Flutter off the bottom

[damo1]

Right ive got the bike finally running on four cylinders after a lot of fucking around to find the problem.

It pulls quite strong and its a little hesitant in the top but i think it may be running a little rich up there.

But im cofused with off the bottom.

If you are off the throttle for any period of time after entering a turn say when you try pick the throttle up again its got a cough/flat spot be for it comes back to life.

Is this the needle that needs adjusting may be to lean it out a tad????

Or is it a pilot screw issue??????

[Seifer]

What was the initial problem out of interest?

[scotty]

^^^
would be easyer to diog.
Have you checked float hight

[Benz]

Have you checked the inlet rubbers for leaks??

[damo1]

The orig problem was what started as a dud plug i thought? but once id put a new one in and (Id checked the spark previous to putting it in)was only part of the prob.

I had spark and thought i had fuel but still nothing.

I pulled the carbs out removed float bowls and the mains there was nothing that i could see,i thought it may have been a blocked main.

i refitted the carbs and it fired straight on to four cylinders straight up.????????????

Its got pods and 130 mains and as far as im aware the rubbers are tight around the carbs so no leaks.

Its actually also got a
bit of a cough through the top at full throttle seems to get better as it heats up (gets better meaning starts to go away but not completely)

[Benz]

Is it backfiring on a trailing throttle? if it is that's a good clue you are running lean,[provided you have no leaks in the exhaust....] so 1/4 turn out on the pilots may help. Give the engine a handful,[free rev, on the side-stand] and listen for a backfire on the rundown.
Check to make sure you are not losing vacuum between the rubbers and the head by spraying soapy water around the rubbers, you should see the water disappear into the inlets if there's a problem there[I just went through all this with my bike]
If the problem improves when it gets warm, it may be running a little lean.
Is it hard to start when hot?
A dud plug is a common issue these days, new ones come from the factory as duds [been caught here myself], but it might also indicate you have too much fuel, but 130 mains are not too big, so it may be spark....have you checked to make sure you are getting good charge from the alternator??
It's a bastard that running lean, running rich, and bad spark all give similar faults.
Check the colour of your plugs, any difference will indicate which way to go, and make sure your battery is fully charged before testing anything.

[damo1]

Sorry for the delay ive been flat out.

Benz: Yes it back fires on a trailing throttle but i cant garentee that the exhaust is not leaking at the link between the collector and the can.

There is something that i have thought of after my orig post,is that the stubbie can i have on it now was not the one it was dynoed with.

Now its running a stubbie short very open gytr can right at the foot peg, orig it had a standard bandit system and end can.

So it will be breathing much better so im thinking taht it must be a lean problem.

What are your thoughts on that????????

[Bear]

Pilot jets effect the first opening of throttle. Mains come in later.

[Benz]

Take it back to the dyno..................

[damo1]

I dont what to take it to a dyno.

I want to try sort it out myself,yeah i hear what your saying but really they used to do it with out dynos years ago so its deffinately possible.

And i keep hearing all these negative things about dyno guys im not so sure its the best way to go.

[Benz]

Some shorty pipes can actually make the bike richer in the bottom end, and a very open pipe will give you a fat bottom end, and then stone wall up top.You may need to lean the pilots,[1/4 turn at a time, you should hear the bike's idle improve as you go] drop the needles one notch,[yes leaner] and then go larger mains, to give it more fuel up top, to match the pipes characteristics.
Try to get the first 5k revs or so right, then concentrate on the top end after.
The pilots DO make a difference to the whole rev range, just a lot less up top.
If that's not going to work, try restricting the exhaust a bit, you may find that's all that is needed.
Good luck mate, do one thing at a time, and test it before moving on.

[The Mad One]

Damo what happened ya mad f@cka [?]

[damo1]

Mate i havnt had a chance yet ive been flat out

[The Mad One]

Cool mate [8D] let me know PLZ.

[damo1]

No dramas i'll post as soon as i have done something.

[hyside]

Pilot jets for first part of the throttle.

[Jay_G]

if you don't wanna get it tuned on the dyno take it to them for a $30 power run and get em to graph the AFR's, it will tell you exactly where it is stuffing up

[damo1]

right ive finally had time to look at this and after talking to Mundy a while back ive started messing with the carbs.

So this is what i have so far

The plugs were really fowled and sooty so it was definatly running rich.

The fuel screws where out 4.5 turns so i wound them back in 1 turn.

The needle clips were right at the bottom of the needle meaning it was at it's richest so ive put them back to half way (five grooves back to groove three)which was dropping the needle down 2 grooves.

Ive put in another set of brand new plugs

Ive checked and double checked every thing so its at a point where its ready to fire up and see what happens.

im crossing fingers with this hopfully it will be a starting point to get it right.

So it reads like this

Fuel screw: 3.5 turns out

needle clip : Middle groove (with stepped needles)

Main :130

Any one got any other ideas before i get carried away.????

[damo1]

Right got it sorted.

After much conversation with verious people and also Exben.

I,ve ended up with this and it now pulls clean from right off idle right to the limiter.

Fuel screws : 2 3/4 turns out

needles : second groove from bottom

Main jet : 140

it now runs and idles sweet.

I,ve checked the imution tubes and the needles and there all sweet.

i'm goinmg to try some 142 mains as i know others are running these and i'm interested to see if they are going to give more pull through the top.

If not back to 140 s and its all sweet.

Thenks for the feed back .

Just proves with a little persistence, who needs a dyno;)

Thanks to Exben for drilling out my jets and also the knowledge he gave me on how to chase down the prob.:D

[damo1]

Righto ive been doing heaps of reseach on this and old school suzuki have a thread going at the moment on this.

And it seems that most are running 2.5-2.3/4 turns on fuel screws bottom groove on needles and 155 mains.

So i thought id go close to these and see what happened.

this is where im at now

2.3/4 turns on the fuel screw

bottom groove on the needle

150 main

This thing is now pulling like a train right from idle:D

There's no hicups no dips just pulls hard right through to red line right off idle.

I'm really happy with the results now so i have a base setting to come back to.

I'm going to try 155 mains like suggested on old school and see what happens.

I'm thinking that i may be at the biggest end of the mains though as this is a GSX engine not an GSXR

Just thought i'd let you know where i'm at.;)

So i'm still thinking that you dont need a dyno just your own time to nut things out.

This thing was apparently dyno'd and it ended up

4.5 turns out

bottom groove

130 main

interesting i recon that its so far out to where it's at now.

[Watto]

what size carbs ya runnin Damo?

[damo1]

36mm, ive got a set of 38's but i'm really happy with it at the moment so not interested in swapping them over.

[Watto]

cheers mate