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Carb tuning Q?

Posted: Sun Sep 11, 2011 9:56 am
by hakx
My 85 ninja 600 sputters around 6000 - 6500 RPM @ 140km / h (6th gear). THe only way I can get around it is to drop to 4th gear (RPM's to 9000) then keep the rev's high through 5th and 6th but the bike sheds speed a little quicker than I like.

By sputters - I mean it hestitate and sorta rattles - the same sensation when you feel leave a stop sign in the wrong gear. (underpowered). You can hear the motor (different tempo), and feel the accelleration slip in an out of a "power band". Its wants to go, but maybe starved for fuel for small instances.

The specs indicate a top speed of 202 km/h (127mph), but I'm guessing thats a fresh engine, nice long stretch - an maybe a tailwind. The max BHP was 76 @ 10500 - 11000 RPM (so maybe 68 at the final drive).

So, do I invest in a carb tuning / jetting, etc, or do I just settle into the fact that its just an older bike with 592cc's with not a lot of ft/lbs of torque doing what it can with my fat a$$ on it? I've already seafoam'd, gas treated, running supreme - or pretty much anything else thats a low $$ fix.

Re: Carb tuning Q?

Posted: Sun Sep 11, 2011 10:18 am
by agraebner
It sounds like its not running right. It would seem to me that once its running right you should be fine. Is there any black color growing around the exit of your exhaust that might indicate a rich condition or improper ignition. Might be as simple as some plugs needed or a bad wire. With the age of the bike I would suspect wire and plug combo. It does not take long to effect the operation of a spark plug when its missing due to another cause. Most standard motorcycle plugs arent very expensive and the manuals suggest changing them every 4k miles. My shadow from brand new would feel a performance improvement with new plugs every 4k miles. My cbr is smoother off idle when plugs are replaced at 4 k. On both of these there is no deposits or anything like that. Spark plug condition just seems more critical on these smaller engines than say a 350 chevy......

Re: Carb tuning Q?

Posted: Sun Sep 11, 2011 11:33 am
by hakx
Plugs are new. Wiring is legacy though. I do notice black growing like a fungus around the the exhaust though. Time to engineer some fresh wiring I guess.

Re: Carb tuning Q?

Posted: Sun Sep 11, 2011 4:13 pm
by agraebner
NGK makes some sets that should be really easy to use and better quality than oe. I would do a few quick checks with the old meter... check coil primary and secondary resistance. Check coil connectors to make sure they are clean and tight. Check the pick ups for the ignition as well. In my experience its a bit odd to have a fuel issue for just a 1k rpm range. If you had a fuel issue it would more likely show up as an idle issue or hit a spot it wouldn't go over. Due to blockage in carbs. The mid- range is controlled by the needle on the slide rising opening for more fuel flow from main jet. If the main is open to get higher rpm then safe to figure the carbs aren't clogged. It is possible that the needles are leaking causing high fuel level in the carbs. Im not sure specifically which carbs you have but the Mikuni carbs on my fzr are famous for wearing out the emulsion tubes the needles slide in dumping in excess fuel. More likely that you are having and ignition issue. If its not to hard on your bike then take a look at the plugs and see if you have a dark plug that might indicate which cylinder your issue is with.

Re: Carb tuning Q?

Posted: Sun Sep 11, 2011 6:44 pm
by hakx
Ingniton wires on 1,2, &4 are now clean, tightened and reinstalled. Wiring to #3 is way out. Should be 5K, but is far beyond that (almost an open). Ordered new cables and NGK caps from Z1. Thanks all

Re: Carb tuning Q?

Posted: Sat Oct 01, 2011 4:23 pm
by hakx
UPDATE:

My order from Z1 showed up. Changed the 5Kohm caps and made fresh wiring up. NOOO more hestation now. Now I'm gonna repack the Hance and Hine can, as well as maybe look at replaciang the throttle and clutch cables (they are getting kinda streched, and I am running out threading on the adjustments.