Running on 3 cylinders | 96 FZR 1000

[noodlemonkey]

Right - That time again - Update time,

So after dropping the slide needles to the highest point and upping the main jet to 128's for all the carbs - We start making progress,

Cylinder no.3 was still intermittent but managed to sort that out by leaning the mixture out on the mixture screw and it seems to be alright now,

But sadly testing came to an end after carb no.2 developed an overflow - why - I dont know - will check it out and see whats happening.

Whilst the bike was running it did become more responsive to throttle movements - but I have a question.

Without the EXUP valve - will off idle revving be a bit slower than normal? the revs dont whip and once it rev's - the rev's dont fall like a rock - they gradually drop - quick enough, but not fast enough compared to when I had the Keihin Flat slides on there - anyone care to shed some light

Thanks once again in advance.

[Stig]

Are you running the standard headers but without the valve installed or an aftermarket set without the valve chamber?

Have you also tried disconnecting the throttle cables and blipping the carbs manually?

[Jordan_Ciaramitaro]

Mine has been the same way with both sets of carbs with or without exup.

Also, my ordinal carbs wanted to overflow when using the recommended float height. I also had one carb that needed the float height significantly different than the others. I confirmed the fuel level was the same by using a clear piece of tubing on the drain to confirm fuel level.

I just confirmed this week much of my hanging throttle is due to the cables. Not sure if it that was the case with the old carbs and cables though.

[Stig]

carbs with or without exup.

Only thing is there's a huge difference in jetting and settings for the 2 different options. The factory headers without the Exup valve installed will leave a massive hole in the power curve that you can't jet around. It'll also be flat as hell before the engine comes on cam at around 6K... Then it'll take off like a scalded cat. You'll also lose out on all the low down torque that these bikes are known for

Aftermarket pipes were never designed to have the valve so run better low down but with less torque than a fully working Exup set of headers BUT they'll give the top end rush which folks who use them on track seek outright power and top speed.

Jetting for the 2 different scenarios is planets apart

If the standard carbs are overflowing at 14mm float heights then there's issues with the carbs.... Either dirt in there somewhere or worn parts

[Jordan_Ciaramitaro]

Stigs explanation is exactly how my bike ran before. Felt like severe turbo lag.

[djalbin]

upping the main jet to 128's for all the carbs

In case you're interested, the stock main jet sizes are 125 for cylinders 1 and 4, 122.5 for cylinders 2 and 3.
.

[noodlemonkey]

upping the main jet to 128's for all the carbs

In case you're interested, the stock main jet sizes are 125 for cylinders 1 and 4, 122.5 for cylinders 2 and 3.
.

Thank you. Although these are the only bigger jets I have but will jet down once the bike is running some what alright.

Onwards towards an update.

After resetting the floats once again and checking the everything and cleaning with a compressor this time. The bike starts and runs better. Although it was shortly lived by cylinder no.2 dying due to a bad plug. Oh and then ran out of testing fuel. So I will check again tomorrow.

Quick question - if I check the diaphragm slides and I slowly rev the bike. They don't all lift at the same time and they isolate quite quickly. Anyone see any issues with that? Or should they lift smoothly and all together. Keeping in mind I'm only revving to roughly 3k.

Thanks in advance.

[Jordan_Ciaramitaro]

I would also like to hear feedback about the slide movement. Mine do not move in unison either, but on the Ducati they do.

[DonTZ125]

They should lift together.

[noodlemonkey]

Right ladies and gentlemen. It's update time.

Okay. So I've had a friend which knows his stuff when it comes to bike have a look at my carbs to find that pretty much all the rubber orings are flat and shot. So I purchased a oring pack from our local auto parts store which we're about to fit and find out what happens.

All the carbs where dumping fuel in excessive amounts causing the bike to do strange things.

Hold thumbs we make progress.

[noodlemonkey]

Hi All,

Some more on the update,

Recently we were able to find out that the carbs were dumping fuel from between the carb body and the plastic emulsion tube carrier - not entirely sure how thats possible as i replaced the o-ring a few weeks back, none-the-less, I've purchased a rebuilt kit for the carbs from a local company which should arrive tomorrow,

It wasn't to bad on price as a full kit which includes float needle and all needed gaskets/rubbers is ZAR225 per carb (roughly $16.00) - if need be, i might get new emulsion tubes and needles - but lets first rebuild the carbs,

Anyone else experienced carb dumping fuel from between the carb body and plastic emulsion tube carrier,

Thanks

[Jordan_Ciaramitaro]

Yep, I believe it's a common problem with this carb even on other manufactures bikes.

[noodlemonkey]

Just as a good source for carb rebuilding - http://www.litetek.co/Guide_MikuniBDST_Rebuild.html

[noodlemonkey]

So I managed to find out why my carbs are dumping mass amounts of fuel,

See in this image - there is a choke outlet/inlet hole - Its been pumping fuel from there with or without the choke pulled which has lead to fuel running down the sides of the plastic emulsion tube carriers,



Can someone please clarify if any liquid should be coming from that hole - I'm not even sure what its purpose is,

TIA

[Stig]

Doesn't that hole feed the toob that pressurises the float bowl to force fuel up the jet into the Venturi?