my 1984 honda spree shuts off when it warms up!

it has a new cylinder, piston and rings, installed properly. autobystarter works fine, reed valve is clean, has all new gaskets. I am mixing the fuel instead of putting it in separatly, to avoid burnign up the engine if the oil injector wears out. What do i do? i am monetarily invested up to its value!

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lemonie8 years ago
Feeding pre-mix into a non-pre-mix engine is not a good thing. Do you think the oiler will be the first engine component to fail?
Could you be really specific about how this problem occurs, such that I might be able to imagine it happening on my own machine?

MechEngineerMike (author)  lemonie8 years ago
ok, i have replaced a lot of crap on this bike, the air filter is pristine, etc. I questioned the oiler because when i bought it the guy tolg me i should mix instead of usein the oiler, that way i would never burn up my engine by running it dry. The problem is as follows. I can start the (50 cc) moped on the first try, it is a little weak sounding. I can ride it for a minute or two or until the enigne warms up, Then it shuts off and wont start again for a couple minutes. I have heard about people having similiar problems, caused by their carbureator not switching the air/fuel mix to adjust for the engine changing temperature. Although i do not know what exacly i should replace!
I bet it is the choke.. my yamaha razz (50c.c.) has it, and if the bike is "cold" and the choke is "ON", the engine starts at the first kick (lol, i need a new battery..) but, when the engine gets alittle bit worm (about 30 seconds) you have to turn off the choke.. if you don´t then the bike gets off..
why? Because when the bike is cold, the choke provides a little bit of an extra fuel to the carburetor (did i write it right??) so the bike can run easily.. but once it gets worm, the "normal" amount of fuel is enough to get it going... so an extra amount of fuel, can turn it off for a few minutes, until that fuel gets evaporated, or something like that, or the engine get´s cold again.. and then you can turn it on for another 2 mins or so...
I hope this helps you..
mikeasaurus8 years ago
Does the scooter have a choke?

I've owned a few motorcycles from the 80's and they have all had a manual choke located somewhere (either handlebar or near the engine itself). This would be one explanation why your bike shuts off while warming up.
If it is the choke, try leaving it with the choke wide open while the scooter is idling, you will hear the engine make a change of sound after about 30 seconds, then close the choke and you're ready to drive.

I hope that solves your problem!


what a choke does.
MechEngineerMike (author)  mikeasaurus8 years ago
well i have the owners manual and it doesnt say anything about a choke. But there is an idle speed adjustment screw on the carb. i think it was set to perfection already by the people i have work on it though. I am kind of thinking i could have an electrical problem, guesing a bad CDI unit
hmmm, well if the bike starts but then shuts after ignition then it doesn't sound like an electrical problem. Try adjusting the idle speed screw, there may not be enough oxygen getting to the engine. Have you checked/replaced your air filter? Maybe it's blocked?
If the bike starts and shuts down after it warms up it sounds exactly like an elelctrical problem. A lot of 1980s Japanese bikes & scooters have electronic problems just like this, and you need to replace electronic components by guess work if you don't have good diagnostic tools.
MechEngineerMike (author) 8 years ago
OK GUYS thanks for your help. I bit the bullet and took it to a professional shop. They had it for 2 weeks but they did good work. The problem was my fuel was not quite right, it needs fuel and oil separate or mixed at 30-1 with special oil. The MAIN problem was that the carbureator is very tempermental and required professional attention.. Since i got it working i drove it 20 miles cumulativly. Then i had to hit full speed for too long, afterwards it shut off! and was dead to the world. back to the shop!
jimdee8 years ago
Had the same problem would run then when I stopped engine would not start again.The next day would do the same.Changed everything but theCDI UNIT ,then did that and solved the problem.Could have kicked myself because I thought if it started the CDI was OK.I had fuel and spark so felt it wasn`t the CDI.I hate electrical problems they get costly before you solve your problem.
MechEngineerMike (author)  jimdee8 years ago
lol what a pain. i found a service manual for my bike so i was able to test my CDI with a multimeter.
paulyz8 years ago
change your coil.........seen this quite a few times on many different engine that i work on
MechEngineerMike (author)  paulyz8 years ago
my ignition coil?
your spark plug has a rubber boot that fits over the opposite end of this is usually where your coil is located............replace your spark plug wire which has the coil on opposite like on ebay put spree will see what i mean...........prefer a new to a used if you can even if cost a bit more.......some coils have a 2 prong thing that you just unplug and some look different since electronic ignition so will just be a black small box with 2 or 3 wires which is also called a pulse coil..........anyway let me know how you make out..........
farmboy-138 years ago
have you checked your atalitic converter?
MechEngineerMike (author)  farmboy-138 years ago
im not sure how this would become a problem that would cause my specific problems, maybe when it heats up it closes the exhaust pipe/?? perhaps a way to test this would be to disconnect the exhaust pipe altogether and see if my problem is solved. i will try it. !
most motors have a auto safty switch so if the converter so when it over heats it will automaticly shut off
farmboy-138 years ago