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+--- Thread: lumpy at low revs (/showthread.php?tid=79655)
lumpy at low revs - reaper1064 - 09-05-18
ok this has probably been done to death and reading the post have given me things to check. However after a lay up the bike started to run lumpy. So here is what I did, plug change, carbs balanced, jets cleaned.leads trimmed. All the issues revolve around Np. 4 carb. pipe is cooler on that one. Is there anything else I can check or have missed. Starting to wind me up. The problem is around the lower rev range and it is like the bike is firing on 3 cylinders.
Re: lumpy at low revs - Fazerider - 09-05-18
If you're still running with the original plug caps, it's probably worth replacing them. NGK SD05 are the ones to go for.
Re: lumpy at low revs - Bretty - 09-05-18
First off, swap the caps and leads over. Put 4-on-1 and 1-on-4. If the problem moves to cylinder 1, the issue is the plug cap, lead or coil.
If the problem stays with cylinder 4, and you've already fitted new plugs the issue must be fuel, air or carb related.
Re: lumpy at low revs - darrsi - 10-05-18
Don't completely rule out moody/fake spark plugs, it happened to me recently, a new set lasted about 10 weeks.
Because i'd changed them it totally throws you off scent.
Check the TPS as well, another common culprit that can slowly break down rather than just stop working, making you look elsewhere for trouble. Make sure the RPM needle sits quite happily on the 5000rpm mark. If it's not there's a good chance it's slowly on it's way out.
Obviously if it's out, then adjust it first, then keep checking it and see if it stays in the same place, if it doesn't then it could be time for a new one.
What about the air filter, what's the history on that as you didn't mention it?
If you do a carb balance with a dirty or stuffed up air filter then you can get a false reading which can make the bike run ropey.
Re: lumpy at low revs - reaper1064 - 10-05-18
Hi guys thanks for the replies, TPS checked, plugs were bought from a reputable bike shop, leads swap tried. Got new caps coming either today or tomorrow. Air filter good.
Re: lumpy at low revs - reaper1064 - 17-05-18
Well got a result with the running issues on my bike. My mate stripped the carbs down and found the past owner had altered the float height, got the mixture screw in the wrong position and a blocked pilot jet,combined with the wrong plugs was strangling the bike. I have owned another Fazer some years ago so know how they are supposed to feel, and mine has felt strangled from the day I had it, happy to say it now goes like it should.
Re: lumpy at low revs - redmandan - 17-05-18
There's much to be said for setting everything back to factory the first time you take the carbs off a new bike. I put all my mixer screws back to factory after a recent rebuild and the bike feels a lot smoother. The previous owner had it running rich and I scratch my head wondering why. It used to start with no choke, even when outside temp was under 5°C.