2008 Optimax 250 Pro XS slow cranking

[jgstuart]

Are these engines know to crank slowly? Mine has since new but always fires up--dealer said it was normal. It sounds like you are trying to start it with a weak battery but that has never been the case. Recently put new 1000MCA battery in and it still cranks as slowly as it ever did.

Anybody else experienced this?

 

[Texasmark]

Re: 2008 Optimax 250 Pro XS slow cranking

Know not, but the engine you mentioned has to have some bodacious cranking compression that would tax the best of single battery configurations. Since you said you have experienced the problem since new, one can't really blow it off as corrosion or bad connections.....and since the wiring harness comes with the engine, it pretty much says that if you want more whoopie, put 2 batteries in parallel. 2 in parallel halves the source resistance and estimating at least 200 amps required to turn that baby over, 12v/200 doesn't leave much room for any resistance and still get 10v across the starter.

My 2c,

Mark

 

[Faztbullet]

Re: 2008 Optimax 250 Pro XS slow cranking

Are these engines know to crank slowly?

Yep as these are a gear reduction starter, if it turns more than 450 rpm at cranking you got a good one.

but the engine you mentioned has to have some bodacious cranking compression

Nope...110-125 psi and starter draw at cranking is 170 amps, if engine is correct it should start with 6 seconds of starter engagement which is 36 revolutions of flywheel....

 

[jgstuart]

Re: 2008 Optimax 250 Pro XS slow cranking

Yep as these are a gear reduction starter, if it turns more than 450 rpm at cranking you got a good one.

Nope...110-125 psi and starter draw at cranking is 170 amps, if engine is correct it should start with 6 seconds of starter engagement which is 36 revolutions of flywheel....

The gear reduction was what I was suspecting/hoping was the case. I felt it had been doing this too long too consistently to have been an impending failure. I failed to mention I had tried multiple batteries via battery switch either and it made no difference. It always fires up within a couple of seconds but you just never get used to that very slow cranking.

Thanks for the help.

JS

 

[Texasmark]

Re: 2008 Optimax 250 Pro XS slow cranking

Nope...110-125 psi and starter draw at cranking is 170 amps, if engine is correct it should start with 6 seconds of starter engagement which is 36 revolutions of flywheel....

Amazing job of engineering. My 90 is spec'd (service manual) at 120 cranking amps and it says" if the compression drops below 120 expect problems...normal (new) is 150-165 range but important thing is matching within 10%"

But why not put a reduction gear on a 6 cylinder 2 stroke....at your 36 rpm's that's 216 opportunities to light off....seems reasonable and you save the weight of heavy cables and big batteries to do the same job. Makes sense to me.

Mark