cylinder too tight?

Mr.GhettoRig

Mr.GhettoRig

Active Member
#1
#1
okay im working on putting my briggs 5hp back together, just had it rebored to .010 oversize, guy had it cleaned and honed as well.

Oiled everything up, piston, rings, more than enough in the cylinder. I got it in there but it's REALLY tight, I had to put the flywheel on all the way to rotate it.

after I finally got it all the way down I poured about 1/16 (maybe less) oil on the piston and continued to rotate it up and down and the oil quickly filled up with metal dust. so I cleaned it out, put another small puddle on top and continued. 4 or 5 more times.

currently it sits with the puddle of oil/metal dust mix and the cylinder had the vertical scoring, its all just about cosmetic though because it feels smooth running my fingernail over them. the piston is still tight enough as if it had been on the compression stroke but the thing isnt even put together yet... I hope to god I didn't screw something up already. :facepalm:

any ideas? :shrug:

EDIT: the title was supposed to be "piston too tight" but whatever.. :doah:
 
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cheezy1

cheezy1

#4
#4
you have to fit them in the cylinder without the piston and check and make sure there is proper end gap...otherwise you are gonna kill the bore. They usually all need a lil taken off.
 
cheezy1

cheezy1

#6
#6
If you caused any slight marks..a quik pass with the cylinder hone will correct it.:thumbsup: Let us know what you find. And dont forget to re-clean everything in mineral spirits or something to remove all lil shavings.
 
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Mr.GhettoRig

Mr.GhettoRig

Active Member
#7
#7
just pulled the piston and sure enough the piston rig had too little of a gap, I lack a hone. there goes my excitement for this afternoon. :doah:
 
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Mr.GhettoRig

Mr.GhettoRig

Active Member
#8
#8
thought I'd share a pic of the...damage? :shrug: it seems the hone marks are still over the vertical marks. should I still hone it? I only ask because I SUCK at honing and I dont exactly wanna drive all the way back to venice to spend another $50. :hammer: but if theres no way around it I'll do what I have to. :doah:

 
Pasta

Pasta

Member
#9
#9
That cylinder is FINE. Just clean it with paper towels and automatic trans fluid. Keep switching to a new towel until it doesn't get dirty anymore. You'll be surprised at how much junk comes out of that cylinder.

File-fit the rings, and reassemble the thing. There's nothing wrong with that at all.

Have fun.

George
 
Mr.GhettoRig

Mr.GhettoRig

Active Member
#10
#10
this ordeal turned out to be a blessing in disguise...

so I took my rings off, top ring and bottom ring are now set to just about 0.007 and should move nice and smooth now. but as I was cleaning up the oily mess I realized that I had forgotten to put the piston clips in :doah: :no:

anyway, rings are fine now, if the cylinder is fine then maybe I'll take another tackle at it tomorrow. For now, I gotta get started on homework. :hammer:

thanks guys. :thumbsup:
 
cheezy1

cheezy1

#11
#11
Cant tell by the pic for sure..but if there is any doubt to the cyl surface..then hone it a lil. Harbor Freight has one for under 20 bucks. If there are any raised spots it will chew up a set of rings fast and send tiny metal particles into the oil and on moving parts. With engine building..its better to be safe then sorry. Just sayin...and good luck:thumbsup:
 
Mr.GhettoRig

Mr.GhettoRig

Active Member
#12
#12
I'll probably rent a hone from autozone, because there is a spot that kinda worries me a bit. my grampa used to say "do it right or do it twice" :grind::hammer:
 
MB165

MB165

Active Member
#15
#15
With a new bore, piston and rings its GOnna be tight. I wouldnt hone that cylinder, plus honing isnt the way to set endgap. .007" endgap is just fine. the marks are typical of aluminum bores. I wonder if the shop used the proper stones in the hone. You CANNOT just throw any old hone in a aluminum bore and get it right.
 
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cheezy1

cheezy1

#16
#16
MB165 said:
With a new bore, piston and rings its GOnna be tight. I wouldnt hone that cylinder, plus honing isnt the way to set endgap. .007" endgap is just fine. the marks are typical of aluminum bores. I wonder if the shop used the proper stones in the hone. You CANNOT just throw any old hone in a aluminum bore and get it right.
Click to expand...
Its not the hone so much as the fluid you use while honing. And why would you hone to set end gap? Did I miss that part? And there should be no marks or raised areas aluminum or not.
 
Mr.GhettoRig

Mr.GhettoRig

Active Member
#17
#17
those rings were TIGHT in there, the oil ring was fine but the two compression ones needed a thousandth or two taken off. I can fit the .006 in and JUST barely fit the .008 if I try, so I assume its just about .007 which is where it should be according to 10 minute research. as for the bore its as smooth as it was before I messed it up, there's just one groove I can BARELY hang my nail on, and thats what was worrying me. I can't feel any rough spots or burrs, but considering they'd probably be microscopic that would explain why. :shrug:

and Buck, yeah I love learning, I just don't like 'learning' on my important engines. which seems to ALWAYS happen. I did keep that briggs that I ran unfiltered earlier this year, I use it as a test dummy on my 'custom' machine work and as a sort of template for my bolts to sit in. :shifty:
 
DZLBIKE

DZLBIKE

New Member
#18
#18
Just in case you don't know, when you go to feeler check your ring end gap, turn your ringless piston over and use it as a tool to position the loose ring in the bore. This makes the ring more square to the bore, so that you aren't checking an ellipse. (I hope that made sense to you, I'm not at home, so I can't take a picture to illustrate what I'm talking about.) :shrug:
 
125ccCrazy

125ccCrazy

Well-Known Member
#19
#19
if you had any end gap at all before taking a few thousandths off isn't going to relieve any pressure...if the gaps were touching then that would make them tight... I would check the piston to wall clearance as well..... unless you wiped the bore down yourself prior to installation the aluminum residue you found could have been from the machine work..

how tight was the piston to move by hand when you were installing it? did you have to push it hard to get the rod hooked up?

if it wasn't hard to push down in the bore by hand did you check the rod bearing clearance?

if the side case cover was bolted on did you check the end play and make sure the cover wasn't binding on the crank?
 
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Mr.GhettoRig

Mr.GhettoRig

Active Member
#20
#20
The rings were touching before I filed them, now they just have that tiny .007 gap. The block was cleaned twice, once at the shop and again in my auto class, and everything was lubed with oil before install. The piston fits In there nice and snug, he bored it to have .003 Clearence and it feels as it should. When I installed it yesterday I could spin the piston but there was no way in hell I could push it down, that's why I had to put the flywheel on. Which thinking now that was a really dumb idea :doah:
 
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