are running. If they’re from the Mk 1 bandit then 3 turns out is too much they should be 1 3/4 turns out. The Mk 2 carbs are 3 turns out. If you need 3 turns on the Mk 1 carbs then your problem is in the pilot circuit either it’s blocked or you need a bigger jet