OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Problems with Briggs and Stratton Engine

Would M14 be suitable for bolt in the middle of the fuel tank, if I purchase a new bolt or threaded rod and nut or would M12 be more suitable.

For the other two bolts what Thread Repair Kits do i use

If I find that helicoil is to expensive, what are the other options?

What many of us would do, is simply run an M14x1.25 tap into the stripped hole, and open up the hole in the starter housing to M14 so it would just barely accept the outside diameter of an M14 bolt, then fit an M14x1.25 bolt of the required length. Not much cost involved, and if you don't already have an M14x1.25 tap, it's time you did. Just be careful opening up the hole in the starter: when opening up holes in aluminium just slightly in that way, the drill bit is prone to grabbing, which can spoil the job, your fingers, or both. Bolt the starter down when you drill it.

I have to purchase a M14x1.25 helicoil and helicoil the tank thread and pull start thread.

Last of all which helicoil size do a choose for the automatic choke cover?

Thank you in advance.

The most practical way to repair the automatic choke cover screw thread, is to just tap it out to the next size and put in an oversized screw. If you tell us the size of the screw that was in there, I'll come back with a suggested thread to tap it out to.

Whoa just a minute there. By this, do you mean the lug in the upper side of the fuel tank, which has a through bolt which screws into the side of the crankcase? If so, yes it has a 1/2" AF head, but bolts and screws are always described by the thread dimensions and spec. Not by the head size, which has put us at cross-purposes here, I think.

In this case, the original bolt will be 5/16"-18TPI UNC. So an M8x1.25 ISO metric would be the nearest equivalent, and the size of coil insert to use. I would not favour going up to the next common size, M10x1.5, in this location.

The bolt you were talking about is indeed the correct one, but the head size of it is 7/16". It is not the bolt on the fuel tank, it is the bolt on the left side of the pull start. The head size of the bolt in the middle of the fuel tank is 1/2".

The bolt holding the automatic choke cover on has a 1/4" head.

Also I have checked the flatness of the fuel tank and carb with the edge of a ruler and it looks fine.

Thank you in advance

Well, the fuel tank one was the only bolt for which you had mentioned any dimension. And that its matching hole is stripped too, so it will also need to be fixed in similar manner...

Righto then, the original starter bolt will have 1/4"-20TPI UNC thread, and M6x1.0 is the ISO equivalent to that. It may be possible to go up to M8x1.25 here, but this will likely also require that the starter housing hole be drilled out, to ~8.5mm.

Where these procedures [coil insert fitting or just re-tapping] get tricky is when the holes are blind-ended, as at least one of your stripped threads is. In this situation, it's rarely possible to get by with a single tap for each thread size, be that for a standard thread, or the 'special' taps required for the inserts.

Hand threading taps are classed into three basic types, according to the amount of 'leade', or taper, ground on their cutting end. In order of use, these are taper, intermediate, and bottoming taps. For tapping blind holes, the bottoming tap and at least one of the others will be needed.

Sets of three, one of each, are available for standard threads, for just this reason. Buying them may not be worthwhile, for your engine. Sometimes 'Neanderthal mechanic' damage just isn't economically repairable, unfortunately.

Yup, but as I've implied above, we need the diameter of the thread. To vernier caliper accuracy, at least; inch or millimetre units doesn't matter. We can convert!

What I might try and do is take my mower down to my local mower shop and getting them to fix the threads, because I don't partially want to buy 3 helicoil kits, which I probably won't use again.

Yep, that would be the go, but get a quote up front.
As the engine is dismantled sufficiently to make the holes readily accessible, that should minimise the cost.

As you say, it's not worth buying these special tools for one-off jobs. I've worked on my own motorcycles for years, but I still only have 6mm and 8mm coil insert kits.

Thanks for sorting that out Gadge - I should have noticed that the thread sizes he gave were impossibly large.

Personally I'd just tap the threads out to the next standard inch size, and failing that, get a less damaged second-hand engine, since it is apparently a perfectly ordinary 92908, available for a negligible fee in the nearest tip shop. However many of us here are hobbyists, and have a personal attachment to some mowers.

I most certainly have a personal attachment to my mower, if anyone touches it in my shed, they will certainly know about it.

I will ring up my mower shop this afternoon and see if he can do it and for how much.

Well I've only got bad news, the Local Mower Shop has closed down to my displease and the other mower shop in my area wants to charge me $82.50, for parts and labour, I asked them if the price would change if the mower was already apart and I just got a blank NO. It looks like I will have to buy the helicoil's myself.

The only other option I can think of is trying a bike shop or something alike and seeing if they will fix threads.

Oh bugger. Can't really offer much in the way of suggestions here. The coil insert kits average around $50 for each thread size, in the smaller sizes we're looking at here, last time I looked.

In former times, many areas had a semi-retired old bloke or two [machinist/toolmaker or mechanic], who would do such small jobs cheaply, and had the gear to do so. They were usually hard to find though, as they didn't advertise, and word-of-mouth was the only way.

My motorcycle mechanic operates like that; he just has a single line in the Yellow Pages, and even when you find his place [outside of town], there's no signage visible from the dirt road he lives on. There are one or two local car mechanics [very good ones] that work the same way. More than a few visiting city types have been gobsmacked to see the gear in his shed though. The full nine yards for bike work, including a Dynojet dynamometer with exhaust gas oxygen monitoring!

My feelings exactly. I looked at a person like that who advertised on the internet, he seemed like a nice guy and knew what he was talking about but he wanted to charge me $200.

The problem there, is that the remaining older blokes in that field often don't want to know about computers. They have no worries keeping busy at what they want to do, without learning a whole new field.

I know a couple around here like that. Perfectionists in what they do. No websites or anything; e-mail at most!

Hi I'm back, with good and bad news. The good news is that I don't need to repair the pull start just yet, as I can just hold it on their to start it. The bad news is that it starts but runs very rough. It does cut grass. I will try and upload a video of how it runs in a few moments.

Here is the video