Piston chrome or aluminum? - Need help

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shane73

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I need some help again. I have been reading on the subject for a couple hours and im going to continue but I am stuck. I need to make sure I have the right piston and rings. The motor is a 130212-1919 86082807 and it came in pieces in a box from a friend. He had bought an overhaul kit back in 2002. The box the motor came in was actually the box the overhaul kit came in when he ordered it and still had the packing/order list taped to it. The kit was this kit http://www.becoparts.com/cgi-bin/ez-catalog/cat_display.cgi?43X310997 #9702. It says the piston assy. is OE #298904/Our #3805 Piston - Std. If I go to the Briggs site and look at the diagram for my motor it says to use 298904 Piston Assy. (Standard). Well I just ordered my Arc rod from a guy and he mentioned something about did I need a chrome piston. After talking with him and reading the forums, I now know I may have the wrong one. I have an aluminum bore motor – even checked it with a magnet. The new piston I have is very shiny and a magnet does not stick to the piston either. I still have the original piston and both the new and old look just alike except for the new one looking new. How does one know for sure a piston is chrome or chrome plated?

This assembly (298904) came with new rings. The oil ring on the old piston is a one piece but the new piston has the 3 piece oil ring. Other than that the compression and wiping ring look the same. Is there a certain kind ring needed for an aluminum bore motor? I read the reason was two of the same type materials don’t make good friction together and they try to fuse together. That’s the reason for the different material but I figure rings would never be made from aluminum. I did wonder if a certain material works better with friction on aluminum so I thought maybe they still might be a certain type ring to use and I may be using the wrong rings.

Both pistons fit tight without rings on them in the bore so I know the bore is good (there are a few thousands around them – I can wiggle them a little). The bore is also smooth and looks pretty good. I can see a few vertical scratches but they are very, very minor. The old piston skirt has a few scratches on it for sure. I figured I could hone the bore a little but I think it will be fine so I don’t want to bore it or sleeve it. I have done spent way more than I wanted to on a yard kart but I also want it to be right and last a long time.



-Is my new piston aluminum?
-It was ordered by the part number Briggs said to order it by – should that say its chrome / plated even though it’s shiny?
-If my new piston is aluminum should I sand the skirt on the old piston and use it?
-Is the old piston aluminum? (looks like aluminum to me – just not new and shiny)
-Will the new rings work on the old piston if I have to use it?
-Do I have the correct rings?

I will try to take and upload some pictures so it can help you help me. Thanks in advance for help on this.
 
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shane73

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This still baffles me. I keep reading about this and it does make since to me. Aluminum against aluminum rubbing against each other at high speeds would seem to want to bond together. Especially if for some reason it didn’t get a significant film of oil to ride on. I even see some bright shiny pistons and some very dull ones out there. But… I have been doing a lot of reading and researching and I see Briggs made a lot of these aluminum bored motors. Now if you are a regular Joe Blow… My dad has one of these motors on his old log splitter. My brother has one of these motors on his tiller. My friend has one of these motors on his pull behind leaf vacuum. I have one of these motors on my son’s go-kart and the list goes on for thousands of people. Say these motors need a piston for what ever reason. These people instead of running the motor down to the local small motor repair shop, local kart shop these people will all buy their own piston online, from that local kart shop, or small engine repair shop and put in themselves. I would have not known the difference if I hadn’t of learned it by mistake. Also the thing is, all these places are giving people the wrong piston. You can pull up the Briggs parts replacement diagram for these motors and they all say to use 298904, 393819, or 555478 Piston Assy. You go online or the local places look up the number and it says replacement part number 793214. Now I keep reading where people are saying how hard it is to find a chrome piston now days and how high they are. Go online and do a Google search for part number 298904 which is thousands of aluminum bore motors out there and you will find thousands of places that have the piston, pin, clip, and new rings for $12 to $30ish. Most all even says Fits Briggs & Stratton 3-1/2 hp - 5 hp Horizontal Engines and I didn’t even think the 3HPs came with a sleeve. A lot of these places show the picture of the piston and its all bright and shinny. So what im so confused on is Briggs has sent these thousands of places the wrong piston assy., the aftermarket places are sending the wrong piston assy. out to resellers / dealers, and say they work with aluminum motors. The small motor places are selling the wrong pistons and people are buying and installing the wrong piston. The place mine was bought from is a very big local place that’s been selling "Quality Parts & Service Since 1920" and they are selling people the wrong piston to people. This model aluminum bore calls for x part number piston and that’s what they give you. Neither the brick and mortar stores nor none of the online places say anything about “if this piston is going in an aluminum bore motor, it will not work as good as a chrome piston” or “x part number has been discontinued or superceded by this part and the new type pistons are not specified to work in the older aluminum bored motors”. Just pretend you are the average person, working on a common aluminum bore motor still found out there today and you look up motor series 130200. It will tell you to use part number 298904. Go online or call your local place and I bet most are going to give you the wrong part for around $20 and never mention anything about the bore.

I have learnt “A LOT” from this place. A lot of the stuff I have been reading on and learning has come from posts from years ago up to now. I just wanted to figure this out so when someone comes here years from now with this same question / problem or do a Google search on the subject, they will have some kind of answer to it. These aluminum bore motors are still out there doing their jobs by the thousands. A lot of them will have a new pistons installed in them and someone else will be trying to figure this out.
 
newrider3

newrider3

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The problem is, most of the hard chromed pistons for Briggs 13 series flatheads have been discontinued. Most general lawn mower places won't even know the difference between the two, you have to talk to someone at an actual karting shop.

Also, the hard chrome coating used on pistons is not the shiny decorative chrome you're used to on car bumpers and such, it doesn't look much different than a non coated piston.
 
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