B&S Intek V-twin Valve questions

[rootuser]

Hello all!

I am new to the forum but I have already been able to learn quite a bit by reading through posts.

I currently have an old (1998) Craftsman Riding Mower with the 18.5hp Intek V-twin motor in it. It is used in rural Santa Clara County climate of the California Bay Area. It is used during late spring through mid fall. Temperatures can range from 80 to 100+F during these times in this area and it is usually dry, sometimes very dry.

The land is extremely rough, hilly, and rocky and beats the absolute heck out of the mower. It does get dusty, but can also get a little bit wet during the first cuttings of spring when the big weeds hold water. The weeds can easily by 3+ feet high.

So far the mower has been great and I just go slow and steady and I know the land really well so I know how to avoid most of the big problems. I am dealing with ~6 acres.

Recently, the mower was blowing smoke (Like smoke screen amount of smoke). I've been around motors and power equipment, motorcycles and cars all my life so I could tell it was oil. I figured the valves weren't adjusted and when I looked at them they were very tight (almost like 0 lash). I did an adjustment and the smoke stopped immediately, but I want to be sure I adjusted them right. Here are my questions:

1. Craftsman says both intake and exhaust get adjusted to .004. I have read this motor uses .003 for intake and .005 for exhaust but I have no way to confirm that. Anyone know? I don't have a manual for the motor, just the mower itself.

2. I *believe* the bottom valve is intake and the top one is exhaust on this motor. Is that correct? I know the intake is supposed to have aluminum push rods, but I can't tell for sure.

3. Finding TDC is easy, and going 1/4 past that is fine, but without marking how can I be absolutely sure I'm on the compression stroke? The way I did it was rotate until the intake valve closed and then opened all the way up and before the exhaust valve started to move (They were both open as wide as possible) that was where I did the adjustment (which was about 1/4 past TDC of whatever stroke I was on). Am I close?

4. Craftsman says adjust the plugs (Champion RC12YC) to .040. Some other places B&S says .030. Is one "Right"?

5. Finally, I could go a step hotter in the plugs to the RC14YC but I don't have any real starting issues when cold. Any thoughts on a reason to go a step hotter?

Thank you all so much, I'm hoping I can get this mower working correctly again!

[KE4AVB]

Need the engine's model and type/spec number to look the specs.

[rootuser]

Appreciate it and I would have provided more if I had it on the motor itself.

This thing literally has no badge on it. All it gives is I/C Platinum, Intek Turbo Cool, exclusively designed for Craftsman.

There is no model number other than that (on the motor).

The mower is a Craftsman 917.242040


Does that help?

[KE4AVB]

The info is on the rocker/valve cover of the engine; although, it could be on the bottom side if someone install the cover upside down.

And mower model needs checking as the number posted doesn't come up either. Look on the mower's serial number tag. Usually under the seat on these Husqvarna made mowers.

[rootuser]

Thanks for the response and I would have written exactly what you did. Every time I have ever seen these motors in anything, you are exactly correct. BUT.... There is nothing on the valve covers. How do I know? I just looked, and I personally took them off to adjust the valves to get it to stop smoking and there is nothing on them top or bottom. I have looked all around this motor over the years to find anything at all, and no luck. At one point there was this badge that said for service to visit Craftsman service centers but that is long gone.

The manual says it is BRIGGS & STRATON ENGINE- MODEL NUMBER 407777, TYPE NUMBER 0121-E1 but I have no way of confirming this against the motor that is in there, so I have always "assumed" that was the one and thus how I got the idea that the valve clearances etc might be different. Craftsman is notorious for putting one thing in a manual but having a slightly different variation in the machine (I have a 42" deck mower that this is exactly the case).

I fat fingered the mower number, you're right, it is 917.272040. Manuals can be found online with ease.

Thanks for the help. What I am really trying to do is figure out if I am using the right specs from Craftsman because this is their variant of a normal B&S motor OR if there are actually better, more accurate specs that should be used to make it run even better.


Thanks for everything so far. Apologies for getting typing the wrong model number on the mower.

P.S. No I didn't spell Stratton wrong, it is spelled in the manual Straton.... yeah, Craftsman.

[KE4AVB]

You are still short one digit on the original engine model 407777-0121-E1 as that is what in the owners manual for the 917.272040. Then some one replace the non fuel pump rocker cover and was too lazy to transcribe the info to the new cover. How dumb of not thinking of others.

Here is the technical details for the 407777-0121-E1 engine. This is per the Briggs dealer's Power Portal site.

Technical Specifications
Model Series 4077
Displacement 656
Oil Capacity 64 oz (1.9 l)
Valve Configuration OHV
Flywheel Torque 130 lb/ft (176.0 Nm)
Governor Arm Torque 70 lb/in (8.0 Nm)
Carb Mount 65 lb/in (7.5 Nm)
Plug Gap 0.03 in (0.75 mm)
Intake Valve .004-.006 in (.10-.15 mm)
Exhaust Valve .004-.006 in (.10-.15 mm)
Idle Speed 1750
Coil Air Gap .008-.012 in (.20-.30 mm)
Flywheel Puller Part 19203
Flywheel Holder Part 19433
Connecting Rod Torque 100 lb/in (11.5 Nm)
Sump Torque 200 lb/in (22.5 Nm)
Head Torque 220 lb/in (25.0 Nm)

From the Intek V-twin service manual which you can download after a few more posts after manual forum section opens up..

ADJUST VALVES
1. Set No. 1 cylinder at 1/4” (6.4mm) past TDC, compression stroke. (Note: both valves will be closed on the compression stroke.)
a. Adjust valves and check.
Valve Clearance (cold) IN and EX .005” (0.13 mm)
b. Torque jam nut and adjusting screw to 60 in. lbs. (7.0 Nm).

2. Set No. 2 cylinder at 1/4” (6.4mm) past TDC, compression stroke.
a. Repeat for No. 2 cylinder.

TDC = Dead Top Center
Note: Number one cylinder is on the left side with the heads facing you.

But I prefer the old way of adjusting the opposite valve when one is fully open. IE EX fully open adjust the IN on the same head. And so forth for all four valves.

[rootuser]

Thanks for that information. That helps. It seems that .004 is on the tight side but within spec. I might go back tomorrow and make them .005 just to be in the middle of the range but I doubt much of a difference will be had.

I had no idea about the jam nut spec of 60 in lbs which is good to know so I don't over do it as I have a tendancy.

The interesting one here is the spark plug gap with Craftsman posting inside the hood, .040 and the manual saying the same thing, and then B&S posting .030. In most modern application with precious metal spark plugs, they all come pre-gapped almost perfectly so I have never even messed with them and they work great, but in the legacy world, I never let my gap drift off more than .005 or so. The idea that these are a .01 seems odd. In these small motors I doubt it matters. The fatter gap is nice to get that big burn assuming the coils can keep up. When I checked the spark itself it was nice a fat and blue so I figure .040 is fine, but odd that B&S would recommend .030 which seems to be their standard for every motor of this size.


Thanks for all the info and I'll see if I can get this mower going strong again!

[KE4AVB]

Spark gap affects ignition timing just like a partially sheared flywheel key. With the gap increased it just delays ignition timing slightly which low power output slightly on these fixed timed engines. Still better then too early as slight sheared flywheel does. These engine actually fires the plugs slight before TDC to make use of the full compression as takes a fraction of second for the fuel load to ignite.

When there is a disagreement in the manuals, I go with the engine OEM specs and not equipment OEM as the engine OEM is in a better place to know their engines. And there are a few engines by Briggs that require 0.020 gap depending the coils and spark plugs used.

Also be aware the color of the spark can change due the makeup of the local air. For example in Hawaii the sparks are more orange due the sodium content of the air and here in TN they more white (or at least that how I see them).

As valve clearances I always just OHV engine on the tighter side of the specs as the valve train wear the gaps tend to open up. BTW .004 isn't tight like the Kawasaki .002 clearances. How I adjust these clearances is say the spec is .004 is where the .004 gauge slips in but not the .005 gauge so it get set at somewhere between .004 and .005. Just how learned to set clearances.

Also note this engine does not have a mechanical ACR (Automatic Compression Release) even through the adjustment instruction assumes one. There still maybe an ACR grind on the camshaft. Also if engine is before 03082800 (2003 Aug 28) and camshaft is bad you only options is an used camshaft or a new short block. Since apparently someone lost the engine date code too you need to go by the mower serial number and assume the engine might be up to six months older than the mower. This very important to know the engine's date code as there are multiple changes to this engine over the years and you can't simply slap just any old part in it and expect to run as the OEM intended.

Now you should be able to access the service manual section so you should go the Briggs Service Info thread in the download, look thru the directory for the Twin Cylinder Intek OHV service manual and download it. Also SB 746 might apply which is in the sub-directory Advance Product Service Info. These manuals are provided for active members and does help a lot of questions.

I actually got quite a few other OEM manuals that are not online but maybe if can get the new forum setup later this year. Having decided on the new name as the current owner is wanting to retire this site so the PPETEN Phoenix project is in the works just awaiting my SS payments to start up which starts in July. I would be trying to duplicate most of the site setup except current will be archived so only new posts will appear on it. We also have to put spammers until I get them weeded out. And I got a lot learning between now and then to do; 65 yrs old takes a while to this while still running a shop.

[rootuser]

Thanks for that info.

The date is definitely before 2003, the mower is 1998. I'll look through my parts bin and see if there is an extra cover that might have the info stamped on it, but I never remember changing the cover for any reason over the years.

Next I need to do the blades again and a carb rebuild. I'm getting surging so I think something is clogged at this point, which wouldn't surprise me because everything was dirty as heck so it's time for cleaning up the carb as this seems the likely issue. The governor is working as intended and keeping the engine going so I expect it's just dirt. This seems to be common with these engines but it already runs better with the valves done.

[KE4AVB]

IPL show a twin barrel Nikki carb so it to note the main jets may just fall out when you remove the fuel transfer tube so be careful not to lose them on the shop floor. The tiny o-rings do shrink and harden leaning to surging problems. Briggs does not sell these o-rings separately from the jets. But good news Kawasaki does sells the o-rings under PN 62055-7013. Comes in packs of five but some vendor will list as individual items so have to order five to get a pack of five.

Another option these o-rings to go to your John dealer as they have them under PN M153076.

Either way these very tiny o-rings so they are easily blown away with your breath or by the breeze so again got to be careful when working with them.