I picked up another Rover Super four with a Briggs 5hp I/C engine for spare parts as my current machine seems to have a possible worn engine.
My current engine on my Super four has a aluminium cool bore cylinder which has score marks but runs fine except when cutting high or thick grass. I suspect that either the rings or maybe the mixture needle may be worn as I can't seem to adjust the mixture much from a closed position. Anyways I managed to pick up another machine cheap this weekend that was a non starter with a 1984 I/C engine and figured it should have a better smoother cylinder than the older cool bore or at worst I could use this needle as a replacement as this part I can only source for $60.00 plus shipping from the states.
I managed to get the I/C engine started as the stop and choke leaver was upside down so you have to start it in the stop position which is why they said it was a non starter. The cylinder on the I/C engine seems good with the faintests of lines you can't feel that don't even leave oil tracks, so it should houne out very easy but it seems to have low compression which I will check again once I lap, adjust the valves and replace the head gasket. I figured considering the condition the engines In and the fact that it's an I/C series that maybe for $30.00 I should replace the rings while the engines off as it's now 36 years old and most likely needs a good service, plus I can make one good engine out of the two. So my question is what rings do you put in a cast iron cylinder? Steel or chrome as the parts diagrams states the two types so I'm guessing there's two options, what are the pros and cons? Std steel # 393835 Std chrome # 298982
Any info or advice would be great as I love this "little" machine plus its the only mower I will let the wife use if she needs to as I won't let her use the SB 45 or the ride on, Below are some pictures of the parts machine I picked up with the I/C engine my complete Super four is in the shed which I will dig out in the next few days.
That's my first thought too, I know Briggs don't use compression readings but any recommended measurement of what's ok? I can't get more than 50psi and I can't get the flywheel to spring back when turned in the opposite direction on the I/C engine. Piston moves and valves open so I'll give it a bit of a clean up and check clearances and go from there.
Not sure if I found my problem but the exhaust valve has almost no clearance, also I noticed that the valve spring and retainer clips are different sizes for the intake and exhaust, I checked these on the parts diagram and they seem to be correct. Guessing it has something to do with being an I/C model as I have never come across this before when working on cool bore engines. I will assess the valves and get back with a conclusion.
Update: I cleaned the valves gave them a quick lap and grinded the exhaust valve to the correct clearance, I also gave the carby a quick squirt and blew it out with compressed air. Not sure why but it had 2 diaphragms so I pulled one out, end result it started first pull which it dident do before as I had to pour gas down the filter to get it to start but it won't idle or rev at full throttle it just sits at a steady slow run and blows black smoke. Also I did another compression test and still got 50psi my other 5hp cool bore reads 80psi so I'm guessing rings are shot on the I/C engine.
I swapped the engines over and got the I/C engine going after adjusting and lapping the valves aswell as giving it a tidy up. It runs good at high revs just below the choke but at low speed it doesn't want to idle and stalls before I can get to the stop switch, I have tried the mixture screw but cant get anywhere it seems to be possibly a linkage or governor issue but I can't put my finger on it as I have the same engine on my mulcher and the setup is the same and works fine. What am I missing any ideas?
Yeah I tried that the idle screw doesn't seem to make any difference no mater what position you move it to the only thing I can adjust is the fuel mixture now here's the silly thing if I pull back the linkages from the governor by hand it doesn't seem to stall but if I move the control leaver to slow on the handle bar it goes to a slow putt till it dies as though it's starving. I thought maybe it's shorting the kill switch early but it doesn't look or sound like a kill stop it seems like it's running out of puff and trying to hang on but cant. It sounds nice on high revs but not over reved or screaming, I also noticed you can drop the speed very quickly with minimal movement of the control but still maintain a good inbetween speeds unlike some engines that just drop from high to low revs with out much inbetweens.
G'day Bon _Scott, To answer the question in your original post, the chrome ring set will tolerate 0.005" or so bore wear, without having to rebore/hone out to oversize. BTW, the Briggs repair procedure is not to hone the bore, if fitting chrome rings.
Compression readings are of very little diagnostic use on these older Briggs engines, due to the compression release system they use. 'Easy Spin starting' is old technology now, and Briggs no longer have any detailed docos on their website describing it. You have to go to an older print edition shop manual for that - even the current Briggs CE8069 'Repairman's Handbook' manual omits it.
The excerpt which follows is taken from the 1981 edition of B&S' 'Service And Repair Instructions'.
Quote
The intake lobe on the camshaft is ground with a small ramp which holds the intake valve open 1/100 of an inch for a tiny fraction of the compression stroke. At slow starting speed the interval of time that the valve is open is relatively long and therefore enough air escapes to noticeably reduce the compression. However, at operating speeds the interval of time is so short that there is practically no escape and therefore horsepower is unimpaired. Actually at 3600rpm the valve is opened for a mere 1/200 of a second. In all other respects the valves operate as in any other four stroke cycle engine.
The force required to start an engine is reduced by 50% with 'Easy Spin' and would be noticed most by a person who has difficulty starting the ordinary engine.
Loss of valve clearance due to wear is a very common fault with these sidevalve Briggs engines.
Cheers, Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
Thanks for the clarification on the rings so guessing the Chrome rings take up the space for a slightly worn bore ,don't think I will do the rings on this engine at the moment as I think the problems mainly in the carb or the linkages. I can get it to start and rev to a nice high rpm but it seems to starve at lower rpm, for now it will run I just have to note how far down I have to put the throttle leaver down before stalling to empty the catcher. I might do a carb overhaul between the 2 engines and see how it goes and if I can get it to a point I'm happy with I might later put new rings in. When I was first looking at the parts diagram it gave me 2 different options for rings and wasent sure which way to go, If I do eventually do the rings I will check cylinder wear to see if I should go chrome or steel. If the cylinder is still within spec can U still lightly hone the cast iron sleeve to install normal rings as I know Briggs don't really recommend honing cool bore cylinders either. The cast iron cylinder doesn't seem to be scored and would probably hone out some light scratches it most likely has some oil passing through the ring end gaps.
Also would you be able to confirm valve clearance for the I/C engine?
G'day Bon _Scott, Yep, for steel rings a light hone/deglaze is OK for the cast iron bore. Not really necessary unless the bore is visibly glazed, though.
Valve clearances are the same as for the kool-bore engine; IN 0.005-0.007" EX 0.009-0.011".
Thanks Gadge your a legend, that service manual will help lots if I decide to rebuild the engine.
I gaped the valves the same as the Kool bore specs as I thought they would be the same I just wanted to double check In case there was a slight difference between the two as I only had the service specs for the other engine. I should be all good now with this service manual. I will also check now the rpm specs with my TinyTach to see if I can sort the linkages/carby out and the stalling problem.
Just thought I would post an update on the super four. I was still having some issues with the replacement IC engine stalling under a load so I put it in the shed and thought I would leave it for a day I was bored. Well today I was bored and thought I would have a look, I started by stripping down and cleaning the carby on the first now spare engine and installed it on the mower and still had the same issues. So I re-checked the valve gap and that was with in spec. Decided I would look at the linkages and governor as I couldn't get a powerfull high rev and the mixture screw had to be screwed in all the way to stop it coughing and pick up a smooth rev. I next decided to loosen the bolt on the governor arm and moved it around and on the next start it was reving it's guts out and was even reving high with the throttle leaver at slow. After a bit of mucking around and adjusting I got it ideling nice at slow and at high it revs hard and loud similar to my Rover Shreeder, mixture screw is now 1 1\2 turns out and slightly adjusted in to the sweet spot. I gave it a test run in some high thick grass and she dident hesitate at all and went straight through it with out any problems. Hoping next time I use it, it starts with out any trouble and performs as it did today.
So with out really knowing what I did can anyone relate to what the problem was? I'm not 100% sure how I adjusted it but I'm guessing it was somewhere in the governor arm where I loosened the bolt. Just curiouser for future problems that may arise or if I have to adjust it again down the track.
