dt175david Posted January 15, 2010 Share Posted January 15, 2010 hello, my dt blew its piston took a chunk out of the top i have a open air filter (pod type) and a pipe with restriction taken out do you think my jetting was out ?? if so what would be some good settings for it at 55 to 100m elevation also i have some new proformance power reeds on the way the carb is mikuni all help would be good as i do not want to kill the new piston.... Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 15, 2010 Moderator Share Posted January 15, 2010 hello, my dt blew its piston took a chunk out of the top i have a open air filter (pod type) and a pipe with restriction taken out do you think my jetting was out ?? if so what would be some good settings for it at 55 to 100m elevation also i have some new proformance power reeds on the way the carb is mikuni all help would be good as i do not want to kill the new piston.... Hi David, you will need to jet up for the pod filter, not familiar with the carb or jetting for your bike, sounds like one of the Aussie ones, but definitely get a few jets, start with the biggest. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 15, 2010 Moderator Share Posted January 15, 2010 hello, my dt blew its piston took a chunk out of the top i have a open air filter (pod type) and a pipe with restriction taken out do you think my jetting was out ?? if so what would be some good settings for it at 55 to 100m elevation also i have some new proformance power reeds on the way the carb is mikuni all help would be good as i do not want to kill the new piston.... I'm with OG here on the jeting but i have a couple questions, first off the best bet is to have the carb to bits to make sure of the jet settings as you would not beleve the range of possibles. And to be sure a fault with the carb wasn't the cause. Now the questions... What is the plug like? black? white? red dots or cracking on the electrode?. You say the bike took a chunk out of the piston, was it near the ring pegs? or possibly at the front of the piston? Or was it a 'hole' in the middle of the crown. The pod filters are not really all that effective, they let a lot of crap in as they are not very good with dust i understand from posts by some of our american members . You are actually better off with the proper airbox in most cases. The pipe will help though and the reeds will make the throttle a lot snappier and give a bit more oomph. Link to comment Share on other sites More sharing options...
dt175david Posted January 15, 2010 Author Share Posted January 15, 2010 I'm with OG here on the jeting but i have a couple questions, first off the best bet is to have the carb to bits to make sure of the jet settings as you would not beleve the range of possibles. And to be sure a fault with the carb wasn't the cause. Now the questions... What is the plug like? black? white? red dots or cracking on the electrode?. You say the bike took a chunk out of the piston, was it near the ring pegs? or possibly at the front of the piston? Or was it a 'hole' in the middle of the crown. The pod filters are not really all that effective, they let a lot of crap in as they are not very good with dust i understand from posts by some of our american members . You are actually better off with the proper airbox in most cases. The pipe will help though and the reeds will make the throttle a lot snappier and give a bit more oomph. ok the plug was black and the chunk that was taken out of the piston was right at the exhaust outlet down to the first ring and the ring let go there as well also i do not run a muffler it has a piece of pipe coming off the expansion chamber the same length as the old muffler...i will tear down the carb down and report back..i will go back to my old air box just need to find a new filter its the flat type do you know some online shops i looked on ebay but no good. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 15, 2010 Moderator Share Posted January 15, 2010 ok the plug was black and the chunk that was taken out of the piston was right at the exhaust outlet down to the first ring and the ring let go there as well also i do not run a muffler it has a piece of pipe coming off the expansion chamber the same length as the old muffler...i will tear down the carb down and report back..i will go back to my old air box just need to find a new filter its the flat type do you know some online shops i looked on ebay but no good. Aah, the plug is black so that would indicate its a bit rich, a much better situation than lean. You should strip and clean the carb and make a note of the numbers on the jets, needle carb slide and clip position just in case you find a manual somewhere to reference to. I suspect that the problem is mechanical failure and not caused by carburation, has the bore been damaged? does it need a re-bore?. Check the bore wear before you order a new piston because it might have a worn bore and you would have wasted your money. Link to comment Share on other sites More sharing options...
dt175david Posted January 15, 2010 Author Share Posted January 15, 2010 no the bore is ok just needs a good hone i orderd the next o/s up 68mm and that should leave the bore all nice i have rebuilt a lot of car / industrial motors but this would be my first bike, i have a 92 dt175 manual and the engine looks the same do you think the piston to bore clearance would be the same on my 88 ?? and do you have any tips for the rebuild.. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 15, 2010 Moderator Share Posted January 15, 2010 no the bore is ok just needs a good hone i orderd the next o/s up 68mm and that should leave the bore all nice i have rebuilt a lot of car / industrial motors but this would be my first bike, i have a 92 dt175 manual and the engine looks the same do you think the piston to bore clearance would be the same on my 88 ?? and do you have any tips for the rebuild.. At 68mm that could well be it, if the bore is the same as the uk aircooled then it starts at 66 and rises from there +2mm is the max i think. If the bore has survived ok then a light hone and a like for like piston would probably be a better bet. That will leave you with an oversize left rather than a scrap barrel if and when it fails again. One other tip, if the bike is at 6 or 7 oversises then there is probably an edge to the ports, you may have just had a ring clip the port and do the damage, thats why i asked where the damage was. To prevent it you need to get in there before its honed with a small file, or a dremil to put a slight chamfer on the ports. Link to comment Share on other sites More sharing options...
dt175david Posted January 15, 2010 Author Share Posted January 15, 2010 At 68mm that could well be it, if the bore is the same as the uk aircooled then it starts at 66 and rises from there +2mm is the max i think. If the bore has survived ok then a light hone and a like for like piston would probably be a better bet. That will leave you with an oversize left rather than a scrap barrel if and when it fails again. One other tip, if the bike is at 6 or 7 oversises then there is probably an edge to the ports, you may have just had a ring clip the port and do the damage, thats why i asked where the damage was. To prevent it you need to get in there before its honed with a small file, or a dremil to put a slight chamfer on the ports. ok will do thanks also i have seen on ebay a while back a sleve and piston kit to take the 175 to 200 .. would they just be a 200 sleve and piston and you bore the barrel to fit the sleeve?? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 15, 2010 Moderator Share Posted January 15, 2010 ok will do thanks also i have seen on ebay a while back a sleve and piston kit to take the 175 to 200 .. would they just be a 200 sleve and piston and you bore the barrel to fit the sleeve?? Thats a good point about chamfering the ports you must do this. I have never heard of a sleeve kit can you post a link to it next time you see it? As 'Cynic' said 68mm is likely be the last available size. Link to comment Share on other sites More sharing options...
dt175david Posted January 15, 2010 Author Share Posted January 15, 2010 Thats a good point about chamfering the ports you must do this. I have never heard of a sleeve kit can you post a link to it next time you see it? As 'Cynic' said 68mm is likely be the last available size. will post next time i see it came from the us and yes 68mm is the last over size but i dont think going the 67.5mm would clean up the bore fully... gess i better start looking for a spare barrel too Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 15, 2010 Moderator Share Posted January 15, 2010 If you get a re-bore only trust the work to a trusted two stroke borers, if you can find one like this one here in UK (if possible) http://www.pjme.co.uk/acatalog/Cylinder_Re-Boring.html Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 15, 2010 Moderator Share Posted January 15, 2010 ok will do thanks also i have seen on ebay a while back a sleve and piston kit to take the 175 to 200 .. would they just be a 200 sleve and piston and you bore the barrel to fit the sleeve?? Wow thats one over square engine, that would be a 72mm piston. Really cant say how much extra umph you would actually get. It would work best with a lot of revs but the DT's don't like revs???? Aircooled DT's have an issue with cooling too and a monster pot like that. Phweew Be an interesting exercise though. Link to comment Share on other sites More sharing options...
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