HI need some help with this one. I picked up a lawn mower that looked to be in really good condition, no identifying marks other than VIP on the front but the engine is a fairly common B&S probably 3.5HP. Model 92908 1818 Type 1 Code 79020208 I will post a couple of pics which may help identify it. Started out with no spark and I discovered that the condenser (capacitor) was faulty but just happened to have an electronic ignition on hand, which gave me good (not great) regular spark. Turning the motor over with an electric drill (poring fuel in the carby) I got an occasional fire but certainly not looking like running. Tested the compression only 50psi, so I assumed it was a piston or rings, pulled it apart and found them to be in excellent condition, I removed the top ring and tested it in the bottom and top of the cylinder, it was pretty similar top and bottom with a gap that I thought was probably about right, I didn't measure it but about 3 millimeters. I did discover what I suspect was a burnt exhaust valve. Spent a bit of time on that and managed to get a compression reading of 60 PSI, but no firing or looking like running. Pulled the head off again and spent a lot of time lapping the valves, reassembled and tested not firing and only 50PSI (The earlier reading of 60 is more than likely an anomaly rather than having gone backwards) The head, head gasket, and top of the cylinder appear to be in good condition. There are some vertical scratches in the cylinder which you can feel with your fingernail you can see them in the photo, I have seen worse on engines which still ran. Valve clearance is intake 0.004" exhaust 0.005" Possible places where I have messed up: Cam shaft timing. I just lined up the marks on the camshaft and crankshaft gears with both valves closed and piston at TDC. When I turned the engine over it seemed logical but could have used a little more thought. Valve Lifters, I didn't look at these and just assumed they were both the same. It is possible that the exhaust valve is bent but it did lap in very evenly. I cannot see that the head or cylinder are cracked but I know that on car engines they often use a special chemical to detect this. The head and cylinder do not appear to be warped but I can only test this with a straight edge and think I would be able to see some blow past evidence on the gasket if that was the case.
At this stage I am thinking that the smart thing to do would be to retrieve my electronic ignition and drop the rest at the tip, but reluctant to give up after investing this much time. If anyone has any suggestions, I am happy to try them out, but may not get to it until after Easter.
Wishing you all a Happy and Safe Easter
If I can get a large enough hammer it will run for awhile just trying to get away from me
The first thing I like to do with a motor that won't run by putting fuel down the carby is to use a coil and spark plug from a running motor as I have fitted coils many times from old engines and they don't work.
You could disconnect the kill switch wire from the coil just in case the switch is loose and earthing out intermittently.
Hi Byomarimba. There is a mark on the cam gear which aligns with a mark on the crank gear. This does not necessarily happen while you're at TDC. Once you've done that recheck your Valve clearances at TDC (In 0.08 +-2 and Ex .0.08 +-2)
Another thing worth checking is to see if the key slot in the flywheel lines up with the key slot in the crankshaft otherwise the timing will be out and this will stop the motor running.
Also don't attempt to start the 4 stroke without the blade plate or cutter bar attached.
Thanks BT and Max for your input, If all I need to do is align the marks on the camshaft gear and the crank gear as per Big Teds video than I have that right. I was thinking that as the big one goes around once and the small one goes around multiple times than maybe there would be a single starting point. Once again thinking has resulted in a red Heering. I am guessing that my valve lapping has reduced the valve clearances and I can fix this by putting a file in-between the valve stem and push rod and wearing them down a little
Max's suggestion of a new coil is a good start, but I may have to wait awhile to come across one. I have checked the crank shaft key alignment and found it was a fraction out, so I removed it and although the key is in pristine condition there is a little room for movement, so I have reinstalled it resisting the temptation of holding the flywheel when tightening the nut, so it is pretty straight now. Picture is from before. Not sure about Max,s suggestion that I should not run it without the blade plate attached, can't see why that would make a difference but I will put it back on and see what happens.
In the meantime, as I have assumed that only 50PSI compression was my problem, and that may not be the case, I have good spark (but lacking the technology or know how to shrink the video file size so all I could do is shorten the video), the possible explanation is that I have put the electronic ignition in incorrectly. I have used these twice before (a Stihl chainsaw, and a very old B&S) with excellent results but this was a different module from a different supplier and the instructions were a little lacking (just a picture). As there is only two ways it can go its a 50% chance that I got it wrong.
I will give that a try while waiting to come across another coil and keep you posted.
If I can get a large enough hammer it will run for awhile just trying to get away from me
Not sure about Max,s suggestion that I should not run it without the blade plate attached, can't see why that would make a difference but I will put it back on and see what happens.
If the cam timing is right it sounds like this engine won't run because there is no flywheel mass. I can see the spark, The blade plate acts as a flywheel because the actual alloy flywheel hasn't enough weight to keep the engine in motion. Without the blade plate the flywheel key will break as the motor kicks back when firing.
A flywheel serves a few main purposes (in most applications): It provides mass for rotational inertia to keep the engine in motion. It is specifically weighted to provide balance for the crankshaft. It provides a means to get the engine started.
Thanks Max I have put the blade plate on and swapped the leads on the the electronic ignition. No spark at all. I was really hopeing that would be the answer.
Changed the ignition back plenty of spark. Tried it with a couple of different plugs, both spark well outside the motor, but it does not fire. Not even once. Even tried putting petrol directly into the plug hole. Does not seem to make sense, got spark, got fuel, it should ignite something. I have turned it over with a drill for more than a minute.
Only things left I can think of, Increase the valve gap New fuel (unlikely only filled it a month ago) A longer reach plug, (it looked OK when I had the head off, so not much room for more) My compression guage is about 30 years old but you would expect it to under read rather than over. The electronic ignition is not firing at the correct time (I could try to find a capacitor for it and put the points back in)
If I can get a large enough hammer it will run for awhile just trying to get away from me
Hi Byomarimba, As long as the valves have no weight on them at TDC then increasing the gap won't help Month old fuel is not the problem Longer reach plug won't help Compression gauge won't give you a true reading although spinning it with a drill might get it close Electronic coil should be spot on but try another coil if you have one but I doubt this is the problem
I'd take the muffler off and start the engine without the muffler as it could be blocked (baffle could have come loose etc)
I usually just use a spark plug that runs in another mower that way I know it's not a spark plug problem as some plugs spark on the outside but don't spark when installed this can be the same for a coil ,when I get a problem like this I like to test the coil on another motor that runs as this rules out a spark problem.
Thanks Max I will try to get the muffler off and swap out a working plug, may need to make a trip to my favourite shop, (the tip) and see if I can get another coil (only problem with that is I will need to get that mower running first to see if it's any good). Most of what they have there is newer than this one but it's probable that the coil will be the same. A few years back when I had an old Viĺiers reel mower I was trying to get running the bloke who rewound the coil and recharged the magnets gave me a capacitor, it's around here somewhere, if I come across it I will put the points back in and try that. That will take a few weeks so may be awhile before I report back. In the mean time if there is anyone in WA who wants a few spare parts and are willing to collect them from City Beach I am your man, at least 3 good wheels. In the back of my mind when I get it running it is not going to be a particularly good mower. The old villiers has become a feature piece for a mate of mine but can't see any one wanting this one. But it would be nice to see it run. My fishing buddy will be back in a couple of weeks so there may be a change in hobbies. Thanks for your help with this and I will report back with the final outcome. Regards
If I can get a large enough hammer it will run for awhile just trying to get away from me
Thanks Max, Norm and Big Ted, I found the condensor which I had but must have thrown out the backing plate for the points. (Not like me to throw anything out) Finally ordered a new ignition from ebay, the link is pretty long so I have put it at the end. Mower started first turn and ran as well as could be expected. Pleasing I guess that my original diagnosis was correct but annoying that I spent so much of mine and your time on it. Just one small problem now, it is very hard to start after you have had it running. I am still starting it with an electric drill, It seems to be flooding, if you jam the butterfly valve open it starts a little easier. I am guessing that I have stretched the governor spring or put it back in wrong, or it may have something to do with the valve that is built into the push rod cover and connects to the carby. I will try a few things tomorrow but any suggestions are welcome.
I mostly don't bother fixing this type of carby , a new diaphragm is $2 .62 and you can adjust the fuel mixture screw but I see lots of the Briggs Sprint 3.75 Hp mowers thrown out or that are $10. so I just fit a later tank and carby.
Thanks Max and Norm, Forgot to mention that at least we have shown that they will run with only 50psi of compression (as measured by my gauge) must admit I was a little skeptical. Would have got this far sooner if I had a little more faith in Max's judgement. Thanks for the photos Max, unfortunately it appears that I have put the spring on correctly. I have been fiddling with the mixture screw, but it does what it is supposed to (lean/rich) but does not seem to help in terms of starting. If its cold it will start on the first or second pull, as long as the throttle is only about 1/5 open, if it does not start by than it is flooded. You can see fuel spitting out of the carburetor throat from the first pull of the rope. If you jam the butterfly valve open it will start, (as long as the throttle is only about 1/5 open) The motor will not rev until it is warmed up, no doubt it is a Carby problem. I know 30% less about carburetors than I know about electronic ignitions which is 0. If I can get a bit of time this afternoon, I will take the carby apart and have a look. I think in my case if a diaphragm gasket will fix it that may be the way to go. As I mentioned earlier when it is running it is never going to be a good mower. The engine runs smoothly but it has a rattle (probably the big end which had more play in it than I would like). A professional person would have replaced the oil seals when they had the crank shaft out, so I would expect them to start leaking. It still needs blades which are an odd size, the mounting hole is D shaped 9.3mm x 7.2mm which does not appear to be on the shelf at that hardware store. And it does not have a grass catcher. Generally, I don't mess with carbys at all as you can usually get an aftermarket Chinese one off from eBay for $20.00 which is less than the cost of a kit for a genuine one. Note that I don't think I have ever had one that was as good as the original, but they do make things run.
I will let you know how it comes out but if I can manage to start it and mow the verge twice, I think I will be able to happy be finished with it.
If I can get a large enough hammer it will run for awhile just trying to get away from me
I just did a tank and carby swap on my SupaSwift which was getting hard to start and faltering when it ran. I got it off a clattering engine that I noticed started easily and now this mower is running well and started first pull after pulling while on choke a couple of times.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!
Thanks Max Norm and Mowerfreak. Sorry it has been a while; it takes time for parts to arrive. No doubt a newer tank and carby would have been the way to go but with the details I had I was not 100% sure that the ones on Ebay would be suitable so I went for the carby gasket. It is a little bit more than what Max mentioned at my local B&S Diamond dealer ($38.95, I was not surprised when he quoted $12.00 for a flywheel key) but I managed to get a non-genuine one off the net for $18.00. It does not flood anymore and runs smoothly as soon as it starts but still very hard to start (not getting enough fuel now). (I don't feel too bad as an acquaintance who is good on carburetors said, "I Have never had much luck with those") Runs surprisingly well with plenty of power despite the scratched cylinder and the low compression, smokes a bit which is to be expected. Mowed the lawn once and it went so well I did the verge too. One more time and it can go. Can't see getting rid of it unless someone local wants it as I mentioned earlier it's never going to be a good reliable machine and I would feel guilty offloading it onto someone. I can't believe how much time and money I have spent on this, mostly time, when all that was wrong with it was my original diagnosis of a faulty capacitor. Thank you all for your help.
If I can get a large enough hammer it will run for awhile just trying to get away from me
Yeah you need to stay away from mower shops unless you know you can trust them Byomarimba , a lot are scammers ,I went to a shop close to me and he tried to sell me an old Victa 18 that he said only 3 were ever made and said Victa had offered him $3000. for it as it was a very rare model but I could have it for $2000. I just said that's strange I already have one and I know another guy up the road who has one and your mower makes 3 , he just shut up then.
My brother just went to his local mower shop with a newish 2 stroke Hitachi chainsaw that had done very little work, all that was wrong was it was idling too fast ,they told him the chainsaw was beyond repair and parts are no longer available and said he had to buy a new chainsaw ,there was nothing wrong with it, just adjusted the idle .
I know of lots of stories from shop owners and Mechanics making up rubbish and over charging.
If you search on eBay " briggs 3.5 carburetor diaphragm kit " you will find the kit for $2.65.
Good that the mowers working now and I've had lots of mowers on 50 psi last many years cutting grass , time wise it's always cheaper to buy a working mower but then you don't learn much about them.
