Fine Tuning Carb Q.
 

Hi Everyone.

I started out with K&N + 190 front 195 back Main + 48 pilots + DynoJet Springs + DynoJet Needle on 3rd from top clip with 2x.020" shims on both needles + additional hole drilled as per DJ install.

New Setup:
1.Stock air filter + 175 front 178 back + same 48 pilots + Stock springs + DynoJet needle 2nd clip from blunt both ends front and back. removed one shim from the front needle so its .020 front .040 back. Slide** plugged 2x holes front and 1x hole back with epoxy.

2.Pilot fuel screw 2 1/2 front + 1/8 or / 1/4 additional turn on back.

3. Synched Carbs 1200rpm idle with ever so slight *surge to ~ 1100rpm.

Good:
1. *Good Idle
2. Highway acceleration and cruising is excellent
3. Acceleration in any gear is excellent
4. I don't smell nearly as much gas in the driveway after riding.

Issues:

1. Pop on deceleration from ~50mph and below which I didnt have before.
2. 35-50mph cruising slight surging at steady throttle which I didnt have before at ~ 2500-3000rpm range. Dropping a gear fixes this, but this was not an issue before.

Any suggestions on fixing the above, I was thinking the pilot jet fuel mixture screw?

*I did not touch the TPS.

I'll throw an "educated" guess into the ring. I'm sure it can be fine-tuned.

the Dynojet needle has a different "map" profile than the stock needle. Using the DJ needle with the stock spring is leaning out the mixture, during decel (closing the slide early), causing a misfire and afterburn in the exhaust tract.

My .02 says install the stock needles.

First is the PAIR system still hooked up or has it been disabled?

The RPM range you list for the "surging" is right when the carbs transition to the needles.

So yes either a pilot screw adjustment or messing with the needle height should cure the problem.

Though first you need to figure out if it is rich or lean.

Pull the choke out slightly and see if the issues get better or worse....if better you are too lean, if worse you're too rich.

I have this 'surging' as well, and as far as I know, my machine has not been tampered with. bone stock

You could probably use a good carb cleaning.

PAIR is removed, I'll test out the choke tomorrow. So if giving it a little more choke fixes the issue, I want to turn out the pilot mixture screws a tad more on both ends and adjust from there. If the choke makes it worse, I want to screw the pilot mixture screw in a tad more and adjust from there.

As far as shimming, how do you tell if you need to shim the front versus the back?

**Unfortunately I only have the DJ needles as I am the third owner.

Thank you,

That is correct, go 1\4 -1\2 turn when you adjust them

Tou do them both ;)

Would that require removal, or running some seafoam thru it? It has just under 22k mi.

Try reversing this. You need less on the rear as you have the bigger main which enriches it. Undoing (anti clockwise) the fuel screw adds more fuel.

With 48's it about 2.5 turns out on the front and 2.1/4 rear give or take 1/4 either way on the front and rear.

You should put the standard needles back in as well.

(:-})

Pulling out the choke certainly reduced the popping AND reduced the stuttering ~ 3k rpms 2nd gear low speed. HOWEVER, read comment #1. :rotf:

1st. Initially, I didn't have my TPS plugged in after re calibration. :congrats:
2nd. Regardless, today I slotted the mixtrure screws and started over again 2 + 1/2 front + 2 + 3/4 back.

3rd. Wanted to test 2nite but forgot to connect throttle cable!:congrats:
4th. Report back tomorrow.

**Funny I always seem to forget something the first time around and it's never the same part when I double check.

***I have ADD....is that an allright excuse?! :rotf:

****4th time pulling carbs from bike! Have not adjusted TPS, one thing at a time!

Please see initial post, originally 190 front 195 back 2x 0.020" shims front & back ~ 3 turn out each equal!. DJ Clips from needles on 3rd clip from blunt end of needle. Additional hole slide drilled and K&N Air Filter. PAIR removed Auto CCT. Full lengh exhaust.

NOW: 175 front 178 back shims 1x 0.020" front 2x 0.020" back ~ 2 1/2 turn front 2 3/4 turn back. DJ Clips 2nd from blunt end of needle.
2 out of 3 holes epoxied front and 1 out of 3 holes epoxied back. Stock Air Filter. MCCT installed. Full lengh exhaust.

******I do not have the original needles! I am the third owner!

The bike feels wonderful under hard acceleration and top end cruising ~ 75 - 90mph.

whord, when you say pilot screws, you are referring to the fuel screws right? The ones you had to slot? Just double checking.

You are lean when the slides are closed - needles down. Try the third slot on the needles, then fine tune with shims.

It sounds to me you're pretty big on the pilots already. When I was working to try to fine tune my setup I tried to lean out the needles slightly and got just what you're describing. I think if anything you're rick on the pilots and lean on the needles. I'd raise the needles one clip position and try that. Maybe go down to a 45 pilot. You could either try to locate some stock needles or go with the Factory Pro jet kit which has much better needles than the DJ kit.

Sounds like you are getting close. Let us know how it runs with the TPS hooked up but I would guess the you need to raise the needles slightly.

You can try adding 1 shim on each needle or just rasie them 1 notch on the needles. ;)

Oh and don't mess with the pilots......

I'm going to stick with 8541Hawk as this new setup is based on his advise and we are ~ same elevation in the same state. With literally stock bikes I believe.

I really don't want to deal with those OEM springs again, what a pain in the butt to re-seat and ensure a good seal!

So I want to move the clip one position towards the pointy end which will make it Richer.

Report back soon!

The trick for the springs is to place the cap upside down on the bench.

Place the spring in the cap.

Take a long screwdriver and put it down the center of the spring.

Compress the spring into the cap and hold it in with your thumb.

With the slides installed and held part way open (I use a screwdriver handle or my thumb on the other hand) hold the cap in place and slide your thumb off the spring and it will go straight on the spring holder in the slide.

Then install the cap and check to make sure the diaphragm is seated properly.

Yep torwards the pointy end to make it richer as it lifts needle futhur out the hole allowing more fuel flow.https://www.superhawkforum.com/forum...ons/icon14.gif

(:-})

Knew I missed something...... it's hell getting old.....:rotf::rotf:

Here we go, have a pic.

Attachment 23749

8541Hawk Don't worry I'm not far behind you. Getting old that is. LOL

(:-})

Haha! I just found and read that entire site during my lunch hour. I forgot to eat......well nobody will notice if I leave for an hour.

Motorcycle Carburetor Theory 101

What I took away from it is. Given the same bike, at the same elevation with the same mods BUT different needles mains pilots......We are all trying to achieve the SAME A/F ratio........Just some carb setups will be easier to work with than others.

I was born in 1983...cars were mostly Fuel Injected and I was too young in 1998 to properly ride a sport bike. BLESS FUEL INJECTION CURSE CARBS TO ....... HADES! I'd gladly shell out $$$ to fix mechanical issues after a few years and never have to worry about A/F ratio going out of synch.

Yeah two bikes side by side with the same parts will often end up with a slightly different set up for optimum performance.

So throw in a few different parts and well that is why I always say "base line" or a good starting point.

It's also why tuning carbs is sometimes thought of as black magic....

Another old adage is the bigger the CV carb, the harder it is to tune.
So these 48mm carbs can get a bit picky at times and small changes can make a big difference.

Just write everything down, your starting point and the changes you make as it might take you a couple times to get right depending on how picky you are. ;)

I just wanted to say how wonderful this community is. :brownnoser:


No really, before the internet....can you imagine the amount of BAD information passed around by word of mouth, by crap wannabe mechanics and the like. The number of people who thought their bike was actually running "perfect." :rolleyes:

I feel so fortunate. I work as an IT server administrator, I don't know crap about engines but can easily digest and understand the information. However, I don't have a chance in hell without all of YOU! :winner:


p.s. Our forum has a wonderful variety of Avatar silly faces AND I would like to nominate 8541Hawk as our community carb. God. :thumbsup:

Yeah Buddy!!!!!!
:kneelking:


This Carb is dialed in....I'm done.... well for a few months or so....8541HAWK dead on with clip adjustment!
See you guys next winter!:winner: Clean powerband.....not perfect but CLEAN ENOUGH!!

Glad to hear you got it sorted out! As I mentioned in my last post I was sure it was a lean needle. Mine did the same thing when I got one clip position to lean.

Actually I think the internet has actually exacerbated that problem. Someone posts one bit of bad info and someone else reads it and next thing you know the whole world thinks it's true because they "read it on the internet." LOL!

Well. I thought everything was good-to-go. Unfortunately it appears my rear cam chain cover is leaking oil....:mad:

I also hear some chain noise coming from the front when the bike is warm and cruising, perhaps I need to loosen the MCCT?

Additionally the Idle is fluctuating alot when warm and is going from ~1400rpm - 1300rpm. Perhaps I need to adjust my TPS to 500ohm? Or re-synch the carbs again.

The stuttering at ~ 3krpm-4krpm minimal throttle is "almost" gone but I still sense it.

Additionally when I go WOT it feels like a turbo kicks in and the bike goes vroom! Perhaps I am still lean on my needles. I rarely if ever go WOT and only did it for testing. However the delivery of power was NOT smooth it literally took off! I normally ride at 1/8-1/4 throttle cruising around town.

I smell fuel on me, perhaps my mixture screws are too rich?

I brought the bike to work today so I was able to test everything a lot more than last night.

Guess I'll answer these the same as your PM. At least it's not the front cover and I would pull the cover and re-seat it to see if that will fix the leak.

As for the noise is it a "rattle" or more of a "honking" noise?


A TPS adjustment and a good sync should help here, I would also make a pilot screw adjustment (go in 1\2 turn)

Adjusting the pilot screw should cure this.

What RPMs are we talking about? If you normally ride at 3-4k and now give it WOT at around 6k or so it can and will feel like this..... it's just the engine coming onto the cams and actually making some HP ;)

Again the pilot adjustment should help here

You are getting close...... :thumbsup:

Agree. The TPS defiantly makes differance to the overall low down smoothness. I would go 1/2 turn in on the rear and 1/4 front. Better still, if you have the right tool then do it by ear and use the idle drop procedure and monitor how the rev needle behaves. If using the idle drop then sync carbs before and afterwards.

At WOT you would be on the mains not needles.

Your getting there and best of all it's a learning curve. You should be pleased with yourself. Imagine how much it would have cost to take it to a garage and have them do it, and even then they may not have done as accurate a job as your doing and you would be going back there for them to correct this and that. I doubt they would even dream of tampering with the TPS.

(:-})

:winner:Hawk, I'll do everything you told me to do, thank you everyone else, GF has ordered me to NOT work on the bike 2nite and we are to go out to dinner which "should" end with a "happy ending" hahaha. Guess the Hawk is on hold 2nite. Report back soon

Update 4/15: Took the bike into work today.

These findings are while the bike is 100% warmed.

I re-seated the Idle Mixture screws to 2+1/4 front and 2+1/2 back after slotting them with Dremel.

As stated previously I moved each clip from the 2nd from blunt end to 3rd from blunt end.

Results: Re-synching the carbs, the bike idles like a champ at 1200 rpm, almost no searching and it feels very good.

3000rpm - 3900 rpm. I am still having some surging. The remedy for this was to richen the needles which I did. The issue is better but not yet perfect!

1/8th-1/4 throttle cruising in any gear at 3000-3900rpm there is surging. Lower than 3000rpm is good. After or at 4000 rpm everything is good.

However, all of my "following around the town traffic" always puts me in the 3000-3900 rpm cruising range, deceleration at this rpm range = popping.

My thought is to either ritchen the clip one notch or install a second shim at .020" on both the front and back. However this would bring me to 2x.020 front and 3x.020 back. Perhaps I should only shim the front shim so I have 2x.020 shim front and back?

TL:DR All is good except for 3000-3900rpm with 1/8-1/4 throttle @ cruising speed 35mph-45mph on city streets.

Pull the plugs and post a pic for us. I suspect they're sooty. What mpg will it get cruising around without getting ham fisted?