Anyone ever change a valve guide in a 5hp??

[125ccCrazy]

My nephews 5hp flathead needs a new valve guide, I started drilling the old one out a step at a time increasing bit sizes, I've got the guide super thin but I still can't get the rest out.... Is there a drill bit with a guide pin to drill these out or another process??

Any help or tips will be greatly appreciated..

 

[minidragbike]

The block is usually heated in a oven, then pressed out.
But now since you have it so thin, you may have to hone it out. You don't want it to big, or you will need to us a custom size guide.

 

[125ccCrazy]

The block is usually heated in a oven, then pressed out.
But now since you have it so thin, you may have to hone it out. You don't want it to big, or you will need to us a custom size guide.

Not sure how you can press the guide out as it doesn't go all the way through, it's about half maybe 3/4 the length of the bore, the lower half of the guide is the block itself..

I figured if I drilled it out to where the wall was pretty thin I could use a center punch and chipped it enough to where the wall would somewhat collapse and fall out but so far that hasn't panned out for me..... I don't want to go too much more and get into the block itself and then I'm screwed..

 

[minidragbike]

It must just be a factory guide. The aftermarket guides usually go all the way through.

You won't damage the block, the sell guides, and over size guides at karting shops. Try american power sports.

 

[125ccCrazy]

It must just be a factory guide. The aftermarket guides usually go all the way through.

You won't damage the block, the sell guides, and over size guides at karting shops. Try american power sports.

it's definately the factory guide, the engine was bone stock, it was a virgin when we opened it up.... The bore looks honeable and the valve seats are good, just that guide.... I been looking for valve guide tools but all I found was a rod for tapping a new guide in, haven't found anything for removal or boring for over size guides..

 

[olajoe808]

it's definately the factory guide, the engine was bone stock, it was a virgin when we opened it up.... The bore looks honeable and the valve seats are good, just that guide.... I been looking for valve guide tools but all I found was a rod for tapping a new guide in, haven't found anything for removal or boring for over size guides..

haven't done anything like this yet but noticed keywords bore and honeable and a brake cylinder hone popped to mind the harbor freight one.

 

[125ccCrazy]

haven't done anything like this yet but noticed keywords bore and honeable and a brake cylinder hone popped to mind the harbor freight one.

No, brake cylinder hones are too big, the bore for the valve guide is maybe 3/8"

 

[beau5278]

You have to tap threads in the valve guide,then put thick washer over the valve seat thread a long bolt into the valve guide with a nut on it above the washer,when you turn the nut down against the washer,it will pull the guide out of the hole.I'm not sure how well it would work now that you have the guide drilled out but I think I'd still try it,if you end up going through the guide with the tap,you should still be able to get a hold of the piece and pull it out in a string.B&S used to make 3 thicknesses of valve guides but it's been quite a while since I checked to see if the still do.Kart shops should have oversized guides of some sort,especially if they build any modified engines.