[Turd Ferguson]

Um, so you couldn't figure out your carbs, so you put those on? Good luck with that.

 

[solidONE]

if you were a little lean with the air box, then you're *way* lean with those pods.

I know... I was just fcuking around with it. I'm currently working on some 2-2 dual exhaust I will eventually install along with them there UNI pods.

I will revert back to the desnorked box after I add the 4th shim and 1/4 turn out richer on the screw.

 

[solidONE]

Just got back from test riding my bike after installing the 4th shim and turning the idle mix screw 2 3/4 rurns out, airbox.

Acceleration has improved noticably. The loud bang is now a mild pop. Pulls realy hard past 5000 rpms. Only problem is now it will not idle. Not that it was idling well in the first place.

I had to change out the springs that goes on top of the needle jet and under the needle jet holder. I was only able to find springs that were slightly more springy and larger at ace hardware. It fits nicely after I trim the springs to size. I'm not sure if this is causing the idle problem or from the 2 3/4 turn on the mixture screw. Idle also fluctuates alot. When I put the vaccume guage on it appears that the vaccume in the front cylinder is inconsistant campaired to the rear cylinder. When the vaccum in the front cylinder goes up the idle moves up and smooths out. And when it the vaccum pressure drop lower during the fluctuations the idle becomes extreamly unstable and low. I would turn the idle adjuster, t would then jump from 1400 rpm to 2500 rpm then back down to an unstable 1300 rpms.
What can cause this?

 

[Endosis]

Here Check this post of mine from a while back
(Click the pic if ya want the post but the pic is the IMPORTANT thing):


mainly: NOTE the graph is in % of throttle, 0 to W.O.T.
This, I think, shows where you're having problems.

You are trying to fix a WOT problem by adjusting a 0 - 1/4th throttle control.
It doesn't matter if you add 5 shims or use a 3 turn Air/Fuel screw setting.

If you are still lean you need bigger mains.

When syncing the carbs the gauges will fluctuate by a lot at low rpm, mine did. You can resolve this by squeezing the line to reduce the amount of air can go in and out or using a shut-off valve. This reduces the release of pressure causing the needles to stay centered longer.

Hooya,
Rob

 

[Turd Ferguson]

When syncing the carbs the gauges will fluctuate by a lot at low rpm, mine did. You can resolve this by squeezing the line to reduce the amount of air can go in and out or using a shut-off valve. This reduces the release of pressure causing the needles to stay centered longer.

Why not just adjust the amount of bounce allowed in the carb sync tool?

 

[solidONE]

The reason I didnt go to larger mains in the first place is because I'm already running 152.5's front and back. Along with the desnork and stock can, "usually" the 152.5 mains would be much more than enough. I'm sure many SVRider's with experience tuning carbs will agree with this assumption. Anything over a 152.5 with a stock pipe is unheard of in SVRiderdom. But my particular SV is an unusual one, apparently.

With my current settings and the additional 4th shim, the acceleration @ WOT is very good. Much, much better than 3 shims. the power dip at mid-revs is all but gone. So, I think that took care of the lean spot at 4500~6000rpms. But mild exhaust popings sounds are still present. I still need to pull the plugs to see whether if the current popping is caused by a lean or rich condition.

Right now my main concern is my idle. Since adjusting the idle mixture to 2 3/4 from 2 1/2 turns, the idle has become much worse. Before, with the old settings, it will have a slightly poor idle at 1500. Now, the rpms wont even get that low without cutting out. It might stay at 1300 shortly, struggling to stay alive. Cruizing at 1/8 ~ 1/4 throttle has similar but less pronouced results. Engine "bucks" at low rpm cruising.

What do I do next? I realy dont want to upsize the mains untill I finish my exhaust. So I think I will stick with the 152.5 and 4 shims for now, turn the idle screw back to 2.5 turns or 2.25 turns and slap some tape over the air filter opening.

Hopefull the spring that I replaced has nothing to do with my current idling condition. The spring that I used are one size larger in wire diameter, therefore stiffer than the stock springs. I lost one of the spings when I was taking the jet needles out for re-shim. So I replace retainer springs in both carbs.

----------New spring on the left-----------------stock spring right

The fluctuation I was talking about isnt the normal kind. I know how to use a carb sync vaccum guage. What I was talking about is the inconsistancy of the fluctuations causing the idle to also be inconsistant. The front carb vacum reading will be high(normal) in one second then it would drop to barely any vacum. When this happens the idle will either drop to an unstable 1300 rpms from a adjusted +2000 rpm idle, or the engine will simply cut off if idle was below 1500 rpms to begin with. Most likely an issue with the idle screw adjustment.

 

[solidONE]

Just tested my bike with the airbox opening taped, and pulled the rear plug.

the plug looks good but a tad lean. note that this is using 152.5 mains and 4 shims on the needle. Strange thing is that the plug actualy looks leaner than previously when i used 3 shims 2.5 turns and no tape. :dontknow:

Idle has improved, so has the backfiring. It still backfires, but much quieter and not as frequent.

I did some 1/4, 1/2, 3/4 and WOT runs in 2nd and 3rd gears. The dip in power at 4500~6000 is very noticable between 1/4 and 1/2 throttle runs. 3/4 and WOT was not so bad, but still noticable.

I think maybe some 155 or 157.5 mains should do the trick with the current setup. The larger mains should bring up the fuel levels throughout all throttle positions and rpms. When I do upgrade to full exhaust and UNI pods, i believe I will need +175 mains. A different needle profile is going to be a must. Does this sound right? Or maybe I need to play with the float height also?

 

[andyauger]

I'll probably get yelled at again, but the reason it won't idle is most probably because you are using the idle mixture screws to fix a problem that is in the needle's range of operation (probably). So now you've got too much fuel at idle causing the fast idle.

Did you notice in the chart that the "circuit ranges" are in terms of throttle opening and not RPMs? There's a reason for that. As the air flow through the carburetor changes the effective vacuum point changes. Very basically, it moves further into the throat. The other circuits will still be flowing, but not as effectively. So if you have a WOT problem you probably need to address your needle taper and/or your mains.

 

[donniej]

I agree with Andy that you have the A/F screws too far open. In my experience anything more than 2.5 is usually too much. Even with cams, race filter and full exhaust 3 turns made for a poor idle.

I'm still wondering about any vacuum leaks. Have you done the carb cleaner or starting fluid test?

If you have no vacuum leaks then you should think about aftermarket adjustable needles.

 

[robfromsc]

Just a thought... How many miles are on it... If your vavles need adjusting, your wasting your time.
Have you checked your float level?
Just an idea.

 

[Turd Ferguson]

The dip in power at 4500~6000 is very noticable between 1/4 and 1/2 throttle runs.

I think you have too many shims on and youre puttin too much gas into it in the midrange. :dontknow:

 

[solidONE]

Have you done the carb cleaner or starting fluid test?

Yes. Sprayed carb cleaner around carbs. No rev changes or reaction.

Just a thought... How many miles are on it... If your vavles need adjusting, your wasting your time.
Have you checked your float level?
Just an idea.

I assure you my bike does not need a valve adjustment. And I have checked the float hight and cleaned the carbs/jets several times.


I havent got the chance to change the mixture screw setting yet. I will do so when I rejet. I'm currently debating whether to purchace a jet kit or just get a pair of 155 mains and 3 shims on the stock needle. Can I get the adjustable jet needles by themselves?

 

[robfromsc]

Seems like something is off if every one else gets away with 152.5s and your lean... What else could it be?

 

[solidONE]

Seems like something is off if every one else gets away with 152.5s and your lean... What else could it be?

Yes, that was what I was thinking too. I've checked everything. If there was a vac leak, I dont think the changes I've made in jetting would affect the performance and it shoud be backfireing just as loud as it was before the jetting change. Obviously, that is not the case. The poping sounds now is most likely cause by a rich mixure from the 4 shims on the needles. But at WOT, it may still be a tad lean. Idle mixure is also rich, though the plugs looks good in terms of coloring and carbon deposit. It does look a little lean, however. Just a little.

What settings would you guys recommend I try next?

 

[robfromsc]

Again, just throwing out ideas..... Diaphram? Maybe a pin hole in the diaphram?
If everyone else uses xxx size jet and you have the same modifications then you'd think it would be the same.

 

[Turd Ferguson]

After you shimmed the needles did you make sure they move freely and dont stick, but spring back?

 

[solidONE]

After you shimmed the needles did you make sure they move freely and dont stick, but spring back?

The was minimal binding in the spring action, but it was kinda stiff because of the new springs I put in. How would this affect performance? Perhaps I should cut a few more coils off the springs. :dontknow:


BTW I just went for a test ride, again, with the current settings. The first 10 min. of riding, it felt as if it was just broken in. Idle was much better. No backfireing at all, and pulled like a freight train @ WOT. 15 min. later it performed just as it did before..., backfire when closed throttle beyond 4500rpms, inconsistant/poor idle.

Again, just throwing out ideas..... Diaphram? Maybe a pin hole in the diaphram?

how do I check the diaphrams? Is there a standard procedure or just visual?

 

[Honda_Fan]

Just another point of view but have you checked all your exhaust connections for leaks? Does your bike have a PAIR system?

 

[robfromsc]

If it ran correct when cold and got worse its carbs.
Did you ever try and tape over the af, block vome air flow?
Take out the diaphram, hold it up to the light, look through it and flex it w/ your finger.
What's up with cutting your springs? Is that common sv carb practice? (sorry got a 05)
Some people brush 2stroke oil on to the sllide before they assmemble it, to help lube it a bit. The slide should move freely.
If your rigging springs it maybe worth it to order the exact spring. And check a parts breakdown to make sure you didn't leave out or loose a tiny oring or something.
I bet your problem is with your slide/spring/diaphram

 

[robfromsc]

See if this link helps you at all.



http://www.motorcyclecruiser.com/tech/motorcycle_jet_kits_carburetion/