I've Got a 'Clunk'
 

Recently I've noticed a 'clunk'. :? What kind of clunk you might be thinking. Well that's my question to you. :)

I only notice it when I'm sitting at a stoplight. Engine is idling away and everyone is happy. Then 'clunk'. It's not terribly loud. Actually you can barely hear it. But I can feel it though my ass and definately through the bars. It'll only 'clunk' once at a time and feels pretty solid if that makes any sense. It'll do it once or twice per minute. I want to say it's coming from the bottom of the engine but I can't be sure.

Any ideas? I know it's not the dreaded CCT's. I've been down that path before and the sound is completely different. It's not a ticking, it's a 'clunk'.

The bike is an '01 with 24,000 miles. Two Bros pipes. Otherwise it's stock. Prior owner rejetted and if anything it's running rich. I still need to pull the carbs to check what jets I have.

Maybe a backfire through airbox? Oh just a cough?

I'm thinking of a backfire, is this clunk slowing down the engine, if so it's a backfire, if not, it may be a timing chain issue, but there is many parts that can cause weird noises.

If you are running rich you could be getting a backfire/misfire from a dirty plug... I'd say pull the plugs and see how they look or just replace with a new set depending on how old they are.

The last thing I'm going to do is rule anything out. I'll pull the plugs and check them. They've only got about 3,000-4,000 miles on them but you never know.

However my gut tells me they will be fine. It feels more mechanical. The engine doesn't sputter or cough. It feels like to objects are binding and releasing or something making contact with something else. I'm being vague as I have no idea what it could be.

I'll check the plugs and let you know what I find. Thanks guys!

Then you really need to chase the sound to at least know where to start checking. Hope it's nothing, good luck

Does the bike almost/sometimes die when you get the clunk?

Sounds like I have the same problem

I think you guys are on the right track. Mine used to do it until we got some mixture issues worked out. The carbs load up then puke up throught the airbox.

i agree it sounds like an air/fuel adjustment issue... yes my bike did the same thing & it does sound mechanical to me ( i about $hit the first time i heard it )

a quick identifier is how stable the idle is.

pull the carbs and find out what idle jet are you running & how many turns out. ever sync the carbs ?


tim

Have you done a carb sync?

Probably a backfire through the airbox. Mine did it too. Search for "clunk die". Sync carbs and you're good.

Richen up the mixture screws a bit and sync the carbs.

Where is the mixture screw located?
I have the same problem
I also need to sync the carbs and clean them.
I just got a chain and sprockets set, I have to buy the tool to rivet the master link.

Actually it controls fuel not air, so you turn it out to richen the mixture.

They are located on the bottom of the carb. There is no cap on it but it does have the Honda "D" shaped head.

To adjust them on the bike you need a Motion Pro 90 degree wrench like this:
http://www.motionpro.com/motorcycle/partno/08-0229/

or something similar.

You can also pull the carbs and set them. While not as precise as doing with the engine running it does work pretty good.

You will still need to purchase a "D" driver or you can dremel a screwdriver slot in the end of the screw and then adjust away.

As for the "clunk" you are hearing. It usually is a carb slide slamming shut that causes the noise.

The Honda factory shop manual recommends inspecting (and obviously adjusting if necessary) the carburetor synchronization every 8000 miles (12000 km).