murp24 Posted June 30, 2012 Share Posted June 30, 2012 Hi everyone. I am having problems with my Honda MT50 Rebuild, it has a lack of starting after installing new piston rings, dont thing that is the problem.I have been restoring & rebuilding a Honda MT50 and had the bike running fine apart from it idling a little fast and being a bit rich. Until the other day when I replaced one of the worn piston rings with a new one as one of the new ones came pre snapped . I put the bike together and slowly pushed down one the kick start and all seemed fine, piston moving fine in bore. However when I came to trying to start the bike, nothing. All i get is the sound of the air filter sucking air in, the engine turning and piston moving up and down.I took the spark plug out and it was dry as if no fuel is geting to it, plug sparks fine. Bike has never had use of any of its electrics, its purely off road as there is no battery.Any help would be apreciated. Thanks Quote Link to comment Share on other sites More sharing options...
Weebl Posted June 30, 2012 Share Posted June 30, 2012 From what you have written you have no fuel getting through? Try the basics first.Fuel in the tank?Petcock selected to an 'on' position (if you have one)Are all the lines on the Petcock/fuel tap connected? Do you have a vacuum line to it? Is it connected to both the inlet manifold and the petcock?Are all the fuel lines you will have taken off to strip the engine all back on properly?Do you have a fuel filter? Is it blocked?Can you open a drain screw on the float chamber (lowest point of the carb, should have some sort of drain there) Does fuel come out? Quote Link to comment Share on other sites More sharing options...
murp24 Posted June 30, 2012 Author Share Posted June 30, 2012 From what you have written you have no fuel getting through? Try the basics first.Fuel in the tank?Petcock selected to an 'on' position (if you have one)Are all the lines on the Petcock/fuel tap connected? Do you have a vacuum line to it? Is it connected to both the inlet manifold and the petcock?Are all the fuel lines you will have taken off to strip the engine all back on properly?Do you have a fuel filter? Is it blocked?Can you open a drain screw on the float chamber (lowest point of the carb, should have some sort of drain there) Does fuel come out? Thank you for the reply much apreciated.The fuel tap is in the the ON position and there is no obstruction from the tank, new fuel is in the tank and ye there is fuel in the float chamber. All lines are connected to the carb, one was left off and is now conected which was a breather. Still wont start, thought asmuch. The only thing I have not tryed is putting a few drops of peterol in the bore and then trying to start it. Quote Link to comment Share on other sites More sharing options...
Tango Posted June 30, 2012 Share Posted June 30, 2012 Sounds like you may have a blocked jet in the carb. Strip and clean...... Quote Link to comment Share on other sites More sharing options...
murp24 Posted June 30, 2012 Author Share Posted June 30, 2012 Sounds like you may have a blocked jet in the carb. Strip and clean...... Hi Tango. Jet is fine I striped the carb and was spotles, took it apart the other day to check the jets again and just the same. Could it be anything to do with the throttle or idle screm needing ajustments on the carb? Quote Link to comment Share on other sites More sharing options...
Joeman Posted June 30, 2012 Share Posted June 30, 2012 ok, silly question - did you put the piston back in the right way round??Many years ago, a mate of mine put the piston in the wrong way round on an old Yamaha DT50 meaning the transfer ports where the wrong side!! Exactly the same symptoms as you have lol... Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 1, 2012 Author Share Posted July 1, 2012 ok, silly question - did you put the piston back in the right way round??Many years ago, a mate of mine put the piston in the wrong way round on an old Yamaha DT50 meaning the transfer ports where the wrong side!! Exactly the same symptoms as you have lol... Hi Joeman, thanks for your post. I took the spark plug out and look into the hole with a mirror and the 'IN' on the piston is facing the rear of the bike (towards engine) as it says in manuel, however I read somewhere that it might have to face the exaust side? ........................ Quote Link to comment Share on other sites More sharing options...
Joeman Posted July 1, 2012 Share Posted July 1, 2012 ok, silly question - did you put the piston back in the right way round??Many years ago, a mate of mine put the piston in the wrong way round on an old Yamaha DT50 meaning the transfer ports where the wrong side!! Exactly the same symptoms as you have lol... Hi Joeman, thanks for your post. I took the spark plug out and look into the hole with a mirror and the 'IN' on the piston is facing the rear of the bike (towards engine) as it says in manuel, however I read somewhere that it might have to face the exaust side? ........................ Not familiar with that engine, but "IN" would likely refer to the "inlet" side of the engine, so as long as "IN" is facing the carb (back of the bike) , you very likely have it round the correct way.However, as another check, if you take the exhaust off, you'll see the piston going up and down, and if you see transfer ports in the skirt of the piston, then you have the piston in backwards! Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 1, 2012 Author Share Posted July 1, 2012 (edited) ok, silly question - did you put the piston back in the right way round??Many years ago, a mate of mine put the piston in the wrong way round on an old Yamaha DT50 meaning the transfer ports where the wrong side!! Exactly the same symptoms as you have lol... Hi Joeman, thanks for your post. I took the spark plug out and look into the hole with a mirror and the 'IN' on the piston is facing the rear of the bike (towards engine) as it says in manuel, however I read somewhere that it might have to face the exaust side? ........................ Not familiar with that engine, but "IN" would likely refer to the "inlet" side of the engine, so as long as "IN" is facing the carb (back of the bike) , you very likely have it round the correct way.However, as another check, if you take the exhaust off, you'll see the piston going up and down, and if you see transfer ports in the skirt of the piston, then you have the piston in backwards! Hi again Joeman I havent took the exaust off yet as I thought I should take some photos of the old piston which I replaced some time ago because from where the exause is situated and with both sides of the piston looking identicle I am not sure how that check would be done. The old piston has a bit of damage to one of the scirts in one of the photos. Whilst giving the bike the once over I took out the CDI Unit and consulted the manuel and checked each connection to the UK specs given in the manuel. Some of the conections gave right reading but some didnt give the right readind or no reading at all. So I was wondering could this be the problem even though there is no battery?[album]360[/album] [album]359[/album] [album]358[/album] [album]361[/album]Second photo is one with damage. Edited July 2, 2012 by murp24 Quote Link to comment Share on other sites More sharing options...
Joeman Posted July 1, 2012 Share Posted July 1, 2012 Think we can safely rule out the piston being in the wrong way round. From the pics there is no ports in the skirt. Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 1, 2012 Author Share Posted July 1, 2012 Think we can safely rule out the piston being in the wrong way round. From the pics there is no ports in the skirt. In away im quite disapointed as I was hoping that would be the problem. Any other sugestions? I just dont understand it. Quote Link to comment Share on other sites More sharing options...
Tango Posted July 1, 2012 Share Posted July 1, 2012 You are definitely getting compression? Take the plug out and stick your finger in the hole and turn the engine over (get someone else to kick it over) and see if the compression will push your finger out of the plug hole.When you took the carb apart did you make sure that the needle circlip was in the correct slot? And have you adjusted the idle jet to the workshop manual setting? Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 2, 2012 Author Share Posted July 2, 2012 You are definitely getting compression? Take the plug out and stick your finger in the hole and turn the engine over (get someone else to kick it over) and see if the compression will push your finger out of the plug hole.When you took the carb apart did you make sure that the needle circlip was in the correct slot? And have you adjusted the idle jet to the workshop manual setting? Hi Tango I checked the compression by putting my thumb over the hole and have some one else to kick it. There is compresion there but it didn't exactly blow my thumb off the hole. Never removed the needle circlip is in right slot and the carb needs ajusting but not familiar with how to do it without the bike running. I noticed yesterday that when the bike is kicked the kick starter hits the foot peg, now I am not sure if it did this before and was wondering whether or not when I droped the engine to remove bore that when I put it back in in might be a little off some how. So im not sure if it is just me but I cant recall whether it was like this before. Could it be that when I am kicking the bike it it needs to go an extra few mill or so to get the right kick to start and the engine is just off a little?If I cant get it sorted today Im going to take the engine out tomorrow, check carb, cylinder, bore and piston. Would a CDI unit stop my bike from starting if it was faulty even though there is no battery because I still get the spark and was wondering was it cutting it out maybe? Quote Link to comment Share on other sites More sharing options...
Joeman Posted July 2, 2012 Share Posted July 2, 2012 things to try..Make sure you have a spark - plug out, connected to HT lead, kickstart, look for spark. if you have a spark, your CDI is probably ok.When testing compresssion your finget should get blow out of the hole - bit worrying that you didnt get blown away... did you install the rings correctly??With plug back in, put your hand over the carb (choking it), throttle wide open, and kick it a few times, then remove your hand. You should feel suction when kicking and when you smell your hand it should smell of petrol.Hopefully by choking it like this, once your hand is removed and you kick it again it might fire. Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 2, 2012 Author Share Posted July 2, 2012 things to try..Make sure you have a spark - plug out, connected to HT lead, kickstart, look for spark. if you have a spark, your CDI is probably ok.When testing compresssion your finget should get blow out of the hole - bit worrying that you didnt get blown away... did you install the rings correctly??With plug back in, put your hand over the carb (choking it), throttle wide open, and kick it a few times, then remove your hand. You should feel suction when kicking and when you smell your hand it should smell of petrol.Hopefully by choking it like this, once your hand is removed and you kick it again it might fire. Have a continuous spark when kicked so that seems fine? I have 1 new ring and 1 older ring on the piston as one was snapped, and i believe they are on correctly. Not sure how to choke a carb, do you mean block air in take (air filter). Also My finger smelt of peterol when i was testing compresion. Im starting to believe the foot rest is to blame stopping me from getting a good kick. Quote Link to comment Share on other sites More sharing options...
Joeman Posted July 2, 2012 Share Posted July 2, 2012 Have a continuous spark when kicked so that seems fine? I have 1 new ring and 1 older ring on the piston as one was snapped, and i believe they are on correctly. Not sure how to choke a carb, do you mean block air in take (air filter). Also My finger smelt of peterol when i was testing compresion. Im starting to believe the foot rest is to blame stopping me from getting a good kick. remove air filter, put hadn over the intake to the carb... "Choking"unlikely the kickstart, but you can try "bump starting" the bike... 2nd gear, run along with the bike, let the clutch out... back wheel turns engine, a healthy bike would start. Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 2, 2012 Author Share Posted July 2, 2012 Have a continuous spark when kicked so that seems fine? I have 1 new ring and 1 older ring on the piston as one was snapped, and i believe they are on correctly. Not sure how to choke a carb, do you mean block air in take (air filter). Also My finger smelt of peterol when i was testing compresion. Im starting to believe the foot rest is to blame stopping me from getting a good kick. remove air filter, put hadn over the intake to the carb... "Choking"unlikely the kickstart, but you can try "bump starting" the bike... 2nd gear, run along with the bike, let the clutch out... back wheel turns engine, a healthy bike would start. I will try bump starting it before i strip it, also tryed choking it earlier and nothing. Got a problem with the clutch, it dosent seem to be engaging, i have ajusted the clutch lever to the specs in the work shop manuel but when i pull it it seems fine and springs back, i can see the clutch lever and spring working fine but when i put it in gear the bike wont move as if clutch isnt engaged. When the bike was running a few weeks ago i tryed putting it into 1st with clutch in whilst engine was running and it stalled. Any ideas?Sorry for being a bother, im not a mechanic just a 21 year old building a bike for the first time Quote Link to comment Share on other sites More sharing options...
Tango Posted July 2, 2012 Share Posted July 2, 2012 Ok mate....I suspect you've not got enough compression to start the bike....the old ring that you used could well be shot. Also when you bought the piston do you know if the bike has been rebored at any time.....was the old piston standard size or oversize?The clutch problem is most likely that the plates have stuck together. Pull the clutch apart and gently prise the plates apart....and clean them up. Not sure if this bike has a wet clutch......if it has then soak the friction plates in engine oil for a few hours and then reassemble..... Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 2, 2012 Author Share Posted July 2, 2012 Ok mate....I suspect you've not got enough compression to start the bike....the old ring that you used could well be shot. Also when you bought the piston do you know if the bike has been rebored at any time.....was the old piston standard size or oversize?The clutch problem is most likely that the plates have stuck together. Pull the clutch apart and gently prise the plates apart....and clean them up. Not sure if this bike has a wet clutch......if it has then soak the friction plates in engine oil for a few hours and then reassemble..... Thanks Tango. Will give that a go tomorrow. The piston and bore are standard size 39mm and I bought a newer but same piston and fitted that with 2 old rings on it and now it has 1 old ring and 1 new, the old ring was in quite good condition but will give it the once over tomorrow, im just praying that the new one hasnt snapped or something because they arent easy to find. Quote Link to comment Share on other sites More sharing options...
Fozzie Posted July 3, 2012 Share Posted July 3, 2012 If the rings have gone next time I suggest you get new ones then rub some 2-stroke oil on the cylinder wall!Then when you get it together just turn it over without the plug in to distribute it better than you did with your finger and then finally wack the plug in and try again! Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 3, 2012 Author Share Posted July 3, 2012 Turned out that one of my rings (top one) had snapped and has grooved a minute line in the bore, also when i put the piston in with just the 1 ring on and rut it into the bore with the 'in' on the top of the piston facing the exaust rather that the engine/manifold side it moves more freely. Now to find some more rings Quote Link to comment Share on other sites More sharing options...
Tango Posted July 3, 2012 Share Posted July 3, 2012 Good luck with that mate.......once you get the new rings you should be on the home stretch. Just a little concerned with the "line" that the broken ring has made in the liner....but hopefully it's not deep enough to cause you a problem..... Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted July 3, 2012 Share Posted July 3, 2012 chances are that if you have put a score down the bore then the compression will vanish as soon as you rebuild it personally i would say that it sounds like it will need a rebore and new piston kit at +,25 or +.50 oversize,and also even if it is moving more freely with the in mark at the front (towards exhaust) dont rebuild it like that as the piston has the cut outs in it to draww the fuel in from the carb and then allow it to flow around the crank using the 2 stroke oil mix in it to lubricate the crankshaft Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 3, 2012 Author Share Posted July 3, 2012 Good luck with that mate.......once you get the new rings you should be on the home stretch. Just a little concerned with the "line" that the broken ring has made in the liner....but hopefully it's not deep enough to cause you a problem..... Cheers mate will keep you posted. The scratch is slight just i dont think its anything major, just a guesstimate maybe two eighths of a mill deep wouldnt know for sure. When I get the bike going again will upload some photos of the finished product. Quote Link to comment Share on other sites More sharing options...
murp24 Posted July 3, 2012 Author Share Posted July 3, 2012 chances are that if you have put a score down the bore then the compression will vanish as soon as you rebuild it personally i would say that it sounds like it will need a rebore and new piston kit at +,25 or +.50 oversize,and also even if it is moving more freely with the in mark at the front (towards exhaust) dont rebuild it like that as the piston has the cut outs in it to draww the fuel in from the carb and then allow it to flow around the crank using the 2 stroke oil mix in it to lubricate the crankshaft Scratch is only slight, and the piston is a mirror image on both sides so dont think it realy matters which way it is fitted, theres a few pics of it on the first page. Quote Link to comment Share on other sites More sharing options...
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