MadMax's Carb headache

[madmax-im]

Originally posted by randy
Alan,

based on your set-up, I'd suggest that you:

Get rid of the stage II kit, go back to stock jet type. Your stock jets were 112.5, so with the 4-1 and the K&N, go up 2 sizes to 117.5.

Make sure your floats are set correctly, refer to the manual, I don't know the setting for your 82XJ.

That should get you to a starting point.

Synchronize the carbs and final idle and transition adjustment can be made with the pilot screws.

Randy,are you relating this to my experiences or Alan's?You adressed it to him but iit sounds like u r taliking abt my setup...

[AlanB]

Hi Max,

I think you are right; Randy's post has the wrong name at the top...... However, most of the rest is pretty good!

If the bike went better on the previous set-up, I would think seriously about going back to it....or at least, back towards it.

I have seldom driven ANY bike with individual filters and old-style CV carbs which was overall better than stock (That should shake 'em up!) The way that the slide in a CV carb (like the XS!) lifts is largely controlled by the flow restriction of the airbox; no restriction, and the slides do not lift until high revs. If the slides stay closed, power is pretty limited!

The classic symptom is no power at lower revs ('cos the slides don't lift), then a big bang at high revs as the slides pop open. feels like big power, but on the dyno, it is usually less than stock, it is just a lot more dramatic because it arrives in a rush....... Anyone else with individual filters recognise that scene?

I know that other members have had different experiences, and some LOVE their cone filters..... but that is not my experience, and I calls it as I sees it.

I am not alone with this mod; there are a few bikes with FJ 11/12 carbs, but they are still "Proper" CVs. PGGG in (I think!) N.Z. and a few others have 36mm carbs from late Kawasakis fitted, with similar results; try a search; there are other voices out there......

AlanB

[TopCatGr58]

A respectful technical discussion.

Hey Alan,

I've got the cone filters, and I don't really have to rev to 3500 rpm to get it rolling, I can roll on easily at 1500 rpm if I want to, I just like revving it higher. When I was rigging up my Lowe's Velocity Stack/filter mounts I decided to see how the slides behaved.

Once I had it warmed up and able to idle, I then S-L-O-W-L-Y rolled on the throttle, and was surprised to watch and see that the slides did NOT rise very much at all, and that the engine was able to rev to 5-6k rpm with very little rise in slide action!? But this was under NO LOAD, just in neutral!

However, without the filters even being on....how I was able to view the slide action...., I then blipped the throttle, or cracked it open from low rpm, and the slides hopped up very quickly as the amount of vacuum on the engine side was much higher than the air filter side, and so the slides rose very easily and quickly, and then as the vacuum levels equalized as the rpms rose, then the slides would then lower back down just like they are supposed to do. But all it took was a slight extra twist of the throttle, not WOT, and the slides would hop up again easily!

I then mounted my little camcorder where my air box used to be, and aimed it towards the throat of the carbs WITHOUT filters, and took a little spin around the block, and a short hop on the highway, and then I watched the tape. The slides rose quickly and easily when the bike was under any load, light or heavy, and I was turning on the throttle, both close to WOT, as well as just normal acceleration, and the slides responded just fine...without any air filter in place at all!!!!

SO....I have to respectfully disagree with the description of the response of the slides with Indy filters. I do agree that the design of the air box with the very long Velocity stack styled intake tubes that stick halfway into the box, and the presence of the box isolated from outside drafts helps to align the airflow and makes it smoother and more evened out running down the stack before it gets to the carbs, but I don't agree with the air box and filter causing enough of a restriction to airflow to contribute ALONE the increased low rpm response.

I DO believe that the use of 4-1 pipes changes the air flow thru the engine, and the loss of backpressure reducing the low rpm response and torque, leaning out the fuel air ratio, but then adding the Indy filters further aggravates this leaning process.
But I also believe that proper jetting adjustments can compensate a considerable amount in alleviating a fair amount of the loss of low rpm grunt with the Indy filters/4-1 pipes!

Bennie's carbs having the Dyno Jet kit...if it was done correctly should have larger venting hole drilled in the slide body which is designed to allow the slides to actually rise even faster than stock allowing the carbs access to the mains even sooner in the throttle/rpm range, or at least equalizing the slide response back closer to stock even with the use of the 4-1pipes/Indy filters!?

It does sound like his carbs are not jetted right, as well as possibly the float heights as well as the pilot screws not right as well. SO...he could play with the current carbs first, and then IF he gets the kind of throttle reponse he's looking for, then he can just do his TRANNY fix, and either continue with the OEM carbs, or put on some newer style carbs, but the Tranny will need to be fixed to handle the power no matter which way he goes!
T.C.

[madmax-im]

Civilized discussion no flame wars here

I have felt for some time that perhaps the DynoJet Stg lll kit was overkill for what i had...I will go back to stock jetting 2 sizes larger as recommended by Randy...I will play around with the Pilot jetting and have a look at the floats as well...It looks as though i am gonna need a service manual...Anybody know where I can git one?

[AlanB]

Hi TC,

That is fascinating; Your research has gone further that mine has.... by a long way! I have tried riding round the streets as a passenger, hanging off the bike to try to see what the slides did (before the advent of affordable "mini" cameras!) and only seen 'em "flutter", then "pop" open at high revs.

I worked in a couple of bike shops during the 80's and 90's, and had endless problems with bikes with the combination of CVs and cone filters/bellmouths (stacks?)/open carbs.... Especially on bikes which we imported from the USA......

We dealt with dozens; some ran better than others, but almost all ran far better with around 70% of the filter area covered over with duct tape......... leaving around the same area as the inlet on the XS "snorkel" per carb. It was ugly, and wasted most of the point of the filters, but got the bikes running properly again quickly and cheaply. We always assumed that it was 'cos it gave back the vacuum to lift the slides, since the ports which link to the chamber ABOVE the diaphragm are in the air-box side of the carb mouth, so a vacuum on the air-box side would seem to be needed to lift the slide?

I later became friends with the owner of a Dyno shop, (still a firm friend!) and spent many, many hours in and around his dyno cell, helping and learning. The same message held there; CVs don't really like open filters, although careful jetting work can give good results......... Congratulations on getting your own bike running well; You are obviously far better at this than me!

Good to debate and pass on information without conflict!; I still regard myself as a beginner, and love to hear all opinions......... I don't believe I am always right, only honest!

AlanB

[AlanB]

Hi Guys,

Are we far enough off topic yet? LOL!

AlanB

[madmax-im]

Good to debate and pass on information without conflict!; I still regard myself as a beginner, and love to hear all opinions......... I don't believe I am always right, only honest!

AlanB [/B][/QUOTE]
Here,here..Kudos to all...

[madmax-im]

Amazing how one thing leads to another...HEY CLINT....you know where i might find some slingshot carbs??????How'd the tranny fix go?

[AlanB]

Hi Max,

I have been told that these carbs never went to the USA, but I don't know if that is true; I think Audijunky found a set? Bandit 1100s have very similar looking carbs; I don't know the sizes.

Later GSXRs have 38 and 40 mm carbs which are too big for the XS, but the 36s are "uncool" in Suzuki-land. Try lurking around some of the GSXR forums; they have even more problems with carbs than us!.... but they remove the 36s to fit the bigger 'uns.......

Watch out for the early 1100s; they have "conventional" CVs, and one of the members on here (Audi??) told us that the 1100 carbs are far wider spaced than the 750 version.

I am sure that at least a couple of members on here have Kawasaki (ZXR??) carbs fitted with similar results to mine.

FJ11/12s have what appear to also be "conventional" CVs; I have heard very "mixed" reports about their success.........

As said before; enjoy your tuning!

AlanB

[madmax-im]

I Thankyou Sir BTW my bike is in the new '08 calendar as well...just look at August and there he is...Thanks Kat...my B-D month as well.

[stoked]

Hey Madmax, my bike has cone filters and open exhaust. And at this point in time I have the stock jets in. The plugs are just barely white. It is a little lean but being that it's winter, I'm not having pinging problems or anything like that. By summer I should have baffles so I'm staying with the stock jets. You should revert back to that to see how it goes with your stock carbs. You may be pleasently suprised. It's just to damn easy to pull carbs off using Pods not to experiment with the jetting to get it right.

[AlanB]

Hi Max,

Kat does have good taste!...LOL.
I just wish she had asked me for a pic after I finished bolting it all back together..... that shot was from a "workshop progress" thread on the UK site...... Fairing, swing-arm and rear brake have all changed since then; and the exhaust is back on!LOL!

Have you seen THIS THREAD? There are several others........

AlanB

[TopCatGr58]

Videos of Carb Slides in action!

Hey Alan,

I'm the first one to proclaim that I do NOT know everything, even hardly anything! I've only worked on my bike and a couple of others. The others were mostly tranny clutch work, nothing with carb tuning, so I defer to yours and others experience in that realm.

But as I said, I was working on mine this last summer, and decided to video it since I was doing some video work for a possible XS11 tech DVD....ahem....we won't go there right now!

This link will show you the first video, about 1 minute long, mostly of the slide NOT moving, slow throttle input in neutral on the centerstand!

I don't have the URL for the second video YET, just uploaded it, was 40MB, Youtube is still processing/converting it to WMV, about 4 minutes long, shows carbs 3-4 in action. But you can/should be able to view the OTHER vids in my folder and see the 2nd video without me providing the link!? And yes, the videos of my pathetic dragstrip attempts are still there....ha, ha, ha!

You all will note some fuel drippage and spray coming from #2 just off camera on the left, this was when I rediscovered my #2 float hanging problem, and it was slightly overflowing, so that's why I was having to keep the throttle up a bit, otherwise it tried to bog down!

But you can see the slide action very well, along with a view of the butterfly lever, and you can see that I only hit WOT a couple of times, and the slides responded accordingly rising almost to the top, but most of the time you see them running from ~1/8 open/up to about 1/2 open up depending on rpm and throttle input! ENJOY!
T.C.

2nd video under load

[boyat68]

TC:

Looked at your carb video, good stuff. Question, Where do you find the clip on clamps for your fuel hoses? I have looked all over for that type, but can only find the "Airseal"type that are too heavy and snag. When I got the bike, it had two missing, and I would like to get several. You have a source?

[TopCatGr58]

Hey Norm,

Are you talking about the screw type clamps, or the squeeze pressure fit type? I think I got the screw type at the local auto parts store, but found 1/4" diameter type.

The squeeze type ones I have are the OEM's!

I think I remember doing a search on McMaster-Carr's web site and found some of the spring loaded type, but I think I've also seen them on sites like Dennis Kirk or BikeBandit!

BTW, MAX, I split the thread and put the carb talk into this one!

Hey Alan, did you check out the videos I put on Youtube?? Don't let the 40MB size of the second video scare you, that was MY MPG file size, Youtube shrinks/converts them to reasonable sized WMV's!
T.C.