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Need HELP with low compression on a Briggs Model WI

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Old 09-18-2019, 01:03:17 PM
buckeyewalleye buckeyewalleye is offline
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Default Need HELP with low compression on a Briggs Model WI

Hi Guys - I bought a Briggs model WI with no compression. I lapped the valves, cleaned the head, and poured about 3/4" of PB Blaster (4-5 times) in the cylinder and soaked it the to see if the rings were stuck. The PB Blaster SLOWLY drained down passed the rings and into the oil pan. Again, I did this 4-5 times with the PB Blaster and it drained down everytime. After that, I put oil in the cylinder and rubbed it all around the cylinder wall and I put it back together thinking the rings are not stuck. Now, I only have 30# of compression in the engine. Good news is that it's holding the 30#. What else can I do to get compression???

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Old 09-18-2019, 02:18:07 PM
Andrew Mackey Andrew Mackey is offline
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Default Re: Need HELP with low compression on a Briggs Model WI

Unfortunately, PB will not always free stuck rings. It will not fix worn or broken ones either. If you have no gasses getting by the valves, there are 2 things you can do, but there is a question to ask first. Does the engine bounce back against the compression stroke? If it does, you can try belting the engine and turn it fast enough that it will start. Once the piston gets hot, the rings may free up, raising compression. If it just mushes to a stop, then you have no choice but to remove the piston and check out the rings. If they are stuck, free up and re-check compression. If free but worn, replace, hone the cylinder lightly, and re-assemble. If the cylinder is badly scored, you may have to bore and install an oversized piston and rings, if available. These engines dont have much compression to begin with - 50-60 PSI tops. It should at least to attempt at 30, unless it just mushes as I described earlier.
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Old 09-18-2019, 03:37:34 PM
K-Tron K-Tron is offline
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Default Re: Need HELP with low compression on a Briggs Model WI

I never run a newly acquired engine that I have not pulled the piston out of. If the rings are stuck there is a good chance that they will do some damage when they free up under any form of load. Opening up the crankcase gives you the opportunity to clean out decades of sludge, check & access the condition of your rod and crankpin, and allows you to remove the piston to clean/remove the rings. With 30 psi of compression, either your rings are stuck, worn out or missing.

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Old 09-18-2019, 08:58:55 PM
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Motormowers Motormowers is offline
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Default Re: Need HELP with low compression on a Briggs Model WI

Ring sets are cheap and you can make a pan gasket easily. I would say drop the base and pull the head again and remove the piston assy. If the rings are stuck just replace them. If not remove them from the piston and check end gap in the cylinder. Just a light hone and new rings will make a world of difference if the cylinder isnt wiped out.
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