minimum compression


Old 06-26-03, 01:20 PM
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minimum compression

I have recently put new rings in a 5 hp Briggs&Stratton engine
as they no longer furnish a short block and this engine was blowing smoke and messing up the spark plugs.
After work completed, I have a compression of 30 psi, however
the engine will not start. By taking the spark plug out and grounding it to the block, there appears to be sufficient fire. Timing has been checked and rechecked and looks good.
Will having the cylinder ground and new piston and rings installed help? Testing other small engines and the psi is around 60.

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Old 06-26-03, 08:36 PM
J A Boggan
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Did you grind your valves, lap them in and check your valve's real important to have the proper valve clearances. If you will post your model number and type number, someone will give you the proper clearances. Try this first, then you may have to do some work on your carburetor.
Old 06-27-03, 04:29 AM
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It does sound as if the valves may need to be checked. Exhaust .011, intake .007. That is for the L head and going on the fact you can't get a S/B that must be what you have. 30 lbs. is not enough to run even poorly. Boring over and new parts would certainly get the compression up if all is in order.....Mike

Last edited by mikejmerritt; 06-29-03 at 07:39 PM.
Old 06-29-03, 05:39 PM
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Thanks for the response.
Looks like I will have to have the engine bored , valves ground, lapped and clearances evaluated. The engine is a Briggs & Stratton Model 130292 type 0793-01. This engine is for a Troy-Bilt rototillerwhich is in great shape.
This will be my first in depth overhaul of a small engine. All people I have checked advises it is cheaper to replace with a new model than their costs to overhaul.
As it seems I have nothing to lose, any obvisous pit falls to this undertaking will be appreciated.
Thanks again...
Old 06-29-03, 07:48 PM
J A Boggan
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According to factory specs, the valve clearances should be Intake - 0.005-0.007, Exhaust - 0.009-0.011. Cylinder bore is 2.5615-2.5625. Examine it real good and make sure there isn't any scratchs or scoreing in the cylinder. If there is it may be more economical to go with a short block. Also see what shape your valve guides and seats are in. You might need new valve guides. In order to do a first class job on the valve seats you need a valve seat cutter such as Neyway. You may also need a valve guide reamer. If you go to and put in your model number and first four digits of your type number, then click on view PDF, you'll get an exploded view and parts list. You'll need "acrobat reader" on your computer...if you don't have it, it's a free download.
Old 06-30-03, 12:30 AM
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They are right, a new engine can be purchased for around $200.00. By the time you buy rod, rings, piston, gaskets and seals, and have all that work done, you will have close to that much or more in it, and it still won't be a new engine. I would check the valve clearances, they are probably too tight.
Old 06-30-03, 09:48 AM
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Also, could be a worn cylinder. Did you check your ring end gap with the new rings???

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