copemech Posted August 31, 2009 Report Share Posted August 31, 2009 In observation ov Clav's post, Firstly, I know these specifics are a bit hard to come by(non exhistant), yet you suggest that you filed the stock rings a bit to open them up? Why? Are those rings cast?(do they break or bend)? Secondly, Ryan is pretty darned good on stuff actually, yet he is not an engineer but he is a good mechanic and a wealth of knowedge due to his vast experience since day one and beyond! His postings are usually concise, therefore I would normally conclude that the spec of .020 would be what is normally called out as a "service limit" on wether to toss it or not! He has shown me a few pointers on the bikes and does know his stuff! You don't even want to watch him ride, friggin nutter will just embarass you! You see, even though I have admitted on a number of occasions that I have NEVER had a reason to take one of mine apart further than the clutch cover, I kind'a keep tabs on this stuff! Long term testing of the '07 goes on! Quote Link to comment Share on other sites More sharing options...
clav3 Posted August 31, 2009 Report Share Posted August 31, 2009 I just help with the top end and fixing of the crank and let one of my riding buddies (the engine reconditioner) take control. We did notice, when changing to the cabestany head, the cylinder had some, (forgive my terminology) heat marks. It seemed the engine had nipped up at some point. New engine, hot aus weather, long hillclimb, who knows? He thought the ring gap might be on the tight side. At that time we couldn't find anything on the net on ring gap so my mate used a standard formular to work out what the gap should be. He's had many years experience on bikes, cars, trucks so I trust his judgement. Yes we did file the gap, and the same when we recently did up the top end. He was the one who straightend my crank, bashing it against his gut with a copper hammer and checking on a pair of blocks with a dial guage until it was perfect. I'm very lucky to have him as a riding partner. If my bike's not going, he's not riding either. Check Ryans forum, but I was under the impression that someone had asked for the ring gap on re-build. Quote Link to comment Share on other sites More sharing options...
copemech Posted September 1, 2009 Report Share Posted September 1, 2009 I just help with the top end and fixing of the crank and let one of my riding buddies (the engine reconditioner) take control.We did notice, when changing to the cabestany head, the cylinder had some, (forgive my terminology) heat marks. It seemed the engine had nipped up at some point. New engine, hot aus weather, long hillclimb, who knows? He thought the ring gap might be on the tight side. At that time we couldn't find anything on the net on ring gap so my mate used a standard formular to work out what the gap should be. He's had many years experience on bikes, cars, trucks so I trust his judgement. Yes we did file the gap, and the same when we recently did up the top end. He was the one who straightend my crank, bashing it against his gut with a copper hammer and checking on a pair of blocks with a dial guage until it was perfect. I'm very lucky to have him as a riding partner. If my bike's not going, he's not riding either. Check Ryans forum, but I was under the impression that someone had asked for the ring gap on re-build. Well, I totally understand where you and your mate are coming from. However I seriousy doubt the factory does such ring matching. Thusly an "A" bore and piston match will recieve the standard rings and start off a bit tighter in the clearances than a "B" or so it goes. In my mind, the biggest problem with piston scoring has been basically the same as starting off from cold. If one lets the bike sit and cool, then rides a tough section requireing high loads and rpm, the piston will heat up faster than the bore! and at these tolerances that is not good. You need to run them about to get heat in the motor and bring temps up together. Fan cycles! This seems even more critical on a low time motor. BTW, did you figure out if the rings are brittle? Do they bend or break? Only thing I can see with a bit of fileing would be to possibly shorten their lifespan, which may be rather short in some cases to begin with. Quote Link to comment Share on other sites More sharing options...
clav3 Posted September 1, 2009 Report Share Posted September 1, 2009 (edited) I just when down stairs to see if I still had the replaced rings. Yes I did, and no, they don't bend , they do break. My piston from new was a B size and the replaced was also a B. We all try to do the right thing by our engines but sometimes we all slip to the dark side. Perched halfway up a hillside, waiting for your turn to ride that section requiring high loads and rpm, while the engine gets colder. It's an uneasy feeling with a fresh tight engine. You sit there not expecting it to go cold as fast as it does. And then you're up. It's funny now you mention it, standard rings in a B size bore and a ring gap of only 0.009. I do know that the second and third set when placed in the bore also had 0.009 gap. I suppose it would only be about 0.0004 tighter in an A size bore, maybe just enough to turn a nip into something really nasty? Edited September 1, 2009 by clav3 Quote Link to comment Share on other sites More sharing options...
stork955 Posted September 1, 2009 Report Share Posted September 1, 2009 Gday, I'll just add my 2 cents... A lot of seizes are caused by too large a piston/bore clearance - the piston is cooled through the bore wall effectively by its contact with it. If the bore is too large, the piston cannot transfer its heat away and nips up. Ring gaps are only an issue if too small - rule of thumb is minimum 4 thou per inch of bore size (whatever that is in metric...) A larger ring gap is not a big problem unless its huge. When your ring gaps are up around 40 thou its a good indication of ring wear, but at that stage Im always measuring the bore to see if the piston is also worn. The best bet is always go with what the manufacturer says, if thats at all possible. Cheers, Stork Quote Link to comment Share on other sites More sharing options...
copemech Posted September 2, 2009 Report Share Posted September 2, 2009 I just when down stairs to see if I still had the replaced rings. Yes I did, and no, they don't bend , they do break.My piston from new was a B size and the replaced was also a B. We all try to do the right thing by our engines but sometimes we all slip to the dark side. Perched halfway up a hillside, waiting for your turn to ride that section requiring high loads and rpm, while the engine gets colder. It's an uneasy feeling with a fresh tight engine. You sit there not expecting it to go cold as fast as it does. And then you're up. It's funny now you mention it, standard rings in a B size bore and a ring gap of only 0.009. I do know that the second and third set when placed in the bore also had 0.009 gap. I suppose it would only be about 0.0004 tighter in an A size bore, maybe just enough to turn a nip into something really nasty? Well then, the rings must be cast as I suspected, which may also confirm the more rapid wear rate. As Stork's theory serves to re- instate some basic guide, which your mate is going on as well, I suspect that the minimal difference in gap between .009 and whatever would change in about the first hours run time on these, so therefore I would stick with the stockers as they come. As Stork did mention, gap in itself can be a negligeable point, up TO a point! If Clav's statement holds true as initially proposed, and the rings condition does indeed change the volumetric efficiency of the motor, thusly effecting the carby, then it would not neccessarily be the gap on the ging ends that is the culprit, but the "tension" ov the ring that is effecting it's ability to seal, or not seal well enough to control blowby! Which in turn may effect mixture! So you see, there must be a logical reason for the claim that Clav and Neo have presented, or else the Kiehin is just a POS, or they are both on drugs! I doubt that, so there must be an explanation. Quote Link to comment Share on other sites More sharing options...
neo Posted September 2, 2009 Author Report Share Posted September 2, 2009 (edited) OK...I've place an order for new rings....and will do the seals (if need be) after that. But with all this in mind, I once read (I think it was you Cope that said this) that too much 2T oil will actually aid the piston ring seal....would this apply to a hot engine too?....Would raising the level of oil in my tank go some way to proving this theory? If so, I run 80:1 synthetic now ...what should I raise it too? Best of balance. Neo Edited September 2, 2009 by Neo Quote Link to comment Share on other sites More sharing options...
copemech Posted September 3, 2009 Report Share Posted September 3, 2009 OK...I've place an order for new rings....and will do the seals (if need be) after that.But with all this in mind, I once read (I think it was you Cope that said this) that too much 2T oil will actually aid the piston ring seal....would this apply to a hot engine too?....Would raising the level of oil in my tank go some way to proving this theory? If so, I run 80:1 synthetic now ...what should I raise it too? Best of balance. Neo I no longer recall if I was the one who speculated this, yet ----- uh really? I do not know that it would make that much difference unless the ratio were swung back to 36:1- 48:1 or something that might put MUCH more oil on the walls. Problem is that way too much condenses and falls to the bottom of the motor at low rpm. I was going to mention the fact that I had started a '09 2.5 for one of our female riders back earlier in the year. (Yes, I wanted to ride it) She had ridden the bike in for a number of hours of practice and maybe a trial, so it had what I would guess 10-15 hours on it. Well, first impressions were, "this thing is still tight" even commented on it! And when I say that, I mean that 2.5 was probably 20-30 percent more difficult to prod through than my well run 2.9. Now all that being said may just tell how well worn my rings are, yet at the same time, as i stated, it does make the legwork easier. Seems to run fine with the dellorto, yet I never got the pinging out of the motor till I went to the 38 pilot, sinse new. All that just serves to tell me the old hag may need a freshen up as well, yet I am doing long term testing, as this bike started out in late '06 as Cody Webb's TDN bike, so I am sure it was broken in well, (yea right) over the weekend! Nearing three years old now, yet I must really discount a year off that as I have laid off the comps this year and some of last. As with Ishy, I have come to like the 2.5's like my old '05 bike. The 2.9 can be smoothed and mine is not bad, actually it is near butter smooth in it's current state, so much so I may either replace the rings or kick timing back up a couple mm. The whole thing about response and power is a balance it seems, all dependant upon the riders needs. Yet when I do have someone like Ryan sit there and tell me off the cuff, that unless he is running big rocks like Cali or Colorado, he is on the Dellorto for ease and reliability, well, what do you say? Now take Smage, he likes the big power, and stick mostly with the K carb, power rider! So all said, I am in fact somewhat still interisted in the OKO carbs, as they are available in 24, and26 mm versions i think. As I have gotton no feedback from Neo on the carb switch from the 125 on the 2.9, think it was a 24mm, which may indeed proove to be lacking, I am not yet sure that a 26mm OKO on a 2.5 may not be a good combo? As I just have no need for the added power, I took the K -28 off my old 2.5 and it has set since! Anyone want one? Just my thoughts, Quote Link to comment Share on other sites More sharing options...
neo Posted September 3, 2009 Author Report Share Posted September 3, 2009 As I have gotton no feedback from Neo on the carb switch from the 125 on the 2.9, think it was a 24mm, which may indeed prove to be lacking, I am not yet sure that a 26mm OKO on a 2.5 may not be a good combo? As I just have no need for the added power, I took the K -28 off my old 2.5 and it has set since! Anyone want one? Hey Cope....I'm sorry to let you down on that ....It just been a combination of many things, these past few months, that's got in the way. I'm deep in study during the week so don't touch the bikes weekdays. And we're praying for rain at the moment....if this dream comes true this weekend I might have time to whip the 24mm off of the 125 and try it on the 250......I'll use the jets/setting out of the PWK 28 to get it going. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
neo Posted September 5, 2009 Author Report Share Posted September 5, 2009 (edited) Hi all, Lifted the barrel off of my engine today. I Edited September 5, 2009 by Neo Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted September 5, 2009 Report Share Posted September 5, 2009 You've got the wrong base gasket on and it looks like it has pulled in a little around the transfer ports maybe this is contributing to your mysterious problem. The line 4mm below the top of the barrel is were the ring go to, I don't know why the other side isn't marked maybe somthing to do with the turning forces acting on the little end bearing, its not something to worry about. It is very carbon coated, you usually get a bit of carbon blow by but your looks very excessive, I think I'd be changing the crank seals as it looks like you may have been burning a bit of gearbox oil. Quote Link to comment Share on other sites More sharing options...
copemech Posted September 5, 2009 Report Share Posted September 5, 2009 Looks like it has been burning something other than pre-mix! Quote Link to comment Share on other sites More sharing options...
stork955 Posted September 5, 2009 Report Share Posted September 5, 2009 Gday, yep agreed to the above - far too much oil coming in there. The base gasket does look like it has been leaking too, right in the middle where it is cleaner than the outside bits. The bore looks glazed too, a light hone would pay unless its a chrome/Nikasil type. You never want a mirror finish these days -its a sure sign of bore wear. It should have a light 60 degree crosshatching visible. Cold parts cleaner will fix the glaze but you need to repaint afterwards. If you do crank seals it will pay to strip the lot so you can clean the crankcase properly. The cleaner it is the better it will run. It would also explain some of the "blubbery" running that it has been doing. Carb cleaner will do the same job if you dont strip it. Check the side and back clearance of the ring grooves too with the new rings before re-assembly. If there is excessive wear there it will need a new piston too. I use the old rings to clean the grooves but watch the ring locating pin at the back. "N" stands for Top, so the letter goes up when fitting the new rings. The clean ring around the top of the barrel could be a coolant leak - remove the head and check the O rings out. It will pay to replace them anyway, cheap insurance. Is there a clean area on the piston corresponding to the clean barrel area? Cheers, Stork Quote Link to comment Share on other sites More sharing options...
neo Posted September 6, 2009 Author Report Share Posted September 6, 2009 You've got the wrong base gasket on and it looks like it has pulled in a little around the transfer ports maybe this is contributing to your mysterious problem. The old gasket is identical to the new one bought from Sherco. The base gasket does look like it has been leaking too, right in the middle where it is cleaner than the outside bits. You guys might be onto something here. As I noticed, on dis-assembly, that the two front bolts were not as tight as the two back bolts... Gday, yep agreed to the above - far too much oil coming in there. What else could I have been burning but premix?....that's all that's in the tank and the carb, air-filter and air box are all dead clean.??? Check the side and back clearance of the ring grooves too with the new rings before re-assembly. If there is excessive wear there it will need a new piston too. Good idea...yep I do that. New rings both have a ring gap of 20 thou. I'm not keen on splitting the case at this time. But I reckon I can do the main seals without doing that. so might try that next....If I mess up I just have to split the case anyway I suppose Many thanks gents. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
tony27 Posted September 6, 2009 Report Share Posted September 6, 2009 I noticed the same thing with the base gasket on my 290 & asked Chris at splatshop about that, turns out that the transfers were made smaller in 05 so maybe find out if the 250 is the same & for some reason your cylinder is old stock(04 or earlier) with larger transfers I've never seen a conrod covered with carbon or whatever it is & think you've got some major blow by problems. Where on the piston did you measure, should be done roughly 19mm from the base of the skirt. Out of interest mine measures about .2mm smaller above the top ring than at the normal point, surprised me as the motor has no piston slap going on You should be able to change the seals without splitting the cases but didn't you try fitting new ones when did the mains & ended up nipping 1? Quote Link to comment Share on other sites More sharing options...
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