QT50 Wont start??

Allright I am new to the forum, so first off Hello, My names Patrick and I am 15. Now to the problem. I have a 1987 Yamaha qt50 and I was running it yesterday and it stalled and now we cant get it to start. We are getting a nice blue spark, and gas is going through the carb. It wouldnt even start off of the starting fluid that we tried. Any ideas on what could be causing the problem? It also has the same amount of compression than when it was running, but I dont have a gauge to tell the exact number. Once again all help is greatly appreciated.

-Patrick

Re: QT50 Wont start??

c'mon soneone needs to know what I could do to get it running. please..

-Patrick

Re: QT50 Wont start??

possible an air leak? torque the head bolts, and intake bolts. make sure that the reed-valves are intact. if not, replace them.check ofr a GOOD fuel flow at the pet cock, and make sure the carb bowl is filling with fuel.

Re: QT50 Wont start??

okay. Can I just put new rings on an old piston? I plan on getting new gaskets and clamp on air cleaner, and new rings aswell. I will check those tomarrow. Thanks.

-Patrick

Re: QT50 Wont start??

also I need to know what kind of filter i can run on it? like where can I get a clamp on filter to fit it??

Re: QT50 Wont start??

allright i took the reeds out and I had a pebble cought in one of the petals, so I took it out and cleaned thedem with startting fluid, put them back in and it still wont spark..

Re: QT50 Wont start??

you were getting a nice blue spark .. and now it won't spark.

What's up with rocks getting into the engine .. and why did you mention new rings?

If you know things about why this engine might possibly be having trouble, list them here... nobody has a clue unless you provide some clues... the more the better.

Re: QT50 Wont start??

Allright it was running and it died out. I was running wih no airfilter because i wanted to make sure it ran and i have no filter for it, and I cant find a clamp on filter to fit it. It is getting good spark, and fuel but it wont start. I was asking about new rings because maybe it doesnt have enough compression to run it. Anything more you need to know?

Re: QT50 Wont start??

no air filter won't cause a no-start situation.. i guess some gravel got sucked up into the engine.. probably more than the one pebble you discovered lodged in the reed valve.

If it's got good spark and fuel is getting into the combustion chamber, the only other thing that could be missing that would prevent the engine from firing is compression. So, check compression.

:

If you can't check compression with the proper tool, check everything that could possibly be leaking compression.. that means everything above the rings..

Check for nice flat head and cylinder surfaces and a good gasket. Check head bolt torque. Check the plug .. make sure its in there snug. Check (if it has one) the decompression valve cable adjustment and the valve itself. See if some carbon (or a pebble is stuck under it :) keeping it open.

Check the rings by squirting some oil around the piston. This should increase compression if they are so badly worn out that they are leaking bad. Remove the cylinder and check see if the rings are carboned up and stuck in their grooves.

Look for a hole in the piston even. If a bunch of gravel got in there while it was running, who knows what happened..

Re: QT50 Wont start??

took the cylender and head off. there are some scores in the cylender and piston itself. Should I bore it out? if so how much and how much money would it need? I put the cylender back on and it started for like 40 seconds and died again, so I think it is in the top end. Thanks for all the help,

Re: QT50 Wont start??

everything depends on the condition of the cylinder and the quality of the engine you need. A moped can run forever with a banged up cylinder and piston.. might not run great and might smoke a little, but it'll run.

im sorta suprised it actually started all of a sudden. Maybe things aren't all that bad.

Re: QT50 Wont start??

i might just get new piston and rings and call it a day...

Re: QT50 Wont start??

Jeremy Cowell /

Have you checked your coils? Sometimes they can go to heck but still produce spark when kicked over. It's just not strong enough to fire. Yamaha peds are kind of notorius for doing that. Check it out, its worth a shot.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account