Whizzer piston rings

[bikewhorder]

Hello, first time poster here, I'm in the midst of my first whizzer rebuild and I was wondering if someone could tell me how critical the gap is on the piston rings. I removed the rings and inserted them in the bore and what I came up with was a gap way bigger than my feeler gauges would measure, probably over 1/32 of an inch . According to the info I have it should be between .012-.018. All the other parts of the motor would seem to suggest that this motor was hardly run. Do I need to get new rings, or is this not a critical tolerance, or am I not measuring it correctly? Thanks -Chris

 

[bikewhorder]

I forgot to mention this is an H motor

 

[jbcruisin]

Hello, first time poster here, I'm in the midst of my first whizzer rebuild and I was wondering if someone could tell me how critical the gap is on the piston rings. I removed the rings and inserted them in the bore and what I came up with was a gap way bigger than my feeler gauges would measure, probably over 1/32 of an inch . According to the info I have it should be between .012-.018. All the other parts of the motor would seem to suggest that this motor was hardly run. Do I need to get new rings, or is this not a critical tolerance, or am I not measuring it correctly? Thanks -Chris

That sounds like a big gap. My book says .012-.018. Rings for an H motor aren't hard to find if you need them.

 

[bikewhorder]

Yeah I know, I'm just feeling poor and not wanting to open my wallet for more parts, I've already spent about $200 @ memorylane and its starting to dampen my enthusiasm for the project. I guess I don't want to be cheap to the point of foolishness though. I'm also wondering if you guys recommend deglazing the cylinder? A co-worker said I need to do it, and lent me the tool to do it with, but I'm pretty nervous about possibly destroying the engine having never done it before. The cylinder walls look so nice and smooth, it seem counter intuitive to spin some abrasives around in there. He assures me that I cant mess it up, and that it should be done but I'm still skeptical.

 

[Quenton Guenther]

It is important to re-surface the cylinder wall. The rings need to be replaced as the end gap shouldn't exceed .018". Sounds like you may also need to bore and move to the next O.S. piston. The distance from the skirt to the cylinder should be under .005", and you can check with a feeler guage. Only check from the front or rear piston skirt, never on the sides with the wrist pin.

If you don't want to spend any extra money you can knurl the bottom of the piston, hone the cylinder and install a new set of rings. If you replace the rings, the cylinder must be honed with a cross-hatch pattern. The cross hatch pattern can be applied with a cylinder hone turning slowly and the movement up and down the cylinder at a rapid pace. Be sure to check to see if the bore is even from top to bottom, if not concentrate the hone on the smaller bore area in the cylinder.

Have fun,

 

[bikewhorder]

Thanks, I was able to take it over to a machinist friend and get the bore checked with a snap gauge and everything looks to be pretty much dead on 2.25" in the bore and the piston was within spec so I just ordered new rings. I guess my first question was kind of dumb since my friend pointed out that if there is a big gap in the rings the oil will flow right through it. I now have two conflicting bits of advice, one mechanic friend of mine told me to use a berry hone and the other insists that I use the three spring loaded flat stones to deglaze the cylinder walls. What do you recommend? When you say "turning slowly" how many RPMs should I shoot for? I'm hoping to get this engine back together soon and I'm very excited to see it run for the first time. -Chris

 

[Quenton Guenther]

Either hone will work, however the "ball" type will most likely work best if the bore is straight, as it is possible to alter the bore "tilt" with the 3 blade type. It may be difficult to find a "ball" hone for the small Whizzer bore.

200 RPMs is a good speed to hone a cylinder.

Be sure to remove any ridge at the top of the cylinder before starting the hone process.

Have fun,