Ninja 250 engine won't start.

[Bwdeaton]

I recently bought a 1996 ninja 250 R motor in a quad frame. Everything look decent most hooked up fine except the wiring. So I went ahead and fixed up the wiring and got it working so at this point it will crank and has spark, but it won't run. Please help me. Every now and then the engine will backfire but it just won't start up. I've cleaned the carburetors put a new main Jets and adjusted the valves and checked the timing; all of that is good. I did it according to the ninja 250 wiki. Still have the same issue cranking has spark, but won't run. The engine will backfire sometimes. And sometimes it blows a bunch of pressure out through the carburetor. Do you know what could be wrong with my motor? Any advice appreciated. Thanks.

[Motofool]

Originally Posted by Bwdeaton

....... Do you know what could be wrong with my motor? Any advice appreciated. Thanks.

Welcome, Ben !!!

Next thing would be checking compression and possible leaks of pressure through the valves or valves' guides.

A compression test will tell you how worn the piston-rings-cylinders are.

A leak-down test will tell you how well the valves isolate the cylinder.

http://www.dansmc.com/compression_test.htm

http://www.dansmc.com/leakdown.htm

[Alex]

Is this one of those starter / resistor problems? Some years of ninjettes needed a 100 ohm resistor somewhere in the starting circuit to fire, if I'm remembering correctly. If you have a wiring diagram for that year, it should be straightforward to confirm.

[Bwdeaton]

I am working on finding a compression tester that is long enough to fit. I will check that and post results so you maybe you can recommend a fix. As far as the resistor in the circuit goes, I will check on that soon and see if I can figure that out, the original key switch is gone and that is apparently where the resistor must have been. Thanks for your replies!

[Bwdeaton]

Thanks for your answers guys. I looked into the resistor thing and yes the previous owner already put a resistor in there I didn't think that was the issue because it cranks and has spark. I borrowed a compression tester from a neighbor of mine who works on cars, bikes and pretty much anything with an engine. He said he was sure it was accurate and it was a nice namebrand tool (snap on) so I tested the compression on my bike and sure enough it is no good. It read 60 on one cylinder or 90 on the other. Specs says at least 139psi and I'm nowhere near that. Do you have any recommendations of what I should do next? Thanks.

[Motofool]

Originally Posted by Bwdeaton

Thanks for your answers guys. ......... Do you have any recommendations of what I should do next? Thanks.

You are welcome

Your next step is to determine if the problem are the rings or the valves and valve's guides.

A leak test and a compression test with some oil are the next steps.

It could also be that the cams time is out of synchrony due to a jump of the time chain or improper assembly.
That would cause the valves not to fully close during the compression stroke.
However, that would be unlikely if you did the valve adjustment properly and check alignment of the cam sprockets per the manual.

[cream]

im having the same exact issue and symptoms, i didnt get to check compression yet but i also found a fried ground wire... i was hoping that was my problem... i know 140psi is ideal on a warm engine but do know the lowest psi it can be ok on a cold engine? +/- 10psi?

lmk how this turns out, ill try and get psi numbers on mine tomorrow
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[alex.s]

check the oil. does it look like glitter?

[verboten1]

https://www.ninjette.org/forums/show...Ninja+250+quad


This one?

[cream]

fixed my bike, somehow the woodruff key grinded down where it wasnt catching the rotor anymore, replaced it and it starts up/runs fine. never got around to check the compression yet though