New Engine too Tight ?

[Scooterbrain]

Good evening follows.
I have my 650 on the bench with the top end fully assembled and adjusted and I just noticed something that I overlooked. With the plugs Out, it takes far more effort to rotate the engine than I expected. It seems obvious that since I can rock it a degree back and forth that the tension is between the rings and the cylinder and not involved with the mains or rods.
I measured my standard bore to be Well within spec and I mean really close to stock despite the 18k on the odometer and the pistons measured out in a similar fashion. I Ordered Standard Rings from MikesXS.

Unfortunately I failed to measure and evaluate ring gap vs cylinder bore. I honed the bore and slid the cylinders down over the ringed pistons with some effort.... pretty tight but they slid on down. I assembled this with some but minimal lubrication so as to facilitate seating of the rings !
The torque does not register on my old cheap Torque wrench when I rotate the engine by that method so its less than my wrench will measure. Feels like about 30 ft lb from what I remember. and it does roll around fine without obstruction. What I am Fearing is that I have ZERO ring gap and I will have to tear this thing back down again so I am asking if anyone here has seen the same thing in one of their builds and what the recommendation is. Its just really stiff when turning over by hand.
Regardless of the crank position I cannot turn the engine with just my Hand on the Alternator Rotor which is well you know, something like 6 in in diameter but with considerable effort it turns fine with 3/8 in ratchet.
Thank You all !

 

[angus67]

When i put together my 6 over, it was tight. It has loosened up quite abit, but i was confident with my ring gap. Are you?

 

[xjwmx]

It seems like if you were able to get the ringed pistons in the bores you must have at least a little gap, or exactly 0 gap. Since it's not in the frame, I would have to take it apart and check it, personally, out of curiosity if nothing else. I got some rings from Japan highly thought of on the web, for about 1/2 the price of anywhere else. My bores had practically zero wear at 60,000 mi and the rings were in the center of the spec out of the box. Also, I didn't hone the cylinders, on the theory that since they weren't bored they did't need it, and was keeping my fingers crossed. There was still faint crosshatching in it from the factory. I immediately had 150 lbs of compression and no detectable oil usage after 500 miles. I broke it in using the recommendations on dansmc site, which made sense to me.

 

[peanut]

as xjwmx says if the ring gap was too tight you wouldn't have been able to fit the pistons without force.
Its probably a combination of new rings , too little assembly lubrication generally , new oil seals and maybe high compression if the spark plugs are fitted.
I'm sure it will be fine

I would pour a little 3 in 1 or gun oil in the bores and turn the engine over few dozen times and see how it feels then. I wouldn't strip it if it was me but then I check tolerances and lubricate generously as I build an engine so I spot potential problems early

 

[650Skull]

From your second paragraph.


Unfortunately I failed to measure and evaluate ring gap vs cylinder bore. I honed the bore and slid the cylinders down over the ringed pistons with some effort.... pretty tight but they slid on down. I assembled this with some but minimal lubrication so as to facilitate seating of the rings !
The torque does not register on my old cheap Torque wrench when I rotate the engine by that method so its less than my wrench will measure. Feels like about 30 ft lb from what I remember. and it does roll around fine without obstruction. What I am Fearing is that I have ZERO ring gap.


If its on your mind and is a worry then do something about it before it is a problem. Doesn't matter how many answers you get that say it will be alright, (and that's what you want to hear), its on your mind, so fix the issue.

 

[Michaelo]

Agree with Skull, zero ring gap = a major repair job, it's easier now to undo the bolts and check you end gap... your choice scoot....

 

[xjwmx]

I would try to get the rings off the pistons without bothering the wrist pin clip unless I had new clips. You could probably reuse the gaskets at this point. If you want, there is a great nos gasket set on ebay that is dirt cheap and factory thickness. It includes tappet cover gaskets about 1/8" thick so you never have to worry about o-rings there again.

Reason I'm posting again is a flaw in your logic occurred to me. The tightness you feel can't be due to lack of ring gap because if the gap was negative they wouldn't go in, but mainly-- a microscopic gap wouldn't exert any more force on the wall than a good gap. New rings are springier and exert more force against the walls, which is probably what you're feeling. While you break in a new motor you need to keep an eye on cylinder temperature because of that friction.

When you make a mistake of this kind it is a good idea to punish yourself for it, so go ahead and take it apart...

 

[weekendrider]

When you make a mistake of this kind it is a good idea to punish yourself for it

HAHAHAHAHA experience is a tough teacher.

 

[xjwmx]

He needs to be punished but If he got by with running it there would be no punishment.

 

[retiredgentleman]

OK lads, I just happen to have a spare XS650 in my garage, so I measured the torque required to turn over the engine.
Conditions:
no spark plugs
20W50 oil
2 degrees C air temperature
engine is cold, has not been run for well over a month ago

I will give you guys a little time to ponder, before I reveal the true torque number. There may be a prize for anyone that comes up with a number that is within 10% of my finding.

 

[xjwmx]

I'd guess 5 lbs with old rings and 10 lbs with new.

 

[retiredgentleman]

C'mon guys lets have a few more guesstemations.
The rings are about 8 years old.

 

[Michaelo]

What's 2 degrees C? We don't get that here

Is it that cold the engine is seized up? Nah, it would have to be in Canada where Max Pete lives....I'd guess 15 f lbs, if not more because of the temp.....

 

[weekendrider]

10 lbs to cycle through the valve train.

 

[Paul Sutton]

I feel brave - 35ftlb.

 

[retiredgentleman]

I can't keep the suspense going any longer. The actual torque required on my engine is 75 in/lbs or 6.25 ft/lbs.
xjwmx came very close, but unfortunately did not come within 10%, so I cannot award the prize. The prize was just a booby prize anyway!

 

[Paul Sutton]

I was way out - but what fun!!

 

[retiredgentleman]

Scooterbrain..........................you should buy some torque wrenches. For these bikes you really need one for ft/lbs and another
for in/lbs.

 

[Paul Sutton]

There are several videos on Youtube regarding end gap on piston rings. My favourite is below and it also appears in this forum somewhere:

The guy in this video gives nice clear instructions and uses a special grinder to adjust the gap, but it would be nice to know how other people are doing this.

 

[Scooterbrain]

Well like I said ! in a moment of stupidity, I neglected to check the ring gap. The bore and the pistons measured soo spot on as compared to standard that i was thinking that with a set of standard rings, that I would have no worries. I neglected to remember that it is possible to get an inferior ring set. I am not saying that I think that the ring set is bad, I am just saying Damit I wish that I had not missed that step because I am now concerned about the effort that it takes to rotate the crank.
It is smoothe all the way around and as I said I can get it to rock a bit with no effort so I am not considering rods or mains an issue, especially as they are the original with 18K on them.