Brigss & stratton "ready start system", I'm stumped

[ILENGINE]

I went back and read through the list of post and from the description of the problem you have a compression problem. Even with compression release anything below 60 would be suspect. 600 rpm should be achieveble with a rope starter, that is only 1 rev per second. the original magnetron was set up to fire above 600 rpm. the newer systems are set up for 250-300 rpm on briggs. the origian tecumseh and kohler CDI are 300 rpm systems.

Sounds like you need to do leakdown test to determine cause of low compression. Most likely valve leaking issue. I have seen valve seat not be cut square with the valve face on brand new engines. As well as improper valve clearance gaps.

 

[mr.farmall]

ILENGINE:
Thanks for the specs on this engine.

600 rpm should be achieveble with a rope starter, that is only 1 rev per second.

I'm not sure I can get up that high with a pull rope. I think 600 rpm's = 10 revolutions per second, you must have mistyped a "0". When I use a drill to get it that high,it is spinning quite fast and it still takes 4-5-6 seconds to get the first pop , then another second or two to get it started.

the original magnetron was set up to fire above 600 rpm. the newer systems are set up for 250-300 rpm on briggs.

I must have one of the newer ones since I am getting a spark at about 300 rpm's

Even with compression release anything below 60 would be suspect.

I spun the engine over with the compression gauge attached at different speed. Up to 250 rpm's I hardly got a reading, at 400 rpm's It was about 6,PSI, at 600 rpm it had climbed to about 30 psi, and at 800-900 rpm's it topped out at 62 psi. It never increased from that point no matter how fast it spun.

Sounds like you need to do leakdown test to determine cause of low compression. Most likely valve leaking issue. I have seen valve seat not be cut square with the valve face on brand new engines. As well as improper valve clearance gaps.

I don't have the leak down tool, but I do have an air adapter that screws into the spark plug hole. I set the pressure at 60 PSI to try it out. It immediately spun the fly wheel moving the piston to the bottom position. At 60 psi it was hard to hold the flywheel from moving except at the TDC location. Any slight movement wold set it spinning back to the bottom without some leverage to hold it in place.
At TDC I could hear and feel air coming out of the Exhaust. All the valves should have been closed at that point. It looks like I'll revisit the valves again to see if something forieng is on the seat or valve holding it a little open.
Were can I get info on the seat angle for these valves?
Thanks

 

[Rivets]

This manual might help.

http://dl.dropbox.com/u/12502267/B&S Service Manuals/01_270962SingleCylinderLHead.pdf

 

[mr.farmall]

Less than 5 lbs. compression? Oh man! I'd focus on that. You've got a compression problem.

Took the valve system apart again today. Clearances are 6/1000's and 9/1000's. Seem to be good until I decided to re-seat the valves with a little re-seating grit compound. The exhaust valve cleaned up in only one small section, about 1/6th of the valve's circumference, but all of the valve seat had a nice seating mark left. I have a bent valve. I placed a bright flashlight in the exhaust port of the block and you could see light coming out of 5/6th of the valve seat with the valve in the closed position. This must have came from the factory this way. Their are no marks on the head nor any on the valve seat. I thought they started every engine after they were assembled. Maybe things have changed now that many are built in China.
It helps to pay attention to the facts from the testing!
Thanks LZN and all others
I have a new one on order and should be hear by the weekend.

 

[lzn197]

You might as well go ahead and fix it. You are almost there!

Another issue that is quite common with smaller, push mower engines that causes compression loss is the valve seat. The poor thing gets cocked in the bore and now the valve cannot seal. Why does this happen? I have found it is because customers either overload the engine with tall grass and a dull blade or never clean the cooling system and the engine gets hot. It also can be the seat or the bore were not to specs and with use over time, the seat comes loose.

I am happy you found the problem. It takes Air, Fuel, Compression and Spark to get an engine to run. Any kind of disturbance with any of them, and the engine (as my Daughter says) will not GO.

Also many thanks to ILENGINE for backing me up and the additional information he shared that was right on!

Gordon

 

[mr.farmall]

You might as well go ahead and fix it. You are almost there!

Gordon

The parts came in today, The exhaust valve looks good, but the plug they sent, the one on their look up screens, it is a RJ19LM, the wrong spark plug. Looks as if they need to upgrade their info. I called Briggs support just to make sure and the lady on the other end of the line verified that in deed it was now a RJ19LMC, so she is sending one out, should be here the first of the week. By the way, the original plug RJ2YXLE is very elusive. It's not on the Champion plug chart and even the Briggs people couldn't find it on their records. No matter, it is now superseded with the new one. I'll let you know how it all works out next week.
Thanks Everyone, your help is very much appreciated.
Rex

 

[wjjones]

I got nothing that is a very strange issue though I hope you figure it out as it will help alot for future info.

 

[mr.farmall]

A big thanks to everyone:
LZN197 pointed at the compression, but was overlooked while preoccupied with the spark.
EngineMan pointed at the Magnets a major component in the spark
Tybilly suspected trouble with the Magnetron, another major part of the spark
Pugaltitude gave info on proving the spark to be good and the new info on the spark plug. (much needed)
Ilengine re-pointed back to the compression and the leak down test (Invaluable)
rivets had the manual for the valve info.
and Wjjones, Yes it is fixed! Yeppi!
I got the valve clearance set by grinding the valve stem to allow 8/1000, then seated the valve with lashing compound. It seated very true, no valve seat problems.
After it was put back together, the compression was 37 psi @ 100 rpms, 70 psi at 300 rpms, and it topped out at 110 psi @ 600 rpms and above. With a new and correct spark plug, I prepped the engine and it started on the first pull. Not even a hard pull, but something my Lovely wife could do!
For a new machine that was given up as Junk after just a few lawn mowings, I think it has many years of service left in it.
Thanks everyone and I hope this will be of help to someone in the future.
Rex

 

[EngineMan]

Nice one Rex....:thumbsup:

 

[mr.farmall]

Re: Brigss & stratton "ready start system", I'm stumped----- now a follow up

[/B][/B]A follow up after using the mower for half the summer!]
This engine starts incredibly easy. My wife loves it!!
But their is one problem I have found, and it is very annoying; starting the engine after it has set in the sun on a hot day. It will not start. It just floods itself until the plug is fouled.
I have tried removing the plug to dry it off, but it just fouls again. I let it set in the shade for a couple of hours and it starts right up again.
To over come this, I hooked a wire over the wind vain arm of the choke mechanism, pulled forward to operated it as if in the hot engine position ( doing the same thing the thermostat would do on a hot engine) and had my wife pull the rope. It started on the first pull.
I have had this experience 5 or 6 times now and am convinced that the engine needs no chocking when the outside temperature is this hot and sunny, but the engine is still cold, (relatively for and engine). The ready start system is still not hot enough to stop the chocking.
Once started and ran for as little as 30 seconds, the engine heats up, the thermostat operates, and the chock is removed just as it should. Re-starting now works great.
I'm about to permanently connect a pull wire that can be temperately latched to hold the chock open and then be released after start up, but would not interfere with the ready start system unless it is latched open. This would greatly reduce my frustration on these hot sunny days, allow me to start the engine by myself, and also let the system work normally on all other days.
I hope this might be of help to someone experiencing this problem on their engine.
Thanks Rex