vuuli312

Hello. I'm replacing the sleeve in my o.s. max .77 vrm. The sleeve is really tight. going in. are there any tips out there to make it easier. I had to heat the block in order to remove the old sleeve. Should I do the same to install the new one? Thanks

1QwkSport2.5r

Make sure you cleaned all the gunk out of the crankcase that was holding the old liner in before. Oil gets between the liner and crankcase that varnishes a bit and if not cleaned out makes it hard to get the new liner back in. Clean clean clean and the liner should slide in with a light interference fit. You *may* need to heat the case to get the liner in, but you shouldn't have to IMO.

blw

My Feedback: (3)

The heat gun should be enough to heat up the crankcase enough to get the sleeve to drop in. You could drop the sleeve in a bowl of ice for a few minutes too.

The parts will have this fit problem from engine to engine unless they are handpicked and hand fitted. Hand fitting was the major expense of the OS Hanno high performance engine made many years ago.

I'm not saying OS does this, but one of the moderators wife worked around an assembly line and she said the parts that had problems were tossed into boxes to be sold as spare parts. Something to think about........

aspeed

If you can get the liner started in the hole, a bit of lapping in a figure eight pattern may get you the right clearance. Even without lapping compound. If you know about a thorough cleaning afterwords and between checking the fits you should have no probs. Sometimes it will stick if you push in too hard and it can ruin your day. Sometimes there is a burr on the outside of the ports that hangs up, which can be carefully filed off too. You will notice this if the liner goes in nicely, and stops half way.

dlegolpolp

Clean clean clean and the liner should slide in with a light interference fit.

Bax

My Feedback: (11)

It's not unusual for the crankcase/liner fit to be a bit tight on some of the high-performance engines. We've found that mild heating of the case will allow the liner to slide right in. Some engines had a tight-enough fit that you could never remove or replace the liner without heating the case. When the liner is in place and everything's at room temperature, you'll be fine. The main thing is how the engine runs. With an engine like the O.S. Max .77 VR-M, you'll want to run it just rich of peak RPM. Use a good fuel with no less than 18% oil content and at least 50% of the oil being castor, and you'll do well. Run the engine too rich, and it will never come in. ABC-type engines need lubrication and need to be run lean of the "2-4 break". Lean to just rich of peak RPM as soon as the engine will accept the needle.

1QwkSport2.5r

I love the term "ABC type". Generic and ambiguous.

blw

My Feedback: (3)

I used to be like a lot of people and think the heat gun as too wimpy for engine work. I learned that it works about half the time and you don't need more heat, like an oven.

1QwkSport2.5r

In reality, you shouldn't need heat to install a liner if the crankcase is clean. If the liner doesn't slide in, something is wrong. A true high performance engine (like Jett for example) has a slip fit of the liner. I should say; I've never had to beat a crankcase to install a liner provided the crankcase was cleaned of all old oil and varnish deposits.

blw

My Feedback: (3)

Tim, parts fit on an OS is a different animal than a Jett! I agree with what you said about any Jett, but not OS, Saito, etc. The hand fitting parts just for the Hanno racing engines at OS is a good example of how this is true. Cutting on Monday may be a little off from cutting parts on Friday.

In hindsight, maybe I would want a tighter fit when it comes to liners.They have to be real snug everywhere to transfer heat. I wish I knew where my picture is that the late Pe Rievers took of a gas engine liner that had been run too hot. The heat colorations showed the heat patterns well. It is very interesting what gets hot and where. I'll try and dig up that old pic that is on some computer around here.

1QwkSport2.5r

The liner should be a snug fit, but it should slide in and out without too much effort. Getting a liner out of a used engine might require heating the crankcase. Once the crankcase is cleaned, the liner should go in without the need for heat. If it does, the crankcase could be distorted or there could be a ridge around a port in the liner - a slight bulge or high spot. I know Jett are in a completely different league than an OS, but if a slip fit is all that's necessary in a Jett, why would a tighter fit be warranted in an OS? Hand fitted parts? I doubt it though I don't know for sure. Mass produced engines aren't hand fitted. It wouldn't be cost effective to do so. I could be wrong, so if someone knows for sure if any past or current mass produced engines are hand fitted, post some information.

I don't think it's realistic to compare an air cooled gasoline engine to a water cooler marine engine. Two completely different operating environments with two completely different operating temperatures. Apples and oranges there.

blw

My Feedback: (3)

Tim, you are getting off into some areas I have no idea what you are talking about- marine engines??? You need to read Clarence Lee's examination and explanation of the Hanno engines. Interesting stuff about hand fitted engines vs assembly line engines. And, people who work on assembly lines will say the same things.

Look- I'm talking about new engines. Never run. Now, if we were talking about engines already run, broken in, run hard, etc like you suddenly brought up just now then I agree with you. it should be a slip fit. I don't know about crankcase distortion since we were talking about liners. I would agree with cylinder head distortion, or a bad case of unequal heating on the liner.

The path of this debate could lead someone to think parts fit is the only advantage Jett has for high performance, which isn't so.

1QwkSport2.5r

If you read the first post in the thread, you would know the OP's engine that he is replacing the P/L in is an OS .77 VR-M engine which is a marine boat engine. I'm going on the assumption the existing P/L is worn out so they are putting a new set in which would mean the engine is used and not new. That is assuming nobody would replace a new P/L with a new P/L.

Make sense now? If I am off base, let me know.

blw

My Feedback: (3)

You got me there, Tim. So, no, you are not off base.

1QwkSport2.5r

Removed content.

Broken Wings

My Feedback: (20)

I have both engines and enjoy them.

1QwkSport2.5r

I know you do. I'm a fair bit more bias, but I still have a lot to learn. I can't assemble anything properly, remember. I forgot to put the piston ring back into my Jett engine once... It still ran great without it! LOL!

Broken Wings

My Feedback: (20)

Well, you can buy parts if you need them....some engine manufacturers are thriving. Others have been forced out of the market by manufacturers that make better products. Fox comes to mind. Gas/Glow it didn't matter, no one was buying it. No one is buying the spew that continues to dribble out of the mouths of the banned...
Buy and fly what you want. I do.

Broken Wings

My Feedback: (20)

Didn't remind us time and time again that glow was dead... as well as this forum... Poor tortured soul.

1QwkSport2.5r

I've heard a few folks say those very things... Don't see glow dying anytime soon, and I don't see RCU going anywhere anytime soon either. It might be slow, but it's still gonna be here.

No Jett engine ever made that I know of ever came with ringed Pistons. They are ALL tapered bore ABC or AAC. But if I did need any parts, Jett is very much still in business and they manufacture first rate engines and still supply parts for most engines they've made. They will do custom machining for other engines too - if you are willing to pay, they can re-fit other brand engines with new parts that are no longer available I believe. Everything has its price.

Broken Wings

My Feedback: (20)

Might be why you forgot to install it...

1QwkSport2.5r

Oh, I just said that to ruffle some feathers. Just like my comment earlier about loving the term "ABC type". As if I was really serious..

The Internet is a great place to not be taken serious.

blw

My Feedback: (3)

We don't need help ruffling peoples feathers around RCU, that's for sure.

I'm with Broken Wings- buy and fly what you like.

1QwkSport2.5r

It's not the people on RCU that are getting their feathers ruffled, at least I hope anyway.

Broken Wings

My Feedback: (20)

Thanks for the address.