[tommygraham]

So I bought another cbr250rr mc22 a couple of days ago, and it isn't running. It hasn't been running for over a year (according to previous owner) and when I bought it the ignition wouldn't even turn on so I got it for a good price. Since I'm very "Switched On" in the electrical field, I had the ignition problem sorted within hours. The bike now turns over and I can hear the fuel combusting but it just wont run by itself. The spark plugs are brand new, the air filter looks brand new, the plugs are sparking. I have tried using some "Start Ya Bastard" starter fluid but that just seems to be making it blow the occassional flame out the exhaust. I have ruled out the CDI as I tested it on my "Good" CBR250rr and it ran fine. It isn't the carburetors as I have put them on my good CBR and it ran perfectly. I have flushed out the carburetor bowls, used fresh fuel and used a few fully charged batteries.

I am thinking that the most likely problem is low compression. I am also thinking but know it is highly unlikely that the timing may be out.
I'm very open to suggestions, so please feel free to post any thoughts or input you may have.
Thanks, Thomas

 

[Lane]

Fresh battery, clean carbs and new spark plugs, i am yet to meet a CBR that they didn't fix.

Otherwise compression test it.

 

[aj26]

idle screw turned too down?

 

[tommygraham]

Fresh battery, clean carbs and new spark plugs, i am yet to meet a CBR that they didn't fix.

Otherwise compression test it.

haha, thats exactly what I'm thinking.... It must be compression related. And I have just checked that the firing order is correct.

 

[tommygraham]

idle screw turned too down?

When i swapped the carburetors over, the idle speed was fine. So I don't think it could be that. Thanks for the suggestion though!!
I'm going to have to turn the place upside down to try and find my compression tester.

 

[vutty]

Tried push starting it? When I fixed my bike I tried pushed started it for 2 hours to get fuel out of the engine. (Bike wasn't running for 6 months or so.) After it spat all the shit out it fired up

Edit: that wouldn't be your problem since it back fired from SYB but worth trying to push start it anyways

 

[tommygraham]

Thanks for the suggestion, but I don't think that will affect it since it is firing. I have put a good, working carby on it which has nothing but fresh fuel within it, yet it still wont start. I will try it anyway. Thanks

 

[Johnnie5]

I have tried using some "Start Ya Bastard" starter fluid but that just seems to be making it blow the occassional flame out the exhaust. IThanks, Thomas

its timing as you are igniting fuel out the exhaust not in the chamber

i would be starting from scratch and checking the cam timing first to ensure the cams are where they should be

after that i would be looking at the ignition timing

My VFR400 timing disk moved as its a 2 piece job and then the timing was out
I thought it was fixed and kept dismissing it , but my old man was always right when i told him it was backfiring out
the carbs , timing

 

[tommygraham]

Thanks for you input Johnnie5!!
I think you might be right about the cam timing. I'll have a look into it.

 

[Madman]

Thanks for you input Johnnie5!!
I think you might be right about the cam timing. I'll have a look into it.

Have you tested the voltage out by the pulse generator... one of mine was stuffed. Appeared to spark, carbies were cleaned, but turned out the pulse generator wasn't putting out enough voltage to fire her up.

 

[tommygraham]

Have you tested the voltage out by the pulse generator... one of mine was stuffed. Appeared to spark, carbies were cleaned, but turned out the pulse generator wasn't putting out enough voltage to fire her up.

Thanks for the suggestion, but I dont think this is the issue. The pulse generator doesnt actually induce the current required to make the spark. all that the pulse generator does in these bikes is induces a small current within its windings and then sends that pulse to the CDI which distributes the sparks and times them throughout the four spak plugs. I can hear that the fuel is combusting but it isnt enough to allow the engine to run on its own.
I will check out the cams and cam timing sometime this week hopefully.
Thanks, Tom