Topic: 72 cb750 k2 somethin wonky goin on - HELP!

[Tunz]

hey guys, I'm a newb to this site, but have been reading lots of forum topics and whatnot...great site!!

I have a 72 cb750 k2 that I just bought...had been sitting in a heated garage for the past 15 or so years, but worked fine before it was stored (I work with the previous owner). The bike worked fine for the first two weeks or so after a couple carb cleans and whatnot, but the past few days it has been struggling a bit...not near as much pull or power as it should have. Theres a slight backfire/pop...nothin significant, but you can just feel it in the throttle. When on the highway now its like im being held back and the bike has to rev higher to achieve good speed...was working it to even get 70mph as only a few days ago I could hit 90mph with ease and still have more. I did just put lower bars on it and had to change my clutch cable...nothin wrong with the cable, but I'm wondering if maybe I dont have it adjusted properly and that it maybe be always slightly engaged?? (if anyone has a good description of how exactly to adjust the clutch cable??) Also have thoughts of maybe its my mixture screw adjustment...right now i have it at about 3/4 turn out, though i did just read that it should be one full turn (dont think that would effect it as much as the problem im having) Maybe valve adjustment? points/timing adjustment?? Only thing that gets me is that it worked fine only a few days ago...when I had my carbs apart I noticed that one or two of my pilot jets werent quite perfect when help up to the light, though I soaked in carb cleaner and blew out with compressed air...nothin I could do to get em perfect(my problem is in all speeds as well...not just the bottom end speeds) Bike idles fine and when in neutral it sounds great when you hit the throttle. Sorry for the long ramble, but its really bugging...I'm actually a apprentice motorcycle mechanic at a local shop here and it really gets to me when i cant even fix my own bike! Its even worse when you roll in to work and your bike sounds like a #$%*bag! haha - anyways, any help would be muchly appreciated! cheers!

[mdclips]

It sounds like a dirt/rust in the carbs to me.  What did you do to the tank to remove sediment/rust etc... something may have worked loose and is now clogging one or more jets.

[Gordon]

When on the highway now its like im being held back and the bike has to rev higher to achieve good speed...

If it really has to rev higher to get to the same speed as before this problem started, then the clutch is slipping. 

[Tunz]

Thanks for the feedback guys...to me it really feels like a carb problem, but I clean carbs every day at work and have cleaned this set 3 times just to be sure...only thing I saw wrong with the carbs were the pilot jets...gonna see if I can pick up a new set here soon.

Gonna shoot er with the timing gun tonight and also try changing out the points condensers with some new ones as well as checking the point gaps etc. just to eliminate those possibilities.

As far as adjusting my clutch goes am I supposed to loosen off the lock nut and adjust the inner flat head screw til iI feel tension then back it off 1/4 turn...or am I supposed to hold the clutch lever in at a certain point where I want it to engage...hold it there and then do the adjustment with the flat head screw and lock nut? might be stupid questions, but its my first sohc..was drivin a xs650 before this and never had to adjust the clutch

cheers

[Duke McDukiedook]

Run a wire through all the orifices you can and blow them out.

[Tunz]

I brought my timing gun home today and found that the timing was off a fair bit...it was lined up to the T mark instead of the F mark...I got it as close as I could, but still not 100% on the mark...bike runs better then it did when I first bought it though, so I'm all smiles.