99superchicken

Ok first of ,howdy, im new here.I hail from from the great state of New hampshire USA lol.
Soo i recently bought my first Superhawk, a 99 model.Runs great, 32k miles..(yes,already ordered New CCT's). It has slip ones, PO said it wasnt jetted, so had some cruising sputter..from 3k-5k mostly.Tons of power on accelerating, just a bit bucky a sputtery cruising.Soo not knowing i have just a slip-on system, i ordered a stage on jet kit and installed it. Btw my air filter is stock and in good shape,And i HAVE dialed in the tps to 550 ohms.it was at 917 stock. I have a carb synch board as well. And i'm no newbie to complete teardowns and carb tuning. And everything in between.

So anyway.....I have tried 5 million setups and have gotten the damn thing to run 85% perfect. Here's my current setup based on things i've read and experimented with: Dynojet short slide springs, drilled slides per DJ recommendations. Stock main jets ( ive read that with slip ons, bike still will be fine past 7k rpms in the main jet circuit) shimmed the rear stock carb needle about 52 thousandths. the front needle is shimmed at about 40 thousandths. Running #48 pilot jets around 1.5 turns out..

OVERALL, the bike runs great, no hesitation, pulls hard,returns to idle well..etc..the problem i'm having is more noticeable at cruising speeds around 3800-5k rpm.Not when accelerating,but cruising at next to NO throttle. I also notice it on the highway when winding it out to high speed and coming back down to more legal speeds. Kind of a slight occasional burble when either coming back on the throttle to maintain speed, or maintaining speed.Also a bit of a surge (presumably from the burble/misfire) more noticeable at higher gears(above 4th) .under 55 mph it doesn't do it so much.Almost like a ram-air effect is causing fuel starvation at speed or something..and yes i have cleaned and checked my petcock and petcock diaphragm, ordered a rebuild kit to be sure.

It seems to be in the pilot circuit, and i can say with some surety i was the first one in there, carbs were SPOTLESS and valves also recently adjusted. My friends say i'm crazy, i say NO, it can run better.I realize some diaphragm chatter is normal and i might notice it more cuz it's a v twin(my first bike was an 87 gsxr 750).
Sooo i need ideas
Thanks
Matt

NZSpokes

Pilots are to lean.

This is my bible for SuperHawk carb set up. I work everything to and from this set up. It works. You dont need a jet kit as its sends you backwards.

https://www.superhawkforum.com/forum...-set-up-24769/

kenmoore

Guess what , I drilled my slides as per the D.J and it was ****.

I had a spare set of slides, installed them and hey presto, all was good again.

Go figure, never had a drama since.

Have a look at Hawks thread on carb set up as well.

99superchicken

the carb bible seems to indicate that #48 pilots are spot on for my setup.But i have drilled the 3rd holes in the slides per DJ recommendations..time to get the plastic welder or epoxy out..maybe even plug one of the stock holes up front..good stuff tho.ill let you know how it works, it's funny tho, i have been finding that she performs better with the front pilot screw set fairly lean.kinda makes sense where they're saying the front slide opens sooner causing it to go rich early..its allll so clear now..I'll letcha know how it works out

99superchicken

haha and after reading on in the carb setup thread, i realized that the needles are different part numbers.guess i'll be going back and checking that too

7moore7

1.5 turns out aren't too many turns. It would almost suggest trying to jump down to 45's. As it's acting up more in that circuit, they may be, but it could be a lean surge as others have also suggested. Hard to tell over the web.

Start by trying to return the slides/springs to stock. Then tinker with the pilots. No DJ needle or mains, right? Remember- that carb setup is a great baseline, but bikes are all slightly different so if you end up with 45's it doesn't mean you're doing it wrong. If you need springs I may have an extra set...

mikstr

Having spent a fair amount of time tuning my carbs through various mods over the years, including the last 3 months making my modded lid work (is now awesome btw!), I would suggest that if your problem is at 4 k rpm or above, chances are it's not your pilots at fault. In my experience, the pilot circuit loses "most" of its direct effect (though admittedly it never goes away completely) at about 3.5K. I suspect your condition is caused by too much fuel and that your excessive shimming of the needle is the culprit. One clip position is equal to 0.040", and you went 0.052 and 0.040.... a lot of gas. Try easing off here and chances are you'll see a nice improvement. As for the drilled slides, most of the effect from the drilling happens in speeding up the lift speed. At constant throttle settings, it has little/no effect, as the system is in equilibrium (your spring determines the height of the slide in such circumstances, since it and the level of vacuum are the two forces at work, battling each other, so to speak). Drilling the slides allows the vacuum to "get in there" and do its work (ie. lifting the slide) more quickly, it doesn't change the final height (ok, it does to a very, very, very minor degree as the added hole reduces the surface area on which the vacuum acts, though I would be surprised it its effect is anywhere near 1%)...

FWIW, if your idle is stable (ie. constant, drops to idle speed quickly) and throttle response from idle is good (ie. no hesitation - lean condition, slow and "diesel-esque" - rich), I would not lose too much time on the pilot circuit.

anyhow, my 2 cents.... I don't claim to be infallible and hope this helps......

99superchicken

it has done this no matter what the settings..however..i did notice a small poke hole in my front diaphragm today..might be new, might have been there all along..and of course happy happy joy joy they're on backorder from honda..any way to reliably fix a small pin hole?

99superchicken

and good point on the diaphragm lift holes.never thought about it that way...Response is spot on off idle..i might try going just stock washers on stock needles with stock mains and 48's.i noticed last night the problem got worse as it warmed up and needed no choke at all on a cool night..so rich might be it. it really needed the 48 pilots tho.badly.now i can make it either too rich or too lean with the idle mix screw.before i couldnt get it rich enough

99superchicken

one thing i noticed about the dynojet needles that i found odd was that their profile matches the stock one to the naked eye almost perfectly.and dynojet recommends 4th position from top (needle has 6 positions).When i set it up like that and put it side by side with the stock needle, it appears the DJ needle would be a good bit leaner than stock. I could understand if it had a more aggressive taper but it doesn't.it looks identical. Anyone have an explanation for this? if i run it like that it is DEFINITELY LEAN.if i go 5th from top it gets better,but 6th from top (richest) seems to be best.

99superchicken

and no, im running stock needle at the moment, but ive tried dj needles and i see no point (no pun intended) in using them

NZSpokes

Thats because DJ uses bigger jets. Dont go by the numbers on them as they use a different number code to stock. So if you mix and match you will get tripped up.

99superchicken

i am aware that dj numbers and OE numbers don't correlate.I havent run dj needles with stock jets or the other way around

99superchicken

Well after more messing around and repairing the diaphragm, it turns on out my front carb to engine boot is leaking .kind of explains some wacky readings i was getting after revving the engine during carb synching.Also explains what appears to be some fuel starvation after extended high revs.The front carb provides the vaccum for the petcock of course.So after 54$ for the boot and rush shipping, ill have the boot tuesday...hopefully that'll be the end of it.The boot lip had a flap that was torn away where the carb sits in.

Scott Shand

one thing at a time or you may be hard pressed to know what is cause/effect.

JamieDaugherty

No offense to anyone, but the carb stickies are just plain wrong. I think your problem is too rich on the pilots. Go back to stock #45's and I think you will find it is a lot better and your problems go away.

Enjoy!

8541Hawk

No offense to anyone but I believe your opinion is wrong.
Though we have been down this road before.

It does seem that you do have major issues with running 48 pilots.

I will point out once again that All UK VTR1000s from 2000 on came stock with 48 pilots ( It is possible that all non-us bikes had this but I do not know for sure so will only list the UK bikes)

So either Honda decided to run all the stock Firestorms too rich or there is a good reason to run 48 pilots in this bike.

The only time I have seen any issues with 48 pilots (on a stock engine) is when the mains are also changed. I also clearly stated this will not give good results but feel free to try if you want.

So for now I will stick with the info that I have passed along as it came from HRC ,Honda and Moriwaki.

I am more than willing to hear other opinions but I would hope they would have a little more meat to back them up than just saying "Oh you're wrong".

JamieDaugherty

Although I don't work on engines (suspension and chassis only) from time to time I will help folks with engine issues. I've tuned several VTR's that weren't running right and every single time the solution was to get rid of the 48's and go with 45's. My personal bike runs 45's and if anything it is still rich.

The OP is having some degree of problems or else he would not have posted this thread. Just trying to point them in a direction that I personally know will help.

NZSpokes

Pilot size is irrelevant in what is wrong with the OPs bike. It has a torn rubber manifold. Once that is fixed then he can look at jetting.

My bike runs much better with 48 pilots, mains are not changed. I would like to see some of your dyno runs to show 48s are to big on stock main jet sizes.

sjscicluna

Do you have your PAIR system in place as this may lead you to the wrong conclusion any tuning must be done without the PAIR system Enabled.

thetophatflash

What's the source on that info?

cybercarl