Aberdeen87....B&S help needed - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 16 Old 07-12-2019, 12:27 AM Thread Starter
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I have an old Ford rototiller with a 8hp Briggs and Stratton engine. I don't have the model number because someone took off the pull starter and the model number is supposed to be on the shroud. Anyway I need new valve guides because when I get it started it runs fine for a while but when I put it under a load it begins burning oil and could out the sparkplug. Does anyone know what model number I should look up to order new valve guides?
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post #2 of 16 Old 07-12-2019, 12:28 AM Thread Starter
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It was fouling out the sparkplug
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post #3 of 16 Old 07-12-2019, 01:51 AM
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re: Aberdeen87....B&S help needed

Hi Aberdeen87, and welcome!

If you could post some pics of your tiller, that'd help immensely. The easiest way to do that, if you're using a desktop or laptop computer to cruise the forum, is to click the little paperclip button in the button bar of your post editor window. That'll let you attach a photo to your post. Let me know if you have any questions about how that works!

Again, welcome to MTF!
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post #4 of 16 Old 07-15-2019, 11:02 PM Thread Starter
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[QUOTE=littletractorguy;12304003]Hi Aberdeen87, and welcome!

If you could post some pics of your tiller, that'd help immensely. The easiest way to do that, if you're using a n or laptop computer to cruise the forum, is to click the little paperclip button in the button bar of your post editor window. That'll let you attach a photo to your post. Let me know if you have any questions about how that works!

Again, welcome to MTF![/QUOTE )

Hello little tractor guy. Thanks for the warm welcome. As you can see from the picture it's a model RT8 don't know for sure but I think it was manufactured in the early 80s or late 70s I found a pull starter that fits perfectly but it's been so long since I put it on I that I can't remember what model numbers it fits. I removed the head and cleaned the carbon from the valves and installed a new head gasket. I let it run for about 15 minutes and it did fine at idle with no load so I throttled it up and started rototilling my garden. It did fine for a short time but then began to smoke and after about 10 minutes it fouled out the sparkplug. So I am pretty sure it is the valve guides that needs replacing. Thanks again for the welcome and I would appreciate any info you or anyone else might be able to provide.

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post #5 of 16 Old Yesterday, 02:28 AM
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re: Aberdeen87....B&S help needed

Hm. Definitely an older Briggs, that's for sure, looking at the carb. Unfortunately, I'm not much help on the older Briggs. How about I move this thread into our Small Engine section and we see if any of the small engine gurus can give you some insight...
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post #6 of 16 Old Yesterday, 07:49 AM Thread Starter
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That sounds good. If I could just get a range of model numbers then maybe I can narrow it down.

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post #7 of 16 Old Yesterday, 11:45 AM
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Re: Aberdeen87....B&S help needed

Roto-Tillers sometimes foul the plug due to it being tipped up and the shaking & bouncing the machine gets subjected too--oil level in the engine when tilted enough can get into the crankcase breather and the oil gets in the carb thru the vent hose and eventually fouls the spark plug..

If it is the valve guides I'm not so sure the engine HAS any,they may be just holes bored in the block,and to fix it Briggs may have had valves with oversize valve stems available that require the holes to be reamed out to the correct specs to restore the proper "fit"..

A machine shop might be able to bore the holes out and install a bushing or sleeve also..
These engines are still pretty common despite their age,I see many for sale often for cheap money..so many won't spend any money trying to fix a problem like this,they just look for another good running used one instead..


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post #8 of 16 Old Yesterday, 02:33 PM
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Re: Aberdeen87....B&S help needed

What color was the smoke? If black, you are likely having a carburetor problem where the fuel level in the bowl is getting too high. Could be the bouncy-bouncy of tilling, or could be a worn float needle valve allowing fuel to raise too high.
If blue, it's likely oil. That could be level related. I think these B&S need the oil level checked while level, which is not fun on a tiller(how do you make it stand up level?). The oil should be at the 'notch' in the threads which the filler cap screws into, or the bottom of the threads if there's no notch, or on the hash marks if it has a dipstick. If too full, it will cause too much oil to get onto the cylinder walls for the 'oil control' rings to push it back down into the crankcase.
Sometimes engines that have been allowed to grow lazy, and sit around a shed for long periods of time(tillers... used in the spring, put away wet), will have sticky oil rings. Changing the oil, or using some ATF in the crankcase and running until hot will sometimes loosen the rings if they are gooey in the grooves of the piston. Even taking things apart, cleaning the piston, rings, etc, and putting back together can make the thing start to run better and lessen oil consumption and that bad habit of smoking while on the job.
They were designed for using straight 30W oil, detergent or not, and may consume more lube than normal if multi-grade oil is used. So, 10W30, 5W20 or 5W30 are not really the oils to use in normal summer weather. If you decided to get an early start, and till when it was cold, they would be fine. I'd go with straight 30W in spring/summer.
Check the air cleaner also as it may be an 'oil bath' cleaner. They have a trough of oil at the bottom, and force the incoming air to 'go around a corner' near the oil. Generally, heavier particles, such as dust, will not corner well, and will get trapped in the oil, allowing clean air to make the curve and feed the carb. If overfull, or there's water in the trough upon which the oil is riding, you'll tend to starve the engine of air, and suck oil in with the incoming air. Blue in two... seconds of operation..
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post #9 of 16 Old Yesterday, 05:40 PM Thread Starter
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The smoke was definitely blue and was not over full or being bounced around too much. I had read that you have to drill them out and then install new guides or like a sleeve and don't really need a machine shop to do this as long as you use your good eye and don't get off kilter.
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post #10 of 16 Old Yesterday, 05:48 PM
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Re: Aberdeen87....B&S help needed

Maybe pull the head and have a rummage around inside... seeing is often worth a thousand speculations.


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post #11 of 16 Old Yesterday, 07:26 PM Thread Starter
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Yeah I pulled the head and had a lot of carbon buildup on the valves. Cleaned them good installed a new head gasket then started it up and let it run for about 10 to 15 minutes and it did fine then I started to till with it under a load and after about 5 minutes it started smoking bad and finally fouled out the sparkplug. Pretty sure it's valve guides since they don't have valve seals. Just need to know if someone might know what model numbers to look for since someone removed the original pull starter and the model number is stamped on the shroud. I put on a new pull starter and shroud but can't remember what model number I used. The pull starter part number was 693900 suppersed number 390391.
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post #12 of 16 Old Yesterday, 09:15 PM
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Re: Aberdeen87....B&S help needed

It will be a model 190402. There are no oversize valves, the guides need to be reamed out and sleeved. Briggs has the guides and required tools but you need to go to repair manual 270962 for the numbers. I would be more inclined to check for a ridge at the top of the cylinder and piston slop indicating wear.
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post #13 of 16 Old Yesterday, 09:51 PM
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Re: Aberdeen87....B&S help needed

Hm... found a post online from somebody with a Briggs model number

190402 Type 0831-01 on his tiller from 1976. Lemme see if I can figure out the Briggs manual finder, it wants the entire model number, not just the first 6 digits....


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post #14 of 16 Old Yesterday, 10:06 PM Thread Starter
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Thanks guys I will look at those and see what I can find. Will look at cylinder carefully also.
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post #15 of 16 Old Yesterday, 11:45 PM
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Re: Aberdeen87....B&S help needed

Wow... These B&S service manuals for the older engines are harder to find than the Deere ones even! Their manual finder only does owners manuals, not service manuals... bummer!
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