Rubber plugs inside the carb?

[turbofb]

When I tore my carbs apart,I didnt see these at all.
If Im not mistaken,then go in the pilot fuel jet sockets?

Ive read plenty about them,but for the life of me I cant figure out why they would be there.Do the pilots feed through the plastic float assembely jets and the rubber plugs are just there to block off an unused circuit?
I also read that the mix will be excessively rich if they are left out,although my bike ran great without them.I only tore the carbs down as a precautionary measure,and I did clean a fair amount of red silt out of the bowls and got a filter inline on the fuel feed.

I do have a problem now of hitting an RPM  brick wall at 8K when WOT.Im gonna pull the slides and check things out,its gotta be something simple since I didnt change any jetting or needles sizes from before.....

[interfuse]

I've had lots of carb problems. But never that. If you didn't change any settings, my GUESS is:

a) You've either messed up your float setting (probably not likely at that RPM)
b) your o-rings are shot (maybe)
c) or you didn't seat the diaphram properly (quite possibly)
d) Still got the little o-rings up in the plastic carb hats? (I've never lost 'em but that could maybe cause that...)

Vauge I know, but so was your post. But that's where I'd start (on D and work backwards).

[turbofb]

Regardless of their condition,I am going to replace all the orings when I get back in there.They all looked OK,but Im not gonna chance it.
I could see possibly mis-seating a diaphram,but all 4 of them?When it hits 8K under WOT it acts like someone just turned the key off,its not just one or two cylinders acting up.....until I roll back on the throttle.Then it recovers a bit,but stil wont rev much past 8-9 without sounding really choppy.The plugs arent black,so Im guessing its starving for fuel,hence my belief that the slides arent lifting and allowing the main needles to meter fuel.

[interfuse]

Choppy at 8k is somthing I can work with. 8k is about where you start to notice it when you're running out of gas. Did you install an inline fuel filter? Is it allowing enough gas through? And I take it you've got a full tank of gas.

[gsxr400 racer]

some times when you clean carbs and ive seen people do it you take them off you dont drain them properly you turn them over let all the gas run out some goes up into the slides you do your business in the float bowl area and button them back up and fire up your bike next thing you know it wont rev up cause the slides are hydro locked with gas . Just a fyi

[turbofb]

Cant say for sure if the new filter is restricting the flow,but since its one of only two things I changed,Im definately gonna try removing it and running without.
The other thing I changed, was removing the airbox snorkle(no holes in the lid yet).....Ill be replacing that tommorow too when I dive back under the tank(which is full of fuel).

I get you about the hydro-locked slides,its unlikely in this case since I drained the carbs upon removal and did a full,100% tear down while they were dry. Good,   call though!

Tommorow's agenda.....
1.Solve this issue,
2.Sync carbs,
3.Attempt (again) to pull the rear cap of the Yosh muffler so I can repack that annoyingly loud SOB,
4.Keep shopping for an USD fork frontend.

[interfuse]

3.Attempt (again) to pull the rear cap of the Yosh muffler so I can repack that annoyingly loud SOB,

If you find something that works let me know. I've been meaning to re-pack my exhaust since I bought the bike. Definately damages my hearing.

4.Keep shopping for an USD fork frontend.

Another thing I've been doing for years. But haven't ever had the cash when a FE was available.

[turbofb]

Well.....this just goes to show how sensetive these little things are to changes.
For starters,I retained the new fuel filter but replaced the airbox snorkle.......all is well now . I also sync'ed the carbs,which werent too far off,but being dead on is a good feeling and the idle is smoother.
She still seems to fall a little flat after 12K,but that seems to be a common issue,and I havent actually confirmed that my jetting is ideal at this altitude(sea level).WOT revs now pull clean and smooth from 8K to 12K,with the aformentioned tapering of power above 12K.The frontend feels very light in 1st and 2nd,which is something my old FZR600 struggled to do.....FUN!

Cracking the cap off the Yosh seems damn near impossible.Even with all 4 screws off,pen. oil down the seam,and an 18" long nylon strap wrench on the outlet....it never even budged.
Getting an USD fork shouldnt be an issue,provided I dont blow my tax return on anything else.....just gotta wait for the right one to come alone.I almost grabbed an 05-06 GSXR 600/750 frontend,but they were more than 2" shorter than the stock B4 forks.Although Id rather stick to the newer stuff and deal with the technical install issues,I think Ill just settle for some early-mid 90's GSXR1000 forks.Thatll give me a straight bolt on set,and the longer tubes so I can put the clip-ons above the top tree....I kinda like the sit-up feel of this bike.

[turbofb]

To get the upper,topend-to-redline range to produce better power,whata'ya think about shimming the needles up a half notch?I dont have adjustables,so shims are my only option for the time being.

[interfuse]

Give it a shot. The bike should pull strong up to the redline. Seeing as you introduced more air into the equation and it wouldn't pull beyond 8k the bike is running lean. Has that bike been running stock jetting with that pipe?

[turbofb]

I figured it would be lean,seeing as how Im at sealevel and the big came from NH,which means it possibly came down from a higher altitude.I just didnt think itd be so close to the lean limit, that pulling the snorkle would cause such a bad reaction.
I have no idea if the needles or diaphram springs are stock,but all the main jets are 102.5's and the pilot screws were drilled and cranked out 5-6 turns by the PO.There are also allen screws on the bowls,which leads me to believe that some sort of jet kit was installed.Strange that they left the factory airbox and filter, after installing a full exhaust system and jet kit in the pusuit of HP.

I have some brandnew 105 and 107.5 jets from my old FZR600's FactoryPro jetkit.Wonder if itd be worth trying them out,even though Im still running non-adjustable(possibly stock) needles.....

[turbofb]

Took her out for a real ride this afternoon.

Man,these little things are fun!Gotta keep em' spinnin' fast to keep your rythm on a tight,twisty road.But that just makes the bike feel even more like a little racer.....and the sound dont hurt either.

Shes actually not too bad now,on the topend.I think I might not have been up to full temp yesterday, when I ran a couple simple drag runs down the expressway.Ill be investing in a temp gauge soon and possibly do more reseach into the hotter thermostat mod.
After some spirted use,she will pull well to redline with much less dip in the upper-topend power as before......that said,I still think theres more availible up there,and my plugs agree.While not blistered white,they are looking pretty clean,with just a little light gray ash.Definately not rich,thats for sure.

[stormi]

Rescued from the other board:

turbofb Posted: Tue Mar 20, 2007 11:01 pm    

Post subject: What exactly is the rubber plug for?    

Well,after 3 days of modding,adjusting and cleaning.I finally got to take my new B4 out for a spin.

The 06' GSXR shock works great,the backend feels planted and solid.The slight rise of the rearend makes the bike feel less like a full "situp" motorcycle,despite the fact I stil have the stock handlbars and frontend.

But........it looks like I didnt heed ya'lls warnings about how picky and finnicky the carbs can be.Although I did clean a fair amount of red silt out of the bowls(now has an inline filter too),I now have a topend problem.She absolutley refuses to rev above 8K no matter what I try.I checked and lubed all the orings on reassembely and kept all the adjustments where the previous owner had them....102.5 mains,non adjustable needles and 2 turns on the screws.

I have plenty of experience working on bike carbs,so instead of asking the standard "what do I do now?" question,Im gonna dig into them again and attack the re-rebuild systimatically and surgically with new parts and super attention to detail.My only real question is,what the hell are the rubber plugs over the pilot fuel jets for?
My carbs didnt have them at all when I tore them down,and the bike ran and revved fine before I tore into it (the standard 4-5K stumble was there,but it redlined no problem)

 

Bartjan Posted: Wed Mar 21, 2007 1:21 am    

my guess its so you wont brake the floater when reinserting it...

i know they can be a pain in the but when you drop them and try to find them on the floor Wink

 

Herr Tod Posted: Thu Mar 22, 2007 3:56 pm    
The pilot jet is fed through a passage from the main jet. The plugs are there to provide for a constant fuel metering. Not all Bandit / GSX-R 400 carbs have the plugs. You can tell by looking for the passage from the main jet, if it's there you need plugs, if it's not there you have to leave it open of course.

[turbofb]

Thank you very much,I almost forgot about my initial question too.

Course' its far too late to determine if I have the passages from the main jets or not,since my carbs are installed and the bike is running!......since it is running well without the plugs,I think Ill just assume that they are not there!

[interfuse]

Depending on how much you want to mess with it you could try going up on the MJ. See if it gives you anymore on the top end without effecting other areas. 102.5's were stock. All of the jet kits I've seen had adjustable needles.

FYI, Six turns out sounds like a lot on the fuel screw (most people run 2-2.5 turns out). But if its running something must be working. 3 turns out with a jet kit and I was fouling plugs so bad I had to remove the air filter to get home.