ryanwilki Posted September 22, 2010 Share Posted September 22, 2010 Hi again ive just redone the top end on my dt50. I did all new barrel, rings, piston, pin and circlips. I also did the studs and gaskets. I used my old head gasket that didnt seem too bad and made a base basket out of a cereal box. Not ideal i know, but somebody sent me the wrong gaskets for my bike and so i couldnt help being eager once id got my piston kit and went ahead fitting it anyway Anyway, i realised that my auto oil system wasnt working and so i disconnected it all and pre-mixed. I mixed 100ml with around 5 litres of petrol. Now, when i kick it it doesnt start. I have cleaned the carb, lubed the throttle slide inside the carb and blew through everything with compressed air. After a lot of fiddling with the mixture screw. idle screw and needle height i managed to get it running by a bump start and took it around the block. i did a plug chop and it appeared to be ok (quite near brown) The bike runs really badly. When i manage to start it (bump start) it dies unless i give it high revs but then the high revs stick on and it starts to go mental. Then it eventually dies down and dies completly. My current needle height is 1 up from the middle. My mixture screw is 1 1/2 turns out and no matter where i put the idle it wont start by kick starting it. I really want this bike running soon so please help me Any help appreciated Ryan. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 22, 2010 Moderator Share Posted September 22, 2010 I think you have an air leak Ryan. Perhaps there's a cornflake stuck between your base gasket and the crankcase. Honestly though, not a fan of this method and wouldnt trust it one bit, i'll put money on it that its one of your gaskets, why didnt you buy the right ones. the copper head gaskets can be used more than once but you need to heat them up red with a blowlamp first. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 22, 2010 Moderator Share Posted September 22, 2010 http://www.wemoto.com/bikes/Yamaha/DT_50_MX/92-95/picture/Gasket_Set_-_Full_-_NE/ Link to comment Share on other sites More sharing options...
ryanwilki Posted September 22, 2010 Author Share Posted September 22, 2010 Hi. Thanks paul. Cornflake!! haha I emailed the guy who i bought the gasket set from just after you said that they look like they are for a watercooled version but he replied that they are not and are for a dt50 mx and suit the year 1993 (as i asked him would they fit mine). However, somebody hasnt packed the right item in the envelope. The invoice says dt50mx gasket set - full. But the packaging inside says they are for a honda ez90 cub ???? Im very annoyed and have contacted the seller. Hopefully he will send the right one this time!!! Anyway, i will wait for the right gaskets, Replace them all (top end) and give it another try. I will let you know how i get on. Thanks again Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 22, 2010 Moderator Share Posted September 22, 2010 You should really use a torque wrench too on the cylinder and cylinder head If you can possibly borrow one (i'm making an assumption here I know) and find out the correct torque. Start right now DO THE JOB RIGHT Link to comment Share on other sites More sharing options...
wild foamy Posted September 22, 2010 Share Posted September 22, 2010 Torque loading on the DT50MX head bolts - 2 white knuckles making a base gasket out of a cereal box is not the way to do it, ive had to do it before on my clutch case but even that leaked, if there is air getting into the system that would explain the erratic running, get it sorted. or if not, i will make you an offer for the salvage Link to comment Share on other sites More sharing options...
ryanwilki Posted September 22, 2010 Author Share Posted September 22, 2010 Torque loading on the DT50MX head bolts - 2 white knuckles making a base gasket out of a cereal box is not the way to do it, ive had to do it before on my clutch case but even that leaked, if there is air getting into the system that would explain the erratic running, get it sorted. or if not, i will make you an offer for the salvage Lol i will get it sorted gaskets will be on the way soon and i will borrow a torque wrench from work. I have checked in a manual i downloaded for my bike and it needs 15 nm. Easy enough I will let you know how i get on. Cheers Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 22, 2010 Moderator Share Posted September 22, 2010 Lol i will get it sorted gaskets will be on the way soon and i will borrow a torque wrench from work. I have checked in a manual i downloaded for my bike and it needs 15 nm. Easy enough I will let you know how i get on. Cheers Dont you mean 15 lb-ft Link to comment Share on other sites More sharing options...
ryanwilki Posted September 22, 2010 Author Share Posted September 22, 2010 it says under the title 'tightening torques' cylinder head = 15Nm (1.5 m-kg) the torque wrench's at work are in Nm what do you think? is there anywhere else i can get a manual to double check? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 22, 2010 Moderator Share Posted September 22, 2010 Oh ok just checking, mine are 15 lb-ft, 8mm diameter studs and I thought you may have mis-typed. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 23, 2010 Moderator Share Posted September 23, 2010 Cor you havent lived. I was making gaskets for my bikes years ago, still do on non essential stuff. My old man (mechanic man and boy, call him a fitter at your peril) has been doing it for years and showed me how. There is a technique to get it accurate using ideally the ball of a small ballpein hammer but done right with a smear of grease its fine. Link to comment Share on other sites More sharing options...
ryanwilki Posted September 23, 2010 Author Share Posted September 23, 2010 Lol the new gaskets are in the post so hopefully I will have them by weekend Link to comment Share on other sites More sharing options...
wild foamy Posted September 23, 2010 Share Posted September 23, 2010 i resorted to making my own gasket out of gasket paper that was donated to me by a friend who worked for a motorists discount centre, that was after my cereal box gasket failed and pissed oil out over the old ladys new driveway... she wasnt happy... and as for the accuracy, to get the holes in the right place, get a ball bearing slightly larger than the hol you want to make, locate it over the hole, press lightly and then give it a wickle tickle with a hammer though come to think of it, that DT did seem to take a liking to pissing oil out, and only ever when on mothers new driveway... funny that Link to comment Share on other sites More sharing options...
ryanwilki Posted September 23, 2010 Author Share Posted September 23, 2010 Hi. My bikes doesn't leak oil one bit, and I don't have a sump plug washer (as of yet). I think the paper gasket may have worked if I had made it from a quality kellogs box but I were using a cheap smart price cereal box lol! I made a perfect template and everything lined up but it was kinda thin. Hopefully will be done by weekend. Oh and when you do a top end jobby, is it usual that you have to adjust the carb set-up? Link to comment Share on other sites More sharing options...
wild foamy Posted September 24, 2010 Share Posted September 24, 2010 DTs dont leak oil anyway. they just mark their territory shouldnt need to touch the carb settings aslong as you havent changed to any performance/upgraded parts, take the carb back to factory settings and start again if your still having trouble Link to comment Share on other sites More sharing options...
ryanwilki Posted September 25, 2010 Author Share Posted September 25, 2010 Hi again. Still having problems I fitted the new gaskets and it was all acting the same. So i replaced the spark plug, cleaned the carb, turned the mixture and idle screws to factory settings and managed some how to get her started. However, it really struggles to run and will only run if i give her full revs (yet it still sounds like idle speed). So i cleaned up the throttle cable and slide and then set up the throttle to only have about 5mm play. But its still the same. Struggles to get going and when she does i have to give it full throttle to keep her going when she was running i sprayed wd40 all over the carb and engine to see if i had an air leak but nothing changed, its all air tight. I took out the spark plug and it was covered in black runny oil. So runny that i just wiped it once with a cloth and the plug was like brand new again. Any ideas there? By the way, i disconnected the fuel pump, blocked up the oil feed line and premixed at a ratio of 50:1. Would this make any difference? please help, i really want to get on it and go riding Ryan. Link to comment Share on other sites More sharing options...
wild foamy Posted September 25, 2010 Share Posted September 25, 2010 the spark most definately shouldnt be covered in oil :S. go back to using the metered (automatic) oil pump, atleast that way you know there cant be any problems with fuel/oil mixture. only other thing i could think of is oil getting past the piston rings and into the combustion chamber, but you'd see that as smoke from the exhaust, try leaning the mixture out a little and see if that helps it, black spark plug = running rich, the oily residue is confusing though... Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 25, 2010 Moderator Share Posted September 25, 2010 That is either flooding out massively or a shit spark, or a combo of both. How do i know. Cos thats the symptoms of my DT to the letter earlier this week. Black liquid on the plug is fuel/oil mix thats unburnt. Check your ignition and check the float height in the carb. Link to comment Share on other sites More sharing options...
ryanwilki Posted September 25, 2010 Author Share Posted September 25, 2010 SORTED!! hadnt tightened the main jet enough so it fell out and was flooding it Anyway, its perfect now but still a bit slow. I can only get 30mph out of it, how did you get 40mph + out of your dt's? thanks again, Ryan Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 25, 2010 Moderator Share Posted September 25, 2010 Well back in the days of twin shock trail bikes lived in my loving care a likew DT50m with:- Ported 60cc Italian high compression big bore kit. Autesia i think they were called. 16mm carb K+N filter skimmed head Point stator plate, moved to advance ig 3deg, additional condenser Full Fresco pipe, cut open smoothed, stinger cut down to concentrate and move power up With octane booster, (rather more than reccomended) after being set up for temperature, points cleaned etc she was good for 70mph in absolutly perfect conditions. A reliable 45mph was doable anywhere, uphill to a degree. Without the rose tinted goggles, the bike was a liability. A bastard to start, expensive relatively on fuel, needed very expensive 2 stroke, needed constant maintainance and very difficult to get the performance from, like a modern pv bike with the PV pegged open but with less bottom end. I loved it, king of the hill breifly as i had the bike to beat till it got nicked. Link to comment Share on other sites More sharing options...
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