oil leaking, puffs of smoke, new engine ask for rings

[Guest]

Hello everyone
I still have the same issue on my bike....
the symptoms are:
- blue smoke when idling and just when re-accelerating, there is a puff of smoke
- 3 spark plugs are ok (brown and dry), the 4rth (on the right) is wet black, with a lot of fouled deposits -6> lot of oil is going by the way...
the bike is:
suzuki gs 550 with 650 pistons, cylinder block and full ported head....
- new valve guides (suzuki, measured in specs)
- new valves (suzuki, measured in specs))
- new valve stem seals (suzuki, also tried with viton ones, same result)

- honed cylinder block (very good state, not ovalized, measured in specs)
- new piston rings (not suzuki ones, ebay aftermarket, angular gap was ok with the service manual, but not measured the ring gap inside the cylinder block)

So, I disassembled (for the 4rth time) all the upper engine, and I can confirm I have lot of oil on the piston dome, and moreover the whole cylinder surface is full oiled and wet... So, I presume the new rings do not their job... I presume also the 2nd ring (oil scrapper) and the 3rd are not ok and seated to the cylinder surface... I measured the piston ring gap, putting it into the cylinder. Using my shims, I find these figures:

- 1st ring: 0.45mm ok / 0.50mm not ok
- 2nd ring: 0.50mm ok / 0.55mm not ok
- 3rd rings set: Nothing to measure, but I find that the round spring between the two little rings is very light and when I put it between the rings, it does not push the rings outside, to allow them expand...

I have the old rings, and measured them into the cylinder block... Even if the cylinder block is honed, and even if the rings are "old" (I thing only 20000 km), I measured values between 0.15mm and 0.40mm....

so, even if I find that, for these engines, 0.50mm is a bit large, I'll order a new set of rings, but I wanted to know what do you think about these figures.... thanks in advance!

[sharpy]

Think like always buy good OEM parts or top quality aftermarket parts to state the obvious

[fastbysuzuki]

I have the old rings, and measured them into the cylinder block... Even if the cylinder block is honed, and even if the rings are "old" (I thing only 20000 km), I measured values between 0.15mm and 0.40mm....

so, even if I find that, for these engines, 0.50mm is a bit large, I'll order a new set of rings, but I wanted to know what do you think about these figures.... thanks in advance!

Before you order anything .15 sounds ok however .50 is large. Have you checked all the bores with the rings that gave you a reading of .15 measuring in three places in area the piston uses it may be you have bore wear in which case a new set of rings will not solve the problem.
it would be better to have the bores checked with a internal micrometer if they check out ok then quality rings are in order.

[boris.h]

yep, I already measured on some points (3, 4..) the diameter of the cylinder and it was good, in specs and almost new.
(do not have the figures in memory but it was ok for me). I measured the cylinders with a cylinder micrometer

[BadBillyB]

When porting a cylinder head on a GS, if you raise the roof of an intake port, you can easily make a hole into the lifter cavity below the valve spring base. Ask me how I know???

[Nessism]

Did you check the oil control ring on the bad cylinder to be sure the expander spring was properly installed? It's quite common for the ends of the expander to overlap, particularly with aftermarket rings, and when that happens you have an oil control ring that doesn't work properly, and burning oil results.

[boris.h]

Ok so thanks for your answers first. The two issues you told on the last posts are the issues i am trying to check..
- intake ports: I checked them precisely yesterday, i did not find any hole where the oil could go. I ported the head while avoiding expanding the ports too much... i will check it again...
- about the oil ring, i found after having disassembled it few days ago that the expander spring was (for me, so it is subjective) too light...when left alone on the table, the two ends overlap.. maybe this is normal... maybe not. I checked with old expander springs but the type is not the same (N...) but they are stronger, I mean when I put it on a table the two ends naturaly have a gap...

So to add some reflexion, I found that the cylinder involved was full a lot oily all along, whereas the other are oily but dryier than this cylinder. Maybe i am wrong but this means that oil come through the piston rings...

I also checked into a microscope the oil scrapper ring (2nd one) and i found that the surfaces look so bad, not shiny, a lot of edges.. maybe a quality issue...
I will check that this morning comparing with the set of suzuki rings i will get this morning. Will compare it also to the suzuki expander spring, and, again, will compare both rings end gaps, because i found 0.55mm on the oil scrapper ring. This is a bit large for a new ring....

Will check also for the eventual holes into the ports...

[boris.h]

ok!!!!!!!!!!!!!!!!!

Annnnnnnnnnnnnddddd the winner is..........BadbillyB!!!!!!!!

You were right, while porting the head I made a little, very litle hole between the valve spring case and the intake port.... which raised while heating.... I put this morning epoxy resin, like cold welding.... I think it will be ok for this big issue...

[roeme]

Hmm if anyone has pictures of this problem, I'd be grateful. At some point far down the road I might convert one of my 550s as well, and would like to learn from any mistakes made by others before making them myself

[boris.h]

Ok, about this issue this is very simple: do not mill the ports of the head!

[BadBillyB]

Actually, best performance can be had by raising the roof of the port and also the floor of the inlet port. This directs the flow more inline with the valve stem. Modern cylinder heads are designed this way. When I ported my GS1000 drag bike head, I raised all 4 intake ports until they just broke through into the lifter cavity. I made aluminum spacers that fit under the stock spring bases and JB welded them in. Heres a pic from long ago. Thanks "A. Graham Bell" for a great book on performance tuning
IMG_0520.jpg

[boris.h]

Yep that is what I did. I broke trought this cavity only on one cylinder.

[boris.h]

ok, some pics to illustrate what I was looking for for more than 6 months.....



Note that I raised a bit the hole with a little knife. the first hole was smaller, much much smaller...