B&S 18 HP valve Adjustment

skjl47October 25, 2010

Hello; I decided to adjust the valves on a B&S 18 HP twin today by following the instructions from another post. The engine is MODEL 422707; TYPE 1522 01; CODE 9308185A. I could not see a rocker arm cover after removing the shielding, so I stopped and put everything back. I could see a finned cylinder head in which the spark plug is located. I suspect this engine does not have adjustable valves such as those described in Vanguard/ non Vanguard valve adjustment post.

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Though the valves are adjustable, in a grinding cutting kind of way- they require the valve be removed from the block to do so. So no actual adjuster. The good news is, this "L head" engine doesn't have the same issues as the OHV family and rarely ever need valve service at all. Are you having difficulty cranking the engine over?

    Bookmark   October 25, 2010 at 5:59PM
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Your engine is about 17 years old and a valve clearance check is probably a good idea. Valve clearance will probably decrease on a flathead engine with a lot of hours. Special tools are required to perform adjustments. This would be a good time to refinish the seats and valve faces.

This has been a great engine for Briggs and for homeowners. To achieve even longer life, pull the sheetmetal off to inspect and clean the cooling fins. Obstructed cooling fins can result in overheating and failed valve seats.

    Bookmark   October 25, 2010 at 6:17PM
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Hello; You have confirmed what I thought. While I have a decent collection of tools, I likely do not have anything close to the special tools mentioned. The engine does seem to bog the starter when first cranked. It has started each time so far. When warmed up there is a tick from what I suspect is the valve train. The mower is my neighbors and I do not know how deep he wants to get into it (It may be more than I want to tackle, I will have to check into what is involved.) I did check the cooling fins today. I have cleaned the battery posts, dismantled - cleaned and adjusted the carb, changed the oil and set the choke. It was running very rich before, but the plugs looked much better today. can anyone tell me what the plug gap is? thanks for the timely response.

    Bookmark   October 25, 2010 at 10:21PM
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The ticking valve train may indicate excessive valve clearance. Excessive clearance may increase compression and overload the starter.

The special tools required for valve work are: (1) valve spring compressor (2) grinder that will grind valve stems square. I use v blocks with a fly wheel grinder. (3) valve seat grinder (neway has a good tool kit) (4) valve face grinder.

before calling the local dealers to see who has the equipment, check the clearances. If clearance is within limits, you will need to decide if performing the work is justified.

    Bookmark   October 26, 2010 at 12:05AM
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Hello: I do not have actual working experience with an L head engine. I think the valves are in the cylinder and not the head. I an unsure of how to get at the valves to check the clearance. I hope to find a repair manual or instructions somewhere. At any rate I do not have the tools for the valve work. I will find out how to check the valve lash and then determine if I want to continue. I like tools and have a number purchased for one job and never used again. This sounds like one of those situations. I sometimes work it out that I do the work for someone if they allow me to keep the special tool as payment. I now only do work for friends anyway. Is there anything else I can do to tune up the engine? Thanks

    Bookmark   October 26, 2010 at 10:07AM
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Coolimng fins clear, cleaning the carb that you did is what keeps these running. My personal experience is when decarbonizing the heads- that not much build up occurs unless they seem to be oil burners. I suppose one could justify it in your situation. You will need new head gaskets if you do. If you pull the 2 small rectangular covers on the front, that would give you access for the valve lash. Again , new gaskets will be needed. Watch over the back cover for leakage whilst you are gasket shopping. Once you've cleaned and checked the battery and other terminals associated w/ the starting system , then how is cranking? With all those bases covered and being good- one would think the starter is worn or tired and is affecting the cranking. Had the owner any other reported issues?

    Bookmark   October 26, 2010 at 12:13PM
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If you are experiencing cranking problems, I have a list of some of the common causes for this. Address below, put in proper format and remind me. It is difficult to remove the tappet/crankcase breather to check the valve clearance without removing the Intake Manifold. ALSO, as with almost all of their engines, B&S recommends checking valve clearance on this engine with the piston for the cylinder being checked down 1/4" past TDC. Hard to determine on this engine since the spark plug hole comes in from the side.

You should be able to download a free Service Manual for your engine at - http://www.mymowerparts.com/pdf/Brig...Spec%20Charts/

Walt Conner
wconner5 at frontier dot com

    Bookmark   October 26, 2010 at 12:24PM
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tomplum is on the mark here. These starters are straddling the fence between being just strong enough to crank the engine, and being woefully underpowered even when everything is brand new. Therefore, it is vital that all electrical connections in the starter circuit be in top condition.
This means clean and secure ALL battery cable and starter cable ends.......hots and grounds both.
I could send you some literature if you send me an e-mail.

    Bookmark   October 26, 2010 at 12:29PM
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Thanks for the input. I will check the rest of the electrical connections. I have not run the engine enough to know about oil consumption yet, but it does not seem excessive. Maybe two hours mowing since work was done on the carb and no additional oil needed. Before cleaning and adjusting the carb, the plugs were showing buildup from the overrich condition. One plug showd some oil fouling, but it was only in finger tight. I looked at the plugs yesterday, they were both looking much better. I think we are finished with mowing here for the season. My yard is self cleaning so far with regards to leaves. Storms scour them away, but it is early yet. We are having strong wind today. Thanks again. As with everything new to me, there is an amazing depth of detail to absorb. I hope to help keep my neighbor's mower going long enough to help me to decide on what to buy based on good information.

    Bookmark   October 26, 2010 at 1:22PM
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For the least amount of effort to check the valve lash. Rotate the flywheel by hand and feel for the compression stroke. The next stroke is the combustion stroke. Both valves are closed and the valve lash can be felt as the springs unload their tension to the valve seats. Just past top dead center listen for clicking noise. The louder the clicking the bigger the valve lash clearance. I think it should be .004 to .007 for intake and .007 - 012 for exhaust. A very inaudible click if valve lash is within specs. You should remove spark plugs and put thumb over plug hole to feel compression stroke. Airplane mechanics use this technique to find TDC.

    Bookmark   November 20, 2010 at 12:42PM
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What would be causing the clicking sound when rotating the flywheel by hand?
Do you need a stethoscope to hear it or just a pair of ears?

    Bookmark   November 20, 2010 at 2:51PM
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