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Interesting running conditions.... input perhaps?

Old 06-21-2011, 10:52 AM
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Interesting running conditions.... input perhaps?

Alright, got one quirk to work out still from the re-build. Here we go:

Bike turns on, runs well, hits rev limiter, idles just fine. It's having some rough spots in running. The first condition is on the highway. The bike pulls strong on the on-ramps, neck-muscle workout status. After cruising for as little as 30 seconds, it seems to bog down quite a bit. It won't hold a steady throttle (I keep it even, and it has bursts of power/lag). Eventually if I run it hard enough it will run itself dead. This seems to happen more in higher gears and when trying to pull hard... I know it's better to be pulling in like 4th gear at 60mph, but I don't see why it would have problems with 6th gear... I've actually killed it twice like this, and can feel the symptoms of it happening almost every time. I avoid it by slowing down and pulling onto a side street. It seems to "recover" when I do this. Dead on the side of a highway isn't where I'd like to be regularly The last thing to note is that I have noticed a heavy backfiring during throttle when this happened on one occasion. It will start back up again in a couple of minutes after it dies.


Ok, the other interesting scenario that I'm sure is related is that it does a similar thing in town. Stoplight/stopsign speedy acceleration is followed by the bike having a hard time holding a steady throttle. It is never enough to "kill" the bike, and is less noticeable than on the highway. Actually, sometimes, it doesn't happen, but seems more likely after I've been riding for a little while (more than a 10 min trip to the grocery store).


From what I can tell, i suspect it to be a choke/flooding issue. Maybe my petcock isn't working correctly and I'm actually not getting enough gas (just thought of this, I'll have to look into it tonight)

Carbs are clean, checked the choke cables, side stand switch is working correctly, fluids are all full, petcock has been rebuilt, in-tank fuel filter is clean, replaced the two choke cable guides that go into the carbs (perhaps there is something here too?). Anything glaring that I should look at?
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Old 06-21-2011, 11:05 AM
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If you're tearing apart everything, might be worth it just to do a quick check in the airbox. It'll only take a minute, you never know if some bird is stuck in there. It's not like that never happened before....to someone on the forum....about a week ago.
haha
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Old 06-21-2011, 11:12 AM
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for the falling dead and dieing on you part, check the timing. mine did the same thing after i did some work on the cams. adjusted the timing and now i dont have the issue.
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Old 06-21-2011, 11:13 AM
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Airbox is sparkling clean . Stock air-filter, I do have aftermarket velocity stacks in there, but I don't see those causing any problems.

I forgot to add, I have also replaced the coils with 600RR stick coils and new plugs. I have not taken the time to see if those are working correctly...
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Old 06-21-2011, 11:14 AM
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Timing is also set correctly... keep 'em comin lol!
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Old 06-21-2011, 11:43 AM
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pinched vacum line? vapor lock in gas tank?
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Old 06-21-2011, 11:47 AM
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just cause the petcock is clean dont mean it works right. could be sticking, if you pull the lines, does fuel come out?
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Old 06-21-2011, 11:56 AM
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My gut is that this is fuel related, so I guess I agree with your first idea. Most likely getting too much fuel from the symptoms you described. But where to start looking . . . I don't know. You changed a lot of stuff at once, and I guess it could be related to anything you touched in the fueling or air pathway.

Here's my reasoning: A cold engine likes a relatively rich condition, so your bike is running ok when cold. But once it gets warmed up, it starts running like crap, because now it's too rich. That could also explain the backfire under throttle.

It could also be ignition coil or timing related, but that doesn't seem to match the symptoms you described as closely.

But I'm probably completely wrong. It's probably a bird or something.
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Old 06-21-2011, 12:02 PM
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Originally Posted by evines View Post

Here's my reasoning: A cold engine likes a relatively rich condition, so your bike is running ok when cold. But once it gets warmed up, it starts running like crap, because now it's too rich. That could also explain the backfire under throttle.


But I'm probably completely wrong. It's probably a bird or something.
I get the same feeling too. I'm just running out of things to check haha! And, yeah, it could be pretty much anything, cause I did everything at once. To be honest, I'm surprised I got it running this well...

And the petcock works. I made the mistake of trying to start it with the vacuum line attached but not the other ones, so the rear valve cover got a quick petrol shower!
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Old 06-21-2011, 12:04 PM
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float problems.....
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Old 06-21-2011, 12:07 PM
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What do the plugs look like?
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Old 06-21-2011, 12:13 PM
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Also have you tried to open the tank right after it happens?
If not try it and see if you are creating a vacuum in the tank.
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Old 06-21-2011, 12:18 PM
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Originally Posted by 8541Hawk View Post
What do the plugs look like?
That's one I haven't checked yet... I'll look tonight. I remember reading that you should check the plugs at different RPM's to evaluate the different jets... as in, run the bike to 8K rmp, then turn the bike off immediately and check the plugs. At work right now, so can't research it that easily. Is this true, or should I just check them cold?
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Old 06-21-2011, 12:20 PM
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Originally Posted by 7moore7 View Post
That's one I haven't checked yet... I'll look tonight. I remember reading that you should check the plugs at different RPM's to evaluate the different jets... as in, run the bike to 8K rmp, then turn the bike off immediately and check the plugs. At work right now, so can't research it that easily. Is this true, or should I just check them cold?
Just check them cold, it will tell you if the bike is running overly rich.

You can do the other tests later to fine tune but it kind of sounds like a tank vent problem.
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Old 06-21-2011, 01:14 PM
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I agree with 8541Hawk on the tank venting problem. Especially since it happens after riding for a little while. It's the easiest thing to check too, i'd start with that. Just leave a spare key in your gas cap and when it starts to bog, pop the tank open. (provided you have a stock gas cap)
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Old 06-21-2011, 02:04 PM
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+3 (or is it 4 now?) tank vent is what it sounds like to me.
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Old 06-23-2011, 09:58 AM
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I've actually troubleshot the vent cap already (there're enough people that have had this problem that I vetoed it early). Just used a spare key...

I'm going to pull the plugs when to see if I'm rich/lean. Haven't had the chance yet as I got home late last night (I know I know, it takes 10 min). I'll look into the float issues... first I might try to throw the K&N back in and see what that does.... if it affects it at all, I can go from there. I'm not fully confident in my pilot screw adjustment yet... wouldn't think that they would be off enough that the bike would run like this, but may as well make sure.

Just happened to be by my mechanic yesterday, and was talking to him about my bike setup... He pretty much suggested to do the opposite of how many of the members on here have dialed in their carbs. K&N, DynoJet, blah blah blah. Seemed pretty confident in his way, and he's been working on bikes much longer than me. I'm tending to trust the guys on here as many have owned and tuned the bike for years (talkin to you guys, 8541Hawk and Tweety), but still tinkering in my head.

Kinda just thinking aloud here, cause I'm at work and the bike is at home. Which also explains my post count, haha!

Last edited by 7moore7; 06-23-2011 at 10:02 AM.
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Old 06-23-2011, 11:11 AM
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K&N & dynojet work for 95% of the carbed motorcycles in the world.. so he is not wrong.

But unless he has specifically worked on superhawks, what he learned working on other bikes does not apply.
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Old 06-23-2011, 11:22 AM
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That's exactly how I've come to understand it.... kinda tough to have a convo with a mechanic who will know more than me on every other bike out there... With my messing around with K&N, K&N with air dam put in, FactoryPro jet, etc, 8541Hawks' setup has indeed worked best on the butt dyno. It is fun from 2K to 10K RPM, so I'll let that settle my worries.
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Old 06-23-2011, 01:22 PM
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Yeah at this point you need to pull the plugs to see if it is going rich or if it is a fuel starvation problem. Also have you tried pulling the choke (enrichment circuit) out just a touch when the problem is happening?

This also could help determine which condition is causing your problem.
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Old 06-23-2011, 01:34 PM
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Originally Posted by 8541Hawk View Post
Also have you tried pulling the choke (enrichment circuit) out just a touch when the problem is happening?

This also could help determine which condition is causing your problem.
Ah, I have not tried this one! Will pull the plugs and try this asap. Thanks
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Old 07-03-2011, 07:27 PM
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Ok, getting a little bit of mixed feelings from the tuning.

Here are the plugs. Front is on the right, rear on the left. From my amateur diagnosis, it still appears that they are running rich (maybe?)
Name:  Plugs.jpg
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What's weird is that pulling the enrichment circuit halfway or even all the way out during the ride would make it run noticeably better in the mid-high range (but would kill it at idle). Still haven't taken it on the freeway yet, but I suspect that it is fuel starved from the way it was acting.

Not sure how important this is, but these plugs were pulled AFTER running the choke test. Not immediately (the bike had been running sans choke for at least 10 minutes before pulling the plugs) but I may have tainted my results.

Maybe bigger mains are needed? Does it look like the front one may be burning oil? I have a little time to tinker tomorrow.

On the plus side, running the bike at 110+ degree temps and the radiator is keeping up better than I would have thought it could. I think my riding will be limited by my comfort before the overheating factor!
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Old 07-03-2011, 08:09 PM
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Check the diaphragm in the petcock. I went through this very thing twice, said diaphragm was a fault both times (torn)....
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Old 07-03-2011, 08:19 PM
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Noted. Was the diaphragm cracked, or just not seated properly? I used a rebuild kit on it, which one member on here awhile back had problems with...
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Old 07-03-2011, 08:47 PM
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Mine were ripped (in both cases)....
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Old 07-26-2011, 08:20 AM
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Replaced the petcock with OEM, conditions still exist .

Been in and out of town, so this last little issue has been slow to fix.

Short summary of what happened this morning: Starts w/out choke, runs great up and down the street. Runs awesome up to about 50-60mph on the street ie. frequent stops.

Try to hold a steady 60mph on the highway and the sucker starts backfiring like crazy, pull the clutch in and it dies. Lugging big time if I keep the clutch engaged... to the point where I'm slowing down and eventually I stop (seems like maybe running on one cylinder). Bike won't start for about 20 seconds, let it rest, then it starts but only if I hold the throttle at about 2Krpm. Manage to get off the highway, where it runs rough, but gradually symptoms disappear in the city and the thing accelerates like crazy and rides very well.

Gonna keep diagnosing...there are a couple of things that I haven't tried yet. Just thought I'd give an update.
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Old 07-26-2011, 09:55 AM
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really sounds like a fuel issue to me..

Bad gas? Try running with the tank cap unlatched / open just to be sure the tank is venting?

Dieing when pulling in the clutch at speed is a known issue on the earlier bikes. Mine never does it, but it is common enough to be listed on hawkrider's website. www.SuperHawk996.net!!!
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Old 07-26-2011, 10:11 AM
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It seems like a fuel issue to me as well... Running with gas cap open doesn't change anything.

That's interesting about the clutch above 40mph... I didn't know that... mine's a 98 so it could be this issue.

Don't think that it's bad gas, as it's been doing this for a few fill-ups now.

I may just need to go through my carbs again and make sure everything's hooked up properly. I'm still not 100% sure that my choke is functioning properly either... Idle mix screws shouldn't be causing anything like this should it?
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Old 07-26-2011, 10:40 AM
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Have you checked the filter screen that goes in the tank under (or actually above) the petcock?
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Old 07-26-2011, 10:49 AM
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Yep, actually it's been replaced recently... but it still looked good when I changed the petcock diaphragm as mikstr suggested.
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