1100 Katana vibration issues

[Uncle Bob]

I got the 1100 carbs finally sorted in July after a year off the road (issue was probably stuck float needles / O rings). The float heights were checked, new viton O rings fitted and balanced up, plus new petrol tap vacuum gubbins.

It all starts and runs but I have noticed (from how I think I remember it, before the carb issues) that there is now a lot more vibration than before. Sitting at around 5k-6k rpm it feels quite bad (cruising along A road or motorway).

Went for ride to the Fenman Classic about 50 miles away Monday and my mates bike light who was following me, in the the right hand wing mirror was a blurred "ring" about the size of 2p I guess (I couldn't make out anything in it). The trip back, after 40 miles, we stopped and my hands were really tingly, feet slightly so. It's a little unride-able like that for me

I have also noticed the exhaust on the overrun now, "farts and pops" quite a bit that I'm sure it didn't before.

So where do I start to look? I take it the overrun issue is unburnt fuel igniting in the exhaust? Would maybe a dodgy coil cause that. My thought was if one cylinder (or 2) was not firing properly that could make more vibration? Other guess is the air screws - I do have a colour-tune kit so I could check those, but would that cause vibration issues?

Anyone else had similar experience and knowledge of where to start looking?

Thanks

Rob

[johnr]

have you checked the valve timing? if the camchain is a tooth out it can still run but roughly! if its fitted with slotted sprockets on the cams, they may have slipped and althered the timing. alternatively, have you checked that all the engine mounting bolts are tight, and that the flywheel on the crank isnt loose, also that the starter clutch on the back of the flywheel hasnt come loose. assuming that its not rattling or smoking then next stop is perhaps a plug chop, see how its running, and more importantly, if every pot is running the same. that might explain the popping in the pipes. you can get digital laser thermometers, you point them at whatever you want to measure and they read the temp in degrees c or f, no contact required. theyre only about a fiver each, get one and take the temp of each cylinders exhaust pipe when its been ticking over for ten minutes, then take it for a good spin and immediately on stopping take each pipes temp again. a cylinder with the mix much too lean or rich will be at a significantly different temperature.

[johnr]

the above test will also identify a coil breaking down, if you find a cooler pipe and then swap the coils onto the opposite pair, see if the cool pipe moves.

[fossie]

The very same issue is common with last edition Kats. This is caused by the zorsts being restricted and the carbs being leaned off at revs that come into call on emission tests .......much like vw but a more basic / cheaper option.
So yep over fuelling would cause the issue ax would a coil.

[pookie]

[quote="fossie"] much like vw but a more basic / cheaper option.

Much like vw but Suzuki admitted that they had done it

[Uncle Bob]

Thanks for all the feedback. I have ordered a Temperature Gun from Amazon (thanks for pointing me at those John) for the tests on the exhaust as that looks like a good place to start (and it was a good excuse to buy another gadget!).
I'm sure it was OK before the Carbs issue so that rules out valve timing I think. The carbs issue was I think failure of the petrol tap to stop petrol when off combined with failing needle jets allowing too much petrol in. I think it sat in the garage overflowing (into cylinder I don't know - it did turn over OK - not hydraulically locked). When coming back from the MOT (25 miles away) I had to put it on Prime to get it to run?! Though it could have been something else I did and thought it was that, as I just wanted to get home).
I did strip the carbs down and got them vapour blasted then I built them up again. I think I'll do a compression test and temperature first and see what that throws up. after that I might get my carb balance checked again.

It'll take me while to find the time to do that so I'll update once I have more info.

Thanks

UB