JW896 Posted August 6, 2010 Share Posted August 6, 2010 I have been retoring a '74 DT-175A. It had low compression. I got it started and ran it for a few miles on the hopes that I could free up the piston rings and improve the compression. Things were going well until the kick starter locked at the low end of the stroke. I pulled the engine and found that the piston skirt had broken off and pieces were locking up the piston rod. I have it in the shop to be rebored, but I am wondering what other parts (seals or bearings) I should replace as long as I have the engine torn down? There does not appear to be much wear. Any advice would be much appreciated. Thanks JW896 Link to comment Share on other sites More sharing options...
philhill Posted August 6, 2010 Share Posted August 6, 2010 I have been retoring a '74 DT-175A. It had low compression. I got it started and ran it for a few miles on the hopes that I could free up the piston rings and improve the compression. Things were going well until the kick starter locked at the low end of the stroke. I pulled the engine and found that the piston skirt had broken off and pieces were locking up the piston rod. I have it in the shop to be rebored, but I am wondering what other parts (seals or bearings) I should replace as long as I have the engine torn down? There does not appear to be much wear. Any advice would be much appreciated. Thanks JW896 Hi, I am no expert by any means so don't trust this without confirming, but if you can get all the bits of piston out from round the crank flywheel then you might get away with just a top end strip down. If the crank is jammed or you are worried that bits have got in the main bearings then you will have to split the cases, if you are doing that then you may as well re-new all the bearings and seals which isn't that expensive, in parts. Main bearings may not come off that easy and you may need help with that, otherwise not too hard. If you ring Granbys they will tell you what you need. Good Luck Phil Link to comment Share on other sites More sharing options...
JW896 Posted August 7, 2010 Author Share Posted August 7, 2010 Hi, I am no expert by any means so don't trust this without confirming, but if you can get all the bits of piston out from round the crank flywheel then you might get away with just a top end strip down. If the crank is jammed or you are worried that bits have got in the main bearings then you will have to split the cases, if you are doing that then you may as well re-new all the bearings and seals which isn't that expensive, in parts. Main bearings may not come off that easy and you may need help with that, otherwise not too hard. If you ring Granbys they will tell you what you need. Good Luck Phil Thanks Phil... a lot of fragments dropped into the crankcase and to be safe, I am going to open up the case. I did some checking and I am planning on replacing the seals. I want to inspect the bearings before I pull the trigger on them. JW896 Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 7, 2010 Moderator Share Posted August 7, 2010 As it's now in bits I would recommend replacing the crank seals, gear shaft seal and kicker shaft seal. Mainn bearings?? give them a good clean and feel for roughness or free play, replace these too if there is any doubt. Link to comment Share on other sites More sharing options...
JW896 Posted August 8, 2010 Author Share Posted August 8, 2010 As it's now in bits I would recommend replacing the crank seals, gear shaft seal and kicker shaft seal. Mainn bearings?? give them a good clean and feel for roughness or free play, replace these too if there is any doubt. Paul - I am running into an issue pulling the flywheel. Can you confirm that it takes a 27MM x 1.0 left hand threaded puller? Thanks JW896 Link to comment Share on other sites More sharing options...
JW896 Posted August 8, 2010 Author Share Posted August 8, 2010 Paul - I am running into an issue pulling the flywheel. Can you confirm that it takes a 27MM x 1.0 left hand threaded puller? Thanks JW896 I also read the long thread on the CT175 and got to the part about removing the crank seals. Are there specialty tools for that or tips. Sounds a bit tricky... Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 8, 2010 Moderator Share Posted August 8, 2010 puller is 27mm lh thread yes, available from yambits wemoto no name but a few, how come you havent filled your profile in...where are you?. These are in UK seals can be got out sometimes by drilling a small hole in opposite sides then screwing a self tapping screw in and pulling on it. Personally I havent tried this but I can see the attraction of not having to strip the motor down completely. Link to comment Share on other sites More sharing options...
JW896 Posted August 8, 2010 Author Share Posted August 8, 2010 puller is 27mm lh thread yes, available from yambits wemoto no name but a few, how come you havent filled your profile in...where are you?. These are in UK seals can be got out sometimes by drilling a small hole in opposite sides then screwing a self tapping screw in and pulling on it. Personally I havent tried this but I can see the attraction of not having to strip the motor down completely. Just updated my profile info. I am in the US - out west in Idaho. I have a Haynes Workshop Manual. It's a good manual with lots of useful pictures, but no specs on the flywheel puller. I was able to make a few modifications to a 2 arm puller, for the first couple of times I pulled the flywheel. Teh flywheel has gotten pretty stubborn and I don't want to run the risk of damaging the crankshaft. I am have the engine pulled so I set it on it's side and I have some penetrating oil around the shaft to hopefully help the cause. I took the cylinder and old piston to the Yamaha shop and they are going to rebore the cylinder. I have a set of gaskets on order, so in the meatinme I am planning to open up the crankcase clean out the old piston fragments and check the bearings. The Yamaha shop suggested replacing the main seals and hold up on replacing the kickstarter and shifter seals since these can be replaced without opening up the crankcase again. Does that make sense to you? JW896 Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 8, 2010 Moderator Share Posted August 8, 2010 I am planning to open up the crankcase clean out the old piston fragments and check the bearings. The Yamaha shop suggested replacing the main seals and hold up on replacing the kickstarter and shifter seals since these can be replaced without opening up the crankcase again. Does that make sense to you? JW896 yes ok that makes sense to me. you should not really be risking a 2 arm puller on the flywheel, pukka pullers are so much better, cheap too. Link to comment Share on other sites More sharing options...
JW896 Posted August 8, 2010 Author Share Posted August 8, 2010 yes ok that makes sense to me. you should not really be risking a 2 arm puller on the flywheel, pukka pullers are so much better, cheap too. Agreed. After looking for parts and seeing the prices I decided to find the right tool for the job. Sorry for sounding like a nubie but what is a pukka puller? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 8, 2010 Moderator Share Posted August 8, 2010 Agreed. After looking for parts and seeing the prices I decided to find the right tool for the job. Sorry for sounding like a nubie but what is a pukka puller? sorry it's slang for 'proper' puller Link to comment Share on other sites More sharing options...
JW896 Posted August 8, 2010 Author Share Posted August 8, 2010 sorry it's slang for 'proper' puller It's interesting, I saw a link on youtube titled Removing Flywheel covers. The guy takes a rubber mallet and gives a short whack on the rim of the flywheel then turns it a bit, does that about 20 times and it pops right off. Since I can't locate a tool on Sunday afternoon, I figure I'll give his technique a try. I had let the crank spindle soak in penetrating oil. I wiped down the flywheel and heated it a bit with a heatgun. After about 20 whacks it popped loose. So now I'm back in business. I am headed out to open up the crankcase and clean it up. I'll keep you posted. Thanks for the advice. JW896 Link to comment Share on other sites More sharing options...
JW896 Posted August 9, 2010 Author Share Posted August 9, 2010 It's interesting, I saw a link on youtube titled Removing Flywheel covers. The guy takes a rubber mallet and gives a short whack on the rim of the flywheel then turns it a bit, does that about 20 times and it pops right off. Since I can't locate a tool on Sunday afternoon, I figure I'll give his technique a try. I had let the crank spindle soak in penetrating oil. I wiped down the flywheel and heated it a bit with a heatgun. After about 20 whacks it popped loose. So now I'm back in business. I am headed out to open up the crankcase and clean it up. I'll keep you posted. Thanks for the advice. JW896 OK now that I have the flywheel removed, I can access the crankcase bolts and I successfully removed all of them. I checked the manual and started removing parts systematically. I have run into the next jam-up. No problem until I got to the removal of the primary drive pinion center nut. The manual does not specify whether it is RH or LH threaded. I heated it, shot it with penetrating oil, and tried whacking the wrench in both directions with no luck (multiuple times). I can't see enough thread to see whether it is RH or LH treaded so I don't know which to direction to direct my efforts and I dont want to damage the nut. It won't budge. I tried the impact driver with a 19mm socket (both directions) no happiness... I have ceased the heating and beating, any suggestions are most appreciated... JW896 Link to comment Share on other sites More sharing options...
bob-c Posted August 9, 2010 Share Posted August 9, 2010 Primary drive , thats the one on the end of the crank ? RH thread . I was once told the only LH thread on DT's is the flywheel and one of the mirrors ! I have never found any other . Bob Link to comment Share on other sites More sharing options...
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