Fuel screw & jetting
 

Ok I am starting a new thread. I just cleaned my carbs, fixed the chokes and added Jack Flash thumb screws.

I have the front at 2.75 turns out and the rear at 2.5. I am getting crazy popping on decal, even more than at stock setting (which I don't know what that was)

I am also getting major carb farts now on the front cylinder.

As mentioned in my other thread my buddy thinks that the carb farts are from ever so slightly bent valves. I am not sure since its a very intermittent problem.

What setting for fuel screws is working for guys with good running bikes? I have 2 bros carbon slip ons.

Also what jetting or even point me to a jetting thread I can read.

Bent valves....don't think so. Though someone really should write up a jetting thread =)

Yeah that was a diagnosis with him in Maine and me in NY. I am not thinking bent valves anymore. Still chasing the issue but its for sure carb fart back thru the front carb. Attempting to richen front cylinder. Also gonna put a longer trumpet on front.

I am looking at this old thread but I have aftermarket needles.
https://www.superhawkforum.com/forum...-set-up-24769/

Joe, hop on FB and message Bobby Kuhl. I noticed him sharing his carb set-up a little while back. The general consensus there was that the one on here was rich for most everyone.

A question concerning decel/closed throttle exhaust popping (afterfire?). I was under the ASSumption that an open exhaust system is going allow popping with no other changes to the tuning of the carbs. That is, take of stock cans and replace with straight through, unbaffeled cans. Also a richer tuning will exacerbate this condition.
I'm, as usual, confused.

I am more trying to eliminate the carb farts than the popping, although the popping is obtrusive now. I am sure the richer fuel screw setting is affecting the popping.
May try to bump each carb a half step richer.

have you set the TPs yet on the carbs?

Hehe, no that is on the list. Had a week in Laconia bike week away from the vtr. Life gets in the way.

My Hawk never did pop like crazy before the pair delete. Once I let the choke out a tad and it did it like nuts, I wondered what the heII was going on before realizing why.

Wolverine missing what youre saying. Its the pair delete? Its the choke?

Yes, the choke was left out just a touch unintentionally. It popped like crazy when I closed the throttle, at any engine speed.

Ah ok. So you think richness causes the popping to some degree? I am about to go richer both cylinders to alleviate popping. I had less with the choke on so I think Im too lean.

So yeah was trying to avoid the sync and tps but those are now 1st on the list.

Can someone link me to the Jack fuel screw adjusting procedure as its running?

Maybe I missed it but can you give the complete setup including air filter, air box mod, jet size, I just went through this with my new motor setup. To get my bike to run right " new motor " had to go with stock air filter and for now took off the Dr Honda velocity stacks and back to the plastic. but after 500 miles or so will start to revisit the intake side of things before the dyno to see what I have gained by all this.

So my long winded rant is we need your baseline of the bike.

Syncing the carbs and tps setting is the first place to start. Have to having it run the best at whatever setup to know which way to go save you a lot of time.
Always go back to a basic baseline and move forward and analyze the outcome of the change you made.
I am sure there are setups to get you close you where you want to be.

But none of this is new to you "have gotten lots of useful and very knowledgeable info from you in the past"

So yeah update.
Did the 2 obvious jobs and got HUGE results.
Did carb sync and TPS.
Synce didn't seem way off but got it pretty spot on with my yard stick & clear plastic tube with valves sync tool.
TPS was almost at 800 so got it to 500.
Turned the front fuel screw back in 1/4 turn which puts it at I think 2.5 or 2.75 out.
Last thing I did was put a 2nd long trumpet on the front cylinder. I believe this worked a lot to stop the carb farts but either way I went from way too many farts to almost none.
BIKE IS TRANSFORMED.
Improvements include quick and easier starts, steadier idle, WAY more low end grunt to the point that I accidentally had the front wheel off the ground a lot on the test ride(!)
So I didn't dig into the needles this time but did clean all the jets at the start of this debacle.
I am pretty sure I have a 45 main.
Also at the start I replaced the choke fittings with the jack flash units.
I am very happy to get my bike rideable again. I am wondering about the bent valve possibility my buddy believes so next will do a leakdown test.

Popping and back-firing on decel is also caused by an exhaust leak at the head...:wheelie:

At the headpipe gasket?

Si, Senoir!

Copper tube crush gaskets required, or flip them around with some Hi-Temp Red Copper filled RTV silicone...

Aye caramba no es Bueno!
Ok yeah I have some of the copper gaskets around. May be an issue. Gracias el guapo.

Just adding the final word on my summer carb tuning/ fuel screws/ TPS/ carb sync.

My bike was carb farting on the front terribly, popping on decal to wake the the whole city and stalling intermittently.

I adjusted the fuel screws out another turn and now all the bad symptoms are gone. Idles fine, not popping and zero carb farts. Hope this helps someone.

set the front carb a little leaner than the rear. the front slide lifts sooner than the rear slide, causing a richer condition in the front.
then again i've heard it said that front cylinders on v-twins run leaner than rear cylinders because they are directly in ambient airflow where the rear cylinder isn't.

check intake boots to carbs
 

Mine was doing same thing ! carb syn, tps, new intake boots and 3.0 turns out on fuel screws, with 48 pilots ,needles 4 th from bottom setting and runs great never pops and will loft front end when rolling on throttle. this was with help of different members .and removing and jetting carbs lord knows how many times .smells a little rich at idle ,may go in 1/4 turn in on fuels screw but it runs so good hate to mess with it now maybe enjoy riding it lol best of luck

First things first, front cylinder should be leaner on the mixture screws than the rear cylinder.

Best place for the mixture screws is where the cylinder vacuum is highest, 1/8 to 1/4 turn in.
Anymore than 3.5 out you need a larger slow speed jet, or have restriction on circuit.
Less than two, and the jetting needs to be leaned out, or you've got other problem going on.
My Superhawk prefers a little more on the front cylinder just backward of normal belief.
Has been this way since new.
Lots of variables affect this so x number of turns may not be ideal, but is a recommended start point.

This is really interesting – I haven't heard of setting idle mixture by vacuum before but I'd like to try it! So do you mean set for highest vacuum and then turn the screw in i.e. lean the mixture by 1/8 to 1/4 turn? I know that's basically exactly what you've written but just want to be sure.

Yep that's it.
​​​​​​Best way to do it unless have an exhaust sniffer.
Be sure bike is at temp, and level (not on side stand, it messes with fuel level in bowls) This is with tps set correctly, and idle speed at recommended high side. Once set mixture to best vacuum resync, and adjust idle speed.
I usually do them at same time I'm syncing carbs get best results that way.
Use a squirrel fan or some other high powered fan moving air over the radiators while you do this so temp stays pretty stable as this has big impact on fuel mixture needed at idle.

So after a bit of time has passed, I finally had some days where I didn't need the bike the next day so rejetted the carbs with #48 slow jets to replace the #45 stockers.
Huge difference!. Smoother idle, carb farts gone, no stalling to name a few benefits.
Really not sure why I didn't do it sooner but bike has never idled or come off idle so well.

Joe, Joe, Joe (head shaking left right after a tisk, tisk, tisk)...
How many years you been on this forum?

I go back to Runlevelzero though didn't find this forum for a couple of years after Greg' former forum closed, and even then 48 pilots were a known solution.

I never went in for plugging a slide hole or using a full kit. Actually am now back to the OEM slide needles shimmed 010 and 020, or both the same one or the other thickness, as it's been SO long.

Just yanking ya chain...