[cris_adder]

Have a 1999 Model CBR600F4. The starter motor really struggles to turn engine over, barely moves the engine. I am using a good car battery at the moment directly hooked up to starter motor (i.e. eliminating all other electrics). I took the alternator cover off to turn the engine over by hand to see if it may be seized (using socket eccentric shaft).

I was able to turn over the engine with socket and bar with reasonable force, but am not sure if the resistance was too high. The pressure was not too bad, but wanted to ask what sort of resistance I should be getting from turning this over by hand? I will measure with a torque wrench - if this helps?

It may be the that starter motor has lost some of its torque, but that would seem an unusual fault... can this happen?

Appreciate any comments....

Thanks
Cris

[jhaggerty73]

There should be some resistance due to the compression in the cylinders. Try removing the spark plugs and then turn it over by hand. It should be considerably easier. You could have a bad starter motor or just some bad wiring leading to the starter, perhaps a bad ground (earth).

[jhaggerty73]

I just re-read your post and see that your connecting your car battery directly to the starter. I assume your using jumper cables or something similar. Althought this might seem like a great way to get lots of juice to the starter motor, you may not be getting a good conection. I suggest getting a battery for your bike and using the start switch on the bike.
Hope this helps!

[cris_adder]

Appreciate the help. I have double checked all connections and these seem to be ok.

I tried moving the bike in 2nd or 3rd gear and the wheel turns, which seems to suggest that compression is ok.

Which then really means that either the starter motor has lost torque, or that there is something else in the starter system that is creating resistance.

I have pulled the starter motor and testing this separately and it seems all good! So I am totally confused as to what else may be causing resistance in the starter system... perhaps the starter clutch?

I will pull the plugs this weekend and see how well it turns over as my next step...

Thanks
Cris

[cris_adder]

Well I have taken out the spark plugs and turned over the engine... no problem at all. However, as soon as put even one spark plug in, the engine struggles to turn over on that one piston.

So it seems to be that the starter motor has lost torque... or some other fault... really very weird.

I will find a replacement starter motor and see if that solves the problem...

Cheers

[cris_adder]

This problem has finally been fixed! In case you did not read the first post, have a CBR600 (1999) and the engine was not starting and turning over extremely slowing (as if it had a flat battery).

In any case, this is what was tried:

1) Ruled out all electrics by directly connecting the starter motor to a brand new car battery. Engine would still not turn over much (if at all).

2) Pulled spark plugs to check for hydraulic lock. When spark plugs were removed the engine actually turned over, but there was no evidence of oil etc in chambers. When the plugs went back in, again the engine would not turn over!

3) Changed the starter motor, on the chance it had low torque. Still no change.

After all this, thought that my engine was in big trouble, so rang up a good repairer and he said that it was common in some models for the Cam chain to slip a tooth on the cog when loose. This has the impact of causing a value to just press up against the piston head, causing slow engine turn over on start -- in some cases prevent all turn-over.

So I sent the bike in and yes this was the problem!

4) Cam chain had slipped a one tooth, causing one valve to only just touch the piston head. It was just enough force (together with compression when spark plugs were in) to prevent starter from turning engine over OR very very slowly.

Fortunately, there was no damage as the compression was checked and was all good.

Hopefully this information may help someone else....