right hand cylinder spluttering

[graciesdadpaul]

So im still having issues. I replaced the right hand carb with a spare on as I suspected the little jet for the pilot circuit was blocked. I made sure it was clean and the float height is within standard tolerances (27mm), jets the correct size and needle in pos4 as per the manual. Synched up the carbs, fitted a new plug and hey presto it seemed much happier. Took it out for a 35 mile ride and it seemed very happy and I thought id solved the issue, oh the joy I thought.

That was a few weeks ago and I hadn't ridden it until this weekend. Started fine and ran ok for a few miles the started to kick and buck on deceleration. When i got to the petrol station the tickover would not go below 2k and i got a very disapproving look from an old lady in the car behind me. The ride home was frankly horrendous and I thought the bike was going to explode it was that bad.
I took the right cylinder spark plug out when i got it home and it was very black and sooty but not wet.

Im really lost for ideas on this now, the only thing i can think of is bad crank seals but they are brand new so im really hoping its not that. I think I need to do a leak down test on that cylinder but dont have the equipment. Is there anyone in the buckinghamshire- oxfordshire area that could help me with that.

Thanks Chaps.

[Rubydog]

I’m no expert but a friend with a K is having similar problems. I would suggest it is running to lean on the overrun throttle position (closed on deceleration ) it looks like your pilot jets are blocked, if not try turning them out by say a quarter or half a turn to see if it changes it. You may also have an air leak causing a too lean mixture hence the high tick over. Check the vacuum pipe from the tap to the carb if it’s a slack fit it will allow air into the system so either change it for a new or smaller diameter pipe or put clips on the pipe at it’s connection points. Small cable ties tightened up with pliers may do this just to prove it.

I would stick with the standard plug rating, as a previous guy said, you risk holing a piston especially if it is running too lean.
Modern petrol is rubbish & goes off quickly too so try some fresh fuel or fuel stabiliser, this can be the reason for the change from standard carb settings now on a lot of old bikes, even straight from the pump it just isn’t the same stuff these bikes were raised on. Good Luck.

[graciesdadpaul]

I’m no expert but a friend with a K is having similar problems. I would suggest it is running to lean on the overrun throttle position (closed on deceleration ) it looks like your pilot jets are blocked, if not try turning them out by say a quarter or half a turn to see if it changes it. You may also have an air leak causing a too lean mixture hence the high tick over. Check the vacuum pipe from the tap to the carb if it’s a slack fit it will allow air into the system so either change it for a new or smaller diameter pipe or put clips on the pipe at it’s connection points. Small cable ties tightened up with pliers may do this just to prove it.

I would stick with the standard plug rating, as a previous guy said, you risk holing a piston especially if it is running too lean.
Modern petrol is rubbish & goes off quickly too so try some fresh fuel or fuel stabiliser, this can be the reason for the change from standard carb settings now on a lot of old bikes, even straight from the pump it just isn’t the same stuff these bikes were raised on. Good Luck.

Thanks for the response. im going to rig up a leak down test and see if I can find the air leak as i'm certain its that now as i've literally tried everything else. ( I must have cleaned the carb at least 10 times) I hope its not the crank seals as that would be extremely expensive as I already shelled out over a grand to have the crank rebuilt 200miles ago.

[stevewharton]

I had a very similar problem a few years back with my 76 kettle and I tried everything to find the cause, I then asked on here for help and was given umpteen suggestions, as have you, but nothing I tried solved the problem.
In the end I took the best advice and got my engine over to Baz at Dudley, where he eventually found that there were several problems, the first big one being that my recently reconditioned crankshaft, had been fitted back in the crankcases with a crank seal not seated properly.
The second big one was a hairline crack/casting flaw in one of the carbs, a problem I would never have found. Got the engine back in the frame and it's ran like a dream since, and I've now got a total of 163,000 miles on the clock!
So my advice is, if you can't solve the problem yourself, take it to someone who can and if you're not too far away from Dudley, I'd highly recommend Blue Smoke Baz.

[graciesdadpaul]

I had a very similar problem a few years back with my 76 kettle and I tried everything to find the cause, I then asked on here for help and was given umpteen suggestions, as have you, but nothing I tried solved the problem.
In the end I took the best advice and got my engine over to Baz at Dudley, where he eventually found that there were several problems, the first big one being that my recently reconditioned crankshaft, had been fitted back in the crankcases with a crank seal not seated properly.
The second big one was a hairline crack/casting flaw in one of the carbs, a problem I would never have found. Got the engine back in the frame and it's ran like a dream since, and I've now got a total of 163,000 miles on the clock!
So my advice is, if you can't solve the problem yourself, take it to someone who can and if you're not too far away from Dudley, I'd highly recommend Blue Smoke Baz.

Thanks for the response , wow thats a lot of miles!! Its been a bit of a struggle and I did find a fault with the carb which I swapped and that improved things a little but im now pretty much convinced its an air leak cause by a bad crank seal. how do i contact BAZ any ideas?

[stevewharton]

Send him a private message on here is your best bet, otherwise I can send you his phone number.