Lumpy at low revs - where to start?

[ShadowTD]

Afternoon all.

Bear in mind I'm a new rider. Katy is the only bike I've ever had. But in the last week I've noticed a bit of a change in her. The power delivery was always very smooth throughout the rev range and she sounded 'even' at tickover. But starting early last week, she's been noticeably 'lumpy' below about 4-4.5k. Above that, smooth as butter (if a little vibey). I put some 98 RON as opposed to 95 RON in last Wednesday to see if that would help but it doesn't seem to have made a difference.

Sparks were replaced 8 weeks ago, carbs had been thoroughly blasted with cleaner. Suggestions what to look for please?

[Apathy]

How's your chain? Is it loose? A loose chain can make it ride funny at low rpm.

Has it been a wet week where you are? Could the plug wires be damp?

[Kreylyn]

I would guess something is causing an issue for only 1 of the cylinders, to make it not want to run at lower rpms.

The first thing I would do is check to make sure they are all running the same temp. Go ride the bike to warm it up well, then park it with it running. Immediately check the temp of the exhaust header downtubes for each of the cylinders. They should be the same temp or very close. If one is much colder than the others, you have narrowed down the issue.

From there, it's just 1 of 3 things really... Fuel, Air, Spark. Check for vacuum leaks, make sure something isn't clogging/dirty in that carb, the plug is in good shape/wires are well connected.

Krey

[ShadowTD]

Update: Being mad busy last week I never got the chance to look in to this but had to ride 70 miles up to Sheffield on Friday. After the return trip and a rideout on Sunday (about 200 miles total) she's running a lot better and I haven't done a thing. Might be too many short journeys.

[SweetLou]

Maybe the carbs are a bit gummed up? Try running Chevron Techron, or Sea Foam through. Dunno what they carry across the pond, but basically high strength carb/fuel injector cleaner. Never run a full bottle though, only run a 3'rd of a bottle, and run it through 3 tanks back, to back, to back. That will clean your carbs pretty friggen good.

[ShadowTD]

Hi Lou. I've some carb cleaner in a can, but it's the spray type. I'll see what I can find in the local shops/ebay. Cheers!

[SweetLou]

Hi Lou. I've some carb cleaner in a can, but it's the spray type. I'll see what I can find in the local shops/ebay. Cheers!

That spray stuff is more for pulling them apart. Honestly, the stuff you run though, does a pretty good job as long as its quality. Seafoam is a quality product. I used to gas up at pretty much only Chevron's in Alabama with the bike, and had lelt the bike sit for close to a year. Before I started her up, I pulled the carbs to clean them thinking they would be gummed up from the gas sitting, but nope, that Chevron Techron they add to the gas had them clean as a whistle still!

After running that stuff through your 3 tanks of gas, I would do an oil change to get all the crap outa your oil.