OutdoorKing Repair Forum Forums Repairs and Maintenance Questions On Ride On Mowers Questions On Ride On Mowers Frames MTD B&S struggles to crank engine

Hi
my MTD lawn tractor has a 14hp Briggs engine. It has been increasingly difficult to start and now won't crank more than one turn of the engine.
I am using a fully charged car battery.
I have replaced the solenoid.
I swapped the starter motor for a known good one.
If I remove the spark plug the starter turns the engine easily and at reasonable speed.
I have checked the earth is ok.
I disconnected and reconnected all the wires on the starter switch.

I have run out of idea's...any suggestions appreciated.

thanks
Steve

Hi Steve, welcome to Outdoorking.

Please post the Model, Type and Code numbers for that Briggs engine. They are always on there somewhere, usually on the top cowl. At present if I take a guess, it would be that you have an Intek engine, and you need to adjust the exhaust valve tappet clearance. On the large Inteks you have to set the clearance to 0.006" - if with minor wear it gets to 0.009", the decompressor stops working and you get exactly the results you have described. It is a very common problem. Briggs specify that you must adjust the tappets every year, and they mean it: if you don't, you end up with it not cranking, and making unnecessary replacements of costly electrical parts.

If it isn't an Intek, we will have to go through a diagnostic procedure, when we know exactly what the engine is.

Hi

thanks for your help

not an INTEk motor..or not marked as such

so exhaust valve is not opening far enough...too much compression for the starter to cope with?

model is 28N707
type is 0166-01
code is 960402Z(the letter after the letter Z is D or O)

thanks again

steve

Hi exasperated, just for your records, your B&S engine was manufactured on the 2nd April 1996.
We would also like to wish you a warm welcome to the forum. Its great to have you aboard.

Hi again, Steve. I think you will find that the last 2 digits of the Code are 20 - the engine seems to have been made at Briggs' flagship plant at Wauwatosa, Wisconsin, where their head office is located.

Your engine is an Intek. Here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/18hnxKXAnfBhU7y.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/flmmwKX-nfBhU7y.pdf
If you refer to Page 11, you will see the required maintenance schedule - tappet adjustment is the last item shown, required once per year.

Here is the section of the workshop manual that deals with adjusting the tappet clearance:


Here are the required clearances:


The Intek is an unlovable engine in my opinion, but with careful maintenance as prescribed it can give good service, though it may require occasional repairs.

The engine has a decompressor, as nearly all OHV mower engines do, because the compression ratio is fairly high, unlike the side valve engines which used to be popular years ago. The high compression ratio results in substantial fuel savings and higher power output, but it makes the engine far more difficult to crank than a side valve engine. The size of starter motor, associated wiring, and battery that would be required to crank the engine at full compression is considered impractical by the engine manufacturers, so a decompressor is used. It bumps the exhaust valve open momentarily about half way through the compression stroke. When the engine starts, the decompressor disengages automatically - it only operates at engine speeds below 600 rpm, which is less than half of the engine's idle speed.

Hi Grumpy

thanks again for the info.

this morning I attempted to adjust the gap and the adjuster nut snapped in half.

A quick trip to my local dealer resulted in a $37 charge and a weeks wait.

I was flabbergasted at the price and outraged when the USA BS sites lists it $6.40 with free delivery...but they won't sell it to australia!

I called BS australia who had no real comment except to say "its the same as all imports like jeans etc". I hung up in disgust.

will let you know how I go

cheers

Steve

Steve, sometimes it is possible to find a cooperative US dealer by looking up the shipping rates for a few of them, but my standard approach is to check for the part number on ebay Australia. Unfortunately in this case, I only found two listings for P/N 691986, and both of them wanted to retire off the proceeds of shipping. Same result you got, in other words. Normally you will find the Outdoorking on-line store has much better prices than dealers, but there is a minimum shipping charge.

Hi Grumpy

I may have an alternative.

I have an old husqvarna LT140 with no cutting deck but it does have a running BS Vanguard engine. 14hp.

Model is 280777
Type is 0117 01
code is 9406024B

I can see some small differences with the carby choke cable and wiring but I am wondering if I can swap this engine into the MTD?

any clues appreciated

thanks
Steve

Steve, the Vanguard is the engine that formed the basis for the Intek. Daihatsu was commissioned by Briggs to design the Vanguard. A Daihatsu-Briggs joint venture factory in Japan makes the V-twin version. Briggs decided they would make the single cylinder version themselves, but found they couldn't, so they contracted Mitsubishi to make it. Then they had commercial conflicts with Mitsubishi, so they reverted to making it themselves. Meanwhile when they first found the Japanese design too difficult to make, they redesigned both the single and twin themselves to make them easier to produce in their own US factories, and called them Intek. Unfortunately, in my opinion their design changes were not for the better. The Vanguard engines, especially the twins, have good reputations. The same cannot be said of the Inteks.

I doubt there would be any difficulty in replacing your 28 cubic inch Intek with your 28 cubic inch Vanguard, which is also a better engine. However I cannot believe you would want to discard the Intek just because it needs to have its exhaust tappet adjusted. The tappets should have been adjusted regularly ever since it was new - personally I think it is unreasonable to condemn the engine just because you didn't do it. No harm has been done, once you spend a quarter of an hour making that simple adjustment, the engine will probably run like new.

By the way, are you sure it is a 280777, not a 28Q777?

Hi Grumpy

well the new adjuster nut turned up and despite my hopes was not made of gold

....it is now installed and timed according to your previous email and has made no difference...the starter cannot turn the motor (but will do so if I remove the spark plug).

In one of your earlier emails you said "The engine has a decompressor, as nearly all OHV mower engines do"...is it possible this is not functioning? if so suggestions on how to fix would be appreciated.

Of course all of this is making the spare vanguard motor looking more attractive!

thanks again

Steve

Hi Steve, these extracts from the Intek shop manual show you what to do to check the decompressor:





You have to open the crankcase, remove the camshaft, and check it carefully. This is quite a hassle, and replacing a defective camshaft is expensive, so it makes sense to be very sure you have checked the tappet clearance very carefully before doing it.

If you turn the engine slowly by hand (spark plug lead disconnected for safety, of course) with the valve/rocker cover removed, if the decompressor is working you should be able to see the exhaust rocker move - just slightly - during the compression stroke. If it doesn't move, the decompressor is not working. I only know of two ways that can happen: too much tappet clearance, or a defective decompressor mechanism on the camshaft.



If you look at the red circle, you can see that the decompressor (the top edge of the steel stamping that sits edge-on beside the cam lobe) is almost in line with the cam lobe: it only rises above it by a tiny amount. If there is excessive tappet clearance, it simply doesn't stick up far enough to lift the tappet sufficiently to take up the clearance and lift the valve at all, and therefore it doesn't relieve the compression.

Note that your Vanguard 28Q777 uses the same camshaft design - the decompressor is identical to the Intek one.

To find out definitively whether your decompressor is working, without dismantling the mower, I suggest you try this. Adjust the exhaust valve tappet to zero clearance, or even less than zero clearance. Then rotate the engine slowly by hand with the spark plug removed (both for safety and to make it easier to rotate). When you find the compression stroke (by putting a finger over the spark plug hole), rotate the engine slowly back and forth, up and down the compression stroke, watching the exhaust rocker for slight movement near the middle of the stroke. Any such movement is the decompressor operating. Remember, the question is not whether it relieves the compression, but whether it moves the rocker at all (you should only expect a few thousandths of an inch - you may have to use a dial indicator to detect the movement). If the rocker moves at all, the decompressor is functioning. Then step by step increase the tappet clearance until it stops working. Measure the tappet clearance at that point. If the maximum clearance at which the decompressor will work is less than 0.004", your decompressor has failed, perhaps by sticking in the "on" position and wearing itself out, or just by normal wear on the exposed edge of that steel stamping that pushes the tappet up. If the decompressor will not work at all, even with a negative tappet clearance, it is probably stuck or broken.

Bear in mind that your engine is now 17 years old, and that decompressor is a tin-pot mechanism to begin with.