I am having issues locating a sound I have coming from my engine. I have a '98 w/51,000 miles. Got the Ape's, and the valves are adjusted(not cct's), I have inspected the valvetrain and the lower end. Everything looks good. But at around 2000 to 2500 rpms I will sometimes here a clunk or a chunk (I think both words are appropriate), and immediately after the engine hesitates and will drop a couple hundred rpms and immediately pick back up where it left off and run like a champ. This happens in or out of gear, with the clutch engaged or disengaged. When I bought the bike I road it home, when I got there I inspected it and found that the clutch fluid reservoir was empty, completely. So I serviced and bled it. It did not feel like the clutch was slipping, and it would not lurch while in gear at a stoplight.Just wondering what kind of damage could have been done and if this could be my mystery noise. Any thoughts would be much appreciated. Thanks

 

I had exactly the symptoms you describe and at the same rpm when I tried to tune my bike to an after market air filter (BMC race). I'd hear a clack, whack sound and the bike would stutter for a second and then pick right back up. I think the noise was the carb slides, but don't know for sure.

What I do know is that when I went back to the stock air filter and tuned the carbs to it, the problem disappeared.

What air filter-jetting-exhaust are you running?

 

+1 RK1, sounds like fuel/air mixture issue to me too!
RC

 

well, I have a k&n filter, and I think I have stock jets, the previous owner said it was jetted but I think he was lying to me because everything below the filter looked like it had never been touched when I tore into it. I also have slip on pipes, just wondering though... what are the stock jets?

 

Original main jets are 175f and 178r. Tell you what, If you don't want to yank the carbs off the manifolds, you could open the rear carb vacuum chamber and check the needle. If it's a dynojet or factory pro with the slots on it, the bikes been rejetted. If it's the OEM needle, you can bet it hasn't been.

One of the reasons I don't like to pull the carbs if I don't have to is because every time you do, the bike won't run right unless you sync the carbs as well.

I think the best thing you could do is borrow or buy an OEM air filter, pop it in and see if the problem goes away. Even a new one is cheaper than a jet kit, and if that makes the clunk/skip a beat go away, you know what it is. Then you can either just stick with the Honda filter or try to jet for the K&N.

 

sounds worth a shot... thanks

 

Sounds like carb farts.

 

Yeah lean backfires, pull the needles one notch...if it has notches, go get a Dynojet kit if not. It comes with all the jets you could need, needles, springs and a drill jig and bit to vent the slides. You could tell if they have a DJ kit by checking if there's a hole beside the needles checking from the carb throats.
Other symptom are whitish plugs

 

I recommend adjusting the mixture screws another 1/4 - 1/2 turn out and doing a carb sync. At 2500 rpm the needles are barely carbureting anything. It's the idle mixture you need to tweak.

 

sounds like this has been an issue before.

 

Yeah, in severe cases you get a clunk-die.

 

I tore the carbs off today, found 162.5 front main jet and 165 rear main jet. This makes no sense since the stock settings are 175 front and 178 rear, and the bike has a k&n filter, if anything the jets should be larger... But thats what the PO left me. I think its time for a jet kit.. any suggestions for k&n with slip-ons.( stock needles with minor wear, and 45 sec or slow jets.)

 

Sounds like it was jetted for high altitude. At sea level shoot for 182f/185r mains, stock idle jets, 2.25 turns out on mixture screws. Start with the clip in the middle notch on the needle.

 

taken notes...thanks

 

FWIW

i had this same issue and it was a RICH a/f mixture. i was having lean backfires with my new leo vince ( had 2 bro high mounts ). i put 48 pilots 3 turns out & had the described problem... adjusted it to 1 turn out & have never heard it since ( & thats probably 1/2 still to rich )


tim

 

are those dynojet #'s as they have a different numbering system.

tim

 

Dynojet doesn't list 162.5 mains and I don't believe Keihin does either.

Even for a bone stock bike Honda only specs one size down (172/175) over 6000 ft. altitude. Can't imagine why anyone would install a K&N, slip ons and then go 162.5 and 165 on the jetting. Also, the numbers on those jets are pretty little. Just to be sure I'd get out my magnifying glass, take a close look and make sure they weren't 182.5/185 already.

 

trust me I looked them over very well, I didn't understand it either.

 

Mine are 178/180 4th clip, slip on but no air filter 2.5 turns out, got lean bacfires from the needle in the middle, I'm about 1500 feets high

 

I get a random clunk sometimes too, it doesn't bother me. It's a reality check so I remember that the Superhawk is not a golden chariot from Heaven.

 

Yeah. The symptom (clunk/skip a beat) might not always have to have the same cause. I've read back over the thread and there's a lot we don't know.

We don't know which make main jets are installed and jets from different makers even with the same # are not the same. We don't know how the pilot screws are adjusted. We don't know if the jet needle is Keihin, Dynojet or Factorypro or which groove it is in. We don't know the make of the slipons or whether they are "street" or "race" baffles.

The only thing I'm sure of is since the mains are reported as 162.5/165, the bike isn't running rich.