Bringing my new toy to life

Ok guys I finally got the 1973 kx900 to fire up today after a little sweat. This bike sat in the back corner of a guys barn for nearly ten years wthout even being moved around (since 1989). I pulled the carbs off and gave them a really good cleaning. Meaning I tore them completely down to every last little piece. I kept each carbs parts in their own little trays so not to mix them up any. I have everything looking shiny new in the carbs. Now heres what I am facing. The bike would idle fine but when I give it a little throttle it bogs down. Does this have anything to do with there not being any filters behind the carbs yet? Also the exhaust has not got a baffle in it, could this cause my problem? Right before I cut it off for the night it started dying and would take a minute of spinning it over to fire back up. I am also hearing a ticking noise coming from the header area where the header bolts to the head, may be a loose pipe? What would any of you suggest I try next?

Hi JD,
The Ticking is probably an exhaust leak. And yes the bike won't run well if you've changed the intake and exhausts without going through one of motorcycling's most wonderful of challenges, rejetting.

In any case, welcome to KZR. We can help!

KZCSI

Before further work on the carbs, if not already done would first check for good quality spark, doublecheck ignition timing and operation of the advancer unit (use strobe-type timing light and watch the advancer move back and forth with changing rpm by blipping throttle), and do compression check (hold throttle wide open during testing), and assure valve clearances are within specs. And assure ample good fuel supply is reaching carbs (could remove and flush tank, remove and clean petcock (especially all the filter screens), and install new in-line fuel filter(s).

Remember -- even perfect as-new carbs can't compensate for faults in the non-carb components.

Don't believe absence of exhaust baffle or the ticking noise has any particular bearing on the immediate problem as reported (but better jetting as suggested may indeed be ultimately required to resolve bogging off idle). New exhaust gaskets to likely prevent further ticking are available from Z1 Enterprises.

Good Luck!

jdsmithinc wrote:

Ok guys I finally got the 1973 kx900 to fire up today after a little sweat. This bike sat in the back corner of a guys barn for nearly ten years wthout even being moved around (since 1989). I pulled the carbs off and gave them a really good cleaning. Meaning I tore them completely down to every last little piece. I kept each carbs parts in their own little trays so not to mix them up any. I have everything looking shiny new in the carbs. Now heres what I am facing. The bike would idle fine but when I give it a little throttle it bogs down. Does this have anything to do with there not being any filters behind the carbs yet? Also the exhaust has not got a baffle in it, could this cause my problem? /////What would any of you suggest I try next?

That will make it run very lean.

I would suggest:

1) Install the stock airbox and filter.

2) put a baffle in the exhaust pipe

The bike may have already been and still be properly jetted for pods and open baffle, and could have been performing well when parked some 18 years ago in 1989. Without knowing performance history of the present set-up, I would consider leaving the pods and open baffle as is, at least for the time being, so as not to introduce further uncertainty.

My best guess as to any carb-related reason for the bogging off idle would be the primary circuits not yet being sufficiently clean.

Good Luck!

jdsmithinc wrote:

...pulled the carbs off and gave them a really good cleaning...bike would idle fine but when I give it a little throttle it bogs down. Does this have anything to do with there not being any filters behind the carbs yet?...

Many a pristine newly refurbished carb has been immediately disabled by an onslaught of crud due to absence of an in-line fuel filter.

Good Luck!

I found my problem, I have no fire at cylinders 2 and 3, I thought it was a little quieter than it should be. I am going to replace the coils, and I am thinking about going with a dyna III electronic ignition, instead of putting points and condensers back in.