ZX7R Tuning Issues

[Taddy]

Okay guys, this is gunna be a long one. I NEED HELP!
Picked up my '97 ZX7R about three weeks ago, on the freeway ride home after about 10-15 mins it was losing power, or chugging at about 5 grand cruising in 5th 6th gear(almost felt like it was choking). In the 98 klm ride home it went through an entire tank of fuel and ran out. Took it to a local bike mechanic with a dyno and he spent 3 days on it (i won't mention what i then spent to get the thing back) only to find exactly the same thing happening again on the way home, although now it doesn't go through fuel. Basically i have been taking things into my own hands and i can't work it out either, It's been jetted (brand unknown) & has a set of muzzy headers. Carbs have been removed and cleaned out about 6 times now, with no difference at all, anything under 5 grand and it runs fine, anything over 7 grand and it has balls to spare, on occasion it also coughs and spurts of the line as well, but that cruising range of rev's it's an absolute pig. i see icing is a major issue with these things but it hasn't been cold and i can't see how thats an issue in this case, but then who knows? The guy i got it from swears blind it was running A1 when he garaged it about 18 months ago, Grasping at straws now, so any idea's people?

[Duane]

Taddy,

Were these particularily cold days?


I had the same problem when I lived in berwick with my 99 7R going down the freeway, or cruising on cold mornings/days


It's the carbies freezing. not much you can do about it

Click down two gears and give the the berries

Note: my bike sounded like a dirt bike when this would happen, as the carbies would freeze over and the bike would start running on only a few cyls

[Taddy]

Taddy,

Were these particularily cold days? No They Weren't Cold at all, in fact the last time it happened it was about 25deg air temp.

[99coconuts]

never had the icing problem with mine, not once ever. but going by what i've heard, those symptoms sound just about right. if its not cold when it happens tho, it wont be that...

i know the carbs have been cleaned and recleaned, but has the jetting been checked out properly? going on my very limited knowledge of carbs, it sounds to me like maybe your needles are sitting a little high and allowing the main jets to open up too much at cruise, flooding it a bit. i take it the bike doesn't appear to have any flatspots when your accelerating normally?


you could always adjust your cruise revs. mine has lean issues due to the exhaust (about to go back to standard) and not having a jet kit or the means to buy one to fix it. below about 6k, i get the stutters at a cruise (accellerates fine) so i just sit a gear or two down unless its a longish stretch where i'll just put up with the problem. not an ideal solution, but if you really dont want to pull those carbs apart again, i'd say it'll work for you

[99coconuts]

oh, and try this forum aswell

http://www.redmonkey.com/7r/index.php?d ... /start.php

its an american zx7r forum, more info on our beasts than you'll ever need i'd be thinking

[Taddy]

Second hand set of carb's fixed it up no probs, guess i'm still none the wiser what the actual problem was, but, hell, who cares it's purring like a kitten............

[Gosling1]

... It's been jetted (brand unknown) & has a set of muzzy headers. ...

a second-hand set of carbs fixed it up ? - Sounds like whoever did the jetting in the first place did a thoroughly shithouse job......

[FrogZ]

not wanting to sound like a total dork but it has been like this since you got it ? If so just ask the guy who sold it to you if he will kick in for some of the carbs, nothin to lose... he must have known you were going to have the problem... yeah yeah i know buyer beware.

[SocialSecurity]

i get very similar issues on the highway when my needles are set too high, with steady throttle/engine speed for a while it fouls the plugs... doesnt seem to be a problem till i open the throttle up a bit more and it chugs till the fouling has cleared up, and then its fine until ive been sitting on the same throttle/speed for a while adjusting pilot screws didnt really help, only needle height really


dale, have you tried adjusting your pilot screws yet? much easier pulling carbs down, usually only need to pull the tank off to get to them.

[99coconuts]

i get very similar issues on the highway when my needles are set too high, with steady throttle/engine speed for a while it fouls the plugs... doesnt seem to be a problem till i open the throttle up a bit more and it chugs till the fouling has cleared up, and then its fine until ive been sitting on the same throttle/speed for a while adjusting pilot screws didnt really help, only needle height really


dale, have you tried adjusting your pilot screws yet? much easier pulling carbs down, usually only need to pull the tank off to get to them.

nope, i went and got a stock exhaust and she runs like a dream again.... just sounds like a pussycat

i'm not out there for high HP or anything, the bike is PLENTY quick at the moment, just not super wheelie happy (which is fine considering how often i get to ride these days). only reason i had the other exhaust on was for looks and sound, but i'll just have to spend up on a bolt on can to suit the stock system when i've got the dollars.

[SocialSecurity]

ahhhh well... if you ever get the tinkering-bug, you could try slap the pipe back on and take the pilot screws out half a turn 1 hour job, including a break for a few beers and a scoob certainly shouldnt need a jetkit to run ok, and certainly dont need a jetkit if its only a cruise problem

[99coconuts]

ahhhh well... if you ever get the tinkering-bug, you could try slap the pipe back on and take the pilot screws out half a turn 1 hour job, including a break for a few beers and a scoob certainly shouldnt need a jetkit to run ok, and certainly dont need a jetkit if its only a cruise problem

it wasn't just cruise, that was just when it was most noticable. trust me, it was a PITA to ride the way it was unless you were riding flat out. below 6,000 it was a pig, stutters on cruise, minor flatspots under light acceleration, bastard to start when left for a few days (a month saw starting the thing turn into a half hour exercise) and just downright sloppy below that 6k line. above it went like a cut cat, but you probably know just how much you'll use that range getting around the suburbs (at least, if you have any thoughts of licence preservation )

but most of all, i just dont see myself frigging around with carbs

[SocialSecurity]

ahhh trust me pulling carbs down is fun

[99coconuts]

ahhh trust me pulling carbs down is fun

nar, done it a few times and i can DEFINATELY think of better things to do with my time

[Burky]

Sound like a prop i had but without the fuel loss. Turned out to be the throtle cable sliding on the mount, when you open the throtle the bike would jerk/buck and then smooth, then would start to jerk/buck again .

Makes riding difficult as ribs and nuts would bounce off the tank

Also found a vacum line off also.