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Tillerman6

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Everything posted by Tillerman6
 
 
  1. jc2, That is the consensus on the Trials Central site. You guys are the Guru's of the engine world. Now the trick is to convince the people at CMSNL. They have the 311 and 438 pictures and part numbers swapped around backwards which is how I came to recieve the 311 piston. I was lucky enough to keep a picture of my old piston which is a 438 and sent it to them. But now they have the ball and it might take some time for them to respond to my emails. I will get back on here when I get a response and let you all know what happened.
  2. Guy53- I don't suppose you would be able to weigh both pistons and tell us all if there is any difference? I would think that the 311 with the sharp corners and thicker walls is heavier than the 438, but if it's just a couple of grams- no big deal.
  3. Now I am straightend out. And I agree with you 100%. However CMSNL still has their documentation backwards. Hopefully on Monday I will be able to contact them and see what they can do. Here is the advert they sent me. You can see the sharp corners in the photo and the 438-11631-01-96 part number there on it. https://mail.google.com/mail/u/0/#inbox/FMfcgxwLsSfJmSnbRtVsLJcFKlDWhnWR
  4. Tony27! That's the info I needed! But CMSNL still shows pictures of the 311 piston with a 438 part number on it. https://mail.google.com/mail/u/0/#inbox/FMfcgxwLsSfJmSnbRtVsLJcFKlDWhnWR So the next person that orders a 438 piston from them will get another 311 just like I did. Either way- it looks fairly easy to knock off the corners near the transfer holes and Wallla! It should clear the flywheel halves!
  5. Tony27, Unfortunately I don't have the old piston. I sent it off to my engine rebuilder and it got lost in the mail. But it sounds like you have run into this before. I think it would be a big problem for anyone that has to replace pistons in these old bikes. And there is a guy on Ebay selling a piston like it but he does not specify in his description which part number he is selling. so he's listing the same piston with BOTH part numbers inclusively. I.E. 311/438 11631-01-96. So I'm not sure if there is really any difference, or what is going on. At least I have a con rod with 311 showing on it. Maybe I do need the real 311 part number for a piston and not the 438??? Here is the ebay listing: https://www.ebay.com/itm/NOS-Yamaha-Piston-Std-Size-1972-77-DT2-DT3-DT250-TY250-438-311-11631-01-96/264984342801?_trksid=p2485497.m4902.l9144 It might dissapear any minute now or get sold so don't wait if you want to see it.
  6. This might be a tough request to make, but I have a small dilemma. I have a stock 74 TY 250A and I have had everything rebuilt on the engine. But when I tried to install the piston, it touches the flywheel before the flywheel can rotate all the way around. So either I have the wrong piston or the wrong Connecting rod installed. My measurement for the piston skirt is 68.3 mm from the bottom of the lower piston ring to the bottom edge of the piston skirt. Does this seem to be about right? The piston is a genuine Yamaha, from CMS, part number 438-11631-01-96. If anyone has a loose TY 250A -1974 model piston laying around loose they can measure- it would be a great help !! Thanks in Advance! Update- CMS has sent me the correct 438 piston now and I installed it this morning- fits perfect!
  7. One more possibility- I found this out today- playing with my own clutch assembly - The pressure plate (item 7) can be mis- aligned over the 6 female mounting points in the clutch boss. The 6 screws and springs will still tighten up, but the pressure plate on top is not seated all the way down. This would put the pressure plate too far away from the push rod end, and put slack in the cable. So if you back off the 6 screws in the pressure plate and wiggle/spin it left and right, you might feel it seat properly. That will get the top plate closer to the push rod and take more slack out of the cable. One note - the steel clutch plates all have a special shape on one edge. These are supposed to be clocked around the clutch basket about every 60 degrees to keep the clutch balanced.
  8. Junglejeff, That's good to know. I sure wish I was there when the cases were opened though. Even with the factory shop manuals there is still some room for error. it's just human nature to screw up. For instance I spent two hours today trying to straighten out an order from Ebay. I ordered a new crank pin with the original part number and the seller had written in pen on the bag the same number, but when the engine rebuilder received the "new part" it was wrong. So I called them up and they said sorry. You have x days to return the part for a credit. So now the rebuilder has to take his time to mail something back before the deadline. So I asked the supplier if they had the correct part - The guy that answered the phone said "No I don't show any crank pins in inventory" (Redline Motorsports) So that outfit is a bust. So I found another supplier that has a good rep on Ebay for another new pin and we get to see if that works. Goo thing I'm not in a hurry. And I ordered a new Tusk puller tool - not sure if I will be the one to use it or not, but again, the company made another kind of mistake. They sent my tool to Mississippi instead of my address in Idaho. How can that happen on Ebay? So they sent me another one. That was good and I got it today. But wait there's more! The puller tool is really beefy and well made, but on the TY 250A, only the magneto end of the crank can be pulled thru the bearing. So the right side of the crank has to be a hot and cold kind of assembly procedure. The tool is only good for the magneto end of the crank, and the instructions say to do that After the other end is seated. So that means the right side cases will be already loaded with the crank inside (stuck there) and now we have to load the gears into he left side and try to line everything up and pull in the crank with the tusk tool. That seems to conflict with the factory manual, as they have everything loaded into the left case first. It's a little much for someone that has never done it before. And the chances of screwing it up are about 90% I would think. I don't yet have the dis-assembly tool, so that makes me a little paranoid about attempting the whole procedure.
  9. I wish I could be sure. There is another one in the steel ring on the back side that worries me a bit more. Can't tell if it goes all the way thru the part or not. I might have it magnafluxed, Its not too pretty. But all the ones I see on Ebay are also cracked on the inside. Just don't know if the cracks go all the way thru. On the other hand, I've never heard of one exploding. Might not shift properly, but never exploded (that I know of)??? I cast aluminum myself and I know what casting lines look like and what cracks look like- they look similar at first glance, but magnified about 50 times and you can tell the difference. Not much I can do about it, but I will shoot some pics with my new microscope tomorrow and post them for you.
  10. Tony27, Thanks for that bit of info about the seal housing clearance. I have my own lathe and mill, so I will look for that when I get the parts in. Not sure when that will be. Then the next issue is to fiure out where they all go. I didn't take the gearbox apart, so I didn't see the relationships inside. Most of it is pretty self explanatory, but there is a good chance of getting something in there wrong or omitted.
  11. One shot that might help. If the ball bearing is missing, the left end would be flush, and on the right end, the "tophat" would bottom out in the hole. If the ball is present, then the positions you see here would happen because of the extra stack length of the parts.
  12. On the ty250 A like mine, the main pushrod cannot be removed without splitting the cases. Reason being- the hole you can see is smaller than the diameter of the pushrod. The other end where the clutch actuator cam is located has an opening large enough for the main pushrod to be assembled into. but the end you can see with just the clutch cover off is too small, and will only accomodate the smaller "top-hat" pushrod diameter and the ball bearing. I took a few pictures, but I don't know how to upload them on here. It's interesting to know that without the ball bearing inserted between the two pushrods, the ends of the pushrods will only come flush with the ends of the gearshaft that they ride in. so if that ball is missing, you won't be able to release the clutch at all and the back tension on the clutch cable would be slack which is the symptom you mention. Since the ball is magnetic, and if you have a magnetized nail or similar, you can probe and see if the ball is really present. It will come right out if it is in there. The hole is big enough for the ball- no problem, just not the main pushrod itself. Your problem is fairly simple if you don't really have to remove the main pushrod. all you have to do is fill up the distance between the inside of the clutch pressure plate and the cam actuator face. And if the cam actuator is in it's relaxed position, the length needed to bridge the distance will be at a maximum. You should also be able to check for the presence of the parts by measuring the depth of the hole. If the hole is just slightly deeper than the length of the small pushrod, the ball is missing. Pulling in the clutch lever will have no effect on the pushrod position. If the ball is present, the small pushrod will protrude out the end of the shaft about 1/8-3/16" and move with the movement of the clutch cam actuator rotation. That is about it. There is no other scenario in which the pressure plate won't move if all the parts are present and the clutch main nut is tight.
  13. So with this teardown and inspection- looks like there are cracks in the clutch basket. And looking at the examples on Ebay, this is a very common problem. Every example on ebay has at least one crack visible, and there are about 5 examples for sale on there right now. Mine looks exactly like most of them, and I'm not sure how to post pictures on here, so if you want to check out what I'm talking about, just go to Ebay and look for ty250 clutch baskets. The crack I noticed first goes directly thru the "9" that is moulded into the part number. Mine is exactly cracked in the identical same place! There is also a crack in the flat steel smooth ring on the other side near the thru hole. None of the ebay examples even show the back side, so I can't show you pics of that, but do you think I need a different clutch basket, or is this a non-issue? I don't think the basket will explode due to high revs, and it has 3 strong rivets that hold it together, but I'm not sure what to do about the "problem" if anything can be done. The clutch was acting a bit strange before the teardown, but that was not the most serious problem (vibration) so I figured that I would check it out later. Well later is now. What is your experiance with this problem and how did you deal with it? I would almost bet anyone that if they have a TY 250 and they take all the clutch plates out of it they will see cracks in the aluminum housing (basket). There seems to be no easy source of new parts for this eitherr.?
  14. Is there any chance that you are missing the ball bearing out of the assembly? I think it rides on the inside end of the pushrod. Also the pushrod is rounded on one end and flat on the other end (at least mine is) and those details are not visible in the diagrams. So it would be possible to get the pushrod in backwards and or forget the ball bearing that rides on the inside end of the pushrod. There is also a spring outside the cases that returns the "cam" rod back to the starting position. If that spring was missing or broken, it would keep the whole mechanism from working.
  15. The rod length for the 74 250A is 125 mm and using the calculator above, the angle you seek is 22.74 degrees on the wheel. That is the starting point anyway. So is your kit from electrex? how do you like it?
  16. I found a piston position/degrees calculator online but you need to know the length of the rod to use it. That should be doable http://www.torqsoft.net/piston-position.html#ex2
  17. the flywheel nut (magneto) gets 4.0- to 4.5 kg-m or 28.9-32.5foot pounds of torque, but you need a special tool to hold on to the flywheel. the timing is normally set with a dial indicator riding on top of the piston with the head removed. the spec is 3.1 +/- 0.15mm BTDC and the engine rotates CCW as viewed from the left side. At that position, if you had points, the points should just open right then. But with your electronic ignition and if you have a degree wheel and a timing light, and your conn rod is 125mm long, then you should get the equivalent timing at 22.74 degrees BTDC on the wheel. This is only a ballpark figure and assumes a maximum amount of advance at that point. Depending on the rpm, your electronic ignition will regulate the amount of advance. At the very low rpm's you would want less than 22.74 degrees to make the bike easier to start and reduce the chances of a kickback. I hop this makes sense to you. I keep getting notified that you are still looking for this information, but this is my last attempt to reach you without feedback. Good luck!
  18. I hear what you are saying about kickback, but it doesn't make sense to me. Let's say the piston is on the way up and it's half an inch from the top dead center and the plug fires. What's it going to do at low rpm? it wants to reverse course because of all that pressure when the gas ignites. Your foot is now indirectly fighting with the piston because you have the starter gear engaged and you are forcing the piston UP. But most likely the explosion will be more powerful than your leg, so you get a little bite from the kickstart lever. So timing is everything and if I am not mistaken, moving the timing so that the spark happens at or just slightly after TDC will reduce the chances of a kickback. Especially if the piston is already on it's way back down the cylinder and the flywheels are moving in the same direction that the kickstarter would spin them. Anyway that has been my experience with engine timing. Last time I did that I think I was at 3.5mm BTDC and it was kicking back about every 10th kick. It had lots of power, but you were always wondering if this was going to be the next episosode or not. Then I decided to try to set it for 2.5mm Btdc and that reduced the kickback tendency by about 50%. it also reduced the available power maybe 20%. in my estimation. So I put it back to 3.5mm BTDC, but on that very crude points system this is only a best guess. I'm probably going to retrofit an electronic ignition as soon as I get the hot setup from you guys. That way you get a system that has automatic timing advance and you are now rid of the fiddling with points and condenser. But just so that i don't offend anyone I want to explain my definition of "advance". To my way of thinking, more advance to the spark timing means that it happens earlier in relation to Top Dead Center. I think this is a universal idea as far as I know. Maybe somebody has another viewpoint, and I am not saying that they are wrong, but just that's what advance means to me. I've never had my engine run backwards under any circumstances except for the times it kicked back and that would only amount to maybe a half revolution in the wrong direction. So does anyone have any good or bad things to say about the elelectrex brand electronic ignition systems from Speed and Sport? or is there another brand that is better in some way? And please forgive me for not sticking to the stock points and condenser. I think I'm all done fighting with that. Let's move on. There is a good video (if old one) about the electrex system being installed onto a TY 250 with a blue painted frame on You Tube. They did not finish the install, but got the major components mounted. It would be nice to hear about the reliability of that system if anyone knows about that system from personal experiance?
  19. So what are the options? It seems pretty iffy to get the timing perfect trying to set the points with a feeler gauge and just a tiny access hole in the magneto wheel, and I am not that strong to give it a mighty kick thru. My chainsaw does the same thing. Thanks very much for the reply!
  20. I watched those and I was amazed. If I can even get my engine back together properly and it runs, I will be very happy. Thanks for the "link"!
  21. I am assuming that since we are in the Yamaha section of the forum that there is some chance that you may have re-built a TY 250A? IF so, are there any tricks to getting everything re-assembled properly? I will have the Tusk puller and probably warm up the cases in my old barbbeque and freeze the crank with some dry ice before I try to put things together, but if there was anything unusual or noteworthy that you remember about your experience, I would love to hear about it.
  22. You might check your TY 250 A model if you still have it and see if the magneto wheel is wobbling with the cover off. I got about .010" of side to side wobble on mine and that ended up requiring a teardown to "parade rest" All the gears and guts are all in small piles on my workbench right now. - not fun. When the crank was out of the engine it turned out to be the culprit, although I can't say if I caused the problem or it was already "spun" when I got the bike. I will also try and test the trueness of the magneto wheel itself when I get the crank back from the rebuilder's shop. Right now there is still a problem with some of the parts suppliers because of the Covid-19 situation. For what it's worth, the stuff on Ebay is pretty much un-affected by any delays. It probably won't affect you if you are not in the States, but Partzilla is reporting delays. Question- Do you think it's possible to add a diode to the wiring harness on my 74 250A like the ones on the 75 and later models? I am still worried about the backfiring /kickback situation I had going on before the vibration problem showed up.
  23. There is an external spring under the engine cases that returns the control arm to the ready position. I had trouble with that once before and was able to remove the arm and replace it and the seal without splitting the cases. But you'll want to drain the transmission oil before you pull out the control arm if you want to work on it. Therre is also an adjuster bolt on the side of the case that sets the end play and that controls how much throw is transferred to the clutch plates when you squeeze the clutch lever. But don't take that adjuster bolt out. I'm not sure the internal parts (a ball bearing and a spring) would stay in place if that adjuster bolt was completely removed. You want to look over the repair manual real close before you do too much tinkering.
  24. I have been trial fitting the cylinder to the empty engine cases to see how the fit is working now that I have a new cylinder. And it went on over the studs but only just. If you put a few pounds of pressure towards the rear it will just slide down over the studs. I spent some time measuring everything and it turns out that the bolt pattern is not rectangular at all. The holes in the cylinder are oversized by .020" and the bolt pattern is actually out of square. None of the distances between the studs are the same. Anyway that's Ok because the holes in the cylinder are out of square the same way. I ordered all new parts for the engine except the piston. It will get all new seals and bearings, new rod and upper and lower needle bearings, washerrs and o ring. Also new pins top and bottom. I's only money and what else could i do to stimulate the economy? i also have been sanding off the rough outside burrs and flashing edges of the castings to improve the appearance slightly. There were several places with sharp edges that are now rounded down to a dull roar. I'm not too worried about the sanding dust getting into the castings now because it wiil get all new bearings later on. I noticed a little corrosion starting inside the front case ears where the front mouninting bolt passes thru. Fortunately this was cleaned out without much problem. The aluminum is stained pretty deep in several places. not sure if it's worth sanding it all out because intend to be riding it more than polishing it. There is quite a bit of cleanup to do to get all the old case sealer off the edges of the castings. I'm using Goof off and a rag for that. Acetone eats up the rubber gloves too fast. I still did not hear from you about how you knew that the weights of the con rods are different between the 74 and 75's? Is it riding weather over there now? Having any fun at all? Probably still no trials meets any time soon? Stay safe!
  25. That's very interesting! I had a similar problem with mine, but I found a couple of things that (on my bike) were bad. #1 was I had a twisted crank shaft, and #2 I had an engine mount broken loose from the frame. I fixed the frame, but I was told by an old timer that the mounting bolts could use beefing up on these bikes- like go to an english sized grade 8 bolt that is stronger. And the factory book has you torque the frame to engine mounting bolts - I doubt if mine were torqued to specs. Note that the front bolt is a different size than the two rear ones. so quoting from the DT250A/360A factory repair manual - the 8mm bolts get 217-251 inch pounds, and the 10mm bolts get 390.6 to 477.4 inch pounds. But how did you find out that the 311-11651-00 from the 74 was heavier than the 431-11651-00 from the 75 TY250B? Could be the pistons are also a different part number and weight- but now you're talking unobtanium.
 
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