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View Full Version : Shop related S.O.T. B&S Quantum 657 series question



PTSideshow
06-17-2009, 04:57 PM
I'm curious if any of the assembled body has had any problem with the B&S Quantum series 675 6.75Hp. The valve seats popping out or valves, springs etc. More specifically the intake side.

I have a Tory-built model 070 chipper/vac/shredder. I was shredding some mulch yesterday as this years bagged batches is to many to large chunks. Making it difficult for the wife to walk on it in the garden. She has MS and arthritis, so I was shredding it and when the bag is removed the safety shuts off the engine. It was working at full speed and song when it stopped as I removed the bag and emptied it. and refilled the gas.

When I went to restart it it didn't want to start. So I cleaned the air filter,carb and started it. It would only work at about half speed and slowed up when I put the air filter back on. It ran only slower than normal. It chipped fine but at a slower rate.

When I removed the fliter on the side facing the carb and engine there was oil on it and some slight oil smoke is coming out.

Spraying carb cleaner, slows it down almost to a stop. It is making only normal sounds like it was brought home it is about two years old.

I haven't put the bore scope camera in the plug hole yet or done a compression test yet. As it is raining out, and I don't have room in the shop :rolleyes:
I know if the vanes in the head and engine block are plugged and dirty it can cause the seats to pop out. The vanes are clean and have been washed once this operating season.

Any body have any suggestions or comments. The
questions section at the website for small engine repair isn't working. http://www.small-engines.com/index.html

And really hasn't been updated since 05 with these new B&S Engines.
My last B&S factory training class was in the late 70's early 80's and these new engines seem to be a whole different really cheaply built engines.
Thanks :D

Carld
06-17-2009, 09:26 PM
Hmm, I was a Briggs dealer in the '70's too. I would check the comp. first and does it have oil and does the engine turn over easy without the plug.

Have you tried squirting gas in the intake while it is stumbling along? Have you checked the ignition, I think all of them are electronic now.

Over heating is what usually causes the valve seats to get loose. Usually when that happens the engine makes all kinds of noise just before it locks up though, especially if it's an overhead valve.

PTSideshow
06-17-2009, 09:58 PM
Hmm, I was a Briggs dealer in the '70's too. I would check the comp. first and does it have oil and does the engine turn over easy without the plug.

Have you tried squirting gas in the intake while it is stumbling along? Have you checked the ignition, I think all of them are electronic now.

Over heating is what usually causes the valve seats to get loose. Usually when that happens the engine makes all kinds of noise just before it locks up though, especially if it's an overhead valve.

Yes to oil, pulls just like it did before, no change, it starts haven't pulled the plug yet. It slows up more with spray into the intake.

Shouldn't have had an over heating problem as it hasn't had plugged vanes or anything to impede the air flow to cause over heating. Had it running for about 40 minutes off and on after it started acting up.

rockrat
06-17-2009, 11:21 PM
I always start with bad gas, air / fuel mix, spark and then to compression. The first is easy. Look in the can you use to fill it. At one point, mine had a pinch of grit in it and I had to separate it out. After a carb clean I was back running again. Smell varnish? Time to change the gas.

The mix issues could be anything from a loose carb from all of the vibration to a screw for the jet backing off.

Compression, I was told (and have used) the old, pull the plug and put your finger over the hole trick. If when you pull the cord your finger gets pushed off then your good. But watch the head temp when you do this. Dont want a burned digit. And dont get near the coil wire when doing this or you will be testing the coil at the same time.

Spark? While the plug is out hook the coil back up to it and ground the threads of the plug to the motor housing. Pull the cord making sure to keep yourself away from the metal and other shocking areas. The spark should be blue or white and easily seen in daylight. If not, it could be the coil. Not uncommon for small engines. Heat will drastically effect these things. The coil should be spaced away from the flywheel correctly. I have been shown and still use a business card for the spacer. All of the rust and crap should be off of the coil and the flywheel before doing this.

Now specifically on a chipper, I did notice that the one I borrow would wrap strings around the area between the cutting disk and the housing. It would run slow and never reach full rpm. But that was only when chipping green branches.

Ok, there are my thoughts for what they are worth.
cheers~
rock

Rustybolt
06-18-2009, 08:05 AM
The valve seat popping out is prettty common in B&S smaller motors, at least in everyone I've owned. When the valve is all the way down the seat will go back in. Take a center punch and go around the edge a half a dozen times . Center punch the soft material around the valve seat. You don't have to hit it real hard, just raise dimple to secure the seat. You won't have a problem after that.

PTSideshow
06-18-2009, 09:25 AM
The valve seat popping out is prettty common in B&S smaller motors, at least in everyone I've owned. When the valve is all the way down the seat will go back in. Take a center punch and go around the edge a half a dozen times . Center punch the soft material around the valve seat. You don't have to hit it real hard, just raise dimple to secure the seat. You won't have a problem after that.

Thanks will keep that in mind, if it doesn't correct it self after flushing the gas (fresh in the last 3 weeks) and cleaning the carb out.