Nikasil liners

[rogermansfield]

I was thinking of upgrading my 1980 R100RT iron cylinders (75Kmi) with newer nikasil cylinders,(plus pistons/rings). I recall reading somewhere that one or more (early?) years liners' flaked. Anyone know what year is best to use or avoid? I looked at Airheads site and didn't see any notes, but I'm sure i saw this somewhere. Thanks!

[tkpinsc]

Do you have current issues with your iron setup? Many bikes at your mileage are still running strong with iron lungs. If you still have good compression, or your cylinders and pistons are within tolerance and a set of rings wil fix you up, I would not consider changing to nickasil cylinders an upgrade. There is no performance advantage, only a slight weight advantage.

If your current cylinders/pistons are shot and you need to replace them, I would search for a good set of nickasil cylinders and pistons. I would also go this route instead of a rebore and new pistons/rings. The nickasil will not offer any performance advantage but will be lighter and probably last longer. It is also easier to find a good condition set of nickasil then iron used.

81 is the year you've heard about flaking. Not all 81's flake and if they made it 25 years without flaking I'd probably trust them, at the right price.

[20774]

There was a recent lengthy thread about a poster who delved deep into this... The one thing that came out of it is that with a Nikasil setup, if for some reason it needs to be oversized, it CAN'T. You're basically stuck with having to replace the barrels. Generally, the Nikasil stuff lasts a long time. On the other side, iron cylinders can be bored a few times and parts are available. It's probably a push either way...you spend money and time boring our the iron cylinders to get to XXX mileage...one set of Nikasil cylinders/pistons/rings also probably gets you out to XXX miles. :dunno

[rogermansfield]

I haven't tested the compression. My friend told me the oil apparently seeping out was caused by worn rings. I have an opportunity to buy some used nikasil cylinders and have heard from "experts" that it is better to use these than try and bore the 1000cc cylinders any more. I have also heard to just hone the cylinders lightly and use new rings. The more I hear, the more confusing it gets. I'm going to take clutch out and replace main seal (hopefully) in the next couple of months. I can't help but wonder if that's where the oil is coming from. It runs out of the airbox cover onto the trans case.

Thanks again for the advice on this!

[20774]

I have also heard to just hone the cylinders lightly and use new rings.

Honing Nikasil is a little differet, ie, you use a different type of material. Aluminum oxide IIRC...there was a recent thread on this. The Nikasil liner is very thin and you don't want an agressive hone to cut through it.

It runs out of the airbox cover onto the trans case.

Breather valve? You might want to take the starter cover off and see more where the oil is coming from. I'm not sure on your engine, but on my /7, the vapors from the breather valve move forward into a small well which is supposed to allow some of the oil mist to condense and drip back into the engine block through a small hole. Sometimes the small hole can get plugged resulting in oil being dumped directly into the carbs...I suppose it could also migrate around under the cover and go places it shouldn't.

What about the rest of the system that routes oil mist from the breather to the carbs...I believe you have a system that splits it to both carbs. My /7 only dumps to the right carb. Check all the connects and ensure that it is leak free.

Also, I recall something about a bolt that's visible in the airbox area that should not come loose. Check it and tighten as necessary. I'm thinking you don't want to take this bolt out as it ties to something in the tranny...a baffle or something. Be sure the bolt is tight...maybe covering the top with some gasket sealant material to keep it from backing out.

I'm going to take clutch out and replace main seal (hopefully) in the next couple of months.

Be sure and block the cranshaft from moving forward before you remove the flywheel. There are some locating pins/shims (I keep forgetting exactly what it is) that can become dislodged if the crank moves. It's easy to devise something to push back on the rotor bolt. Take off the front cover (battery negative removed first) and use a piece of wood to press against the bolt and tied back to the jugs. Or some take a smaller piece of wood (something like a 1/4-in to an inch thick) and place it in front of the rotor bolt and then loosely reinstall the front cover.

[tkpinsc]

I haven't tested the compression. My friend told me the oil apparently seeping out was caused by worn rings. I have an opportunity to buy some used nikasil cylinders and have heard from "experts" that it is better to use these than try and bore the 1000cc cylinders any more. I have also heard to just hone the cylinders lightly and use new rings. The more I hear, the more confusing it gets. I'm going to take clutch out and replace main seal (hopefully) in the next couple of months. I can't help but wonder if that's where the oil is coming from. It runs out of the airbox cover onto the trans case.

Thanks again for the advice on this!

What 20774 just said is all good stuff.

How much oil do you use in 1000 miles? Are you filling it the proper amount. About the middle of the range on the dipstick is enough. Many airhead motors blow excess oil out the breather quickly until they reach the level thay want then oil blowby will decrease.

BEFORE you strip anything perform a proper compression test. Carbs disconected etc. There are many write ups on the internet on the procedures to follow, and they vary from some other motors. Once you strip it down this opportunity will be lost. The results should help identify if you have a ring, valve, breather, or seal leak of some type. You need to do this to determine if it is worn rings. It would be a real b--ch to find you have the same problem after replacing the top end.

I would not pull the flywheel and chase a main seal leak unless the oil is clearly dripping out of the bottom of clutch housing or the clutch is slipping. If you do determine it is the main seal change the oil pump o-ring and flywheel o ring at the same time. If you do have a main seal leak and excessive blow by you need to resolve the cause, likely worn rigs or excess oil level, before you replace the seal or you may blow the main seal again.

If you have excess oil mist passing the breather and leaking at the main seal, it further supports to much engine oil. Overfilling can blow the rear seal, A blocked breather can also cause engine seals to fail.

Of course excess ring wear showing as low compression can also blow seals and
cause excess breather blow by. Your friend could be right, however it's prudent to explore the easier to repair causes first such as excess engine oil level. Do not rely only on the dipstick, try completely draining and refilling with the exact measured amount and see where that volumne shows on the dipstick. There are a variety of dipsticks and yours may be the wrong one for your bike.

And again, even if you determine you have worn rings, with only 75k I would get someone with the experience to measure correctly the cylinder and piston wear. Many iron lungs last twice this with out problems. Only if I needed a bore job and pistons would I start shopping for a nickasil top end. Otherwise I would lightly hone, replace old rings with new rings and ride it another 75k.

[20774]

Back at you tkpinsc...that adds more to the picture of how to proceed with the investigation. The root cause of the problem must be determined before making major changes. Simply adjusting the oil level or fixing a breather can help quite a bit. But changing things out, only to have them happen again is a real downer.

[sumran]

I have an opportunity to buy some used nikasil cylinders ...

If the price is right and you verify they are in good condition, you may want to pick up the cylinders for future use, even if you do't need them right now. They aren't getting any cheaper. Having a good top end on the shelf will serve you well down the road.

[rogermansfield]

Thanks for the advice. The cylinders i was thinking about are already sold, so I waited too long. I see a lot of oil in the airbox and some seeping from behind the front timing case cover at the top. The clutch slips a little and I replaced it about 25k ago, so it shouldn't be. I know I overfilled once, but then drained it back down after I realized I had overfilled. Still not sure how i did that.

I want to find this breather valve and check it out. I already pulled the rear drive to fix the stripped fill plug and I want to repaint the swingarm. I plan on a spline lube anyway, so figured I would just do the main seal/oil pump seals. I'm sure I can get by for another season without the new cylinders, so I'll check compression when it's all together.

Thanks again for the advice!