Hi there. I was looking at some you tube videos on the Briggs Intek motors, specifically the 15.5HP. This particular video gives them a bit of a hiding Just wondering if those here who have used them have seen these failures first hand?
I am looking at a 2005 15.5HP Intek with AVS, pressure lube and spin on filter. It has clocked up a big 500 hours with full service history. It runs beautifully with minimal noise.
Would one pull the head off to prevent the further issues of a failed head gasket or assume that if it has made 500 hours it should go another 100 or so ok in a ride on application?
They seem to be prone to blowing head gaskets Aldo, but that is a relatively minor problem because it is easy to diagnose and easy to fix. They also seem to wear out their crankcase-pulse fuel pumps, which again is easy to diagnose and fix. There are more important problems which are not so easy.
First and foremost, the decompressor wears down so it stops working and the starter burns out trying to start the engine on full compression. There is no way to avoid this except to keep adjusting the exhaust tappet clearance at least once a year, until you find you have had to reduce the clearance below the nominal setting to get the decompressor to work at all. Then you have to replace the whole camshaft, because the cheap piece-of-tin-on-its-edge that is the decompressor, is not replaceable. Most people seem to fail to diagnose the problem at various points along the way, and consequently keep replacing starter motors, wiring, and batteries, which can be quite a burden.
The other serious problem only applies to the twin cylinder version: until the last couple of years, it had a badly designed air cleaner box which was very prone to dusting the engine.
If the engine you are looking at has run 500 hours without its camshaft being replaced, it is most likely now in need of that operation. You can probably tell by seeing whether the decompressor is working (if the engine will crank properly, it is working), and if it is working, check the exhaust tappet clearance. If it is already less than the nominal setting of 0.005-0.007", it may be because it needs a new camshaft and somebody has been trying to keep it running.
The other thing I'd suggest, is that if it is a twin cylinder, don't buy it. There is a completely redesigned later air cleaner box that works properly, but I think it may be quite a hassle to convert an old engine to use it.
Thanks Grumpy. I will investigate these possible issues.
It is a single btw. I will need to pull the rocker cover off as it seems there is a leak there. Apart from that it looks like a well maintained motor. The intake side of things look spotless and as I've mentioned before well maintained mower engines seem to be a rarity at the prices I look at anyway.
Between ambient temperatures of 40F and 140F, SAE 30 is recommended, with automotive rating SF, SG, SH, SJ or higher. Below 40F this oil may result in slow cranking and you may need to use multigrade, but at higher temperatures 10W-30 will result in high oil consumption. Briggs says synthetic 5W-30 can be used regardless of temperature, but I personally doubt this would result in low oil consumption in hot weather.
In case you care, the blown head gasket pretty much always is between the cylinder and the pushrod cavity. The reason is obvious if you look at the design: in that position it is a long, long way between head bolts. If you look at a Vanguard (the Japanese design the Intek was cheapened from) it has a properly designed head gasket (but has the same poor design of decompressor as the Intek - in fact it is the same camshaft).
I'd worry about about that oil leak. Since the head gasket usually blows from combustion chamber to pushrod cavity, a gasket leak pressurises the crankcase and this will often cause oil leakage from the rocker cover.
Last edited by grumpy; 14/06/1407:51 PM. Reason: Add warning on oil leak
I just did the basics, oil, oil filter, air cleaner and pre cleaner, adjusted valves and replaced rocker gasket. I ran it for around two hours and it ran perfectly. Apart from checking things periodically whilst using it, I checked the oil level again this morning and it was where I filled it to yesterday. It was also the same red tinge the 30 weight Briggs spec oil normally is.
Just keep monitoring it whilst using it or perhaps try a compression reading?
So, it cranks over at a reasonable speed on the electric starter? This implies that the decompressor is working.
Because they are prone to blowing head gaskets (meaning, a minority of engines will blow one at some point in its life) I think it is useful to establish a baseline for compression pressure now, while you are satisfied with the way it is running. If the pressure is sensible (no pressure is given in the workshop manual), all is probably well. Please tell us the pressure - we need to develop our own baseline pressure for large Intek engines.
