I purchased an engine on ebay RB S7(yes I am aware I may have gotten screwed) But since it is freezing balls here in Michigan I cannot really run it. So what symptoms or characteristics do you look for when evaluating the pinch condition? I have now been scared by another post saying his engine "was so worn out he could turn the flywheel over by hand with a glow plug in". Well if that means worn out, then both of mine(RB & stocker) are trash. There is definitely compression but how would I know what good is. So what should a solid engine feel like when turning it over by hand with the flywheel? Maybe you have an even better test? Thanks

?

It's late, I thought that made sense, maybe not. I am asking if you guys have anyway of telling me what my engine should feel like when turning it over by hand using the flywheel. Thats all.

I think that was my post you quoted.

I was a little brief when I typed that. I should have said that it was easy to turn over by hand. With the glow plug installed, you should feel a lot of resistance when you get to top dead center. A brand new engine will be so tight that you can't turn the flywheel by hand past top dead center. Some high end engines, for example, need really really beefy starter boxes and high amp 12v batteries just to turn the new engines over. If you can run the flywheel over without much resistance, it's time for a rebuild (or resize).

You can also check "pinch" by taking the glow plug out and running the piston towards top dead center. When it gets close to the top, you should feel a little reistance. At a microscopic level, the sleeve is a tapperd cone shape at the top and the reistance you feel comes from the piston forcing it's way through the narrowing in the sleeve at that spot. If you can run the piston all the way up the sleeve without any reistance or "pinch", then it's time for a rebuild.

This next way to check this is kind of hard to explain without a picture. A friend of mine showed me this and it's pretty unique. Take the engine out of the car with the flywheel attached and the glow plug installed. You then hold the engine by the flywheel at an angle in the air. The idea is to get the engine's compression to hold the weight of the engine in the air. Eventually, the weight of the engine will over come the compression and the engine will turn over (the engine's head will now be facing the ground). "Good" compression will hold the engine in the air for at least 2-3 seconds before flopping over. If it's less than 2 seconds, it's time for a rebuild.

The last way I know only applies to small 1/10th scale vehicles with a pullstart. If you can lift the car off the ground by the pullstarter cord, then you have good compression. That's kind of dumb, but an easy way to check.

If your engine is in this conidition, you've probably looked to the cost of a new piston/sleeve assemble. They are not cheap. There is a guy on ebay called "OSRocket". I sent the piston/sleeve from that engine I messed up in the cold to OSRocket. When I got it back, the pinch was so insane that I can't budge the piston in the sleeve PERIOD. It's stuck. I have yet to follow his instructions and get it up and running again (still cold around here). I spent about $27 total including my shipping costs to him and I'm tickled so far. If you go this route, however, you should buy a new conrod and anything else you'd normally change in a rebuild. The conrod and the wrist pin are the real humdingers. They get a ton of abuse and if you don't change them out after a resize, your conrod may break before you get all the life out of your resized sleeve. The conrod and ect are thankfully the cheapest parts of a rebuild.

Anyway, I wrote a book. sorry. I hope your engines aren't hosed. [&o]

-RobH

No need to apologize, that was great! And way better reply than "?" Exactly what I was looking for, now if I can get some confirmation on your theories I will sleep better I am pretty sure the 45 degree angle test would be easily passed by my S7, I don't think it would ever rotate the piston past TDC using its own weight. I don not really feel a pinch without the plug in but compression seems fine based on your info. Maybe she's in the "sweet spot".

Ye, he is right, it should be impossible, or atleast near it, to turn a brand new engine over by hand with glow plug in, especially for a RB.

Well how about a broken in engine. What I am getting at here is when are they worn out? Imagine you happen to be at a garage saleor swap meet or whatever and there is an RB WS7 sitting there for $100 or some other reasonable number. Obviuosly you cannot run it so how would you make your decision as to whether it still has life in it or if it is a paperweight? Thats what I have been getting at.

I'd say if it passes any one of those tests, it's still in good shape. The "45 degree angle test" was shown to me by an engine builder / modifer whom I have a lot of respect for. If any of the above methods is the "right way", I would put my money on that one.

It sounds like I made out good on the engine. I hate buying stuff on ebay only to find out that I've bought a boat load of crap. I'm strickly a NIB kind of guy these days.

-RobH

I hear ya, it was an impulse buy I just wanted a solid cheap runner to learn with before I go balls to the wall this spring.

Yeah the RB engines tend to last and last too.

One thing I just remembered about the S7. I remember reading on the RB forums that the conrod in the S7 isn't the same "competition" type that is used in the WS7 and WS7II. The advice given on the RB Forums was to upgrade the conrod to the competition type after "5 liters" of fuel. I think that's a little silly, but if that engine has 2-3 gallons of fuel on it, you should do the conrod upgrade. A broken conrod will ruin your day in a heatbeat (not to mention kill a good piston/sleeve assembly).

Another think about changing the conrod. During break in the conrod stretches so if you slap a new one in there and go balls out, it wont stretch properly again and the engine will act weird and the conrod won't last as long. If you change any engine components, it's wise to do a "mini break-in".

Anyway, just stuff I've heard,
-RobH