Tillerman6

Will do. And looks like there is a slight difference in the threads on the studs so that the longer end is down in the aluminum. Thanks for the info!

Maybe someone knows this one? I got the rebuilt cylinder back from Millenium with a chrome bore and new piston,(ended up being a Wiseco piston) but the 6 studs that hold the head on were not installed. The threaded holes are in fine condition and very clean, but can someone tell me what sort of chemical(s) should be used to keep the studs from backing off? I am thinking some sort of Locktite, but I am not sure. Also, the studs have more thread on one end than the other. Which end should go down?.

You could call Millenium Technologies and they would know for sure. They do hundreds of cylinder overhauls a month. I have no connection myself. Or email them on the web. Sales/Customer Service Millennium Technologies/ Revolution Performance 1404 Pilgrim Rd. Plymouth, WI. 53073 1-888-779-6885 EXT.351 www.mt-llc.com

I apologize for my ignorance, but you must be saying that the rear brake can be used to help balance the bike? Can you elaborate a bit? And are you saying that the kits will move the pegs even further back than the rear most position of the TY 250 A model?

If anyone would care to post a picture of a trials gear shift lever for the TY 250 A and / or just tell me what the length is supposed to be? I think mine is non- standard as the original owner had the bike set up for trail riding and I want to switch it back to trials mode for the time being.

Could you please please post some pictures of your TY? I am starting to understand, but without pictures it's a lot harder. Also I was thinking of getting a TY 175 as a second bike, but I don't know much about them, and they only come up for sale rarely around here, so I was hoping to see what your bike is like and boost my knowledge. I am especially interested in mods for better control and rider comfort if that is what you are doing.

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.

Johnnyjazz, A little more researching and looking at clutch replacement kits and I discovered that the brown tips of the plates you showed in your picture are actually made from friction material which is naturally brown already. So that is not rust you are seeing in the photo, just normal friction plates! Makes sense to me. Every other plate is steel, and every other plate is friction material, So I would leave it alone until you know you have a problem. But since you drained the oil you might want to try some Belray 75 weight gear oil. That stuff is great and the clutch pulls in like butter. Does not seem to need as much clutch lever force as before to get it to release either, so I think I will stay with it. If you are still thinking about replacing the main seal under the magneto (mine was leaking 2 stroke mix) I put in a photo of the seal that was removed with sheet metal screws and some very carefull shallow drilling of the metal ring which is built into the seal itself.

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.

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.

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.

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?

That is a very good point. The company that does the Nikasil says that after the plating of the bore is done they hone the surfaces lightly. And they did not mention anything about having to use special ring materials, but the old tried and true cast iron liner and honing is probably more predictable because of the simpler process.

I will see if I can locate all the Yamaha piston sizes tomorrow. The Wossener pistons were on my radar because they do list all the sizes as being available and up until today I did not have a source for the Yamaha pistons. The other advantage for going this way is that you would stay very close to the original weight for the new piston, and balance is still an important consideration.

turbofurball, What was the reason that you decided to "lower the pegs"? on your bike?

Johhnyjazz. I am just guessing, but by looking at the pictures it looks like that brown on the clutch plates may not be rust at all but just some sort of brown coating that looks like rust. ?? It seems hard to understand how rust could develop inside a sealed clutch compartment that is filled with 1000 cc's of gear oil? Unless it is only on part of the periphery? Unless you have lost most of your gear lube before you took the clutch cover off? And if that was the case then all the gear teeth should have also been rusty too, and they are not, So it the clutch was working properly you might be better off just checking out the parts manual diagrams and know that when the time comes, you will know what you are looking at in terms of parts placement and how a motorcycle clutch is constructed. P.S. Thanks for the encouragement on my bike. It is a labor of love for me. I wish I had another one to ride while I'm waiting for my cylinder to get overhauled.! It is a slow process and I would have waited until the snow was flying to tear into it if I could have, but it was making so much noise that I was afraid to run it any more without seeing what was causing all that racket. As it turned out it was mostly (I think) just a clogged up silencer that was the culprit, and not so much the piston slap, So when you put that new gasket on the clutch cover and fill it back up with 75 Weight gear oil (I use Belray) and lube and clean your clutch cable and lever and adjust the linkage, Then go have a look at the condition of the silencer and see if it needs cleaning too. Mine was so bad that it almost would not start, and when it did, it would blow blue smoke out of every joint in the exhaust system for a second or two until the carbon in the restriction portion of the spark arrestor finally opened up enough to let the gasses out the rear end! That "modification" to the cylinder wall is still a mystery, but no longer a factor with the "new" cylinder now on it's way to Millenium. Thank God for Ebay! And P.S. I only changed the main seal on the left side of the engine under the magneto. And that was enough of a challenge to get the points to work again that if you really want a challenge, look no further than that. (or the spark arrester) P>P>S There is a trick to pulling those seals, so you don't have to split the cases to get the seals out. Just drill a 1/8" or smaller hole in the hard part of the seal ring and insert a wood screw with the tip ground off slightly blunt on the end so that you don't scratch your bearing inside. I did it that way and used two holes at 3 and 9 oclock so that I could get some equal pull on both sides of the seal. Mine was really stuck in there! Be very carefull with your drill and use a drill stop on the bit to only allow a 1/16" deep hole! The bearings are right behind the oil seal so use extreme caution and be sure to clean out any chips that may fall behind the old seal. Good luck!

Below are some pics of the installation of the Trials version brake pedal which is installed on the bike now. Please note that I did have to remove the rear wheel and swing arm to get enough access to remove the brake pedal. don't know if you can see it, but the standard Trials pedal is a lot more accessible to the right foot now and I will probably leave this one on the bike for the forseable future.

Feetupfun, I do not have a bore gauge, but my telescoping gauges and micrometers are fairly accurate. From what I could measure the new cylinder was still at nearly a stock size. There was a "lip" at the top of the cylinder that you could feel, and this and the taper of the whole sleeve inside may cause them to take it out one or two sizes to get it straight again. But since I am a complete beginner at the whole idea of Nikasil and what it can do and what it is best used for, I thought it would be a good idea to find out as much as I could about the process and get everyone's opinion. So now I see that it can be applied to either the cast iron liner or for other bikes with just aluminum cylinders it can be used to improve the hardness and durability. Sounds like a must have for those situations where there is no cast iron liner for sure. Thanks again for everyone's input!

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??

Guys, Well, Millenium got a look at the original cylinder and decided to pass on it. They said it could be re-sleeved, but the aluminum part of the cylinder had been modified and would not be an economical candidate for further repairs. The problem would have come when trying to make the aluminum part of the cylinder match the original contours under the liner which had been cut away by the modification of the previous owner. So rather than pouring more money into something that may not work, I bought another cylinder on Ebay. I inspected it for signs of damage or deterioration or modifications and there was just the normal wear. The intake port was symetrical and had not been modified. So it's on it's way to Millenium now.

Section Swept, That brake lever on your bike is about where I want mine to end up. I'm hoping that the ebay lever I bought will work, (see picture below) It does not seem to be exactly bent like the one on the first Craigslist pictures, but maybe I can tweak it or modify it to work. Anything would be better than what I've got now. Apparently there were different versions (of the shorter stock Trials version) or everyone tweaks them to taste. Main thing is to get the pad end out from under the side of the case where my big foot can find it. That problem is what eventually led to me changing my riding style and using the engine for braking. And that would be OK for a 2 foot hill, but where I ride the hills are very steep and long, so I really have to change and use the brakes a lot more. I got lazy with the clutch and I think it was doing damage to the cylinder with all my "Jake Braking" on longer downhill stretches. Anyway, the Ebay seller said that this was from a 74. See what you think.

Have to agree with Feetupfun. About the brake lever. The bike has the big seat and most likely has the trail kit installed. I did not know that the trail kit included a different brake lever. But now I do. Agree on the size of the pegs, but I wanted something big to make standing on the pegs more comfortable. And they are, but I think I went too big.

2stroke4stroke, Yes, I think I will do some more modifications on those pegs. They are a bit too large in all directions. But you would be surprised how much grip they do have. It's the outer rim that is doing all the gripping of the boot sole. Not the inner peg surfaces. And you won't cut your shins to pieces on those if you get crazy and ride in your shorts. But they are definitely not for trials use. Just for casual trail riding. And up till now that is all I was doing with the bike. It might get a little expensive to convert it back from a trail bike to a trials bike. At the very least I need a trials seat and maybe a different gear shift lever. The gear shift lever is also too long for the trials position of the pegs. Oh well, it's only money.

OK, Here are some more pictures of my own bike rear brake lever. You can see that is is not set up right for trials, and does not really work for trails either. Too low and too far forwards. And tucked in too tight to the cases. It hits the cases at one of the bends. So this one is scrapped as soon as my Ebay purchase gets here. looks like you have to remove the swing arm to get the brake lever off and on?