5hp briggs oil in top end

waffledude376

waffledude376

Member
#1
#1
So I just rebuilt my briggs and it smokes since oil gets into the top end. And when I say oil, I mean a lot of oil. My rings are good and properly spaced, also, the cylinder is good, valves lapped, guides good. The only thing I can think of is that I milled the head too far down, I think I went .0040, so I don't know anymore, this is the third rebuild I have had to do, I scrapped the original block since the casting was really crappy and the flywheel side bushing was worn out. So if anyone knows why I'm getting so much oil in the top end please,please let me know. Thanks.

P.s... I have a billet rod and a mild cam (PC-150) and I had double springs but I removed the innerspring, maybe I need more spring tension? I don't want to wear out my seats or guides.:shrug:
 
125ccCrazy

125ccCrazy

Well-Known Member
#2
#2
cylinder might be worn too far and could be tapered....You'll have to check end gaps on the rings at a couple spots in the cylinder and compare the difference...

make sure the breather is clean and clear..

milling the head won't cause oil to get by the rings or valve guides...
 
Neck

Neck

Growing up is optional
#3
#3
Only three places for oil to get in, past the oil rings, through the intake valve guide, or getting sucked into the carb through the crank vent tube.
 
creia

creia

#4
#4
waffledude,
You stated, in part: "... the cylinder is GOOD..." (emphasis added)
By "good" did you mean (only) that the cylinder wall is smooth with no visible scoring? If so (suspected), while that is encouraging, unfortunately it only tells PART of the story. With extended use, these cylinders can get out-of-round and/or tapered from top to bottom, sometimes significantly so. The new rings you installed are perfectly round, and if the cylinder wall is not, THAT is your oil working its way past the rings into the combustion chamber and top of the piston. Briggs recommends a 6-point measurement of the entire cylinder wall- (2 near the top, 2 in the middle, and 2 near the bottom, which are taken at 90 degrees of each other.), prior to installing new rings. They also provide "reject sizes" which are maximum allowable differences between these measurements. If your measurements are past "reject" size the cylinder wall must be bored and honed oversized to get it round/uniform, and matching oversized piston and rings must be used. Also, when installing new (cast iron) rings, Briggs recommends a light honing of the cylinder wall to re-establish that visible "cross-hatch" pattern on the cylinder walls. An added benefit of honing is that it will quickly reveal if the cylinder wall is out of round or tapered by the way it takes the material off (i.e., uniform or skips).
Michael
 
waffledude376

waffledude376

Member
#6
#6
So what I did was hone the cylinder lightly, this is basically a new motor,I scrapped the original block,piston and rings since the block was shot, the piston scored to :censure: and the rings really worn. I kept the valves from the original block so I could keep clearance for my lifters. I lapped the valves, the cylinder on the replacement block was clean, no scoring, I think I'm going to put a stock head on and see if that fixes it, it probably won't, but we'll see. I didn't measure the cylinder before assembly. And when I honed it it seemed in round. Also how can I repair a bad intake valve guide? Sorry if this is really ramble, but its 12:30 in the morning and I'm tired, sorry about the jibberish
 
125ccCrazy

125ccCrazy

Well-Known Member
#7
#7
waffledude376 said:
So what I did was hone the cylinder lightly, this is basically a new motor,I scrapped the original block,piston and rings since the block was shot, the piston scored to :censure: and the rings really worn. I kept the valves from the original block so I could keep clearance for my lifters. I lapped the valves, the cylinder on the replacement block was clean, no scoring, I think I'm going to put a stock head on and see if that fixes it, it probably won't, but we'll see. I didn't measure the cylinder before assembly. And when I honed it it seemed in round. Also how can I repair a bad intake valve guide? Sorry if this is really ramble, but its 12:30 in the morning and I'm tired, sorry about the jibberish
Click to expand...
to fix a guide it has to be replaced and in the case of most 5hp briggs the intake guide is the block itself so it has to be reamed to install a bronze or steel guide..

This won't be the oil issue but did you check the valve lash or did you take it for granted that the lash would be ok with using the factory used valves?... lash can change significantly between engines, cams, lifters and how far down the valve sits in the seat..

did you check ring end gap? I have found stock (oem) briggs rings to have upwards of .020+ gap.... I prefer to get .010 rings and file fit them so I can have tighter end gaps for better sealing.. One other thing... if the compression and scraper rings are mixed up or if the scraper ring is installed upside down you can have issues also..

as far as the added compression the only thing I can see that doing is if the rings are not sealing it will have more blow-by causing more crankcase pressure forcing oil out the breather and into the carb as Neck mentioned... in a case like this you have more than one issue to address..
 
creia

creia

#8
#8
Have you had the engine on the bike yet? If so, how is the performance? With as much oil as you are describing getting past the rings, the compression should be significantly reduced and the power/torque (take off speed) would be noticeably less.
Michael
 
waffledude376

waffledude376

Member
#9
#9
so ill tahe pics of the amount of oil gettin to the tope end and upload them soon. to 125cc, i checked th lash on my cam card and the motot, it wanred .006 and .005. both of my valves measured in with .006 vlave lash after lapping, sdo i figured i was good. im running an updraft crab wiht a cone stule aircleaner. i vented the pcv into the air cleaner aqnd when i noticed it smoking, i disconnected it figuring it the problem.

to ceria: last summer when iu firast put my new cam in i had tons of torque, but then it went away. so i was confused and rilled it all apart. i think i wore my valve guides out. now the tinkg has so much compression, i can almost pick it up by the rope. its not measured, but its sure alot.
 
waffledude376

waffledude376

Member
#12
#12
hmm, im goint ot try that, gotta run to wally world or advanced auto parts. i hope that fixes it.

Edit: how much oil am I supposed to run? I fill to the bottom of the filler threads? Is this too much?
 
Last edited:
waffledude376

waffledude376

Member
#13
#13
ok as promissed, here are the pics. i bought this oil today. and earlier before christmas break a teacher of mine gave me this un cut 5hp briggs cam straight from the briggs factory. i hope these pics shed some light on the problem:thumbsup:







 
creia

creia

#15
#15
The first photo of the cylinder wall-
Is this the same cylinder wall that you stated you honed? I do not see ANY of the typical "cross-hatching" that you should see after a cylinder wall is properly honed. Also, what was your piston to bore clearance? Ideally, you want .007"/.008"
Michael
 
creia

creia

#16
#16
waffledude376 said:
also a note, im running 5w30 motor oil, is thsi too thin?:shrug:
Click to expand...
Are you running this engine at higher rpms? (5,000+) If so, you should be using a high quality synthetic racing oil, not just "regular" oil made for lower rpm engines that still have governors installed. My son has been using "Redline" 30wt synthetic racing oil in a built Briggs "Raptor" engine (5,500+ rpm) on his Bonanza with good results.
Michael
 
old-timer

old-timer

Scamming Member
#17
#17
That cylinder doesn't look that good to me. I see some scoring that should have been cleaned up . It doesn't take much to create a problem however, I'm not sure if that is your whole problem.

Vic
 
waffledude376

waffledude376

Member
#18
#18
The motor was run for a while after being honed. I don't typically run more than 4 grand. I don't have a billet flywheel. And that was an old picture with the half of an oil bath filter on there. The black piece on there now is a PVC pipe adapter I made for the cone style air cleaner. I'm going to put it together tomorrow and try the sae 30 oil. But my question is, is the amount of oil I show in the pic a normal amount to have in a top end?i toyed to catch my nail on some of the scores and none were big enough to do that, so I guess that is fine
 
waffledude376

waffledude376

Member
#19
#19
creia said:
The first photo of the cylinder wall-
Is this the same cylinder wall that you stated you honed? I do not see ANY of the typical "cross-hatching" that you should see after a cylinder wall is properly honed. Also, what was your piston to bore clearance? Ideally, you want .007"/.008"
Michael
Click to expand...
I just checked the piston to bore clearance, it measured in at a snug .006" all the way round and all the way down. I know the cylinder is round, the piston is good its from a low hours 1994 briggs 5hp, there was alight scratch in the piston skirt, so I buffed it out with a scotch Brite pad! The scratch was about 1" long and very very shallow. May have removed some of the chroming in a small spot? Would this effect anything?:shrug:
 
Neck

Neck

Growing up is optional
#20
#20
I would say no, that amount of oil is not normal, and I would also say it was too much for it to be coming past the rings even if you left the oil control rings out when you put it together! It sure seems the the oil is being ingested through the intake tract.
 
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