Lumpy at low revs
#1
Lumpy at low revs
Hi guys, I'm after picking your brains, my '90 is running ok but at low revs when creeping along it is slightly lumpy, it feels like it is missing or choking as you slowly accelerate. There is no black smoke, the plugs are fairly new, the carbs have been cleaned out and sync'ed. Am I missing something obvious?
The problem is not serious, just chuffin annoying, if you roll into a slow corner as you pull out of it, for a split second it feels like the bike is going to "fall" into the corner!
Over 2500 rpm its fine and runs like a dream. I have been ironing out teething problems on this bike for a few months (since buying it) and hopefully this is the last of them. The problem has always been there I think but has been masked by the other problems,now they have gone it seems to show up more.
The problem is not serious, just chuffin annoying, if you roll into a slow corner as you pull out of it, for a split second it feels like the bike is going to "fall" into the corner!
Over 2500 rpm its fine and runs like a dream. I have been ironing out teething problems on this bike for a few months (since buying it) and hopefully this is the last of them. The problem has always been there I think but has been masked by the other problems,now they have gone it seems to show up more.
#2
Sorry to hear about your probs mate , you said plugs are new , have you checked for a nice strong spark from each one ? If not maybe the leads . Have you checked the air filter/fuel filter for dirt /blockages . I'm no expert but that's where I'd start (if you haven't checked these already)
If the weather was better I'd suggest you take a trip to Brighton and we could try swapping a few parts around as we have virtually the same bike . Maybe the summer if its not sorted by then.
Good Luck!!
If the weather was better I'd suggest you take a trip to Brighton and we could try swapping a few parts around as we have virtually the same bike . Maybe the summer if its not sorted by then.
Good Luck!!
Last edited by hawkwind; 01-29-2009 at 01:45 PM. Reason: new info
#4
Guest
Posts: n/a
Little things like this could be just about anything ..
You do need to start from scratch and check all the basics then check the tuning settings for ignition and carbs ..
I will add that these old girls are not real comfortable under 2500 in any case .
I know she should be smooth under 2500, but as a rule I keep mine up around and above the 3000 mark anyway just about everywhere, except may be when slowing at lights or parking ect ...
You do need to start from scratch and check all the basics then check the tuning settings for ignition and carbs ..
I will add that these old girls are not real comfortable under 2500 in any case .
I know she should be smooth under 2500, but as a rule I keep mine up around and above the 3000 mark anyway just about everywhere, except may be when slowing at lights or parking ect ...
#5
off idle problem
Sounds like you're having a slight problem in the transition from slow speed circut to high speed in one or more carbs. Two potential problems. One, you might have a slight build up of varnish in one or more slow jets causing a lean condition before the mains take over, Or, two, the springs that sit on top of the slide have lost some tention and the slide/needles are coming up just a hair fast. I'd replace/clean the slow jets as a fist step. Go to a paint store and get some methylene chloride (paint stripper) and soak the jets overnight. If you use streight methylene chloride you wont attack the brass jets, but it will go after rubber so be careful.
#6
#7
#8
Before you start pulling the carbs around again, there are some rubber seals on the sides. If you place your fingers over then when the bike is at tickover and the revs increase then you know that these seals are dry. Place some vaseline over them to help lubricate them and repeat process untill they soften. Good luck
#9