124 Piston Clearance

[D-1]

This is the first S&S 124 kit i am fitting to an engine. Its a kit that comes with 91cc heads, flywheels, finished cylinders and pistons. I fitted torque plates and measured the cylinders and found 0.0015 taper in one, and both have the piston to cylinder clearance between 0.001-0.0015.  If i measure the piston and allow 0.0025 clearance the taper will clean up. Is this clearance/procedure OK? S&S dont give a piston to wall clearance in the instruction.

Are the 91cc S&S heads a good performer? Are they the same as whats fitted to the T124 engines?

Thanks

[1workinman]

This is the first S&S 124 kit i am fitting to an engine. Its a kit that comes with 91cc heads, flywheels, finished cylinders and pistons. I fitted torque plates and measured the cylinders and found 0.0015 taper in one, and both have the piston to cylinder clearance between 0.001-0.0015.  If i measure the piston and allow 0.0025 clearance the taper will clean up. Is this clearance/procedure OK? S&S dont give a piston to wall clearance in the instruction.

Are the 91cc S&S heads a good performer? Are they the same as whats fitted to the T124 engines?

Thanks

Not a mechanic but I been told that if you have a little extra clearance that the pistons can be Line2k coated to help in that area for a good fit .

[RTMike]

Talk to S&S maybe they will give you another set that have the correct clearance 

[Ohio HD]

Go here and then click on notes.

https://www.sscycle.com/products/4-one-eighth-inch-bore-forged-piston-kit-for-1984-16-hot-set-up-kit-standard-dished/

[D-1]

Thanks Ohio

Should be sweet. Does anyone else check these before installing and find similar clearance issues? 0.0015 taper and probable 0.001 clearance at the tightest spot wont make for a happy engine.

[prodrag1320]

as far as the heads go,S&S leave a lot to be desired straight out of the box.after porting they work OK.our "go to" heads on our 124 " builds are CVO 110 castings where we`re getting 325+ cfm @ 28" after porting

[Don D]

Thanks Ohio

Should be sweet. Does anyone else check these before installing and find similar clearance issues? 0.0015 taper and probable 0.001 clearance at the tightest spot wont make for a happy engine.

I find worse lately, not happy. I fix them and add line2line coating. Not the way to sustain a business.

[D-1]

Can you buy unfinished cylinders from S&S? Or are there any other cylinders to use, Axtell or Daytona? Would love to use a set of ported 110 heads, maybe next time.

[Ohio HD]

Yes, I've bought them unfinished and have my choice finish them. I also will use other than the S&S pistons.

[1workinman]

Thanks Ohio

Should be sweet. Does anyone else check these before installing and find similar clearance issues? 0.0015 taper and probable 0.001 clearance at the tightest spot wont make for a happy engine.

I find worse lately, not happy. I fix them and add line2line coating. Not the way to sustain a business.

I not a mechanic but I was wondering if a fellow could send them out and perhaps the is a method to season , heat cycle the cylinders then have them bored honed with a torque plate and hopefully stay round 

[Don D]

This is what I have done on the serious builds.
In theory S&S cylinders purchased without pistons will be bored and not honed. In my experience this can be fine and occasionally not. Sometimes they are not straight. And recently I got a set of 124 cylinders that were already honed.  Opened one box and measured the spigot to find that +.0015. Back they went.
Good company but something is not right in that department right now.
I am sure they will get things squared away.

[prodrag1320]

Can you buy unfinished cylinders from S&S? Or are there any other cylinders to use, Axtell or Daytona? Would love to use a set of ported 110 heads, maybe next time.

yes,thats what we do here,bore the S&S cylinders & use CP piston kits

[D-1]

Are the CP pistons a stock item, or special order? What oil ring thickness do they have, i hate these super thin ones the S&S have. And, the oil rail gaps are below the min 0.015" and they say not to file them. One out of the three are 0.015". What now, send them back for another set which might be the same. 

[Ohio HD]

Check with the major engine builders, they stock CP. These were for HD 110 heads, but there should be a flat top version, or they can mill the domes off.

Oil rings are 3.0mm, compression rings 1.5mm.


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[prodrag1320]

Are the CP pistons a stock item, or special order? What oil ring thickness do they have, i hate these super thin ones the S&S have. And, the oil rail gaps are below the min 0.015" and they say not to file them. One out of the three are 0.015". What now, send them back for another set which might be the same. 

CP has them in a flat top & they have 3mm oil rings,not the 2mm like S&S/wesico

[D-1]

Im going to ask, although i probably know the answer. Can the oil rails be touched on a linishing belt or similar if the end gap isnt quite enough? Its only a thou or two to get the minimum 0.015".

[Hillside Motorcycle]

.001", or .002"?
You'd be better to use a ring file, if really only looking to remove that very small amount.

[Barrett]

I had my S&S/Wiseco pistons opened up to a 3mm oil ring. The rings that I bought are Wiseco GFX.
The paper I got with them has a tighter oil ring gap spec. .010.

[tdrglide]

S&S calls for oil rail end gap of 0.015" to 0.035" on instruction sheet I got. Last set I did had a couple or so at 0.015. The rest were tighter. Some as tight as 0.009. I opened them all up to 0.018-0.019 with a ring file, carefully. Deburred with a stone.

[Barrett]

I guess those skinny oil rings expand more. I'm glad I did away with them.

[D-1]

Cylinders fixed and pistons installed with 0.0025" clearance. Pistons 0.003" down the hole and S&S supply 0.045" head gaskets. I considered using 0.030" HG but cc checked the 91cc heads and came up with 86.5 and 87.2cc. Is my burette wrong i wondered??? So i checked 2 stock 96" heads and got 84 and 83.5, not far off and still had a carbon coat in the chamber.

Even at 86.5cc with the 0.045" headgasket, ccp comes out at 194psi. That's still an acceptable level for a bigger engine that needs to be ridden city and country with decent fuel and a good tune would you think?

[Hillside Motorcycle]

200 psi ccp is not an issue, EFI.

[turboprop]

My carb'd TC124 shows 210 CCP, but it is in a light bike with tall gears. No issues with street gas.

[jsachs1]

Cylinders fixed and pistons installed with 0.0025" clearance. Pistons 0.003" down the hole and S&S supply 0.045" head gaskets. I considered using 0.030" HG but cc checked the 91cc heads and came up with 86.5 and 87.2cc. Is my burette wrong i wondered??? So i checked 2 stock 96" heads and got 84 and 83.5, not far off and still had a carbon coat in the chamber.

Even at 86.5cc with the 0.045" headgasket, ccp comes out at 194psi. That's still an acceptable level for a bigger engine that needs to be ridden city and country with decent fuel and a good tune would you think?

Most of the 124" S&S heads that roll through here are @ 89 cc. Should be fine with easy start cams.

[D-1]

Most of the 124" S&S heads that roll through here are @ 89 cc. Should be fine with easy start cams.
[/quote]

Are they the ones advertised at 91cc?

[Don D]

I use KBs 4.125 pistons and alter them