Blow-by solution

[humbucker88]

Replaced the barrels in my engine as the last one was cracked in cylinder 3, but couldn't afford to replace the piston rings at the time. Well the obvious happened and the old piston rings aren't bedding in to the new barrels so I'm getting combustion pressure going into the crankcase and forcing oil into the airbox. It's not a huge problem, but...should I replace the piston rings and hope that solves it (ca. £200) or buy a "new" engine for £250-300? I'm confident in changing the piston rings, but I've never replaced a whole engine and it sounds a pain in the arse considering the tight fit, opinions?

[limax2]

If you are confident changing the rings then swapping engines should be easy, although it is a weighty lump and another pair of helping hands would be a great benefit. Obviously you want to be sure the replacement engine is a good one. Using rings that have already bedded in one barrel in another barrel is always likely to allow some blow back and the rings will probably never bed in fully to the replacement barrel. I've done it in distant hard times with the old British stuff with moderate results, but these sewing machines are a different kettle of fish.

[unfazed]

I would go the second engine route. It is easier to replace an engine than strip it down and hope it works.  As these bores are nikasil coated you would end up with the problem as before, therefore wasting money. In any case fitting new rings on an old barrel is never good practice due to "stepping" of the bores.
Taking out and putting the engine back in and is best with 2 people but can be done with one person. Just make sure you remove the front engine mounting bracket as the engine cannot be removed without removing it.

[snapper]

not sure if its possible but many years ago you used to be able to buy some thing called cord rings , I only know this because my dad use to tell me about them !
 
 not sure if you cab still buy them !
 

[humbucker88]

Yeah, maybe the most sensible option is swapping the engine out. Although a third option would be to buy some second hand barrels and pistons that are already married up and put them in the engine. Not sure how feasible that is but it would only be £50ish

[limax2]

not sure if its possible but many years ago you used to be able to buy some thing called cord rings , I only know this because my dad use to tell me about them !
 
 not sure if you cab still buy them !

They used to be a popular thing to fit in the past when engines and oil wasn't as good as now and things wore quicker. They were meant to be better than standard rings in a worn bore. You can still buy them for some engines but probably not for our fazers. Probably not the way to go either in this case.

[humbucker88]

So after some research it seems there's actually an O-ring at the bottom of the barrels that I wasn't aware of? It's in the service manual, however, it's not in the parts catalogue... does this thing even exist? Section 4-25 in the service manual, item 6. Can't seem to find it anywhere else, nor have I seen it. If it exists I thought I'd change that first to see if it helps.

[limax2]

I'm pretty sure those O rings don't exist on the FZS600. The cylinder base gasket shown as item 4 in section 4-25 is also the wrong shape. Ours is a much more open gasket to match the crankcase face and that O ring would have nothing to locate it or to sit against on the crankcase side.
I suspect (i.e. just guessing) what has happened is that when preparing the the manual they have used another similar manual as a basis, possibly the Thundercat manual. This would be normal practice in industry and unfortunately errors sometimes creep in.
The O ring is probably used on an engine with separate cylinder liners and may be intended to stop oil creeping between the liner and cylinder block. The FZS600 has the bores plated direct onto the block (i.e Nicosil) so no use for an O ring.
I'm afraid it's back to the piston rings or the other options mentioned.

[humbucker88]

Damn it! Thought as much as I hadn't noticed them when previously removing/fitting barrels. Cheers for the info.

[unfazed]

No seals on the bottom of the barrels of the 600.
The service manual was mostly likely a rehashed version of the 400 service manual which has the oil seals and is almost identical to the 600.

[Captain Haddock]

Theres a dodgy trick to be done at your own risk to help bed the rings in, involves a dose of abrasive  down the inlets, done it a few times on light aero engines when the bores have glazed up and compression dropped down usually using the old style of vim cleaner, get it warm and under a bit of load and chuck some vim down the inlet to rough up the bores and rings and allow to settle in again, most times compression comes back up and oil consumption drops.
Never tried it on nicosil bores only on nitrided steel bores and chrome bores.
As said at your own risk but may save a strip down.

[Ianboydsnr]

how long since you replaced everything?


it will take a while to sort itself out, try doing an italian tune up!