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Briggs stratton 8hp valve guide repair?


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  #1  
Old 03-08-2013, 11:54 AM
fungus fungus is offline
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Default Briggs stratton 8hp valve guide repair?

Hello all,
I've got an old 8hp briggs and stratton with a 5kva generator on it running on propane. Burns a lot of oil, big cloud of white smoke when starting it and light blue smoke afterwards but otherwise runs fine.
Took the cylinder head off and had a look at everything, the cylinder and piston seem fine, a little bit polished and some very light scratching but it still gives good compression.
Was told by a mechanic friend of mine to try pouring a wee bit of water inside the bore and if it seeped down then the rings should need replacing but I did that, left it an hour and measured the depth of water again and it was exactly the same. So I assume that the cylinder is ok.
Three things that might be causing the trouble but the last is probably the major.
1)One corner of the cylinder head where the exhaust bolts on is snapped off but still holds together/ is bolted on, the part that's broken off only covers a small part of the head gasket so there seems to be enough of a seal, if I can get a new cylinder head then I'll replace it but seems to be something not to bother too much about.
2) I didn't realise not to take the oil breather apart and think that might be a bit leaky! Put it back together best I could and made a new gasket out of a piece of bicycle tyre inner tube (!) as a temporary measure, seems to work ok. If I've had the generator running for a wee while, shut it down and then start it again then there seems to be smoke coming from the breather tube into the air inlet, which suggests there might actually be smoke inside the crankcase?
3) Is what I really need help with, the main route for the oil getting in seems to be the intake valve, I can wobble it to and fro quite a bit and the whole intake port (and actually the air intake) is covered with tarry oil..
But the valve guide on this engine just seems to be machined directly into the cylinder block? Could I just get one of these(not a B&S but seems to be the same size), a 5/16 and a 5/8 reamer , drill a hole a bit smaller than the 5/8 into the cylinder block, ream it to 5/8, bash the valve guide in and ream the inside to 5/16?
In theory this should work but I'm not sure how accurately centered the guide needs to be, what clearances I should give for an interference fit on the outside of the valve guide, and even if there's enough metal to drill it out that much..

So my overall idea is.. Get a new set of gaskets and seals, probably a new oil breather and cylinder head, get a new intake valve guide and install that and it should be good .. (?)

If all of the above just sounds a bit silly, does anybody have any experience of a direct replacement engine? If I can find a honda GX240/270 with a tapered shaft then that looks like a pretty good replacement but then there's the question of the propane carburetor and fitting it on.
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  #2  
Old 03-08-2013, 03:33 PM
oldschoolwisconsin oldschoolwisconsin is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Thank god I know E.U. talk, coz I can read your post. They do make a repair sleeve for those valve guides. Thank god Ive never had to do one. I dont wanna, coz they look like a royal PITA
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Old 03-09-2013, 01:19 AM
DriverR DriverR is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Water in the cylinder bore? Forget that advice. The only real way to diagnose and eliminate potential problem areas is with measurement tools and inspection.

Pull the piston and use a bore gauge. Most folks will not have one so the next best tool is a feeler gauge which everyone can get. Measure clearance between bore and piston, simple.

Removes all guess work.

Broken heads and inner tubes?
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Old 03-09-2013, 12:48 PM
GaryH GaryH is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Chances are you will find the rings worn and the cylinder looking good. Not uncommon.

You will still get good compression with worn rings as the oil ring wears out first beyond specs while the other rings are not too bad.

Briggs made replacment valve guide bushings for most all thier engines.

Gary
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Old 03-09-2013, 02:35 PM
fungus fungus is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Thanks all, so they do make a replacement bushing but does anybody have experience of machining the block to accept one; what it requires in terms of accuracy and trueness?
And any ideas on sourcing a replacement engine?
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Old 03-10-2013, 11:29 AM
GaryH GaryH is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Assuming you have a Model 9,14,19 or 23 ... The Briggs procedure is to ream out the worn guide with reamer 19183 using guide bushing 19192. Only to 1/16" deeper than the new valve guide bushing 230655. Then press in the new bushing with the briggs press tool. Can not find the Briggs no on that tool. Maybe you cold find a Briggs dealer with those tools if there are any dealers there.

Of course, you have to grind the valve inafter this repair.

You should buy one of the older style Briggs "Service and Repair Instructions" manual. They are always on ebay. It is the red covered one and an EXCELLENT manual on these old motors. Should be able to get one for 20.00, or under, used.

Gary
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Old 03-11-2013, 07:45 AM
fungus fungus is offline
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Default Re: Briggs stratton 8hp valve guide repair?

So I've been looking around for replacement engines, but all the briggs 8hp I can find are vertical engines, any way to change the orientation or would that just be a bit mad?
But I'm still up for trying to fix the valve on this, I'll have to do some more research, try calling around a few places to see if I can get the job done for me, if anybody would have a detailed description of what's needed I'd like to try though.
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Old 03-11-2013, 10:32 AM
oldschoolwisconsin oldschoolwisconsin is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Quote:
Originally Posted by fungus View Post
So I've been looking around for replacement engines, but all the briggs 8hp I can find are vertical engines, any way to change the orientation or would that just be a bit mad?
But I'm still up for trying to fix the valve on this, I'll have to do some more research, try calling around a few places to see if I can get the job done for me, if anybody would have a detailed description of what's needed I'd like to try though.
what is the model series of this engine? you need to figure tht out. Then you get the reamer for the valve guide FOR YOUR ENGINE, along with the reamer guide. Then you ream the hole/valve guide and then press in a repair sleeve, which you can get from briggs.
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Old 03-11-2013, 08:35 PM
JonH JonH is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Briggs makes a repair kit with all reamers, guides, pullers, etc. necessary to repair valve guides. For 5/16" valve stems, you need part no. 19232. I think you need bushing no. 231218. You'll need to check the model of your engine to be sure that is right.

For sure, the first thing to do is to get a Briggs shop manual. The manual that I have is part no. 270962. It has the procedure outlined in it. Read through it BEFORE cutting any metal.

I installed a bushing in my 5S some time ago. I took a few pictures and put them on my site. I'll put a link to that page below. There really is nothing to it. If you don't want to do it yourself, any competent machine shop can take care of it in a few minutes. While you have the valve out, measure the stem to be sure it is not worn.

Good luck with it and let us know how it turns out.

Jon

http://www.jonsmachineshop.com/projects/valve-guide
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Old 03-22-2013, 06:16 PM
Beanscoot Beanscoot is offline
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Default Re: Briggs stratton 8hp valve guide repair?

I encourage you to repair the old engine instead of replacing it.

Like JonH, I have also replaced the guide in a Briggs Engine. I bored the block first, then I machined up a new guide from a likely piece of phosphor bronze a thousandth or two interference fit in the block. After pressing this in the seat needs to be reground since even with the utmost care it is almost impossible to get the new guide exactly concentric with the old.

An Engineering Works that works on old motorcycles probably would be a good place to get this work done. I wouldn't bother getting the special tools for this since you probably will never use them again.

Since propane has a much higher octane rating than gasoline, it would also be fine to skim a bit of metal from the cylinder head to increase the compression ratio.
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Old 12-10-2013, 08:02 AM
bluejean bluejean is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Have you ever rebuild a stihl chainsaw crankshaft, since there is no rebuild kit?

---------- Post added at 07:02 AM ---------- Previous post was at 06:32 AM ----------

I have a b&s 5hp engine with a exhaust valve being too loose. I'm starting to see a lot of the exhaust valves being loose due to the fact of epa regulated carbs (too lean), or lack of doing oil changes. There is a way to avoid this. Buy a older carb with adjustments, before a bad exhaust valve. Or replace valve guides ever so often. I bought briggs valve guide kit and i'm getting a too much play with the oversize valve. Has anyone used one of these kits and had tight tolerances? What can I do now? Trying to master small engine valve guide thing
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  #12  
Old 12-10-2013, 09:27 AM
I like oldstuff I like oldstuff is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Fungus, I've seen hundreds of Briggs aluminium block engines with a lot of valve guide wear and they run fine. For yours I'd just put a set of rings on the piston then run it. Some had an aluminium bore and some had an iron sleeve cast in. Be careful honing it if it's an alu bore as it's easy to gall the metal with a conventional hone. I'd take the block to a motorbike shop and have them do a light glaze breaking with what is called a ball hone. A new ring set and a few gaskets is probably around 45 gbp.

If the oil smoke stops you're in good shape. Sometime in the future you can always go back into it and replace the valve guides if you're bored.

The hardest part may be getting the generator rotor off of the tapered end crankshaft.
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Old 12-10-2013, 11:23 AM
Rob Kuhlman Rob Kuhlman is offline
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Default Re: Briggs stratton 8hp valve guide repair?

JonH -- Thanks for posting your photos of cutting and installing a valve guide on your 5s. I'm fascinated by your muffler! Is this home made? If so, can you tell us more about it? Thanks in advance!

Rob K.
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Old 12-10-2013, 11:49 PM
JonH JonH is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Thanks Rob. I found that muffler on E-bay a few years ago. The seller had at least two sizes like that. It was listed as a muffler for a Maytag. He built them with 3/4" pipe thread. I asked if he could build one with 1/2" for the Briggs and that is exactly what he did. It's pretty free-flowing so it makes cold starts tricky. Other than that, I like it. I did build the one for my REO.

Jon
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Old 12-25-2013, 11:17 PM
JonH JonH is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Bluejean, I've never pulled a Stihl down that far. You may find what you need on E-bay. If not, measure all bearings and seals (ID, OD, thickness). I expect they will be metric sizes. Inspect the faces for numbers that can be cross-referenced. An industrial supply house should be able to source your bearings and oil seals. If gaskets are not available either, measure the existing gaskets and any auto parts store should have gasket material in stock.

I hope that helps.

Good luck.
Jon
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Old 12-26-2013, 12:34 AM
Klicknative Klicknative is offline
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Default Re: Briggs stratton 8hp valve guide repair?

Any Stihl dealer can get the crank seals. A good one will have them on the shelf.

If you don't have a dealer close by try Madsen's.

http://www.madsens1.com/
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Old 12-30-2013, 11:26 PM
Tom Schaech Tom Schaech is offline
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Default Re: Briggs stratton 8hp valve guide repair?

All:

The key here is to identify exactly what engine we're looking at. I've done several valve guide repairs, all based on plug gauge reject measurements. It's actually quite easy as long as you take your time. That being said, a word of caution here regarding the "honing" or "glaze breaking" of aluminum cylinder bores. Briggs does NOT recommend any procedures of this sort. Their stance is to replace with standard bore rings if the cylinder is within tolerances or to oversize the cylinder to .010, .020, or .030 (based on degree of damage to the wall). Cast iron bores (block or liners) MAY get a LIGHT glaze breaking prior to replacing rings with standard ones. In any case, after honing, glaze breaking, or oversizing a cylinder you must wash the bore thoroughly with hot water and soap. Simply placing it in a parts washer or using gasoline/kerosene to clean the bore will not remove all the residue.

I agree that repairing an existing engine is most likely cheaper and preferable to replacing in most cases. As far as the breather goes, the orientation of the disc and oil return holes located on the breather assembly are critical to achieving proper crankcase vacuum. Get some good stout gasket material from an auto parts store if you're reusing the existing breather. New breathers will come with a new gasket.

I'm providing this based on many years of service on Briggs engines, as well as everything else that's come my way. Learned a lot, made mistakes, and learned from them.

Bottom line, to correctly recommend what you need to repair the valve guides we need the model number, type number, and code or serial number of your engine.

Good luck!!

Tom
Old Briggs Fart
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