# Hard starting with fresh rebuild



## ryan68bug (Sep 18, 2005)

Well, after many months of work, gathering parts and just finding the time to do it (never enough of the last one, there) I rebuilt my 1968 2-hp horiz. shaft Briggs and Stratton engine for the mini bike I acquired off of Ebay. Only problem is where there was very little compression before the overhaul the engine is so tight now that I can't turn it fast enough with the recoil starter to get it started. Any suggestions? All my tolerances were correct, had the cylinder honed, installed new rings, valves, and springs and a new head gasket as well as thoroughly cleaned everything. Needless to say, this sucker is fresh and tight, just waiting to hear the fruits of my labor come to life! 
Any suggestions would be greatly appreciated...


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## bugman (Aug 12, 2004)

i'm sure the valves are set right?


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## midwayfreak (Nov 3, 2005)

Those old 6ci B&S engines normally feel like they don't have much compression. If it feels tight there is something wrong. Did you have it line bored for new main bearings? My guess is it's one of these 3 things, seezed main bearing, insuficiant crankshaft end play or, since you made the mistake of honing the cylinder, the most likely cause is galled cylinder. Good luck. One thing I learned years ago is don't break the glaze in a cool bore Briggs unless you are resizeing.


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## scrench (Dec 8, 2004)

coil might be rubbing the flywheel , something is not right it should turn over easy , double check things might take the pan off and make sure its not binding on the crank shaft , make sure the rod and piston are right the notch or arrow points @ the flywheel on the piston , but something is for sure not right , rod cap or rod might be bass akwards


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## scrench (Dec 8, 2004)

midwayfreak said:


> Those old 6ci B&S engines normally feel like they don't have much compression. If it feels tight there is something wrong. Did you have it line bored for new main bearings? My guess is it's one of these 3 things, seezed main bearing, insuficiant crankshaft end play or, since you made the mistake of honing the cylinder, the most likely cause is galled cylinder. Good luck. One thing I learned years ago is don't break the glaze in a cool bore Briggs unless you are resizeing.


 
line bored ?> i would think that would be a tiny bit too much 



mistake of honing ? most likely cause is galled cylinder ? <------((((( no way i would love for you to explaine that to me / i can see where it might make about an knats you know what< ammount of end shaft play but i think everyone knows that you have to take off the glaze with cast compression rings they wont seat if you dont period ,,,, gualding is caused from high heat 
from friction lack of oil ? cyl has to be honed out to final size after re-boreing you dont just bore to final size and thats it ,,, i dont want to sound like a know it all , i like to learn but im self taught and learned a long time ago to listen and its always payed off


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## ryan68bug (Sep 18, 2005)

Given I've built a couple VW engines, I'd be real interested to see how in the heck you go about line-boring a horiz. shaft Briggs engine. Lol. No offense, but that just doesn't jive with me, and with this engine there are two bearings for the crank, pressed into the back cover and the front of the block, and they are just fine. It doesn't feel like it's binding per say, just like it has a lot of compression. I guess the only real solution is pull it apart and take a look see.


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## bugman (Aug 12, 2004)

yeah, the coil would be one thing to check, kinda forgot about that, it'll catch olt to the flywheel. one test you could do, just pop the plug out, and then try.


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## ryan68bug (Sep 18, 2005)

I did set the air gap of the coil to around .007", within the spec of .006 to .010", as the antique repair manual recommended, if I recall. didn't seem to be any interference issues when I assembled it. It doesn't feel like the engine is binding, per say, just hard to get it to turn fast enough to fire up--as I mentioned earlier, compression.
I did pull the plug once and while it did turn over a little earlier, still not what I would consider as quickly as it should.
Keep the suggestions coming, they're definiitely appreciated!


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## scrench (Dec 8, 2004)

if the recoil and everything else checks out ok , i would pop the pan off and loosen the rod cap and see if it frees up , the chain isn't too tight is it ? does it have a cent clutch or what ?


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## ryan68bug (Sep 18, 2005)

It does have a centrifugal clutch, but not installed yet. Whatever the issue is it's gotta be internal. That's the good thing about these little motors, not too tough to take apart and go through! Lol. I'll recheck the torque on the rod cap, while I"m at it the rest of the internals. We'll see what happens, I guess. I initially thought maybe it was because of the new rings, honed cylinder and just overall "newness" that she was tight, but obviously we're not looking at a hi-po automotive engine here or anything. I shall continue tinkering...


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## ryan68bug (Sep 18, 2005)

Well, good news is I got it running! I went through everything and it seems it was just tight. Went through and rechecked to make sure everything was lubed up inside and double checked that all the tolerances were right, put her back together and eventually--after playing around with the mixture a bit, got her to fire up. 

Now to pull the tin, sand it down and repaint. Eventually this mini bike will be sold, as I've pretty much had my fun with it. Just need a new centrifugal clutch and finish the cosmetics.


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## ryan68bug (Sep 18, 2005)

New problems...engine does not seem to want to run with the choke turned off...should I be looking for a vaccuum leak? If the choke is partially on, it seems to run and rev fine, but fully closed, no dice, will not idle or run for that matter. The only hole I can spot is where the former retaining rivet (I think that's what it was for, at least) used to be--I removed it when I cleaned the carburetor so I could remove the choke itself and now am thinking perhaps I need to install a new one to keep it from leaking air.

Any thoughts? I've tried fiddling with the mixture and idle adjustments, but the bottom line is with the choke turned off she does not want to run.


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## bugman (Aug 12, 2004)

yes, i would try replacing it to see if it helps


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## midwayfreak (Nov 3, 2005)

Well it looks like some of you want me to explain some of what I said, and I will be glad to. First line boring, the old Briggs cool bore engines have no main bearings. The crank just goes through holes bored in the aluminum block, if the bearing surface is damaged you can either throw the engine away or you can use the special tool that Briggs used to offer to bore the holes out bigger and press in a replacement steel backed babbit bearing that were offered to repair it. After these bearings are installed they must be line bored with a special reamer that has a pilot that lines the bearings up dead straight, the crank will not fit unless they are finish bored because the ID of the bearings is not finish sized when you get them. Next galled cylinder, this is NOT caused by over heating, it happens to a cool bore engine when raw gas gets on the rings and washes off the oil. The gas WILL cause the rings to stick to the aluminum cylinder, some of the cylinder ripps off and balls up between the piston and cyl. causing the piston to bind. Galled cylinder always happens when trying to start the engine, not when it is running. It is uasally caused by a leaking carb. or by someone putting gas in the carb to try to start it. Now honing the cylinder, this is a touchy subject, with a cool bore engine, honeing if you want to do it it must be done just right, I have seen hundreds of them come through my shop belching clouds of blue smoke after someone has just honed it and put in new rings, the engine will never quit smoking and the rings will never seat. This problem is caused by improper honeing. I stopped honing cool bores years ago. If the cylinder is not out of round or badly tapered leaving the glaze in it will NOT hurt, and the engine will not need time to seat the rings. Also breaking the glaze will expose the soft aluminum to the rings (the nice hardened surface is removed) making galling of the cylinder happen much easier on initial start up. And FYI I am a certified Briggs & Stratton master service technition, with 20 years experiance, and I own my own shop, and do warrenty repairs on many brands. I have overhauled hundreds of cool bore Briggs engines without honing, maybe you should try it, you will probably get better results.


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## scrench (Dec 8, 2004)

line boring i know what that is, and i know it can be done and, y it is done but ,
yeally is it cost effective ? how much would it cost our customer ? i could see doing it on something that you would want to keep original , how much is the tool ? 
i would think a new sump would be cheaper on a 2 pony ? 

heat is not the only cause of galled cylinder? i agree washing will also cause it to happen , it washes all the oil off the cyl wall and piston ... causes friction ,things get hot and they expand i am thinking the piston swells and takes up all the piston to wall , so will jetting , which will cause (heat) improper timing which will cause (heat) improper lube that causes( heat) and the two most important, break in being first on my list , and second the surface of the cyl (the hone job) i was always taught that 60* is where its @ , on the cross hatches i always break the glaze ,
and i guess you could throw in the quality of the piston and, in my opinion briggs has a verry verry nice piston , most of the engines i see with trashed cyl walls are the ones that are ran out of oil ,, do you think its possible to guald the piston with a pull start ? 

i'm certified also but i dont tell anyone , i dont want anyone to know . 

thanks for the info 



oh yea wheel horse rules


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## scrench (Dec 8, 2004)

ryan68bug said:


> New problems...engine does not seem to want to run with the choke turned off...should I be looking for a vaccuum leak? If the choke is partially on, it seems to run and rev fine, but fully closed, no dice, will not idle or run for that matter. The only hole I can spot is where the former retaining rivet (I think that's what it was for, at least) used to be--I removed it when I cleaned the carburetor so I could remove the choke itself and now am thinking perhaps I need to install a new one to keep it from leaking air.
> 
> Any thoughts? I've tried fiddling with the mixture and idle adjustments, but the bottom line is with the choke turned off she does not want to run.


 
clean the carburator good and throw a kit in it and make sure the tank is flat where the carb sets on the tank belt sander works well , also make sure the pick up tube is not split and fits tight in the carburator and be sure the carburator bolts up tight to the engine and the gasket is good ,


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## midwayfreak (Nov 3, 2005)

OK Scwench now your talkin like you know something, You are right , replaceing main bearings in a plain bearing engine is no longer cost efective, but he was restoring a 35 year old engine, they dont make the tools for that engine any more, and refrences to it are found only in the new antique service book. Lets talk about galled cyl. . First galling and heat seezure are 2 very different things, they leave a different mark on the cyl. Galling happens during a cold start, and yes it happens with a recoil or electric starter. Have you ever seen an old 8 or 11 hp riding mower, comes in with the old 1 piece flowjet dripping gas from the drain under the carb., the engine probably has gas in the oil and is locked up. You pull the head and find nothing wrong with most of the cyl. but there are several very deep gouges and the metal ripped from the cyl. is jammed between the piston and cyl. below the rings. When you see that you can put money on it , it happened on a cold start. The owner didn't check anything he got on jammed the throtle up to choke and turned the key, the engine turned over 2 or 3 times and locked up, if you break it loose it will turn tight and will most likely never start again. This kind of damage uasally gouges the cyl. so deep that not even a max oversize .030 rebore will fix it. I don't see it as often as 5 or 10 years ago, mostly because most engines are sleave bore now, but I still see it sometimes on Quantums, seldom on Classics because the carb doesn't leak into the cyl. Classics will do it if you turn it over on it's side with the tank up to drain the oil.


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