TOPIC:

Hey everyone. Can I get some tips on reassembling the cylinders and pistons on a new set of bored out cylinders?

After getting the cam timing adjusted back to stock I also discovered the rings weren't apparently seated properly. I did a leakdown test with a homemade setup and and I heard the air hissing out into the crankcase from each cylinder as I checked them. When I added oil to the cylinders I couldn't find any air leakage at all. I figured I'd better get that fixed because it may be the source of some maybe a lot of the engine overheating, oil heating up from cylinder blowby?

I already had the cylinders on it bored out but ignorantly used a car machine shop to do the work. I took them to a REAL motorcyle machinist and found out the cylinders had been bored too big and had a coarse crosshatch. I had also used my engine assembly lube when reassembling which has Mobil 1 synthetic and STP in it. Again ignorant.

Anyway I have yet another set of stock cylinders at the motorcycle machinist for boring and I am confident it will be a proper job this time. If anyone can help me with some assembly tips to get it right this time I would really appreciate it.

Thanks much!

Well I was told a time ago that you dont put two of the same materrial together in a(n) engine. for instance cast pistons with cast rings for a cast block. Due something like hyperuetectic pison chromoly rings with a steel or cast bore. makea for a better running engine. The guy also told me that when assembling an engine dont use any lube on the cylinders, at the very most just a squirt of wd 40 for the piston skirts. The reason for no oil on the rings is because when you start your engine for the first time your rings seat and as soon as the oil hits the rings it stops the breakin proses. What do you guys think? The guy builds all kinds of engines all of wich run very well.

First, coat the bore walls with either Marvel Mystery Oil or Automatic Transmission Oil. Both are petroleum based and will burn off quickly, allowing the rings to seat as normal oiling begins once the engine is started.

Second, take a piece of wood about 1" thick and about 4" long and cut a slot in one end so that the slot is about 3 inches into the wood. Looks sort of like a flat clothes pin. The wood piece should be about 1.5" wide I guess. You will turn the engine over so that 2/3 cylinders are UP (TDC). Get your gasket on the lower mating surface. I ALWAYS use NAPA brand spray gasket sealer. It looks like red spray paint. It is messy. Anyway... set the block down on the studs where it isn't quite lined up and pull your cam chain through. You should have a wire attached to the cam chain that you can tie to something... If the engine is out, use the ground bolt. This is to keep the chain from dropping into the engine and having to fish it out. Put the clothespin-like piece of wood under either the #2 or #3 piston so that it can't drop when you sit the block on it and it helps stabilize the 2/3 pistons as you go to set the block down.

Next, set the block down OVER the studs and onto the pistons.... ROCK them just a tad to get them straight under the bores. The block should slide down to the top ring on each of the two pistons. Pinch the top ring on one side and gently push down on that side till the liner goes over the ring on that side. I sometimes use a small, flat blade screwdriver to help compress the ring which is hard to pinch once it is half way under the liner.

Pinch the other side's top ring and push it down... Repeat for the middle and scraper ring... Once both liners are over the 3 rings on the 2/3 pistons, remove the wooden pin and gently lower the block onto the 1/4 piston crowns. They will try and rock some so it works better if you concentrate on getting them started straight in the lines. Then just repeat your pinching of one side's top ring; push down the block gently on that side and do the same for the other side. Repeat for other rings.

Once you have the block down near the engine cases, I suspect you should button it up (put head on) and torque it down if you use gasket sealer.

I would also advise you dry test fit the block (before installing the pistons) to make sure that it fits easily over the engine studs; especially if you changed blocks.

I haven't tried it yet, but someone else on the list has reccomended using large zip ties (1/4" wide) as ring compressors.

I had a terrible time compressing my rings on a similiarly improperly bored block (not enough chamfer left at the bottom).

The zip ties seem like a simple no brainer to me. As the block comes down it simply pushes the zip tie down the piston. Then you cut the tie when the rings are in the bore. I haven't tried it, but it seems like a great idea to me. Much easier than pushing on the rings w/ fingers or screwdrivers!

Old-skul - If the piston ring is JUST inside the bore, I am not sure how you would cut the tie. I understand your frustration with the finger pinch and screwdriver method but if I take my time, it works pretty much every time without a lot of fuss. The secret is to not push too hard down on one side... just barely enough to settle the block down but not enough to get the block slanted where the other side is hard to push down.

Try out the wire tie thing and give us a report. Lots of things have sounded good till they were tried out bwhahaha. Once, on this board, some suggested stuffing the pistons/rings in the bottom of the bores and then setting the block (with pistons/rings) onto the rod ends and pushing the piston pins through. This sounded nice except there isn't 17mm of room between the pistons to get a piston pin in there. (I hate to admit I like to try different things). I have also tried using piston ring compressors as I have a nifty set from Snap On. Those are a bust as well... at least I couldn't get them in place and have enough room to get the rings in the bores. I have also thought I would buy one of those Kaw ring/piston tools you see on eBay from time to time but they usually go for more than I am willing to spend... would be good to hear a report on how they worked! Cheers...

WG, I thought about trying the put the pistons in the cylinders before you pu the block on idea and would have thought it would work if you did 1&4 first then put 1&4 at TDC whilst you did 2&3. you've got at least 70mm between con rods surely?

I have used hose clamps to pinch the rings, they worked pretty good, just have to go slowly and make sure the flat part of the clamp does'nt slip into the cylinder between the wall and piston. On a thin wall sleeve it can break, been there - done that once.

Hi all. I got my cylinders back and I'm about to put them back on. However I have a question. In one of the previous posts it was mentioned about using WD40 as a cylinder lube when reinstalling the pistons. The machinist who did my cylinders ALSO said to use a little WD40 on a shop towel and wipe the cylinders out, not to put oil in the cylinders.

This has me bugged. I have always put some oil on the rings and on the cylinder walls to prevent bad things from happening on initial startup.

I REALLY don't want to screw up this time, has anyone done this with the WD40 or what?

Thanks!

I generally use a fella named Robby to do my machine work. He has been a leading racer for years and does all the machine work for most sucessful drag racers in South Texas. He swears by lubing the cylinder walls with ATF... it is lighter and burns off at about the same time as oiling starts and allows the rings to seat. He mentioned Marvel Mystery Oil does the same thing but costs more. I have used ATF to lube cyliders for about the last 20 engines I have seated pistons rings in and it works fine. I have also left the bores dry and used motor oil and they sealed doing both those things with no apparant ill effect. I suspect WD40 would also work. I don't think it much matters what you do but it makes me feel better to not cut them in dry although I have done it and it works. Oil doesn't take long to get in the area... I think this type question is like asking what type oil is best or what type tire is best...If the WD40 machinst seems like the man you want to trust, use WD40 with confidence and then you can tell everyone that WD40 is the way to go... I suspect WD40 will work just great!

Thanks much WG. I will let you know how it goes.

Hey Willo, are you sure he meant NO oil? I just got my cylinders back yesterday, and my builder said to use WD-40 and paper towels to CLEAN the cylinders before assembly, but he also said to us regular oil for the assembly and break in. I asked him about the ATF thing and he wasn't very impressed. I'm guessing that he has just never tried it and didn't want to take a chance. It sounds like WG has had good luck with it. Either way, I think oil or ATF is a must. I'm curious to see if we get any other opinions.

Post edited by: 79MKII, at: 2006/03/24 19:07

WG-

MMO may cost a little more but it sure smells nice.