All About Briggs & Stratton Synchro Balance crankshafts and how to remove counter weights
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- čas přidán 7. 09. 2024
- Detailed video on removing counterweights and how to replace the dogbone connecting rod that connects the counter weights to the block. Thanks for watching!!!
My friend has a syncrobalanced 12 hp on a gokart. We run it un governed. It's been going strong for a couple of years. No knocks doesn't run hot. Oil is never over dirty. We may get around to removing the syncrobalancer but it's never failed yet.
thats what it was, the sleeve for the crank. i honed it out a bit with a brake tool, and cleaned the crank end up. assembled it all and it moves!! awesome stuff, kinda getting hooked on this small engine thing. this is my first rebuild
yes and no, if the dogbone wasn't there, the weights would be loose and would sling out and hit the block, it keeps everything together. thanks for watching!!!
glad to help. haha appreciate you watching my videos. thanks! more to coem soon. let me know what it turns out to be, i'm curious! no problem!
thanks for the quick response. I actually found another site where a guy was asking about the very exact thing - in 2006. After the second dog bone he said he was going to scrap his engine. On the way to the Snapper Store now to see if they can explain it. A glance at the pin(s) look like both ends are the same, but they are not. Slight difference to the bevels at the ends - one end is slightly more blunt. There appears to be nothing inside the hole to press the pin into.
Always great information in your engine videos. Thanks for posting Bro!
thanks man! Your engine videos are great too! thanks for watching!!!
i appreciate your input, i think this is the first thing i ever come across i havent solved by watching your videos. awesome stuff by the way. ill keep tinkering with it and im sure something will figure out. thanks for your time
Thanx for the ignorance relief. Fixin to ring '89 mod. that's had a rattle a long time & never been into one with the balancer.
yes and no, generally speaking you don't have to switch out the counter weights on a stock engine, its usually for ungoverned racing engines going past stock RPM. it might be a little better on gas i figure the brass weights weigh alot less than the stock cast iron synchro balancer. they are about 80 bucks for 2. thanks for watching!!!
Hey man I really thank you for posting this video a long long time ago because I have a Briggs & Stratton 8 horsepower synchro balanced engine and I had no idea that the synchro balance counterweights could destroy my engine and see there's a reason why I say that is because I'm making it into a race engine but thankfully I'm going to try to use a 3.5 horsepower Craftsman edger engine it should not have those synchro balancers and I could probably just Rob the crankcase off of that but I thank you for putting that on there
I just ordered some of those counter weights off eBay cause after 20 years the weight closest to the flywheel was worn about a 1/4 inch. crazy I'm surprised it didn't come apart on me I'm going to up load a video when the weights and gaskets get here in about a week.
+Rachel Matt I hear ya, wow thats worn quite a bit, i'm surprised too that it lasted! heard that, let me know when its up and i'll check it out!
Were they new or used ???
It helped me out so thank you very much
good vis good info wish this was up about a year back thanks
Let me tell you a cool trick about rust prevention. What I use is a propane torch and a regular candle. I heat the part and use the candle wax pressed and moved all over the surface which prevents rust and oxidation in its tracks. Real cheap and works excellent too.
I have heard of this before but i've never tried it! Thanks for Watching!!!
your welcome! i hear ya! I did a 4 part video on rebuilding a 12.5 (same as a 12) horse briggs, i go into alot of detail on it. thanks for watching!
then start it and it will probably smoke for a few minutes but it should clear up after all the excess oil is burned out of the muffler, if this doesn't help write back and we'll figure something else out! thanks for watching!
I do but I'm not willing to let go of them haha, I have a 11 horse block that needs bored out, and i'm saving the crankshaft for that project. sorry about that, you might want to check on ebay, parts pop up on there all the time. Thanks for Watching!!!
No problem, its a fun hobby! Yeah if you take to much off it will make it fit loose in the bearings, I recommend using sandpaper, and kind of like cup it in your hand around the shaft and turn it back and forth, use about a 220 grit paper, if its really really rusty then go with 100 or so. I would not go below 100 grit. A wire wheel would probably scratch it up to much. your welcome! Thanks for Watching!!!
Great video!! Very thorough.
Yeah I saw that in your video the brass counterweights that take place of the synchro balanced counter weights I was looking at that but I had already ordered the original counter weights when I heard of brass counter weights. I didn't set up the engine for racing I just did pulley swaps so I don't think I have anything to worry about I don't even run the engine above 1500 rpms half the time except for when I'm in the mud or going up the hill I might punch the throttle down but besides that the RPM's don't get up there too high.
+Rachel Matt yeah, I've been wanting to try the brass weights but they are expensive. I hear ya, its surprising what you can get out of a stock-governed engine with the right pulley setup on it, because it takes advantage of the lower RPM torque. Alot of people do away the governor with stock pulleys expecting a ton of speed, but all you get is a rod out the side!
yeah i remember i think he did a video talking about that. you would have to have someway to do away with the synchro and use the brass weights i would think. person could have a oil pump and pipe it so it throws oil on all parts. i don't know
Thanks! I always try to keep them as simple as possible. There's only 1 bolt on the crank, the long 1, the other end of the dogbone just slides onto the stub in the block, no bolt. Will Do, i just put up a new one today of a old start of my 12 horse briggs. Thanks for Watching!!!
thanks man! thanks for watching!!!
thats right. because once the synchro balancer is out, theres no place for the dogbone. thanks for watching!!!
Very helpful video I just finished doing connecting rod pistons and rings in a Briggs 21hp after it dropped a valve and smashed up the piston and head I started it up it was running good then a loud bang and the back of the case was busted open and I could see the balancer not moving as I turned the flywheel. I’m thinking that dog bone rod you showed is going to be what broke. Going to split it open next week and salvage what parts I can Thank you for the helpful video
i bet you find the compression release mechanism
is in the bottom of the crank case along with some other goodies thats usually what lets loose sometimes you get lucky no damage and other times it grenades like yours
thanks! haha sorry i didn't make it sooner. did you have one let go of the counter weights? thanks for watching!!!
hahahah i know right! i'd love to get a hold of a old 12 horse without the synchro! thanks for watching!!!
No problem! Yeah, I hate to see a engine scrapped. but sometimes they just can't be fixed. I hate to say this but the only thing that comes to mind is degrease it really really good then JB weld it, but thats chancy might last the life of the motor might last 5 minutes, just don't know haha It might work, If it was mine, i probably would try it. but thats up to you!
dont thank me for watching its a pleasure ..thank you for making the videios
I hear ya haha your welcome, good to hear you like them so well!
no actually its still a on going progect dew to a j b weld problem but me and chargermilles thought wee could use them as a splash although i did hook up a separate oiling system
alright, let me ask a few things first, do you have the connecting rod (the rod from the crank to the piston) hooked up yet? If it is, sometimes these motors are stiff to turn over after reassembly. Or it could be a tight bearing on the connecting rod. Be sure to put plenty of oil or stp all over bearing surfaces and the walls of the cylinder and piston. does it spin over at all i either direction? thanks for watching!!!
no the connecting rod is not hooked up, and everything is oiled up. the crankshaft will not turn in either direction. the only thing i havent replaced is the cylinder bearing in the crankcase, that just looks like an aluminum sleeve to me. just checking if you ever ran into this before
i got a 12 hp with a broken connecting rod with the synchro balancer the bottom or the rod was destroyed when I look to buy a new connecting rod how dose the oil dipper fit on the rod or is there no oil dipper with the synchro balancer i cant tell on my engine if there was it was destroyed my block and everythig else looks good
oh no we got it figured out were i just increased the oil level to that at the bottom of the old slinger it still throws it around the weight splash and so do the bottom cm of the crank
Are those brass counterweights recommended if you want to keep everything else stock. I figure less weight would be better on gas consumption. Are the brass counterweights expensive ?
I just came across this video. If I wanted to eliminate the Syncro stuff on my 11 horsepower I am getting ready to rebuild is there a source for non/syncro style crankshafts ??
If it was a overhead valve engine i'd say it would be the head gasket, but its a flathead so its not that, what probably happened (very very common by the way) is when you shut it off the float stuck or the needle valve didn't seal in the carburetor and it flooded the crankcase with gas (gas ran past piston into the oil, making it act like there's to much oil in it) don't run the engine anymore, check the carburetor to make sure the float is working free, then do a oil change>>>>>>
your welcome, thanks for watching!
The reason I watched your video is because I'm trying to see what happens if you don't run the synchro balanced counter weights I'd rather not put them back in and just run the crank.
+Rachel Matt I hear ya. Some have ran them without any weights at all, and they say it causes alot more vibration, but i don't know about long term, it could wear the crank bearings more if its excessive vibration. They also make a racing crankshaft for these that do away with the weights, its built more like a push mower engine for example.
Good video
If it is a flathead motor, a blown headgasket will not cause it to smoke/burn oil, because the headgasket only seals the head to the block, there is no oil being sealed off by it (not like a OHV motor), but it does sound like it needs a new headgasket, which should help the backfiring problem, but I don't think it will help the smoking problem, sounds like its just burning oil, replace the head gasket then we'll go from there.
Can i ask what happends when i dont have counter weight in briggs&stratton engine?
ohh ok. that makes perfect sense. i'll keep that in mine if i ever make one.
Good vid bro!
I have a 15.5 and 17 hp briggs that both have knocks. The 17 gets worse and worse every time it runs to the point where I'm not gonna start again, and it seems like its coming from the camshaft area. Also the exhaust push rod is worn and about to blow, so could that be the same problem? The 15.5 has the AVS system on it and I can't really tell where it's coming from. I've been told that it might not be the counter balancers. So I guess it could it be a million different possibilities, right?
Those are bad about knocking, we have one on a troybilt with low hours and it knocks at idle, just enough to aggravate you, and another i did in a 2 part video. They way the avs system is made is very strange and almost looks like its made to wear out on purpose. I like the older synchro balancers much better. It could be the valves out of adjustment causing it, could be rod, piston slap, etc, your right, never know until you dig deeper into it. Thanks for Watching!!!
Hello,
Thanks so much for taking the time to make these videos for us. I have a quick question. The ends, or shafts on my crankshaft are a bit rusty. What do you recommend using to clean the rust off?
I have a wire wheel, but don't know if that will take to much off, or if it even matters? Appreciate your time, and any help you can offer. Have a great weekend, and thanks again for helping us out with these videos.
I have toro xl model (old) came with 13 hp 28m707-0122-01 please help
oh no! I've never seen that happen before, its supposed to be like pressed into the block so it can't move or come out. The pin will need to be fastened somehow to the block again, I don't know what the best method would be right off hand, pressing probably won't work since it done came loose, can't weld it, if there was some way to drill through the block where it is, then tap it and put a bolt through it? I don't know what to tell you! i've never had that happen. Thats about all i can think>>>
yeah thats a good idea to hone it, should have mentioned that! heard that! yeah its a fun hobby! i love it. thanks for watching!!!
thanks! thanks for watching!!!
hmm. the only thing i can think of is that the crank bearings are to tight and is not letting it turn. you mean cylinder sleeve? usually don't have to worry about the cylinder much when rebuilding, i can usually get by with just honing. If a engine has a sleeve its a cast iron sleeve, if no sleeve its aluminum bore, the block itself is the bore. no i don't think i have, i've had several thats really tight after rebuilding but after it breaks in it loosens up. don't really know what to tell you!!
The Eccentric on the Magneto Side ( Not timing gear side ) has a dot on it and has a groove on the inside. What is the proper way to install the eccentic ? Dot
Well if you're talking about the crankshaft gear ⚙️and the camshaft gear what you have to do is on the crankshaft gear make sure that the dot is pointing towards where the camshaft would be then take your camshaft and align the dot with the crankshaft gear the dots should be touching each other perfectly aligned with each other and then once you do that try pulling the engine and see if it opens and closes on the right time and I hope this helps you
I think it would be neat if you haven't already made a video on what to look for and look at when you're considering buying a used riding or push mower like look at the oil tires general condition of lawn mower and maybe talk about how much u should give ( ball park). Just an idea. Thanks
That is a good idea, I might do that! Thanks for Watching!!!
Great Video!!!!
hello i think you do great easy vidios to undastand..i have an 8hp briggs in bits .i was wondering if there was a bolt on the end of the dog bone i see how it fits up but unsure if parts are missing?..........keep up the vidios
I replaced the weights and the dog bone on my B&S. Started and ran great for about 2 min and then bang! Took apart to find dog bone broken in two, again. The pin holding the end of the dog bone (the end away from the weights) in place was laying in the bottom of the crankcase. There appears to be nothing that keeps this pin from falling out of the crankcase and out of the dog bone. When the pin falls out, one end of the bone is loose and breaks. Any suggestions? Your videos are great!
I'm looking to see if I can just find a crankshaft that doesn't have the synchronous balancer. so I can just do a way with it.
McCuneWindandSolar They do make them, not briggs brand but aftermarket for racing engines, go to eccarburetors.com they have them on there, just checked they are 300 dollars though! thanks for watching!!!
Hi thanks for the great info found in your videos. Great job. I too had the counter weight closest the flywheel excessive wear problem and can't believe it still ran. I had an extrA counterweight but my problem is the rear replaceable counterweight journal indeed needs replacing but can't find one any wear not even on the engine diagram for this model. Can someone tell me wear I cAn find one? I would really appreciate some help.
+lasso atrain your welcome! I hear ya, its really hard to find them, I have heard of being able to replace the bushing/sleeve and get by with that, but never done it myself. Thanks for Watching!!!
Do you know if the dog bone is replaced with a better quality one will it servive un governed engines for racing ??? Thanks, just wondering. Or is this just more of a headache with more reciprocating mass ??? What is max RPM for a stock crank also ???
Good day also fella.
They do make a billet aluminum dog bone, that will help out alot but its highly recommended to put brass counterweights on it. The dogbone is cheaper at around 20-30 bucks as the brass weights are 80 - 100. Not sure of the exact rpms a stock will take, but the crank itself is pretty durable, just the weights are the weak part. Thanks for Watching!!!
@@fnaguitarplayer9 Thanks for the information fella.
yeah ebay should have it, or you might get a good buy on a whole crankshaft, just never whats on there haha thanks, really appreciate it!
Would you have the model 28 engine seating around your shop
wish i could be more help, only thing i can think of is the bearing clearance is not enough.
Thanks a lot very helpful
Where can I find the brass counter weights for 11 hp Briggs , and can you make a video on how to delete the synchro system and install the brass weights?
eccarburetors sell them and a few other places still might. If I ever build one i will definitely make a video on it. Thanks for Watching!!!
so the only things these counter weights do is help the engine from shaking and vibrating as much as something like a push mower engine?
Yeah it keeps the vibration down, and balances the engine. The counterweights in engines without them (like the push mower engine) are made bigger to compensate more, but still not perfectly balanced. Thanks for Watching!
can you run the engine without the weight system in it? thanks
Yes, but it will cause extreme vibration, they do make brass counterweights that take the place of it. Thanks for Watching!!!
I race model 19 briggs motors. Is their away you can tell if it has the synchro in it or not without knowing the exact full model number and without removing the sump?? Thanks, Don
I hear ya.I looked up the diagrams on it, and its not showing a sychro. I think they started that on 11HP and bigger engines, because i tore down a 10HP (model 22 or 23 can't remember now) and it was a regular crank. no problem! Thanks for Watching!!!
Where do i buy the bearing shells?my lawnmover started to vibrate and run ruff.opened the engine and found a lot of small metalflakes.
Its hard to find to be honest, you may have to have a machine shop make them. Thanks for Watching!!!
Nice video :)
So im just curious what would happen if u were to put that crank in without the balancer and use just the crank? Would it blow up?
gbody mod shop People have done it before, it just causes excessive vibration, its possible that something could crack from the extra vibration but I'm not sure on that. For lawn mower racing they actually sell brass counterweights that bolt on in place of the balancer, because in a ungoverned engine, it is the weak point, as well as the rod. But the crank with the weights added looks more like a "traditional" crank, with no balancer. Thanks for Watching!
Do u need to have the balancers in
can u run it without them?
Well if you do take them off I don't recommend running the engine with no synchro balancers because the way that I see it you may have to change out the crankshaft in order to do it because I'm building myself a racing lawn mower engine and it has those balancers in there and see what I'm thinking about doing is putting a 3.5 horsepower Craftsman edger crankshaft and I'm going to change out the crankshaft and hopefully it's the right type because I don't think those engines have balancers like that because take a look at where the balancers have to go on the crankshaft if you take that off ,the engine won't be balanced correctly and that could cause the engine to run rough
Hello I'm new to this ..when it said that you have a AVS engine ...what type differ from what you shown in your video? Iam building a Race engine but I was told I need a non AVS crankshaft ? What's the difference? Thank you Great video.
Its a similar design, if you watch my video called "overheated Briggs 18.5Hp.....) you will catch a glimpse of it on the teardown, i didn't remove the crank but you can get a idea of the design of it. It doesn't have the dogbone rod, but has a slightly different set up, and the main difference they are referring to on the racing sites is the crank journal and shaft are different sizes so the brass counterweights won't go right on without having it machined down to fit. And the billet crank they sell doesn't fit as far as i know. They can be used but it will take modification to make it work. Thanks for Watching!!!
What the specs for the counter weight cranhshaft play got every thing clean up and checked to put back together
I've never actually found any specs for them, and now you can't even get the sleeves for them. Best advice if you got one thats worn out and cant find another then upgrade to the brass counterweights that they use in racing engines, pricey but will fix it, and eliminate future problems! Thanks for Watching!!!
Ok so the Brass counter weights are no longer available at EC carburetors or ARC Racing.. or anywhere else i can find that did have, so will a flywheel counter weight fix the shakes or be to far off from the center and add more wobble?
And does anyone know where i could find the specs on the brass counters i know a CNC wizard who could probably mill something out..
Found ummm.. www.ombwarehouse.com/
didn't know that!!! I'll have to check omb out! Thanks for Watching!!!
Good to know thanks guitar
Your welcome, Thanks for Watching!!!
good job, thanks
Thanks for Watching!
can one run the engine without the balancer
You can, but they will be shake alot, they do sell aftermarket brass counterweights for racing lawn mower engines that can take the place of them. Thanks for Watching!!!
was wondering can you use the 12.5 crank in the 11hp b;ock
the 12.5 (model 28) has a longer stroke than the 11hp (model 25), now if for some reason both engines have the same model number, then it should, should, work, they both use the same rod though, and the piston is the same, at least diameter, some used different styles of rings. I actually have another video on plans on building a 28-25 stroker motor, but i never did any more with it, its been done before, but takes alot of clearancing. thanks for watching!!!
would be nice to see video
here's the one i have that i show what would have to be done, if you could machine a new rod that keeps the piston from popping out as you will see, it would work... czcams.com/video/H1kiFqCDCh0/video.html Thanks for Watching!!!
Do they make a metal dog bone instead of aluminum to help durability?
Not steel, but you can get a aftermarket billet aluminum one, made for racing lawn mowers. And they make brass counterweights that replace the synchro. Thanks for Watching!!!
nice vid!
Oh I had some play between the crankshaft and the balance weight alright. Apparently the vibrations were so violent that the piston rod broke in pieces.
That can happen! Thanks for Watching!!!
does anyone know where do get the brass weights he mentions, I cant find them anywhere
+Donny Johnson You can buy them from eccarburetors.com, the only place i know of that sales them, they also have a solid billet crankshaft to do completely away the balancing system. Thanks for Watching!!!
Hi, does the big end on these have removable bearings? Thanks.
Yeah its like a sleeve bearing, its not really thick. I have heard of people changing them, but I can never seem to find the bearing or even a part# for it. Thanks for Watching!!!
Hey man, been a while lol. Do you happen to know the part numbers for the synchro bearing shells? I'm going to take my 12 HP apart soon because with ear plugs in I can hear a slight bit of rattle come from the engine. Can't really hear it without the ear plugs in. Figure I'd better check it before something happens, especially with about 1,000 hours on the engine.
1972FordF150 Hey! It has been a while! Nope, I've been asked that before, i just double checked my diagrams and the only thing i can find is the counterweights themselves, which should have the shell pressed into them, but i checked a couple different model 28's and there are different #'s for them, whats yours, i'll see what it is for that. They don't cost a whole lot, like 30 bucks on ebay. I thought it would be more than that. Heard that, best to be safe than sorry haha I had a tick in my truck (s10 with the 2.2) and this past weekend me and my buddy put a timing chain in it, took care of it, if it wasn't that i though it might have been a lifter. Good to hear from ya! Thanks for Watching!
My model number is 281707, type is 0139-01 code is 881013xx. Can't remember the rest off hand haha
1972FordF150 haha That was enough, usually I can go off of the model and type. The part # for yours is 399891 just checked there is some on ebay.
Have you got any counterweights and connecting rod for a l/c quiet 12.5hp engine I can't find one anywhere
Not extra ones no, you probably wont' find a new couterweights but may be able to find a good used one on ebay, you can get new con rods from ebay as well. i order alot of parts from tulsa engine warehouse (tewarehouse.com) Thanks for Watching!!!
Do you have to use those counter weights? I have a set of the other style. The kind that doesn't have a rod to hold it in place. Can I use those counter weights or do I need to use that kind?
willy68057 If that crankshaft will fit the block (same stroke, and same size shaft/journal) yes it will work fine, but I'm thinking the older style won't fit the bearings on the newer style, not for sure on that, try it and get back to me, i'm curious to know. Thanks for Watching!!!
fnaguitarplayer9
yep fits but went with the older style. They are built a whole lot better
willy68057 Heard that. Yeah, I'd like to find me a older style 12 horse, the ones with the starter-generator. Good motors.
Can it make motor knock right
Yes, it will sound almost like rod knock but with a deeper sound to it. Thanks for Watching!!!
Is it normal for one of these engines to knock a little when hand spun?
Some will do that, the synchro can have a little play in it, but you may be hearing the oil slinger/governor sometimes they will make a noise when you turn it over slowly. If you don't hear it when its running then it should be ok. Its hard to say for sure, it could be the rod or even piston slap but I'd say its some play in the synchro / counter weights. thanks for watching!!!
fnaguitarplayer9 thank you.
haha no problem!
The balance weight are terrible ideal and have not helped the engine last longer or run better
Best to remove them, they will last longer I think 😊
Are the balanced ones iron sleeved?
some are and some aren't, just depends, never know until you tear them apart. Thanks for Watching!!!
My crankshaft seized to the weight for some reason
I have heard of it happening, its more rare though. Thanks for Watching!!!
@@fnaguitarplayer9 I assume the weight and crank need to be replaced right!
@@dailylifewithsteve4460 more then likely i'd say yes, but there always a chance of being able to save it
well thanks any how :)
were do you get the brass mods
McCuneWindandSolar eccarburetors sell them. And you could probably find them on ebay. thanks for watching!!!
What would happen if you run an engine without these
It will vibrate excessively and can work on the crank bearings. I have a old 11HP engine that is knocking, I'm thinking of doing a experiment this summer, taking the weights off of it just to see how much it will vibrate, might do some other experiments as well. Might be interesting! Thanks for Watching!!!
The synch
whose idea was it to invent that giant thing instead of using normal counterweights?haha