Driveline lash?
 

I know, more questions from the new guy. I've got my new regulator and battery in and have had about fifty trouble free miles. But now that I'm back out on the road I am being far more critical of the bike.

I think what I am experiencing is driveline lash but only really being familar with in line fours I thought I'd ask. I'm experiencing a little bit of a stumble around 3k which I'm assuming is a lean spot in the carburation, I have D&D's and I'm assuming they are to blame. When this happens there is a small but audible clunk that I can also feel in the clip ons. I'm assuming this is just slack in the drivetrain because of the stumble in power and nothing to worry about besides taking care of the lean spot.

Also all of these CCT threads are making me paranoid. If these fail is it simply catastophic with no warning or can you hear it at idle as a loose chain. I'm listening to my bike way too much now as well.

As always any advice is appreciated and maybe sometime soon I can be a guy with answers instead of just questions.

Kendrick

Sounds like slack in the driveline. Main jets kick in at around 3 grand, so it likely is a carburetion issue.

CCTs generally do not just simply fail. You can usually hear it close to idle, and most people say it gets louder as you rev the motor.

Sometimes I listen to my bike too much, thinking I hear something. Based on what you've said, it seems unlikely it has anything to do with your CCTs.

Fix the jetting problem. Sounds like a small backfire through the carb(s). Those D&Ds will definitely get you lean.

From what I have read on this site, there is some disagreement as to whether or not you can hear the CCT let go. Some say it got noisey as hell right before hand. Others just say it is farked as soon as it let go.

But none of them described what you are describing, so it doesn't sound like CCT.

So, I finally dealt with the jetting on my bike, or more specifically my mechanic did. He took it apart and the needles had no numbers, so I just had him put a Stage 1 dynojet kit in so we knew what was in it. I know, nothing like throwing money at a problem.

Bottom line the bike ran exactly the same. He ended up putting in a stock air filter instead of the K&N. Now as long as the bike is hot it runs great. It would seem since the D&D pipes have essentially no baffles in them, with a K&N there is so much air rushing by a Stage 1 can't feed enough fuel.

So I was just wondering if anyone else has had a similar experience and if eveyone elses hawk is so sensitve to being fully warmed up. The bike runs great now but it feels alot like I just ran in circles, when all I really needed was a stock air filter.

Kendrick

You're still running lean. If it idles okay then you have to assess where the bike is not running well when cold.

If you have problems at very small throttle positions and low rpm then your problem is with the mixture screws. If you can't adjust the mixture screws out any more to cure the problem then you need to go to a bigger idle jet. Stock is #45. Many are happy with #48. A full exhaust system generally requires #50. Think of the mixture screws as a "fine adjust" and the idle jet as a "coarse adjust". The fine adjust only has so much affect before you need to adjust the coarse.

Next, if your problem is at smaller throttle openings (about 1/8-1/4) and between about 2500 to 7500 rpm then you need to adjust the needle height. With an aftermarket jet kit you can raise and lower needle height by moving the clip height up and down. If you have stock needles you can shim by using washers to raise the needles for a richer mixture, but you cannot lower them because there is nothing to remove. The only solution is to buy aftermarket.

Lastly, for the main jet, this controls fuel metering at wide throttle openings and high rpm, when the slides are almost all the way open. You will generally swap main jets by performing dyno runs with an exhaust gas analyzer. This should be your first step, even though I mention it last. The reason is, when you change the main jet, you affect both midrange and upper range carburetion. The needles slide in and out of the main jet, so if you change the main jet and go say a size or two larger you are now allowing more fuel pretty much across the entire usable rpm range of the motor. This is why you select main jet size first.

I should write an article on this for our knowledge base but there is so much information out there already on jetting I think I'd be wasting my time.