philhill Posted September 3, 2009 Share Posted September 3, 2009 Hi, just wanting some advice before attempting a strip down of my DT 125 MX engine. I was enjoying the improved performance of the 125 after fitting a bigger carb purchased from Oldgit. I was experimenting with the jetting and was getting 10mph better than previous ie 70 when previous best was 60mph when I lost all power and a little later discovered I had holed the piston, fun whilst it lasted though!! Anyway this is now the opportunity to convert to 175. I have stripped the left hand side but before I strip the right side I wanted to check if it is possible to just remove the clutch basket before i split the crankcase. I just want to remove the crankshaft so I can clean the debris out of its housing. The manuals show the engine stripped with left side of the engine down and everything stripped from the right side of the engine. Does it matter if you do it the other way round, I was thinking this should save me some time but usually when i try to cut corners something goes wrong and i regret not being more thorough and following the instructions so can I or not. Anyone in the know can you please let me know! Thanks Phil Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 3, 2009 Moderator Share Posted September 3, 2009 Hi, just wanting some advice before attempting a strip down of my DT 125 MX engine. I was enjoying the improved performance of the 125 after fitting a bigger carb purchased from Oldgit. I was experimenting with the jetting and was getting 10mph better than previous ie 70 when previous best was 60mph when I lost all power and a little later discovered I had holed the piston, fun whilst it lasted though!! Anyway this is now the opportunity to convert to 175. I have stripped the left hand side but before I strip the right side I wanted to check if it is possible to just remove the clutch basket before i split the crankcase. I just want to remove the crankshaft so I can clean the debris out of its housing. The manuals show the engine stripped with left side of the engine down and everything stripped from the right side of the engine. Does it matter if you do it the other way round, I was thinking this should save me some time but usually when i try to cut corners something goes wrong and i regret not being more thorough and following the instructions so can I or not. Anyone in the know can you please let me know! Thanks Phil Its an idea and in all probability its sound. I cannot think of a reason why it wouldn't work. BUT (you knew that was coming) If you are stripping the motor down that far with the intention of cleaning it up it is only slightly more to do a full rebuild. Worthwhile reasons being the output shaft bearing and seal which WILL be buggerd due to spending their entire life stressed and coverd in grit loaded sh1t. Also whilst its out you can fit new crank seals and bearings also well worth the effort. When i did mine it cost about 80quid for all the seals bearings and gaskets to do the job, thats genuine Yam stuff to from TY trials. While i'm about it. On ebay and such you will see bargain priced crank bearings and output shaft bearings AVOID. Any bearing supplier will be able to give you bearings the right size for about a fiver but bearings are speed and load rated like tyres and high stress bearings like the crank and output shaft bearing are up there with the best of em. They are listed as 'specialist automotive' in most cases. Link to comment Share on other sites More sharing options...
philhill Posted September 3, 2009 Author Share Posted September 3, 2009 Its an idea and in all probability its sound. I cannot think of a reason why it wouldn't work. BUT (you knew that was coming) If you are stripping the motor down that far with the intention of cleaning it up it is only slightly more to do a full rebuild. Worthwhile reasons being the output shaft bearing and seal which WILL be buggerd due to spending their entire life stressed and coverd in grit loaded sh1t. Also whilst its out you can fit new crank seals and bearings also well worth the effort. When i did mine it cost about 80quid for all the seals bearings and gaskets to do the job, thats genuine Yam stuff to from TY trials. While i'm about it. On ebay and such you will see bargain priced crank bearings and output shaft bearings AVOID. Any bearing supplier will be able to give you bearings the right size for about a fiver but bearings are speed and load rated like tyres and high stress bearings like the crank and output shaft bearing are up there with the best of em. They are listed as 'specialist automotive' in most cases. Yeh, you may be right there i think the output bearing/seal is leaking as the chain is always well oiled!! I will give Granbys a ring for prices. They have original stuff and are handy for me. Thanks for making me do the right thing. Phil Link to comment Share on other sites More sharing options...
philhill Posted September 19, 2009 Author Share Posted September 19, 2009 Hi, eventually got round to stripping the rest of the engine. Have split the cases though this took some time and excessive rubber mallet and WD40 treatment as the rear large dowel was clinging hard to the cases! The rubber/steel rear engine mount inserts in both cases are seized in and need replacing any suggestions how to remove. I have soaked in WD40 type stuff and then whacked with a screw driver and rubber mallet but still refusing to budge!! Considering a drill next but does anyone have any other ideas? Also the crank is still in place in the left hand case but I am wanting to get it out so I can clean in there and replace the bearings and seals. The Clymer manual states that I need to take it to a Yam dealer to get it removed but can't I just whack it out with my trusty rubber mallet? Also the crank oil seal on the right case looks like its the wrong way round i.e. the metal spring round the seal lip is facing outwards away from the crank. Is this right? its the other way round on the left and not shown this way in the manual. Has someone put it in the wrong way? Any help gratefully received. Thanks Phil Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 19, 2009 Moderator Share Posted September 19, 2009 Hi, eventually got round to stripping the rest of the engine. Have split the cases though this took some time and excessive rubber mallet and WD40 treatment as the rear large dowel was clinging hard to the cases! The rubber/steel rear engine mount inserts in both cases are seized in and need replacing any suggestions how to remove. I have soaked in WD40 type stuff and then whacked with a screw driver and rubber mallet but still refusing to budge!! Considering a drill next but does anyone have any other ideas? Also the crank is still in place in the left hand case but I am wanting to get it out so I can clean in there and replace the bearings and seals. The Clymer manual states that I need to take it to a Yam dealer to get it removed but can't I just whack it out with my trusty rubber mallet? Also the crank oil seal on the right case looks like its the wrong way round i.e. the metal spring round the seal lip is facing outwards away from the crank. Is this right? its the other way round on the left and not shown this way in the manual. Has someone put it in the wrong way? Any help gratefully received. Thanks Phil I'm afraid its big hammer time as far as the manual goes, a swift tap is how its described in mine. Almighty wallop is nearer in my experience. With hindsigt stuffing it in the oven on max or heating it with a heat gun may have been a more sensible move. The ally will expand quicker than the steel of the crank bearing and should allow you to tap it out. The crank seals should be 'letter side' out in both cases same as the bearings and are fitted although the 2 seals are very different in their duties and as such cannot be mixed up. As i recall the ring should be on the gearboxside of the seal, otherwise there are clearance issues on the crank. Whatever the side you tap it into place with is the letterd side so it has no relevance esp as you are going to junk it anyhow. As far as the rubber bush/damper thingg (tech speak) in the words of the man at TY trials, 'for what it is it costs a bloody fortune and does next to bugger all if you can save it then do so.' You are looking at 40 odd quid+ JUST for that fancy bushing. Unless its falling to bits leave well alone. Hope this helps........ Link to comment Share on other sites More sharing options...
philhill Posted September 19, 2009 Author Share Posted September 19, 2009 Thanks Cynic, i'll get my rubber mallet out again then and give it hell with a bit of heat. Bushes look like shit and are mangled and misshaped so will try to get them out. If they tun out to be too expensive then i will get my mate to turn me something solid out of ally to replace them as I also can't see what they do if you are going to tighten up the other too solid fixings to the frame. Thanks Phil Link to comment Share on other sites More sharing options...
philhill Posted September 23, 2009 Author Share Posted September 23, 2009 Hi, have used a heat gun and mallet and got the crank and bearing out, bearing still attached to crank. I am going to have to buy a tool to remove the bearing! When done i presume I put the new bearing in the casing first heating the case to get it in, then heat the bearing so I can get the crank to fit through it? Just to confirm the lettering on the bearing will be facing out away from the crank, will it? Help to confirm would be great so I don't balls it up. Thanks Phil Link to comment Share on other sites More sharing options...
philhill Posted September 23, 2009 Author Share Posted September 23, 2009 ps, have got new mounting bushes from Granbys for £30 which is still expensive but not as bad as you quoted as decided to do it properly in the end. Also the crank bearings from Granbys where only £5+ each and they have confirmed they are the right ones, so not too expensive in the end. Thanks Phil Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 23, 2009 Moderator Share Posted September 23, 2009 Hi, have used a heat gun and mallet and got the crank and bearing out, bearing still attached to crank. I am going to have to buy a tool to remove the bearing! When done i presume I put the new bearing in the casing first heating the case to get it in, then heat the bearing so I can get the crank to fit through it? Just to confirm the lettering on the bearing will be facing out away from the crank, will it? Help to confirm would be great so I don't balls it up. Thanks Phil What you want to do is first off, get all the bits sorted out in the order they will be fitted and note the orientation, this is best done the night before (I did) as you can stuff the crank and bearings into a bag/clingfilm and stuff it in the freezer overnight. Once you start there is no stopping, so. Get the cases nice and hot, don't worry about melting anything as long as you are using a heat gun you will be ok. Iron hot was the description i was given (as in your spit wont stick). Once you have the cases ready nip in the house and get the bearings from the freezer if the cases are hot enough they should litterally drop in no violence required at all. Now keep heat on the cases and let the bearings grow into place as the temps stabalise. Once the bearings are fixed (and putting them in this way they will be) heat everything right up again and pop the seals in the same way, they will also drop straight in. Dont forget the output seal and bearing. At this point i went and got the crank and then proceded to give the left hand bearing a good warming and then slid the crank through, it should slide easily if you have enough heat. There you go, easy. It really is done in about tem minutes with some slightly singed fingers. When you put the cases together (DON'T FORGET THE O RING ON THE RHSIDE OF THE CRANK) use the heat gun to warm the RHside bearing centre and the cases will slide together much easier. Oh crank bearings, lettering faces the rod, on the seals the lettering faces away from the rod. And dont mix up the seals or bearings they look similar but ARE different and can be swaped inadvertently. Hope this helps. Link to comment Share on other sites More sharing options...
philhill Posted September 23, 2009 Author Share Posted September 23, 2009 Thanks for explaining that Cynic, I now know what to do. The crank and bearings are in the freezer! Phil Link to comment Share on other sites More sharing options...
philhill Posted September 28, 2009 Author Share Posted September 28, 2009 Hi, another question regarding the rebuild. I have nearly completed the rebuild but had a couple of problems along the way that i will just mention first. I didn't get a gudgeon pin or small end bearing with the stuff i bought for my 175cc conversion. Just so others are aware you need a new pin and bearing as these will need to be longer and wider. I assumed I could use the 125's and this created 2 extra trips to Granbys which is an hours round trip each time for me, so loads of time wasted on Saturday getting these bits. Also I have got a standard 175 pin and bearing and my piston is 1.5mm oversize so there is till some lateral movement of the bearing on the pin and I'm hoping this won't have any detremental effect when I get it running? Anyway what i really want to know is why the nut on the crank, flywheel side won't do up all the way and protrudes a few mm from the treaded shaft. I'm fairly sure it was all the way on when I took it of. The nut has been properly torqued to 70 Newton/meters and there is minimal gap between the flywheel and the base plate and I have taken it off and put it back on about 5 times but it still won't do up ?? The flywheel appears to be well up against the taper with no wobble so can't understand what has happened ?!! Should I just swap the thick washer for a smaller one and hope its ok?. yours perplexed. Phil Link to comment Share on other sites More sharing options...
Moderator Cynic Posted October 2, 2009 Moderator Share Posted October 2, 2009 Hi, another question regarding the rebuild. I have nearly completed the rebuild but had a couple of problems along the way that i will just mention first. I didn't get a gudgeon pin or small end bearing with the stuff i bought for my 175cc conversion. Just so others are aware you need a new pin and bearing as these will need to be longer and wider. I assumed I could use the 125's and this created 2 extra trips to Granbys which is an hours round trip each time for me, so loads of time wasted on Saturday getting these bits. Also I have got a standard 175 pin and bearing and my piston is 1.5mm oversize so there is till some lateral movement of the bearing on the pin and I'm hoping this won't have any detremental effect when I get it running? Anyway what i really want to know is why the nut on the crank, flywheel side won't do up all the way and protrudes a few mm from the treaded shaft. I'm fairly sure it was all the way on when I took it of. The nut has been properly torqued to 70 Newton/meters and there is minimal gap between the flywheel and the base plate and I have taken it off and put it back on about 5 times but it still won't do up ?? The flywheel appears to be well up against the taper with no wobble so can't understand what has happened ?!! Should I just swap the thick washer for a smaller one and hope its ok?. yours perplexed. Phil Got to be honest the only thing that comes to mind is if the wodruf key is moving, as you put the flywheel on. Oterwise? Got any photo's Link to comment Share on other sites More sharing options...
philhill Posted October 4, 2009 Author Share Posted October 4, 2009 Hi Cynic, in the end i omitted the thick washer to enable the nut to be fully tightened, as it tightened it receded into the flywheel threaded area allowing less purchase with socket wrench and so perhaps there was some benefit in the nut protruding? I checked multiple times that the woodruff key was insitu, as best as you can without being able to see it and I feel sure it is in the right place. The magnetism in the flywheel did have a tendency to pull it out of place at times but I believe/hope it is seated properly now. I have put 100 miles on it now with no problem but will keep checking. One problem that has arisen since is that the old exhaust keeps cracking near the U bend i have had it welded but as soon as one crack is repaired an other appears. I think I may get a plate welded over the top of the existing metal but am also considering a new exhaust. Any suggestions on make, sound reduction is more important than extra power as the noise gets wearing after a while. Phil Link to comment Share on other sites More sharing options...
Moderator Cynic Posted October 4, 2009 Moderator Share Posted October 4, 2009 Hi Cynic, in the end i omitted the thick washer to enable the nut to be fully tightened, as it tightened it receded into the flywheel threaded area allowing less purchase with socket wrench and so perhaps there was some benefit in the nut protruding? I checked multiple times that the woodruff key was insitu, as best as you can without being able to see it and I feel sure it is in the right place. The magnetism in the flywheel did have a tendency to pull it out of place at times but I believe/hope it is seated properly now. I have put 100 miles on it now with no problem but will keep checking. One problem that has arisen since is that the old exhaust keeps cracking near the U bend i have had it welded but as soon as one crack is repaired an other appears. I think I may get a plate welded over the top of the existing metal but am also considering a new exhaust. Any suggestions on make, sound reduction is more important than extra power as the noise gets wearing after a while. Phil No real fix for that i'm afraid once you start welding the cracks the heat of the weld stresses the metal next to it and that cracks, you end up chasing your own tail. After a while you will find it difficult to get the exhaust to seal and then a stud will snap. I have been down this road myself. Get saving for a new pipe and scower ebay and such they do come up. The big one pipes seem to be the commonest, although the chrome doesent do much for me. It would be a good base for some VHT black tho. Link to comment Share on other sites More sharing options...
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