I've had several threads going in the past month about vacuum leaks and such, but despite all efforts so far I still have the same problem.

It's not rolling off idle onto the throttle that's really the problem...my problem is holding steady at 1/16th to 1/8th throttle...the bike feels like it's not getting enough gas. It sputters & chuffs & farts out the carb every so often, and the part I hate most is it happens a lot in slow speed 90 degree turns...no fun lurching in the middle of a turn.

It does it in every gear, and always from the 2000-2300 RPM range. Before that and after that, it's better, but still feels "not right". Pulling out the enricher to the first tick at low speeds is like night & day...it actually surges forward like it got a shot of adrenaline & smooths out and even sounds better in the exhaust tone. Leads me to believe it's lean down in the PMS circuit.

I've got a 35 pilot, DJ needle on 3.5 from blunt, and a DJ 175 main. Now, I saw a comment from Gram recently that made me think...he said (paraphrasing) the main jet is active, to some degree, no matter which circuit (PMS, Pilot, Needle, main) you're currently using most.

All this started after I changed from a DJ 190 & 37.5 pilot (too rich), and at the same time I surfaced the manifold flanges & ported out the manifold again (did it about 1/2 as much as I should have a couple years ago) and sealed it up with Hylomar.

I do the vacuum test with starting fluid & can make the idle drop & stumble, but only after I spray A LOT in on the manifold from the fuel pump side...I kinda think at that point it's going past the manifold & into the carb throat through the back of the air cleaner, because if I just do quick shots on the manifold where it meets the heads and on the sealed vacuum nipple on the manifold, it does nothing as far as idle change. I started with the PMS at 2.5 out, and now it's all the way out to 3.5 turns out (testing every 1/2 turn)and it's no better.


SO...given all this, does it make sense that because of that really small main jet, which remains active all the time, it's too lean at the lower throttle range & causing the chuff/stumble/fart?

I'm stumped...

RK

Have you thought about putting the 37.5 pilot back in?

hey man. i feel ya. i had that problem really bad when i first bought my * and had it rejetted as per the instructions on the Dynojet kit. helped out tremendously now i just think its a bit rich. i am not carb savvy so to get it dialed i am having it sent to the dyno. i wish i could help with this issue but like i said mine was rejetted per the instructions from dynojet and the 200 main was used.

3 1/2 on the PMS tells me your lean. You did jump a bunch on your main as well I would have gone with the 180 and left the needle on 4. Remember you should change one thing at a time to trouble shoot.

the 175DJ is smaller than stock, not a good idea. the 180dj falls between a 167.5 and 170, or a dj185 falls between 172.5 and 175. so need to up main. as far as over lapping of circuits, I've read a few articles over the yrs on CV carbs, you can remove the main jet, and stay below 3/4 throttle and all will work.
As far as needle setup, at a leanest setting that could work would be clip on 3rd groove counting from blunt end, spacer and 1 washer. If you added a 2nd washer it would be equivalent to a Barons needle set-up on clip 4th groove, spacer 1 washer.

if you go to 4th groove spacer 1 washer, it would equal 4.5 on a Barons.
the DJ needle with always be a half step richer compared to a barons when clip on same groove spacer 1 washer set-ups. DJ needles are shorter by the thickness of 1 washer.

Curt wrote:
3 1/2 on the PMS tells me your lean. You did jump a bunch on your main as well I would have gone with the 180 and left the needle on 4. Remember you should change one thing at a time to trouble shoot.

I know, I know...but, y'know, I was already in there, so...

The reason for the big jump on the main is the jet kit left that gap in there...it came with the 165, 170, 175, 190, 195 & 200. So it' the next biggest one I have from the 175. Not a great excuse, but it IS the truth.

Lean is exactly what I figured, I just couldn't (haven't) figured out why it's wonky where it is on the low end & PMS out didn't help any. In my mind, that means either a bigger pilot or richer needle is in order.

RK

Roadkill1962 wrote:
I've had several threads going in the past month about vacuum leaks and such, but despite all efforts so far I still have the same problem.

It's not rolling off idle onto the throttle that's really the problem...my problem is holding steady at 1/16th to 1/8th throttle...the bike feels like it's not getting enough gas. It sputters & chuffs & farts out the carb every so often, and the part I hate most is it happens a lot in slow speed 90 degree turns...no fun lurching in the middle of a turn.

It does it in every gear, and always from the 2000-2300 RPM range. Before that and after that, it's better, but still feels "not right". Pulling out the enricher to the first tick at low speeds is like night & day...it actually surges forward like it got a shot of adrenaline & smooths out and even sounds better in the exhaust tone. Leads me to believe it's lean down in the PMS circuit.

I've got a 35 pilot, DJ needle on 3.5 from blunt, and a DJ 175 main. Now, I saw a comment from Gram recently that made me think...he said (paraphrasing) the main jet is active, to some degree, no matter which circuit (PMS, Pilot, Needle, main) you're currently using most.

All this started after I changed from a DJ 190 & 37.5 pilot (too rich), and at the same time I surfaced the manifold flanges & ported out the manifold again (did it about 1/2 as much as I should have a couple years ago) and sealed it up with Hylomar.

I do the vacuum test with starting fluid & can make the idle drop & stumble, but only after I spray A LOT in on the manifold from the fuel pump side...I kinda think at that point it's going past the manifold & into the carb throat through the back of the air cleaner, because if I just do quick shots on the manifold where it meets the heads and on the sealed vacuum nipple on the manifold, it does nothing as far as idle change. I started with the PMS at 2.5 out, and now it's all the way out to 3.5 turns out (testing every 1/2 turn)and it's no better.


SO...given all this, does it make sense that because of that really small main jet, which remains active all the time, it's too lean at the lower throttle range & causing the chuff/stumble/fart?

I'm stumped...

RK
====================

Assumming stock 40CV carb if you ensure theres no more vac leaks then its plain old running lean in transition when you said its acting up in the 2k-2300rpm range.

But also ensure accell pump is working & is also adj properly so as soon as throttle cabel oves/butterfly in carb more the accell pump is shooting a shot of fuel .

If accell pumps isnt working or not adj properly it will cause stumbling too.

If all that chks out ok (no vac leaks & accell pump is working good and adj properly )then since you say it seems to run decent in all rpm range but when at light load part thorttle cuise in approx 2k-2300rpm range i'd say carbs lean in transition from low speed to higher speed main circut and i'd bet my bottom dollar a half or at most full step richer on needle clip adj will fix it,been thetre done that on my R* and many other bikes over the yrs too.

My 06 with pipes was doing same thing and pms out to 3.5 with stock 35 pilot jet didnt richen it enough so i put pms back to a more reaonsable 2.75-3 turns out from light seat and installed an additonal washer under neeld clips for slight tweake richer .

Doing that fixed the lean part throttle cond in 2k-2300rpm range in my bike.

After doing that thin washer under needle clip slight tweak richer adj on my 06 silverado when Riding 2 up with bags fully loaded inc more/addiitonal aftermarket bags mounted on rear luggage rack,tall windscreen,31T pulley (turns slightly more rpm at cruise then stock) i still get 40.5-41mpg @ 65-68mph open road cruise speed & get 36-38mpg in mixed city/open rosd riding.

No matter what people say theres a slight overlap in circuts that neelde clip postion can affect lower throttle positons too which i have found to be true so many times over the 40+ yrs tuning motorcycle carbs esp for aftermakrket pipes/BAK-aftermarket air filters etc.

You may find it needs a full step richer needle clip adj but 1st try half step richer on needle clip setting with 1 additonal thin washer under needle clip.

Then see how that does before going a full step richer on needle clip adj if its not needed.

But if 1/2 step richer helps a bit but doesnt fully fix the lean cond in 2k-2300rpm range then remove the additonal washer used for half step needle clip adj and go a 1 full step down richer from top-blunt end of needle and that should hopefully fix it.ort is a 20 mins needle clip adj

So long story short is if it still acts lean post ensuring the accell pump is in fact working properly a quick needle clip like i suggested could very likely fix your carb issue just like it did on my 06 silverado that had the same issue yours does.

Maybe on 2nd thought i'd opt for a 1 full step richer needle adj for 1st try because you said its really farting/stumbling in showing its excessive lean in 2k-2300rom range and not just a little mushy with little to no stumbling that would show only slightly lean.

BTW,pulling carb appart for larger 37 pilot could poss fix it too but the slight needle clip effectively does same thing enriching where it needs it without going into carb. It didnt kill mpg in my case either riding 2 up bags fully loaded inc more/addiitonal aftermarket bags mounted on rear luggage rack,tall windscreen,31T pulley(turning little more rpm at cruise vs stock pulley) & i still get 40.5-41mpg @ 65-68mph (70mph at times) open road cruising inc plenty of hills/mountains in NY state & get 36-38mpg in mixed city/open road riding 2up too with all else the same on the bike.

Scott

Here is a link to the Mikuni HSR tuning manual. Tuning
Yes I know it for the HSR but what it tell you applies to all MC carbs. Read it and fit the problem you are having and take the steps it gives.

Erbman02 wrote:
the 175DJ is smaller than stock, not a good idea. the 180dj falls between a 167.5 and 170, or a dj185 falls between 172.5 and 175. so need to up main. as far as over lapping of circuits, I've read a few articles over the yrs on CV carbs, you can remove the main jet, and stay below 3/4 throttle and all will work.
As far as needle setup, at a leanest setting that could work would be clip on 3rd groove counting from blunt end, spacer and 1 washer. If you added a 2nd washer it would be equivalent to a Barons needle set-up on clip 4th groove, spacer 1 washer.

if you go to 4th groove spacer 1 washer, it would equal 4.5 on a Barons.
the DJ needle with always be a half step richer compared to a barons when clip on same groove spacer 1 washer set-ups. DJ needles are shorter by the thickness of 1 washer.

Erb--

I agree the DJ 175 is way too small (about a Mikuni 164), but even the DJ 190 is smaller than stock...it's equivalent to about a 179 Mikuni, and stock main is 182.5 Mikuni. Everything I've seen here and has pretty much said the the stock 182.5 is a tad rich from the factory, right?

Thanks much for the comparison of the DJ vs. Barons needle... I didn't know the difference. I swear if I wasn't so cheap (and broke) I'd just ditch the Dynojet stuff altogether & get Barons/Mikuni stuff...

Gonna play with it tonight as it's SUPPOSED to hit 70 this weekend for the first time this year!

RK

RK the one thing that was not mentioned for an air leak where the carb attaches to the manifold. If it's increasing rpm's when you spray alot in there it could be going in there instead of the air cleaner. Just a thought.