TylerP Posted June 24, 2009 Share Posted June 24, 2009 I've replaced many as well. It's a piece of cake. If you heat the cases hot enough for the bearing to drop in (which is good),it will likely melt the outer edge of the new seal. The ONLY crank seals that have a lip on the outside edge are for cases the split up & down. Like an RZ350. Cases that split side to side can not possibly have a seal with a lip on it cause you could never drive it in without damaging it. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 24, 2009 Moderator Share Posted June 24, 2009 If you heat the cases hot enough for the bearing to drop in (which is good),it will likely melt the outer edge of the new seal. So 40odd degrees from a heat gun will melt seals designed to operate under pressure/vacume extreems at temperatures of over 100. I said 'reliable methods', and stated 'there may be more imaginative ways' of changing the seals. Obviously I'm all wrong. I know absoloutly nothing about DT175's i wont coment on this thread again. Link to comment Share on other sites More sharing options...
JimR Posted June 24, 2009 Share Posted June 24, 2009 i have done this on dt and it motors,it is possible. Hi , I'm stuggling with how you can remove the mag side seal without distroying the crankcase. On the primary gear side you could 'dig' the seal out but how would the new one be installed without distroying the seal (defeats the object I would have thought ?) but if you say it can be done go a head and do it but the owner may find more problems doing it rather than spending an extra hour or two doing the job correctly. Regards Jim Link to comment Share on other sites More sharing options...
TylerP Posted June 25, 2009 Share Posted June 25, 2009 So 40odd degrees from a heat gun will melt seals designed to operate under pressure/vacume extreems at temperatures of over 100. I said 'reliable methods', and stated 'there may be more imaginative ways' of changing the seals. Obviously I'm all wrong. I know absoloutly nothing about DT175's i wont coment on this thread again. I did not mean to rub you the wrong way. When I heat up cases it's usually with the shops propane torch. Then the case is HOT. Link to comment Share on other sites More sharing options...
TylerP Posted June 25, 2009 Share Posted June 25, 2009 Hi , I'm stuggling with how you can remove the mag side seal without distroying the crankcase. On the primary gear side you could 'dig' the seal out but how would the new one be installed without distroying the seal (defeats the object I would have thought ?) but if you say it can be done go a head and do it but the owner may find more problems doing it rather than spending an extra hour or two doing the job correctly. Regards Jim Sometimes you can slip a thin screw driver in there and pop it out. The screws in the side method will work to. I have used a spring puller to get some out. You can drive it back in with a piece of PVC pipe over the crank end the same size as the seal. I have a wide plastic punch I use to that I go around the outside edge and tap the seal flush with the case. Sometimes the seal is already out anyway if your lucky. Certainly removing the crank is the best way but I would much rather save the time when it can be done just as well without the extra work. Link to comment Share on other sites More sharing options...
JimR Posted June 25, 2009 Share Posted June 25, 2009 Sometimes you can slip a thin screw driver in there and pop it out. The screws in the side method will work to. I have used a spring puller to get some out. You can drive it back in with a piece of PVC pipe over the crank end the same size as the seal. I have a wide plastic punch I use to that I go around the outside edge and tap the seal flush with the case. Sometimes the seal is already out anyway if your lucky. Certainly removing the crank is the best way but I would much rather save the time when it can be done just as well without the extra work. Hmm, so the locating section of the seal would be distroyed by fitting it this way round which in turn could allow the seal to spin with the crankshaft rather than being installed in the crankcase correctly but if you feel you can get away with it go for it but I do feel that installing the seals this way will be ultimately a waste of money. Regards Jim Link to comment Share on other sites More sharing options...
TylerP Posted June 25, 2009 Share Posted June 25, 2009 We must not be talking about the same thing cause that did not make sense at all to me. The only difference by installing a seal the way I said is that the end of the crank is sticking thru the hole. Other than that it's being installed the same way it would if the cases were apart. Who cares if the old seal gets destroyed,it's getting replaced anyway. Put them in however your happy doing it. Link to comment Share on other sites More sharing options...
JUST ME! Posted July 1, 2009 Share Posted July 1, 2009 This bike is 29 years old, I bought it 18 months ago with 2,000km on the clock. It's been running good, the boy has done a further 2,000km on it. Then when on a trip up the highway after about 50km it seized up (while doing about 80 - 90 kmh) So I rebored it and put it back together. I found a mis-fitted gauze in the fuel tap with a build-up of crap behind it. This I summised caused a reduced fuel flow, leaned out hence excessive heat and seizure. I was 100% confident with that theory so sent the boy off to put some miles on it. Next thing, I get a phone call from the roadside, it's seized again - F*%K I said, several times over. He was not experienced enough to know it was about to seize again. So I pulled it down again and found that it was not too badly messed-up. I had my engine recom man clean up the piston and bore and try and suggest what went wrong. He reckoned it had got really hot, probably due to lean-ness. So I've put it back together today and had a short test ride. It seems OK under load (anything upwards of half throttle) but seems flat below that. Feels like it's got a blocked pilot but the carb is all sweet and correct float level. The plug is correct, the exhaust isn't blocked and the air filter is brand new. I'm a bit knackeded as to where to go next. I'm thinking perished crank seal on the magneto side letting in air?? That's a 'split the cases' job isn't it? How can I test that theory? Any further theories or suggestions welcome. Thanks Johnny Wellington NZ G'day mate. This is just my view re your drama. Leave the crank seals alone. Run in properly ensuring all jetting is correct. Then do not ride a Dt175 at 80 kph for 50 kms. They simply were not made to do it. 2 stroke singles will tolerate short bursts of full power for many years. Sustained periods of high revs will continue to cause the piston to pick up on the bore. Larger bore to piston clearance and synthetic oil may allow you to possibly get away with sustained high revs but it is not worth the risk. Also worth checking that the plug is the correct heat range. Also, has the expansion chamber ever been cleaned out properly? Hope this helps! Paul. Link to comment Share on other sites More sharing options...
yamahait Posted July 1, 2009 Share Posted July 1, 2009 G'day mate. This is just my view re your drama. Leave the crank seals alone. Run in properly ensuring all jetting is correct. Then do not ride a Dt175 at 80 kph for 50 kms. They simply were not made to do it. 2 stroke singles will tolerate short bursts of full power for many years. Sustained periods of high revs will continue to cause the piston to pick up on the bore. Larger bore to piston clearance and synthetic oil may allow you to possibly get away with sustained high revs but it is not worth the risk. Also worth checking that the plug is the correct heat range. Also, has the expansion chamber ever been cleaned out properly? Hope this helps! Paul. hi we have just sorted my mates dt175 out that was doing exactly the same thing as yours,two seizures,rejetting,different front pipes,had giannelli on,tried fresco,no change,removed most of the baffle from standard silencer,no difference,tried a fresco performance silencer,SORTED,cut open standard silencer to see what was happening,main inlet pipe is capped off with two 10mm holes drilled for gas escape,backing everything up,over heats,seizes,REMOVE rear silencer and i am 99.9% sure that will solve your problem which was the mirror image of the problem we had. cheers Link to comment Share on other sites More sharing options...
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