SOHC.co.uk Forums > CB650
Carb issues
K2-K6:
It just doesn't look like there is anything there that would stop it running on those cylinders to me, maybe a bit underpowered or some compromise but you'd expect it to be firing at least.
I've seen engines that are far far in excess of this and although a bit ropey they still run and not bad either, think you are really looking at fueling/igniton as the original problem.
Silicon gasket can be the death of these motors as any loose bits can often be bigger than an oil supply route and very often trash the top end of the motor fom oil starvation.
As Bitsa says, the bores have quite a nice taper at the base so feeding the pistons/rings in there is not a bad job, just take it slowly and you'll feel them go in quite easily usually.
Bryanj:
I would suggest an accurate bore measurement in several places to see if tapered, oval or out of spec and work from there.
Cylinder bore dial gauge is best---I got one but it might be too far to Gloucester!
M0WBY:
Hi guys,
Thanks for explaining things oddjob... Please excuse the questions just trying to clarify things in my head! I was a little confused by things and over what exactly I was measuring! I had to go back to the manual and do some revision! ::) I have to put my hands up and confess that I have not had to look at piston ring gaps and bores in a long time! I was using the rings with the cylinder they came off. I will order a new set and see how they compare. I think it is the rings that are worn on Cyl 3. Probably was due to the carb issues I am guessing. One thing I noticed the online manuals have you measuring the rings at the bottom of the bore as opposed to the top in HBOL. Measuring them at the bottom makes more sense to me.
I am hoping that I can just get away with a hone of the bores.
It says in the manual that each ring is marked so you can tell which side is up and also that one should be marked with a T to denote top ring. I have looked at mine and none are marked with a T! In fact the only difference is that each ringset have one ring with the marks 'R N' and the other is just marked 'R'. You are meant to be able to tell which is Top and which is second as second ring is tapered but I can't see any difference! They all look the same to me!
I am hoping the new ones will be marked with a T so I can tell the difference!!!
Cheers
John
M0WBY:
Hi oddjob,
OK so they are different colours when new that helps...
I am confused now about end gaps and worn rings! I understand measuring the three points to see how the bore is worn. But how does one tell you if the rings are worn and need replacing?
With mine it was obvious because with Cyl 3 rings it was really easy to compress and put them in the bores. The others were a lot harder. The other three seemed to have more spring to them. Is this how one tells they are worn? Seems a bit subjective to me... Still if you are in there you must have suspicions and you would be a fool to pull it all part and not change the rings as part of the course!
But if you had all fours sets that were all as bad surely they would all feel the same and unless you compared them against new ones you would never know! Does this make sense?
Cheers
John
tom400f:
Yes you are making sense.
Without a way to measure the bores independently (micrometer instead of using a new ring) I suppose you cannot tell. However as Oddjob suggests, one new ring set is unlikely to go to waste but while you are waiting you could:
1) choose one bore and measure all ring sets against it (bore is constant) so you get some idea of how the rings compare
2) use the "best" set of rings to measure all your bores (ring set is constant)
Then you have some comparable numbers for both.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version