Tight pistons

[yellowdog]

New year ,new problem.
Just spent the last few hours fitting the new rings ,standard size ,into my honed cylinders and they seem to be a little tight ,I can move them up and down by hand but I seem to think that when I took them out they moved fairly easy,is it a case of because they are new rings they take a while to bed in ? I have measured the gaps on the rings and that seems ok ,I even put the old rings back on and they moved a little easier than the new ones.
Any thoughts please.

 

[fredintoon]

Hi 'dog,
of course the old rings move easier, they are clapped out, right?
Once the new rings bed in they'll be fine.

 

[arcticXS]

Yellowdog,
Did you check the ring end gap before fitting the rings to the pistons?
If not, I recommend you do just that, otherwise there is a chance you may end up with problems.
On the other hand, if you did check the ring end gap, then most likely Fred is right, that new rings gives more friction than old, worn rings. And you should be good to go!

 

[yellowdog]

Yes ,gaps checked,Iwas expecting that after having the bores honed the pistons would slide fairly easy.
The honing has left the bores not as smooth as before so hopefully you are both right in saying they will bed in ,Thanks.

 

[chizler62]

Honing the cylinders basically is to leave scratch marks for the oil to lay in order to lube the walls etc. So there are now hundreds of little sharp grooves in your cylinder. Typically it'll be a touch tighter than when taking it apart. Did you make sure that all the stamped(sharp) edges of the rings? What assembly lube did you use for wrist pin, walls etc??

 

[yellowdog]

Just used some new engine oil for lubrication,the pistons are not stuck just a little tight .I can push them up and down using two fingers but not having had much experience in this I was concerned that they might be to tight ,Thanks

 

[kevski]

Just used some new engine oil for lubrication,the pistons are not stuck just a little tight .I can push them up and down using two fingers but not having had much experience in this I was concerned that they might be to tight ,Thanks

That's all normal yellowdog, I will be in Lincolnshire in April my daughter lives in Gedney, and I will be staying in wisbech st mary, I like it up there nice and flat and not so many people.

 

[member3480]

Ok here a couple tips for you guys who don't do motors on a regular basis.
When you get your cylinders back from machine shop look closely at top of bore and bottom of bore. Some older boring bars do chafe the tops and bottom as it is going in and out. NORMAL!!!! if done correct piston rings don't reach that point up or down.
When I get my parts back I take both pistons and mark them 1 and 2 now that never changes. Put both pistons in cylinders without rings and push them up and down. There should go up and down easy because of the piston to wall clearance that the machine shop left. Take top ring (again mark 1 or 2) push ring 1/4 down with piston upside down so you don't damage ring CHECK GAP. Do same with 2nd ring both cylinders. If all good what I do is put rings on marked pistons and set them in the bore from the bottom tapered end and with just very little oil push pistons up and down there should be some effort to push up and down if bore was done correct. DONE
Now I am anal and one thing I do with top and bottom ring is when I put them in the bore I place ring 1/4 from top 1/2 in bore and 3/4 down and read all three readings. Should be the same if boring bar is true. I have had bad bores and there was a difference which will wear rings fast and oil rings that are so thin can bend. Had one come in shop like that and only had 600 miles on new bore and oil ring was bent. Used bore gauge and 3/4 to 1/2 from bottom was out with bore gauge. BUT THIS IS ALL THE STUFF A GOOD MACHINE SHOP IS LOOKING FOR before you get back your stuff.
Bottom line you get what you pay for. Me my machine shop does more car motors than motorcycles so I got the model number and brand name of boring bar and bought new motorcycle boring stones for his machine and that's what he replaces when bad.
Many people don't know but there is difference in stones and the cross hatch left in bore. Some look like lines and others look like X marks. I asked that question to a major boing company and they said no difference just the way bore was done. Me I just had to ask.
Hope some of my info helps with future builds.
Rich

 

[yellowdog]

Kev ski,hi ,I am in Grimsby ne lincs,did you know the late great Barry Sheene used to live in March near Wisbech