Discosef Posted May 29, 2013 Report Share Posted May 29, 2013 Ok started having a problem just after Xmas where my ZZR is running as rough as fook between 3-5K rpm. Engine is hesitant at that range and the throttle is kind of aggressive from idle (making mini roundabouts a very interesting and arse tightening experience in the wet.) Bike had not been ridden for about a month due to the weather . Above 5K it runs sweet as a nut. I have ....... Ran through several tanks of fresh fuel (although i doubt a month lay up would do much). Changed the plugs. (Old plugs looked fine, no signs of oil or running lean.) Changed the Ht leads. Tested the Coils....OK Valve clearances checked adjusted. Cleaned and serviced the carbs. (Float heights ok) Balanced the carbs. Gone back to stock air filter from a K&N. Changed the fuel filter. Checked for suction leaks on the pipes. Compression test seems fine. When i changed the oil it had some white froth which I had put down to condensation due to the bike doing a lot of short commutes and not really having had a good run out after last years amazing summer. Changed the oil a couple of time since then and no signs of further water and the bike ain't losing any coolant. The only other thing I can think of is that I replaced the stock downpipes after they had corroded through with some non stock stainless ones. I knocked this on a speed bump and had to cut them open to repair a baffle splitter that had come loose and was rattling about in the collector (This was last winter and I hadn't noticed any problems after the repair). I know that fuelling on ZZR600 is sensitive to the exhaust being fannied about with. I've adjusted the pilot screw to try a slightly richer mix with no change and don't really want to start changing jets. I'm thinking about changing the downpipe to a Motad (which seems a closer design to the original then the one I have on now, and a good condition original is difficult to find) but before spending £300 on it I thought I would see if anyone else can think of what might be causing the problem. Link to comment Share on other sites More sharing options...
timbrell Posted May 29, 2013 Report Share Posted May 29, 2013 If you're sure the carbs are ok and you've checked for air leaks on the rubbers then I'd be thinking exhaust. I've not got a ZZR but I had a small hole in a link pipe on my bike that made it backfire and run like a bag of crap at low revs, changed it and it was good again. Check the whole system for blows and the tell tale black area around any pin holes, worth a cursory glance before coughing up £300 or messing about with jetting! Good luck with it. Link to comment Share on other sites More sharing options...
BudgetBoy Posted May 29, 2013 Report Share Posted May 29, 2013 Id say carb problem still.. Are all settings in spec? Are needle valves,emulsion tubes etc all ok? Did you carbtune then to balance them all up? Are the rubbers where the carbs mount to all ok.. and are they all tight.. Are exhaust mainfold gaskets all a tight seal. As already said the smallest of air leaks will make it run rough. Link to comment Share on other sites More sharing options...
Discosef Posted May 29, 2013 Author Report Share Posted May 29, 2013 Cheers for the replies guys. I'm gonna check again for suction leaks, so difficult to find. Haven't checked the exhaust for leaks, so that is something to try. Carbs are stock and pilot screw is turned out 2 turns which I'm lead to believe is about right. (Haynes doesn't give the stock setting for this but the Googling it has it between 1.5 and 2.5 turns out. It was about 2 turns when I first looked at it.). No sign of any emulsion and everything looked in good condition. Rubber mounts are OK. Used standard vacuum gauges to balance the carbs. Aaargh.....It has a Scottoiler fitted and it has just dawned on me that I stupidly haven't checked it. Plenty of things to check and triple check now. Cheers again. Link to comment Share on other sites More sharing options...
ssray Posted May 29, 2013 Report Share Posted May 29, 2013 when running spray gt85 etc around the carb rubbers, you will hear a change in not if any gets through-not wd40 its no good on rubber Ray Link to comment Share on other sites More sharing options...
Discosef Posted May 29, 2013 Author Report Share Posted May 29, 2013 I had used some engine start looking for a rev increase. Gonna do a more methodical check right through the vacuum system and stick a straight through connector to take the Scottoiler out of the equation. I kept getting broke off the when I did this check so may have missed something. It's probably staring me right in the face shouting you thick barsteward I'm right here. Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted May 29, 2013 Report Share Posted May 29, 2013 I'd also be inclined to double check the carbs over.Is it a high mileage zzr?check the needles and seats aren't worn and buggering up the lowdown fuelling Link to comment Share on other sites More sharing options...
Discosef Posted May 30, 2013 Author Report Share Posted May 30, 2013 It's a ZZR600 E7 done 33K. 23K of which are mine. Been through all the pipes no sign of any suction leak or signs of blowing exhaust gases. I had a good look at the needles and seats when checking the carbs all looked in good condition. I understand that worn needles would make the bike run slightly rich and it seems to be running slightly lean. Everything keeps coming back to the down pipe and the changes made to the collector, if the gas is getting out faster then the bike will run leaner. This is what the original pipe looked like.... This looks like what I have fitted now........ This is the Motad...... Can't help but wonder what difference the bit of pipe between cylinders 2-3 makes. Probably thinking Zebras when I'm looking at a horse (or a mule in this case). Link to comment Share on other sites More sharing options...
BudgetBoy Posted May 30, 2013 Report Share Posted May 30, 2013 cylinder 2&3 will run hotter (leaner mix) as they are in the middle, and i think that what that pipe helps with..Along with the bigger main jets. Have you made sure you have the correct jets in the correct carb? 1&4 the same and 2&3 the same. Its been know for people to clean them and not put them back in the right order. I have your model as 3 turns out on the pilot (not what you posted, 2 turns was the F model 95-98) 1&4 should be 137.5 mains 2&3 should be 140 mains Id still say your carbs are the issue mate.. Edit spelling Link to comment Share on other sites More sharing options...
Discosef Posted May 30, 2013 Author Report Share Posted May 30, 2013 Stripped the carbs individually to avoid mixing parts up. Looks like I have bad info on that pilot screw, hope it is just as simple as that. Never had to touch the carbs on a bike before so this has been one hell of a learning curve for me. Link to comment Share on other sites More sharing options...
Discosef Posted May 30, 2013 Author Report Share Posted May 30, 2013 Took the pilot out to three turns, checked the balance again and it is still running the same. Link to comment Share on other sites More sharing options...
Discosef Posted May 30, 2013 Author Report Share Posted May 30, 2013 ZZR international forum 0 - PBmagforum 1. Ignore my last post, that was revving the bike while on it's stand. Just took it for a ride and there is a noticeable difference, it still has it's burble between 3-4K but the smoothness of the throttle is improved. I can sit behind a bus at 3-4K in second gear and the bike isn't acting like a bucking bronco. It's certainly more pleasurable to ride. Hopefully that is it sorted. Big thanks to Budgetboy and everyone else who had advice, this has been doing my head in for a couple of months now and I wouldn't like to think how many times I've pulled the tank and airbox off. Richard. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.