Popping out the carb in cruise
 

I know, I know, this issue has been beaten to death, but the issues keeps coming up, and I can't seem to find what I need in the searches. I recently bought a '98 Superhawk, and the PO used it as a track bike, so he wasn't concerned about the driveability. He installed a K&N and high mount Jardine's (black cans). In cruise at around 2800 to 3200 rpm, I am getting a popping out of the carbs, as well as sometimes when I accel from a stop, and give it anything more than a leisurely pull away it pops, and pull the front wheel off the ground. Not good if there is a cop there that I didn't see. It's also extremely cold blooded and doesn't run well until the temp comes up half way on the gauge.

Right now, the pilot jets are both #48's. Main jets are 175 and 178. Needles are both shimmed (I am removing the shims) and on the second from the top clip.

I am planning on putting #50's for the pilot jets, 180/185 mains and putting the needle on the center clip without the needle shims(why would I shim when I can adjust them?).

Thoughts.......

As for a jet kit, from what I can gather, all they are is jets and new springs. Whats difference in the springs? If I can avoid the expense of a jet kit (I can get all the jets I need for about $25.00 shipped to my door vs. $70.00 without shipping or head to Cycle gear and get reamed all together) I will.


Thanks.

-Mike

Leave the carbs alone and throw the POS K&N filter away. Replace it with a stock unit and see how it runs before messing with the carbs. Then put the clips on the top groove, 1ea shim on the front needle and 2ea shims on the rear needle with the pilot screws turned out 2 turns front & 2 1\4 turns rear and see what you have.

As for the jetting you are thinking about, maybe if you had pistons, cams and some major head work it might run ok. With your stock motor that is waaay too rich. ;)


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Won't that make it run leaner then it already is. The plugs have almost no color to them at all. Problem is, I don't think the shims that are in there are anything other than washers, because they are different sizes(diameter). I haven't put a micrometer on them yet. Why not just adjust the e-clip on the needle?

+1 on canning the K&N. You're getting too much air flow on the intake side.

And did the PO modify the air box? That includes the snorkel on the front that points down behind the triple. Modded air boxes usually don't work well.

Air box is stock, snorkel is still there. Why is the K&N so bad? Why not just re-jet the bike to make it work. Common sense tells me that if I improve the airflow, power will increase. Why else would people put cans and a free flowing airfilter on? Just trying to understand.....

Honestly, I could care less about fuel economy. It's a toy for me. So if I gotta gas it up a little more frequently, thats no big deal.


BTW, before I took off the carbs, I checked the sync, and they were fine.


A little background on myself so ya'll know what kind of person your dealing with here. I spent 9 years as an auto dealership tech specializing in Heavy Line/Tune-up and Driviability and worked all over the country for one of the "Big Three" auto companies. I played with muscle cars for a while building a few engines and playing with Holley and Carter carbs and EFI systems of every conceivable manufacturer. I have been riding for nearly 25 years, with about a 6 year break from street riding while I moved for CA to FL back to CA and started a family. I would consider myself an experienced wrench, even though I don't make a living doing it anymore.


The SuperHawk I bought has had the suspension gone through. It has a resivor on the rear shock that was done by th PO of the PO, and had the front suspension done as well (different springs/gold valves I think). It was a track bike. It has Vortex clip-ons, a 520 chain conversion, and Sharkskins fairings. It has a machined aluminum piece for where the clutch slave goes(no idea who makes it). And lastly, it has manual CCT's.

So far, the only things I want to change are the jetting (I think this will help the popping/stumbling), and lower the forks in the tripple a little to make it turn in quicker. If I do that, I will probably get a steering dampner.

From what others have posted in the past of experiences with K&N type filters, dialing in the carbs can be quite difficult. You can always try though.

But I don't think there's that much to be gained in performance with a K&N, for street riding anyway. When I'm doing a fast canyon run, I never think, "I need more power". I just keep the revs at 5k or higher, and I've got plenty.

I was a Vocational Automotives instructor for 34 years before retiring 2 years ago, and I worked as a tune-up mechanic (we weren't tech's then) in the early to mid '70s...but I've never claimed to know everything, because I don't.

Working on these bikes is fun, but I'm lazy, so I'd try a stock filter first.

Good, now I know I'm not getting advice from some 16 year old kid sitting in his moms basement! Thanks. I'll try a stock filter before I go dicking with everything.

Edit to add: I still may try to get the bike to run right with th K&N though, I just want to try a stock filter and see if there is a difference.

I just bought my SH not to long ago and it had a K&N filter in it when i got it. I cleaned the carb and did the TPS fix. ran great but the filter was white (no oil) so i brought to work one day (honda tech) cleaned and oiled it put it in and would not rev past 5k with out falling on its face. then if i could get it to rev past there it would take off again around 7k. went back to work grabed a stocker and now it revs great still pops a little but not to bad.
the bike has micron exhaust and a dyno jet kit in it. will have to fix that at some point
IMO take the K&N out or be ready for big jets, I would take put the stocker in anyways just to give yourself a starting point to know what good it.

oh and just so you know, went to MMI for 2 yrs head tech for 6 yrs at honda dealer and been restoring bikes before all that for 8 yrs and working on cars and trucks with the old man b4 that. age=25 so age not everything

Cured the issue about an hours ago, had some dinner and sitting to write the follow up.


So I adjusted the pilot screws as per 8541Hawk, and the idle seems to surge a little, but the cold start performance and stumble from off idle are much better. After re-installing the carbs and running it down the street some, the issue was still present with the popping. Brought it back in the garage, pulled the tank and air box off again and figured out how to get the carb top off with it in the bike still. Adjusted the needle on the carbs to the middle position, and the issue seems to have cleared up. The true test will be when I can actually adjust the pilot screws properly.

Very interested in how this works out. PO installed K&N also. Doesn't accelerate as smooth as it should and takes a lot of choke upon startup. Been thinking about removing he K&N and start fresh from there. Keep us updated on your progress.

Well in a way it is understandable that you believe that you can get a K&N filter to work. Hell I had the same attitude and stuck with it for a good 2 yrs. Every time you fix one hole in the power band, caused by the filter, you create one somewhere else.

Yes there are some folks who run them and claim good results, I'm just not one of them.

Now to give you a little background here is a quick read for you: https://www.superhawkforum.com/forum...-set-up-24769/

So needless to say. I have messed with they carbs on a SH just a little bit.... ;)

The one thing no one has asked is which jet kit was installed on the bike? The way to tell is the length of the slide springs & the number of lift holes in the slide.

If the slide spring is around 6" long and you have 3 lift holes it's a DynoJet if the springs are closer to 12" long and you have 2 lift holes, more than likely a FactoryPro kit.

Lastly, first you need at least 1 shim on each needle as it is bad practice to have the "c" clip on the needle resting on the slide. Second, the recommendation to drop the needles is for when you change the air filter.

These bikes don't have a lot extra to give. They came after the days when a jet kit and exhaust would give you an easy 10-15hp. The most you should expect from a set of slip-ons and a "good" carb set up is around 3-5hp.

There just isn't a whole lot to be gained unless you start changing hard parts.

So throwing large mains and pilots is just going to dump fuel out the exhaust and slow you down....

Also if you really need to run a aftermarket filter, your best bet would be the BMC street filter (the race filter will give you the same issues as a K&N)

So I had a chance to put some miles on the bike. I had to ride out to work to so some paper work. Seems like the issue is gone. I didn't look at the holes in the slides when I had them off, so I couldn't tell you what jet kit is installed. I honestly don't think there is one installed. The springs are long, and I think they are factory. The main jets are 175/178, and I think that is a factory jet for the bike. Also, all the jets are origonal Keihin jets(they have the Keihin emblem on them) and most jet kits from what I remember come with aftermarket jets. I honestly think the person who put the slipons/filter on just threw the parts on and called it good.

Also, I can't find any flat spots in the bike. It seems to pull strong all the way to the rev limiter, and cruising around town to work, I tried to find flat spots where it was running crappy and couldn't. It does have a little funny idle, where it surges about 100 rpm when the temp is about 1/4, but when it's fully warmed up, it runs fine.

What does everyone else see the temp do? Mine seems to have a broken t-stat (open all the time). It takes a long time to warm up, the fan almost never comes on, and it is usually around 1/4 to 1/3 on the gauge.

FWIW,
I have been using a K&N filter and Dynojet kit for about 7 years now and it works well for me.
Also, I have Jardine high mounts.
My setup is the following:
-Jets are at 180/185
-Mixture screws are at 2 1/2 out
-clip is at 5th from the top

Well the factory needles don't have adjustment clips on them so something was done. I would have to see the needle to even begin to guess what it is though.

1\4 to 1\3 on the temp gauge is pretty normal in ambient temps of up to 90-95 or so and then it goes up a little. The fan should kick on at the 1\2 way point but you will only see that in heavy traffic or really wringing its neck on a hot day.