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B&S engine


mrbill1's Avatar
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11-14-07, 08:10 AM   #1  
B&S engine

400707 122201 14 hp twin IC. I have a hard start problem when it is cold, once it starts it is fine. New starter , battery load tested fine. Does this engine have valve adjustment?
I am thinking of possible fuel pump rebuild kit also.
Mower is 17 years young and almost looks new

 
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11-14-07, 08:35 AM   #2  
When you say 'hard start', this mean it turns over slow? or, just takes a while for it to fire ?? I'm assuming choke plate closes when choke cable pulled out ??
If carb hasn't been rebuilt before the fuel pump diaphragms are probably stiff.
Is this on a Murray ??
thanks,

 
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11-14-07, 01:56 PM   #3  
hard start

it is a MTD product and it spins over slowly and it needs to jump start to spin over at the normal rate to start, when warm it spins fine.The electrical system has been checked amnd is fine. Does this motor have adjustable valves?
During the summer I do not have this problem only in the fall [cooler weather]

 
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11-14-07, 03:47 PM   #4  
Continuing to jump it will eventually, and may already
have damaged the starter, so you need to address the
main problem soon. Once it has been started, the oil is warm
the battery has had a fresh jolt from the charging system/
jump, etc.
The battery may still be a little suspect, the "load"
test is not totally conclusive. The starter could probably
use a little disassembly and cleaning, that may help.
But the first thing I would do is remove both heads and
clean all of the carbon buildup from the top of the piston
and cumbustion chamber of the head. Older engines had
head gaskets that could easily be reused, with the newer style, sometimes you can get lucky.


Fish

 
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11-14-07, 03:50 PM   #5  
Posted By: mrbill1 it is a MTD product and it spins over slowly and it needs to jump start to spin over at the normal rate to start, when warm it spins fine.The electrical system has been checked amnd is fine. Does this motor have adjustable valves?
During the summer I do not have this problem only in the fall [cooler weather]
yes you have to adjust the valves.. do a search or chesse or puey can tell you how to do it..

 
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11-14-07, 04:00 PM   #6  
Posted By: cf1 yes you have to adjust the valves.. do a search or chesse or puey can tell you how to do it..
Well adjusting the valves on this model is quite involved,
and my suggestion is much simpler and cheaper. and the
valve adjustment is likely not the problem.

Fish

 
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11-14-07, 07:02 PM   #7  
Most small engine have what is called a mechanical compression release (MCR) mechanism which is integral to the camshaft that, during starting RPM's, lifts a valve (or two valves on 2-cylinder engines) slightly and relieves some compression on the compression stroke of each piston. Just enough to allow the starter motor to spin the engine over easily. You have one of the very few engines that does not have this feature and, with such, you need a high amperage battery and good, clean starting circuit cable connections and a good starter motor. By design, boxer engines (opposed cylinders) are tough on starter motors, whether it be a small engine, mototcycle engine or automobile engine. I recommend a battery with a minumum of 375 cranking amps and make sure you have battery cables no less than 6 gauge wire. Another option is to install a heavy-duty starter motor and the Briggs part number for this is 498148 provided you have the physical room to install such, it is about one inch longer than the standard starter. FYI, the valve clearances are .005", intake and .008", exhaust. Removal of the intake manifold/carburetor assembly is required to access the valve covers (breather assemblies) along with the cylinder heads, of course.

 
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11-14-07, 10:53 PM   #8  
Something that I've noticed on these opposed twins, especially older ones like yours, is the starter wear at the top bushing. The bushing wears away from the flywheel (from the pressure of the gear forcing away from the flywheel during cranking). This is ok until it gets bad enough that the armature begins to scrub on the field magnets. This causes excessive resistance and makes the starter drag. I've seen this happen pretty often, and it's not hard to check. The bushing can be replaced, or the entire top cap of the starter can be replaced with new bushing included. When this is done, it would definitely be good to clean the starter, replace brushes or the brush cap if needed, clean the commutator, and apply a small amount of white lube to the bushing areas on the armature during reassembly. Make sure to be sparing with the lube. (not so much that it slings out and gets on the brushes when the starter spins).

Valves on a flathead may eventually need adjusting, but I doubt that's your problem because the valves on a flathead, by design, wear in such a way that would probably ease cranking, rather than make it more difficult.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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11-15-07, 08:02 AM   #9  
B&s

the starter is new, I cleaned up the heads ,valves.
maybe the oil is contaminated with fuel

 
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11-15-07, 09:44 AM   #10  
I cured a slow, nostart cond on an old Craftsman GT earlier this year by cleaning all battery and solenoid connections, even batt neg cable conx to frame. symptom was ammeter showed discharge when ele clutch engaged.
After thorough brushing/cleaning, worked great.
What weight oil you using ??
thanks,

 
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11-15-07, 10:36 AM   #11  
B&s

sae 30
all connections have been checked and cleaned

 
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11-15-07, 11:38 AM   #12  
Of course fuel in the oil will generate excess fluid in the crankcase and then create higher crankcase pressure. Do you smell fuel in the oil? If so, this will be caused by a faulty carburetor inlet needle & seat and/or a float that no longer floats due to gas in the float. Have you checked all six battery cable ends? How strong a battery do you have?

 
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11-15-07, 08:02 PM   #13  
I see the mention of the new starter in your original post now. I guess I skim through these posts too fast sometimes.

Question, does it blow a good cloud of smoke when it cranks up?


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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11-16-07, 07:57 AM   #14  
B&s

all cable ends have been cleaned
after all these years she does smoke at times
the oil is changed 2-3 times a season

 
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11-16-07, 11:49 AM   #15  
Well then, make sure your battery is good and have it load tested professionally to be sure it is sufficient for this engine.

 
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11-17-07, 08:24 AM   #16  
B&s

thanks for all the help

 
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