[AT] Need some help, hard starting CR950 Briggs

Stuart Harner stuart at harnerfarm.net
Mon Feb 14 06:59:03 PST 2022 

Remember the old fire triangle? Fuel-Air-Heat.

With the ever more restrictive regulations filtering down to the smaller 
engines the manufacturers have had to lean out the mix as far as 
possible. If you were to put a pyrometer on one my guess is that at 
operating temperature they are running on the lean side of peak.

As air temp drops it gets more dense but without a choke to compensate 
the mix is just too lean to light off. To make things worse they have 
taken all of the adjustments away from the end user to prevent us from 
becoming criminals against the regulations. I suspect it also makes the 
carbs easier and cheaper to manufacture. If a bad one slips through, 
just replace it or the engine because it is cheaper than figuring out 
the problem. We see this in a lot more then carburetors.

Changing to a lighter hydraulic fluid will help make it easier to spin 
the engine faster when pulling the starter. I am not sure if that will 
help make a hotter spark or not considering it probably has electronic 
ignition anyway. Faster starting RPM could help with sucking in more 
fuel each stroke but then that means more air to, so back to lean.

I suspect that Farmer's engine sputters once in a while is that the raw 
fuel builds up enough in the cylinder to cause a rich enough mixture to 
fire once or twice. Once that is burned off, back to square one.

I am not sure that adjusting the valves would help any unless there is a 
way to lengthen the duration. Taking out all the backlash might cause 
the valve to open a fraction sooner, but once everything is warm and 
expanded there is a risk of it not closing fully and burning the valve 
or seat.

To get a more rich mixture for starting you could try to restrict air 
(like the old choke plates did) or add fuel like a primer does.

I have a Knipco stye heater that will not light off at any air temp 
unless I use both hands and cover as much of the air intake as possible. 
It lights in less than a second and then runs fine. I have tried 
different nozzles and moving the igniter around, but it still needs less 
air to get going.

On the 1978 motorcycle I once had it was a victim of early tampering 
with emissions on motorcycles. When new it would not start on a cool day 
and it had a manual choke. I rigged up a way to inject a little ether 
into the airbox that was buried under the seat. Had to put 10,000 miles 
on that bike before it got over that problem.

The idea of using an unlit torch to add a little fuel sounds like a good 
one. Red Green would just slap a little piece of duct tape on the air 
intake until it warms up.

Best of luck to Farmer getting this working.

Stuart


On 2/14/22 01:34, Greg Hass wrote:
> I have a JD Zero Turn with 27 hp. Briggs engine and electric start. 
> Anything around 45 to 50 degrees and it just wouldn't start. It does 
> not idle good either, but the book says that is because of emissions 
> control. My brother has a Simplicity zero turn 3 years old and several 
> times has tried to start it in 40 degree and it just won't fire so it 
> is not just my mower. Both engines have fixed jets so no adjustment is 
> possible. It is possible other things could be wrong, but my only 
> other idea is to make sure it has fresh WINTER blend gas.
>        Greg Hass
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> On Sun, Feb 13, 2022 at 8:15 AM Moe Fretz <tubetester at gmail.com> wrote:
>
>     Try this site, they should be able to help  you.
>
>     http://ppeten.com/forums/search.php?search_id=newposts
>
>
>     On Sat, Feb 12, 2022 at 18:51 Mike M <meulenms at gmx.com> wrote:
>
>         Hi Farmer,
>          Just a thought, my log splitter was hard to start in cold
>         weather, until I changed the hydraulic fluid from the OEM 
>         fluid to transmission fluid,a whole world of difference.
>
>         Mike M
>
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>         On 2/12/2022 9:24 PM, Stephen Offiler wrote:
>>         Hi farmer:  I'd have to think you've already been down this
>>         road, but, I'll say for the record that I've had pretty
>>         decent luck downloading manuals from the Briggs site.  But I
>>         haven't done it lately, and it's always 20-year old stuff
>>         when I do.   The other thing I'll mention is the good old
>>         unlit propane torch in the intake trick.  That's my go-to
>>         when they're almost trying to start.  There's spark and fuel
>>         but the modern carburetors are set lean for emissions and it
>>         just seems that the choke doesn't quite get the mixture rich
>>         enough.
>>
>>         Good luck,
>>         Steve O.
>>
>>         On Sat, Feb 12, 2022 at 7:43 PM Indiana Robinson
>>         <robinson46176 at gmail.com> wrote:
>>
>>             We have a log splitter a couple of years old that has a
>>             OHV CR950 Briggs. It only has a few hours on it but has
>>             become quite hard to start (recoil start). It is way too
>>             recent for my knowledge base... It seems that most things
>>             are these days. Apparently the OHV Brigg's have a cam
>>             bump "compression relief" I also understand that there is
>>             an important valve adjustment procedure that can normally
>>             improve starting problems. We can't find a site that
>>             gives a clear and understandable explanation of the
>>             procedure.
>>             Does anyone know of a site with a clear description of
>>             how to do it? It will usually start if it is sitting in
>>             the sun and the temp is at least 50... Yesterday at 45
>>             degrees it "ALMOST" started 837 times... It keeps firing
>>             enough to keep you trying and trying...
>>             Thanks
>>
>>             -- 
>>             -- 
>>
>>             Francis Robinson
>>             aka "farmer"
>>             Central Indiana USA
>>             robinson46176 at gmail.com
>>
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>     Moe Fretz
>
>     L’Orignal ON,
>     Canada
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