Topic: New bike noob question.

[Blitzburgh207]

Hey guys. I've been lurking the forum for quite a while and just bought myself a 78 cb750. I'm already in love (my girlfriend is jealous haha).
But anyway, my question is:
The bike is real jerky at lower speeds, and I cant tell exactly why. I feel like I'm being pretty smooth on the throttle, does it have to do w the keihin carbs?  (stock airbox and I believe stock 4 - 2 exhaust)
Thanks for your help! (:

[chimmychong86]

Welcome! Describe more this "jerky" feeling. What have you already done? Lube the cable? Sync the carbs? Post pictures of the bike ?

[bollingball]

Four into two is not stock. have you done a 3000 mile tune up?
what does your chain & sprocket look like? Is this a K or F model? need more info.

[Blitzburgh207]

Well the cables run smoothly.  I just took the carbs apart/cleaned/reassembled them - I don't know how to sync the carbs.  This is the first bike I've owned so I'm not too familiar w tuning or adjustments yet, but I would rather learn and work on it myself.  But when riding at like 15-20 mph in 2nd, it feels like it sort of lurches forward awkwardly when I turn the throttle. I guess she just wants to go fast (:
p.s. I'll post some pics soon. You guys might be offended tho because it's fairly obvious that a previous owner (not the guy I bought it from) wanted a harley lol. It's painted black and orange w straight bars... I like the riding position w the bars but that paint has got to go

[Blitzburgh207]

The exhaust just looks/sounds stock so I figured it was but I guess not.  I'm getting a tune up next week. 6-12 inches of snow forecasted for friday so i guess I can give it up for a week...  I know it's pretty ignorant but I dont remember the model I thought it said "E" but it must have said "F" and I misread it haha. I guess I should know the information necessary to properly ask a question huh? (: sorry guys

[Gordon]

Jerky running in 1st or 2nd gear could be as simple as the drive chain being too loose. 

[Johnie]

Any chance the clutch is slipping? What kind of oil did you put in there? Some oils are to slippery for the clutches on these vintage bikes. Last, there is a section on bench syncing a carb in the FAQ section under carbs. It will tell you how to do it without a vacuum gauge, but you will need to remove the carbs again to do a bench sync. Welcome to the boards.

[Blitzburgh207]

I acutally ended up bringing it to a local shop to get tuned up...  I caved and brought it in because my riders course is in a couple weeks and I have a ton of stuff to do. I really want it to run tip-top so I can just ride when I get out. 
@ Johnie: That bench-tune write up is very helpful though. I'll remember that for next time.  I'm getting rid of the stock airbox right off the bat - so that will fall into this tune-up, but I plan on putting an exhaust on this summer at some point so I'll probably do the tuning myself at that point or whenever she needs it next.  Also, the clutch and cable were replaced last year by the previous owner - I'm not sure what type of oil was used?  Should I call him?
@ Bollingball: It's a K model (although the guy at the shop was completely convinced that the K's stopped in '76?)
@ Gordon: The chain is pretty well oiled and looks ok to me (like that makes a difference  ) Is there a way I can check for the proper tension?
Thanks everyone for the welcomes btw (:

[Johnie]

Well, see if it jerks when you get it back from the shop. Maybe whatever they do to it will fix it. If it was my bike I would call the previous owner and find out what oil he used and when it was changed last including filter. Get that service manual as it will tell in there how to check chain tension. The service manual is available in this site. Oh, and K's did not stop in 1976 as I had a 1977 CB750K and I am sure there was also a 1978 CB750K model. Maybe the mechanic meant the old school model K stopped in 1976? In 1977 the went to a different tank design and stuff.