To Nikasil or Not to Nikasil - That is the question.

[Tillerman6]

metisse,

  You must be the guy that mentioned it first on here?  I could never find your post about Nikasil again.  Thanks for the input.  Wish I knew more.  The hard part about it seems to be getting the rings to seat without any seizing in the process. Some of the other guys mentioned that you might need special rings to keep them from sticking since a high percentage of the ring material is nickle to begin with.  Another guy who was running 2 stroke  750 cc  four cylinder sidecar engines said it worked well after a cylinder has seized once as a repair, but the pistons would wear out sooner with the Nikasil and have to be replaced again. (see other comments in this thread)  So it looks like the idea has not caught on well here in the states except as a repair when no oversized pistons are available.  Sort of a "plan B" ? And finally the Nikasil is the only way to go if there is no cast iron liner in the cylinder and you are on bare aluminum.  This would be the case if you are running a non sleeved 320cc cylinder in a bike that uses the same outside cylinder with a cast iron sleeve for a 250cc displacement.

  All that being said, however, I would still like to hear more about your friend's Nikasil improvements.  We all would if that is still possible?  How has it been doing lately and how many hours are on it now?  What piston was used as a replacement and has there been any problems or changes made? 

[jon v8]

Too much thinking going on here,those old Yams are simple, but well made. Just get it bored by a decent place.(From recommendation,not adverts) Put it together and ride. The old banger I have is built up out of junk from the remains of 3 engines,the piston was secondhand,not even run from the same barrel. I just bought new rings,circlips and a base gasket. Rattles like a bag of spanners,but everyone comments on how well it goes. 

It must have done 20 years of chasing cows before I got hold of it...

[Tillerman6]

jon v8,

  I wish I had 3 other "donor" engines to take parts from like you do. Then I could have quickly determined that my cylinder was junk from the get go. 

I had nothing to compare it with, so I sent it off for inspection.  Glad I did that because the machine shop said it had too much damage to be economic to repair. 

So I found another cylinder on Ebay and had it sent to me first.  This all took some time, but that delay caused me to start looking for other problems that might have caused the hard starting and

kickbacks that were happening if the engine was cold.

  As soon as I got the next cylinder it was obvious that it was different than the original in that area around the intake port.  All the edges were equal distances from the top, so the old cylinder was definitely bad after all.

So I sent in the next cylinder for Millenium to work on.  It has some wear, but should be useable.

  And this waiting time that was created from having to swap cylinders actually worked to my advantage because I started working on the expansion chamber and spark arrestor.  I think I found enough caked on carbon to say that it was causing a restriction for the gasses and most likely contributed to the hard starting while cold.

Feetupfun clued me in on the Yamaha "swirling" gas spark arrester, and I found that these are built with an aluminum bullet shaped cone that is supported in the spark arrester by a "web" which causes the gasses to spin as they are exiting the restricted area.

However, the clearances for the escaping gas are very small, and the carbon can easily clog the area in question. (especially in 44 years)  It is sort of a man made "bottle neck" situation.

  I cleaned out the silencer with solvent and de-greaser only because the aluminum bullet would be destroyed by a "burn out" of the carbon, but I did a slow burn out of the main expansion chamber itself in an effort to rid myself of any restrictions.

I think some of that "rattles like a bag of spanners" might be from the restrictions in the silencer you have or possibly from missing rubber vibration dampers  that were put there by the factory to dampen out some of that rattling.

The cleanout is very straight forward and just re-pack the spark arrestor, but the rubber dampers themselves my be hard to come by.?   Maybe some high temperature silicone sealer would work as well.

 Nikasil-

  I have a feeling that Millenium will not do a Nikasil plating on this "new" cylinder after all.  I don't have enough positive "votes" for it from the guys here to make me want to order that process.

There are some new variables that tend to make it a more risky proposition than just plain cast iron for the bore, and so I am not so keen on having it done.

 

 

 

 

 

 

 

[2stroke4stroke]

Rattling like a bag of spanners was pretty much the norm for these bikes in the Seventies.   Indeed somebody trying to sell me one actually claimed the horrendous noise from the motor was the spanners rattling in the toolbox.

[Tillerman6]

1 hour ago, 2stroke4stroke said:

Rattling like a bag of spanners was pretty much the norm for these bikes in the Seventies.   Indeed somebody trying to sell me one actually claimed the horrendous noise from the motor was the spanners rattling in the toolbox.

So you didn't buy the bike from him right?    In my case I developed a bad habit of closing the throttle and coasting down hill letting the engine do the braking.  That might be OK for a couple of feet, but is not a good idea for much more distance than that.  All my fault.  Could not find more brake shoes to replace the worn out ones I had, plus the brake pedal was pretty hard to catch with my foot. It was the longer version and the pegs were already moved back to the trials position.   I was never in competition with the bike, so it did not seem to matter much..  At that time the rattle was bearable, but later on the bike developed a "detonation" sound that I could not figure out, so I took the cylinder off looking for clues.  I don't think I would have done that if it was not for the detonation banging on down hills with the throttle closed.

 

Anyway, I still am hoping for a much quieter bike after the exhaust is cleaned out and the new piston and bore is put back together.  Also hoping I can rule out the possibility of a lost pin from the upper end needle bearing that might be floating around somewhere inside the cases. I discovered the missing pin when I pulled the piston out.

[metisse]

This bike I mention does not rattle, and goes very very well. I have ridden it several times and I have to say compared to my original 434 that in itself goes well, its chalk and cheese.

I have sent him an email and posed the questions and will see if he is happy to divulge further what he has done beyond the barrel,  will update if and when. 

[Tillerman6]

metisse,

   That would be great!  The more detail we can get on this subject the better.  And if there are any other mods to the piston or cylinder such as a ceramic coating on the crown of the piston, or porting mods, or changes to the flywheel weight, or the head itself that has been done?   Depending on how long this takes, I might be able to still have it done to my cylinder while it is being overhauled. 

Way back when I started riding, there was a story in one of the Dirt Bike magazine issues that ran an article on two stroke mods that one shop was doing to some of the engines.  It had mostly to do with balancing the piston to the crank shaft so that the vibration was minimized.  This was around 1972 and I have long since lost track of the information, but this was also about the time that everyone started using reed valves and adding or changing the shape of the ports in the side of the piston.  This had a real postive effect on the low RPM torque of my motocrosser and was not that difficult to do.  It made a drastic difference in the way the bike would pull and made the power band much wider than it was before the mods. 

 

[Tillerman6]

On 9/4/2018 at 2:20 PM, Tillerman6 said:

Guys,

   Need your opinion.  I still have time to specify what happens to my "new" cylinder from my TY 250A.  It won't get to Millenium Technologies for another few days.  And originally I was going to have it Nikasil plated, But now I am wondering if that is still a good idea?  It will get a new Wossener piston too unless there is some reason not to??  

The TY 250 barrel has a cast iron liner.  But the cylinder is still the old air cooled type.

There will be more heat expansion on this setup than would be the case with a water cooled cylinder, and it's a 2 stroke of course, but what are the advantages of a Nikasil lining for this application?

I will probably be riding trails most of the time rather than trials for whatever that is worth. So is the Nikasil worth it for an air cooled TY 250A??

New info on 9/11/18 ***

 

Got a call from Millenium today 9/11/18 and they said the new cylinder was within limits for the Nikasil process.  This has the advantage that it keeps the cylinder at the standard size with the addition of the plating material. Apparently the process can be repeated over time and the cylinder never has to be taken over size.  They also said that their shop does about 3000 cylinders a year with this process and has only had one failure.  So I told them to go ahead and Nikasil the cylinder.  This will probably take another week to 10 days, but I have a lot of other activities that are taking all my time anyway, so the extra time is not an issue for me.  I am going to be using a Wossener piston kit and they said they would get me a discount on that, so as to keep the cost down a bit.

 

On 9/4/2018 at 2:20 PM, Tillerman6 said:

 

 

[metisse]

Had a reply re the nikasil,  Nothing really apart from,  before the nikasil he worked on the ports a little... his words, and then had the barrel treated, used standard rings after t hat Carburation standard, as mentioned as well he nikasiled the clutch for a smoother action. Hope that helps and good luck.

 

 

[Tillerman6]

21 hours ago, metisse said:

Had a reply re the nikasil,  Nothing really apart from,  before the nikasil he worked on the ports a little... his words, and then had the barrel treated, used standard rings after t hat Carburation standard, as mentioned as well he nikasiled the clutch for a smoother action. Hope that helps and good luck.

 

 

Metisse,

  Well,  that's good information.  Hope mine turns out as well. Millenium called today and could not get a piston from Wossener, but he could get a
Wiseco, so my Nikasil'd cylinder will now eventually get back to me with a new piston and be the original size.