mcferreira100 Posted October 24, 2014 Posted October 24, 2014 Would like to get some more advice here. Piston melted a hole and some bits went in the crankcase. Was advised I should be able to get away without splitting the engine..just put in engine cleaner turning the crank then turn engine upside down. Repeat process until rotation is smooth. Then use a hair dryer to dry out crankcase. Also the cylinder already bored out 2mm oversize. Luckily it still looks fairly ok so been advised to go over it with some water paper. Apparantly even a light hone could ruin it.
nayruf Posted October 24, 2014 Posted October 24, 2014 Oh dear, My DT did the same, What I did was to split the case, cleaned out the big end rollers in the conrod by continually washing the crank in diesel till they felt smooth, cleaned out the casings with diesel till every 'knook and cranny' was spotless, change the main brgs, and fitted new crank seals then built the motor back up with new a piston and lightly honed out the cylinder, I now run the bike with a bigger main jet in the hope that the motor will run a bit cooler, so far so good, I reckon the possible extra water content in todays ethanol blended fuel can add extra oxygen via the water content, and as my motor was running a bit weak anyhow the extra air allowed the motor to get that little bit hotter and the piston went. I recall hearing the motor occasionally making 'pinking' noises when the throttle was pinned open, so I asked for it really, hope you fix yours as easy as I did mine,
dt502001 Posted October 24, 2014 Posted October 24, 2014 For the amount of time it takes better off to pull it appart and clean it,1 little piece left in there could ruin a new rebuild.Or worse kill the crank.Also you can check the main bearings condition who knows how much dammage they took?Personaly I would never go the flush and pray method. The barrel well if it is still round? 1
slice Posted October 24, 2014 Posted October 24, 2014 Ok Mc so a rebore is not going to happen, but if it was mine I would split the case and clean the crud out, but some will say not, there does seem a lot of crap in there so if the bearings are ok you might get away with it but still going to be a worry if some of that got into the crank bearing. Just my ten pence worth but your the one who has to do it.
blackhat250 Posted October 24, 2014 Posted October 24, 2014 New liner, or S/H barrel... then fit a spark plug temp gauge. bigger jet, and check float level, -fuel flow too, she must been flat out was she?
mcferreira100 Posted October 25, 2014 Author Posted October 25, 2014 Bike was stolen and recovered so who knows what the buggers got up to. She was running too lean looking at the plug.
Moderator Airhead Posted October 25, 2014 Moderator Posted October 25, 2014 Bike was stolen and recovered so who knows what the buggers got up to. She was running too lean looking at the plug. advanced ignition also does that
slice Posted October 25, 2014 Posted October 25, 2014 Just a question, what is a spark plug temp gauge? Never heard of this & what does it do and how do you know what temp your plug should be when running? Sorry to hijack the thread but Blackhat has me curious.
YPVS TONE Posted October 25, 2014 Posted October 25, 2014 What grade of plug was fitted when it went ?
Moderator Airhead Posted October 25, 2014 Moderator Posted October 25, 2014 Just a question, what is a spark plug temp gauge? Never heard of this & what does it do and how do you know what temp your plug should be when running? Sorry to hijack the thread but Blackhat has me curious. 1
KevtheRev Posted October 27, 2014 Posted October 27, 2014 Does the bike have the standard air filter fitted ? If I was you I'd split the cases and if the big end feels ok after a clean I'd fit new main bearings and seals (after cleaning the cases ) . Best of luck .
mcferreira100 Posted October 27, 2014 Author Posted October 27, 2014 Standard air filter.Rotated crank briskly with fuel in there then turned engine upside down a few times. Now it feels smooth as silk after oiling it again. Plenty crap came out, so not going to split it...lets see how we go. Replacing small end and piston and rings. Will take waterpaper over the bore and also flush with fuel to get crap out the ports. Then skim the head on waterpaper on some glass.Learned something interesting..it was pointed out to me if u can see a sort of flower insignia inside the piston..then its cheap crap..stay way.
NE0 Posted October 28, 2014 Posted October 28, 2014 Plenty crap came out, so not going to split it False economy mate............ Plenty of crap came out......plenty of crap still in there too! I guess its all down to trust.....personnally I wouldn't trust it. BTW Learned something interesting..it was pointed out to me if u can see a sort of flower insignia inside the piston..then its cheap crap..stay way. here's something interesting to learn too.......if you see crap inside the engine....don't replace the piston and rings and small end with new as they won't last long Good luck with that one . Hope it turns out all right for you.
slice Posted October 28, 2014 Posted October 28, 2014 Sorry Mc have to agree with NEO, I know you don't want to but splitting the cases is really the best thing to do. If you washed out a load of crap then there is still a load more smaller crap in there, just one small shaving will turn your nice rebuilt engine into a paper weight. I watched a mate of mine, many years ago, take a large 5 gallon drum half fill it with paraffin drop his engine inside then shove his air line into the engine casing and bubble the thing clean, he left it for about 4 hours and pronounced it clean, 2 days later he seized it on the way to work.
mcferreira100 Posted October 28, 2014 Author Posted October 28, 2014 Thanks guys, I appreciate your concern..and I do agree with you. But you must know you`re talking to an idiot who tried to hammer out the front axle shaft without realizing there`s a collar under one fork holding it in place..(different to the first DT I did with leading forks))luckily I realized it before hammering too hard on the castle nut.If I attempt splitting this engine myself I WILL cock something up and end up with leaks, gears not shifting, clutch not working properly or who knows what (even following the manual)...not to mention I don`t have tools like flywheel pullers, dial gauges etc..don`t even own a torque wrench). If I had one of you knowledgeable blokes here to guide me I would do it no question.The guy who did a great job of rebuilding my RD engine assures me it should be fine.Will get one more opinion though from another friend of mine who if he has time, might be able to help me split it (he did the hone job on the first DT and fitted new piston and rings for me..and he has the tools..even a parts washer setup).
slice Posted October 28, 2014 Posted October 28, 2014 Yeah at the very least plunk it in a parts washer and leave it for a few hours and give it a good wiggle during that time to loosen the crud up, if you can find a way to get a hose inside the thing and squirt fluid around the back of the crank then you should be able to get most of the crud out, unfortunately MOST might not be enough.
dt502001 Posted October 28, 2014 Posted October 28, 2014 Mac as you have 3 of these bikes now it is time to learn how to get the eng apart and back together,it's not like you need the bike running. The few tools needed flywheel puller 20 bucks,torque wrench is a must have tool for all your bikes so BUY ONE,for setting the timming you can go with a dial indicator or a piston indicator,I would suggest buying a dial indacator you can use it for many more things,checking rotors is a good one. The money you will have waisted putting in new parts to only have it blow up again will cost more than the tools to do it right.The dt 175 has to be one of the easiest motors to rebuild.The knowlage you learn doing it will save you money in the future.And you have all the help you could ask for Paul AKA air head knows everything you could ever possibly need to ask about. So what if it takes you a month or 2 to get it appart and back together,as for it not shifting or the clutch not working these are not hard to check befor the motor goes back in and realy it's almost impossible to get it wrong and back together the parts only fit 1 way.If you realy take your time disassembling it taking note of each piece then the reassembly will go rather smoothly.The only part that is difficult is holding the tranny pieces as you slip them into the cases.But as you dont need to even pull them out of the left half of case you could leave it in place and clean up the case and then just put it back together with new crank seals ect. parts wise it wont cost much more.And you wont chance blowing it up because of one small piece of piston you dont get out. This mechanic who said it will be fine I would not trust,to do anywork,any good mechanic would say not to do it that way as you have no way of knowing if you got it all out.Each and everyone here has said that! why because we know splitting the case is the only way to do it RIGHT.If anything is left behind and you kill the crank then you out another 600 bucks or more. So ask yourself is it realy worth chancing it,or is it time to get serious and learn something new.
mcferreira100 Posted October 29, 2014 Author Posted October 29, 2014 The manual shows a case separating tool..is this required?
KevtheRev Posted October 29, 2014 Posted October 29, 2014 Alright man , a crankcase splitting tool is not essential , a flywheel puller is but they're quite cheap and you'll have it forever . The only other tricky bit is locking the clutch , but you'll make up a clutch locking tool easy enough if you don't want to buy one . Being honest I have put engines like this back together without splitting them but I wouldn't do it now as it only takes a tiny metal shaving to shred a seal or ruin a crank , meaning you'll have to split it anyway . The Haynes manual is a great guide , the gear cluster can be kept as an assembly with no need to dismantle it . Take your time on dis-assembly and you'll have a good idea how it goes back together . Good advice from all above . This way , when you get it back together you won't have any niggling worries about your engine and nobody with a brain would like to give advice that could cause a failure and maybe serious injuries if you are on the bike when it fails . And just think how good that celebratory beer will taste when you get it back together . Best of luck !!
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