copemech Posted September 6, 2009 Report Share Posted September 6, 2009 That type of "coking"of the oil residue does suggest entry of the gearbox oil, as compared to the cleaner pre-mix oils. I cannot recall what you are running in it, yet modern synthetics or even simi- synthetics do not leave that type residue. If the drive side crank seal was leaking(suspected) then it could suck in air or oil. Meeting your wierd running problems. Doubt the volume in vs. volume out has been checked. May well tell! Coolant monotoring? My fan cycles, so I know there is coolant in there! As they will not without! Funny the new ring spec on the 250 came in at .020 as Ryan suggested. He probably has not checked one since he was on a 250! Cleaning it up, well that is another issue. Personally, I would likely use a bit of solvent such as gasoline or stoddard solvent(oil based paint thinner), hit the bore along the same hone lines as factory with some scotchbrite, not too much, I think the paint will resist the gas, maybe not too much so use care, then a good hot soapy water rinse to remove any abrasive. Carby cleaner should clean up the piston, if it is in spec, did it rattle much? Admittedly, we just are fixing a problem here, and not overhauling it, there is a difference! Quote Link to comment Share on other sites More sharing options...
neo Posted September 6, 2009 Author Report Share Posted September 6, 2009 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? No that was my son's 125 I did...this 250 has never been split.....And Id like to keep it that way if possible That type of "coking"of the oil residue does suggest entry of the gearbox oil, as compared to the cleaner pre-mix oils. I cannot recall what you are running in it, yet modern synthetics or even simi- synthetics do not leave that type residue.If the drive side crank seal was leaking(suspected) then it could suck in air or oil. Meeting your weird running problems. Doubt the volume in vs. volume out has been checked. May well tell! Coolant monotoring? My fan cycles, so I know there is coolant in there! As they will not without! Funny the new ring spec on the 250 came in at .020 as Ryan suggested. He probably has not checked one since he was on a 250! Cleaning it up, well that is another issue. Personally, I would likely use a bit of solvent such as gasoline or stoddard solvent(oil based paint thinner), hit the bore along the same hone lines as factory with some scotchbrite, not too much, I think the paint will resist the gas, maybe not too much so use care, then a good hot soapy water rinse to remove any abrasive. Carby cleaner should clean up the piston, if it is in spec, did it rattle much? Admittedly, we just are fixing a problem here, and not overhauling it, there is a difference! I'm running 98 with Synthetic 80:1 I didn't measure the coolant when it came out....but I know there was a lot in the bucket and it was a clean fluorescent green...Identical to what went in and it's been in there about 6 months now. All water ways are also very clean inside. But I'm going to try and measure the oil when it comes out....to me that RH seal is now a very strong possibility...so I'll change both this week. I also remember some time back changing the oil and and finding it odd that only 370ml's came out. I only discovered that by chance, when I pored the old oil into an empty oil bottle. Can I do any harm spraying carb cleaner in and around the top of that crank area?.....I know I can dry most of it out with the high volume warm air blower I have. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
copemech Posted September 6, 2009 Report Share Posted September 6, 2009 No that was my son's 125 I did...this 250 has never been split.....And Id like to keep it that way if possible I'm running 98 with Synthetic 80:1 I didn't measure the coolant when it came out....but I know there was a lot in the bucket and it was a clean fluorescent green...Identical to what went in and it's been in there about 6 months now. All water ways are also very clean inside. But I'm going to try and measure the oil when it comes out....to me that RH seal is now a very strong possibility...so I'll change both this week. I also remember some time back changing the oil and and finding it odd that only 370ml's came out. I only discovered that by chance, when I pored the old oil into an empty oil bottle. Can I do any harm spraying carb cleaner in and around the top of that crank area?.....I know I can dry most of it out with the high volume warm air blower I have. Best of balance. Neo This is what, an '07 bike with the sealed bearings installed? I would be very cautious about the reaction to the seals on the bearings when subjected to this type of solvents. "Better to play safe and let it be." Also would leave all residues laying in the bottom, unless you flipped the bike for a douche!! Carefull with all that! Quote Link to comment Share on other sites More sharing options...
neo Posted September 6, 2009 Author Report Share Posted September 6, 2009 Ok Gents....here's the update.... After some fuss I managed to get that main pinion off (without a puller and without marking anything). The seal came out dead easily using a "Seal Hook" (which I made myself some months back). I saw this tool on an old motorbike article and it works a treat. It a hook but it also curves around the shaft (hard to see this curve in the photo below) when it pushed past the seal lip. Even the old seal is barely marked..... Having said this the came out so easily I wonder if it was tight enough to seal against the case in the first place. .....And this old seal does not appear to be a Viton seal because it's black....I'll make sure I replace these with Viton (brown) seals. And if you look into the crank shaft you can clearly see that similar tarnishing and traces of oil on the side of that main bearing. There's no traces of movement in the main bearing on that side....but I guess it was well oiled Measured the amount of old oil, with precision, but it only came to only 350ml .....I think this problem could have been an even bigger problem in the future You know what gents....I'm getting really excited....this is starting to look like we've found the problem Also, if anyone wants the number on that water pump shaft bearing it's .."BC+ SKF HK 0808 GERMANY" Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
stork955 Posted September 6, 2009 Report Share Posted September 6, 2009 Gday Neo, looks like things are looking up. Check the crank where the seal runs for damage - sometimes seals will wear a groove into their shaft and that will make sealing difficult for the new seal. You can fix this by using a speedy sleeve or if possible fitting the new seal in a different position if it has occured. As far as cleaning the bottom end out fuel would be the go as Cope said, if the mains are sealed Carb cleaner might not do the seals any good. You could get a lot using an old toothbrush in the crank etc. and rinse out well, even lifting the bike up so the fluid can run back out afterwards. Cleanliness is next to godliness! A scotchbrite pad stolen from her indoors will work well for removing gaskets, but make sure you clean all that residue out well also. Cheers, Stork Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted September 6, 2009 Report Share Posted September 6, 2009 The old gasket is identical to the new one bought from Sherco. I think they have sent you the wrong one, you need is M681 which is a little thicker around the transfer ports, you can clearly see your doesn't fit correctly in your photo. Quote Link to comment Share on other sites More sharing options...
tony27 Posted September 7, 2009 Report Share Posted September 7, 2009 When I first got hold of my new seals I thought they weren't viton either but if you look closely you'll see that they should be a dark grey & not black, nitrile seals generally have a slightly different design as well. If you get hold of a normal nitrile seal & compare it with your old seals you'll see what I mean Quote Link to comment Share on other sites More sharing options...
neo Posted September 7, 2009 Author Report Share Posted September 7, 2009 Hi trialsnutterman, Gasket for my 250 is M037 ...which is what I ordered....but I can see what you're saying now. The coverage is wrong....but I know the 290 uses the same crank case as the 250. So I can't understand how the gasket could be wrong. Anyone know how to tell the difference between a M037 and a M681 gasket? Thanks Stork...I'll be sure to check all you say. :-) Hi Tony, I was looking at it in the sunlight today....definitely Black......Hmmm..maybe we're looking at a bad/incorrect batch from Sherco Viton Seals on order. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
neo Posted September 7, 2009 Author Report Share Posted September 7, 2009 Just checked the 2005 parts book....M037 is the part number for both the 290 and the 250. .....The difference for the 2006 onwards, must be in the thickness. And the M037 carries through all the way to 2009 for the 250. Although 3 other thicknesses are now available.....All of them with different part numbers to the 290 ones....I think all this is making my head spin Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted September 7, 2009 Report Share Posted September 7, 2009 The parts book isn't always right there are loads of little errors. I though you had a 2007 bike but even so the engine casings changed sometime late in 2005 and by the look of that photo you have got the newer casings. I've only owned 290s so I'm not a 100% sure but I think I would get the newer gasket and try it as I'm fairly sure it would fit much better, possibly you may have to trim it slightly if it protruded into the ports. Quote Link to comment Share on other sites More sharing options...
neo Posted September 8, 2009 Author Report Share Posted September 8, 2009 (edited) It's funny how all comes clear when you look at the other side....the barrel side that is The old gasket shows a good fit on the barrel (apologies for not aligning the gasket precisely). New seals arrive tomorrow.. Best of balance. Neo Edited September 8, 2009 by Neo Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted September 8, 2009 Report Share Posted September 8, 2009 Ah ok you have got the right gasket then, my apologies. You'd think Sherco would have matched the cases to the transfer ports a bit better, there must be 5mm step between them which can be good for the flow, on the 290 they match quite well considering it is a casting. I wonder if they have changed the design on the later bikes. Quote Link to comment Share on other sites More sharing options...
neo Posted September 12, 2009 Author Report Share Posted September 12, 2009 Hi All, Just a bit of an update. I found the seal on the RH (oil) side had a hairline crack in the outer lip. And found that the seal on the LH (gen side) had a very swallow v-grove inside...as if both inner and outer lips had worn out....So I think I was experiencing problems from both sides. Both new rings and both new seals are operational. Finished putting her back together late last night and rode her on the driveway (because it was a bit dark to venture onto the rocks ) ...Once the engine had warmed up she was running like sh** ...far too rich and would not idle. Carb setting were 48 pilot, 120 main, JJH needle, Clip in the top position....been like that for 8 months or so. Fresh start this morning and changed the setting to Clav's settings....well as close as I could get....35 pilot, 114 main, JJH needle, Clip in the middle position. Ran better but now running very leak and hunting....And at this point I was starting to get worried .....Swapped the 35 for a 39 and bingo! all has came good......Not sure if my 35 was a bit blocked but she's now running good with an airmix screw 3/4 turns out, so I'll probably leave it there for now. A ride on the rocks reveled a softer/smoother low speed move off and a more consistently controllable level of power higher up too. So I'm happy so far.......It's all really looking good but the real test is after a days riding. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
copemech Posted September 13, 2009 Report Share Posted September 13, 2009 I just wish you would quit dinking around ang get this thing fixed so you can try the other carby! Quote Link to comment Share on other sites More sharing options...
clav3 Posted September 13, 2009 Report Share Posted September 13, 2009 Hi Neo, When I was running a 35 pilot on the 290 I was using Boysens. Had to change to a 42 when I went back to standard reeds. A 45 would still run, just in air screw range. It sounds like you have the results of a nice fresh engine with good seals. Enjoy the feeling. Just make sure the carb stays ultra clean to avoid any frustrating confusion on how it is running. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.