Intek 40 Series Pushrod Length vs Adjustment Range

[gregboggess]

Lawn mower has a B&S Intek V-twin 19HP
Model 407777
Type 0137 E1
Code 980422YG

Does anyone know what the spec is for the pushrod length?

It overheated, valve guide slipped, bent one or more pushrods. I got the pushrod part #s, 690981 (steel, exhaust), and 690982 (aluminum, intake).

I was sent a generic kit labeled CT160 (or CTM160, something like that), which is supposed to be the above two part #s but compared to a bent steel exhaust rod that was pulled, the new pushrods look about 1.5mm shorter.

I checked the engine service manual # 273521 and it doesn't spec the pushrod length.

Is there an acceptable range of length that can be adjusted for, is something 1.5mm shorter likely to work okay? I'd just throw it in and try to adjust it but the mower is at my mother's place and I'd like to have viable parts when I get there.

There is 25.4 mm to an inch, so are you saying they are 1 1/2 inches shorter?

 

[Peva]

Infact from what I can tell I'm the only one that's ever heard of valve spring shims. Again engines are engines there's an odd misconception small engines are in a different category. Yes you want the spring compressed they even last longer that way. Now it is just a small engine yes it will run no it will probably not be a noticeable difference. When I cut valves seats I shim springs on my engines but not so much on customers as I fear faster damage would result in going to far and again it's a small engine cost is the issue not function. These guys getting 6 and 7 grand in RPM achieve this mainly due to (amongst others) heavier springs to reduce "valve float" without the heavy springs they fall on their face at about 4500rpm. The last thing I would do is trim the guide. Pound it in, peen it in, run a drill bit through by hand and wrap a piece of fine grit sandpaper to a stiff piece of wire and hone the guide take a scotch Brite pad to your stem and adjust your valves to spec. The smaller side of spec as you've gone past break in period your 1.5mm will not affect your overall valve lift as your taking it up on the adjuster only way to loose valve lift would be taking the cam lobes down or loose clearances
. Shim the spring if you feel the need I see no need as you haven't changed anything.

I was only meaning that if you put the step washer in to retain the valve guide, the bottom end of the washer acts as a shim for the spring. Depending on how thick you make that inadvertent-new-spring-shim part of the washer, you could be over-compressing the spring, which may shorten it's life (could yield/weaken or break).

Again - I may be overthinking it. But if you make it 1/16" thick or more, perhaps that would become a spring life factor. Perhaps OK if maybe 1/32 or 3/64" thick. Anyway, with me being OCD, if I were doing it, I would grind the end(s) of the spring to remove maybe 0.01" shy of whatever that thickness is - ounce of prevention kind of thing.

 

[Peva]

There is 25.4 mm to an inch, so are you saying they are 1 1/2 inches shorter?

I think you had a brain fart,

1.5mm = 0.060"

 

[Dave_C]

I haven't completed the repair yet but got a lot done. Cleaned fins, removed/cleaned head, checked flatness, lapped valves, decarboned valves/stems, drove valve guide out, tapped a hole in side of head and dimpled an adjacent spot on the valve guide, ground a notch in the valve guide near the rocker arm facing end, put it back in with some Permatex high heat red threadlocker on it, and on a set screw and now that's curing. Also staked the head aluminum around the top of the valve guide.

I already had a generic gasket kit, bought years ago when the muffler bolts came out, and one of the muffler gaskets was lost. Upon checking it, and having the head off to compare, I now realize that the new head gasket has a little bit (maybe 4mm, I didn't measure it) larger cylinder bore hole, but has just as much coverage of the machined areas on the cylinder and head, and bolt holes line up. Since it's larger rather than smaller, it's probably going to work, right? I mean in theory it might reduce the compression a (tiny?) amount but hopefully not a problematic amount.

It also means I will be trying to reuse the muffler gaskets since I'd already used those out of this gasket kit, and if they don't seal well enough, can come back later and replace those without having to take off many additional parts for access.

Something occurred to me, that by lapping the valves, I regained at least a fraction of a millimeter in how high the valve stem sits in the head, which places the rocker arm that amount lower on the pushrod end, making up at least a little of the difference in pushrod length which was the issue that started this topic. We'll see, and if at some point in the future the guide pushes back out, I'll be sure to update the topic with that info.