Topic: Would you install new rings?

[denward17]

Got my pistons out today, cleaned them up and measured end gap of top and 2nd rings in each cylinder.
Rings visually look good, 22k miles on engine.  I cannot feel any scuffs in the cylinders.

Would you install new rings?

End gap measurements

#1 T .016, 2nd ring .014
#2 T .016, 2nd ring .013
#3 T .018, 2nd ring .013
#4 T .016, 2nd ring .014

[denward17]

more pics.

[Don R]

  The rule I was taught is once they are apart, they need replaced. 

[Ujeni]

Yes, install new rings. They don't cost much and when is the next time you plan to be in the engine? In other words, now is the time!

Did you do a compression test before disassembling the top end of the motor? If the test was good, then you may be able to get away with just rings. If the test had low results or you didn't do the test, then it is time to measure your cylinders to see if you need to go up a step in piston size.

Your mileage is low, but that can sometimes be misleading. The engine may have been abused in those 22k miles for example. My suggestion is to do the measurements if you haven't and get the top end done right.

[grcamna2]

Yes, install new rings. They don't cost much and when is the next time you plan to be in the engine? In other words, now is the time!

Did you do a compression test before disassembling the top end of the motor? If the test was good, then you may be able to get away with just rings. If the test had low results or you didn't do the test, then it is time to measure your cylinders to see if you need to go up a step in piston size.

Your mileage is low, but that can sometimes be misleading. The engine may have been abused in those 22k miles for example. My suggestion is to do the measurements if you haven't and get the top end done right.

+1 

[Tracksnblades1]

+4 New Rings..

Old ones have 22k. Your there, start new..
Make it better. Use top quality Honda Parts

[newday777]

more pics.

Did you measure in 3 different depths of each bore?

[PeWe]

I should do a quick hone with a flex-hone brush and reuse the rings that have a little high end gap.

I have lifted cylinder from pistons  and on again before without changing rings without any oil smoke due to the rings. A light hone will help rings to seal.
Rings are constantly rotating on pistons.
Most important to assemble them on same piston as they sat.
But if you can find new rings for a good price and get gaps down to 0.25mm (0.010") it will last longer.
- What about piston-bore total clearance?
Bore diameter- piston diameter at the skirts, 1/2" up from bottom.
If much over 0.05mm it might be a good idea for an overbore. +0.25 or +0.50mm.

[denward17]

more pics.

Did you measure in 3 different depths of each bore?

I did not, but will do today.  Will this tell me if the cylinder is out of round if I get different measurements in the same cylinder?

[newday777]

more pics.

Did you measure in 3 different depths of each bore?

I did not, but will do today.  Will this tell me if the cylinder is out of round if I get different measurements in the same cylinder?

Yes. The lower will usually get bigger and you will need to rebore bigger size pistons and rings.

[BenelliSEI]

My rule is if they are on the bench, deglaze, new rings, set gaps, install. Then you know it’s done...

[denward17]

I should do a quick hone with a flex-hone brush and reuse the rings that have a little high end gap.

I have lifted cylinder from pistons  and on again before without changing rings without any oil smoke due to the rings. A light hone will help rings to seal.
Rings are constantly rotating on pistons.
Most important to assemble them on same piston as they sat.
But if you can find new rings for a good price and get gaps down to 0.25mm (0.010") it will last longer.
- What about piston-bore total clearance?
Bore diameter- piston diameter at the skirts, 1/2" up from bottom.
If much over 0.05mm it might be a good idea for an overbore. +0.25 or +0.50mm.

The only guidance I see in the workshop manual for end gap is  .0079 to .016, so that pretty much answers the question that I should change the rings.

Was thinking of taking cylinder/pistons to a local machine shop to get measurements done, I don't have the tools for inside bore measure.

[PeWe]

Typical not good enough to assemble but no reason to take it apart for
This happens all the time when wrenching with the old bikes.

Easy that a domino effect will happen when cylinder is off.
-Is the chain tensioners OK? Rubber wheels not harden so it has started to fall in pieces.
After only 22.000 miles chains should be fine.
I guess you have addressed head work. Guides, valves and seats.

[denward17]

Typical not good enough to assemble but no reason to take it apart for
This happens all the time when wrenching with the old bikes.

Easy that a domino effect will happen when cylinder is off.
-Is the chain tensioners OK? Rubber wheels not harden so it has started to fall in pieces.
After only 22.000 miles chains should be fine.
I guess you have addressed head work. Guides, valves and seats.

Probably need to change the rubber wheels, they are hard.  Head work has to be done, just looking at options right now.

I measured all pistons:
#1 -- 2.403
#2 -- 2.400
#3 -- 2.412
#4 -- 2.403

Book indicates if less than 2.3939 they should be replaced.

I assume pistons are ok.

[denward17]

Measured end gaps of rings again, this time near top, middle and bottom.

I only used the top ring in these measurements.


What do these results indicate?  Hopefully that the bores are ok?

#1
T--.015
M--.016
B--.016

#2
T--.016
M--.015
B--.015

#3
T--.018
M--.017
B--.017

#4
T--.016
M--.016
B--.017

[PeWe]

You can compare bores if you use same ring in all bores.

[Mark1976]

   This is a no-brainer, replace the rings, your reconditioning the head, correct? New head and base gaskets,  new cam chain adjusters, o-rings, your going that far why not replace them. Reusing old rings under a freshly reconditioned head is like taking a shower and not using soap, ya can, but why would ya. I'm not saying you can't, its your bike, but anything worth doing is worth doing right. They're cheap compared to what you'll spend getting the head back to spec.
   Its like in the "Godfather ", when Clemenza has Paulie shot in the car, "Leave the gun, take the canoli." He didn't even have to think about, it's obvious.
   

[Shtonecb500]

new rings - i learned u dont even think about.

[denward17]

Best source for rings?

Assuming Honda doesn't make these anymore.

[grcamna2]

more pics.

Did you measure in 3 different depths of each bore?

I did not, but will do today.  Will this tell me if the cylinder is out of round if I get different measurements in the same cylinder?

Yes. The lower will usually get bigger and you will need to rebore bigger size pistons and rings.

Good idea if the bores are worn 'out of round. 
I hope you're able to find those same type OEM pistons with the nice rounded dome.

[denward17]

more pics.

Did you measure in 3 different depths of each bore?

I did not, but will do today.  Will this tell me if the cylinder is out of round if I get different measurements in the same cylinder?

Yes. The lower will usually get bigger and you will need to rebore bigger size pistons and rings.

Good idea if the bores are worn 'out of round. 
I hope you're able to find those same type OEM pistons with the nice rounded dome.

Was hoping to install a fresh set of std. rings on existing pistons.

[bryanj]

If the bores are worn its false economy, as Hondaman states when the bore ovals new rings are a waste of time, only cure is oversize kits and rebore. Cruzinimage in Japan do reasonable priced kits if you dont get stung for import tax but the boring aint cheap and needs to be done by a person who knows what they are doing NOT A CAR SHOP

[denward17]

If the bores are worn its false economy, as Hondaman states when the bore ovals new rings are a waste of time, only cure is oversize kits and rebore. Cruzinimage in Japan do reasonable priced kits if you dont get stung for import tax but the boring aint cheap and needs to be done by a person who knows what they are doing NOT A CAR SHOP

I have an appointment Friday am to visit a machine so they can measure the bore and pistons.  I really hope it is ok, don't really want to bore if I can help it.

[grcamna2]

more pics.

Did you measure in 3 different depths of each bore?

I did not, but will do today.  Will this tell me if the cylinder is out of round if I get different measurements in the same cylinder?

Yes. The lower will usually get bigger and you will need to rebore bigger size pistons and rings.

Good idea if the bores are worn 'out of round. 
I hope you're able to find those same type OEM pistons with the nice rounded dome.

Was hoping to install a fresh set of std. rings on existing pistons.

I do hope you're able to re-use those pistons;it will depend on the inside measurements I.D. of your cylinders as they have a close specification for cylinder to piston fit.
I've found it a problem to re-install a piston that has too much clearance in a bore because it will cause the piston to rock back and forth in it's bore and then the rings don't properly seat which causes it to burn oil;I had to do the entire job over again with the addition of new pistons and rings.
I hope you can find a Powersports Machinist (have you sent a message to member 'dragracer' here on the forum? he knows of a good Powersports Machinist in NC.) to have those parts measured and then see if it will match the 'standard running clearance' for new parts;the 'Service Limit' is too big of a clearance for new parts.Do you have the Honda factory Service Repair manual, or HondaMan's book ?

I just posted and noticed your post: Good,I hope they understand the correct tolerance of 'installed new clearances'.
I've found that,9 times out of 10 automotive machinists think our Honda clearances are "too tight" and then set the clearances about .002" which is Too Much.

[denward17]

I'll report back what they find, no machine work tomorrow, just measurement.
I'm using the online version of the Honda CB750 workshop manual which indicates:

If the diameter is greater than 2.406 in.
(61.1 mm), the cylinder should be rebored
and honed. Further, if the taper and the
out of round is greater than 0.0020 in. (0.05
mm), the cylinder should be repaired in
same manner as above.