Weisco Cylinder/Piston Clearance

[wheatdog]

Time to put the next oversize in my '83 1100E.
Just sent my block and new Wiseco 1166 pistons to the shop for rebore. The Wiseco recommended clearance cylinder to piston is .002" . Is that a good spec. I know Wiseco makes excellent stuff but that seems a bit tight to me for a forged slug. Anyhoo, youse guys that have more experience building these things, please chime in. I need to call the machine shop and tell them what clearance I want.

Wheatdog

[rapidray]

I usually set them up at .0025-.003. piston to wall clearance. Ray.

[posplayr]

and don't forget to check the ring end gap, and to chamfer the bottom of the cylinders.

[wheatdog]

As long as I've got your attention:

What size ring gaps should I be running with that size piston? Kinda figured the stock gaps wouldn't be quite right since I'm running a larger ring which may expand sufficiently to butt the ends with less than amuzing consequences.

Wheatdog

[BadBillyB]

From my experience, Wiseco pistons should be fitted on the tight side. I would say .002" is very liberal. If you go more than that you will find that the ring end gaps are NOT going to need attention as they will already be larger than desired. I have run Wiseco pistons in my drag bike with the clearance at less than .0005" (measured at the fattest point of the skirt) and had really good results. Granted a drag motor is not going to get as hot as a street motor and I am NOT recommending this spec to you. This allowed me to set the ring end gap at the measurement I wanted....The pistons were so tight in the bore that they would actually almost hang in the bore, under their own weight, without the rings on them...After cleaning them and re-checking them for clearance, I got nervous and called the place that did the bore and hone job for me. They let me talk to the machinist that did the work and he basically said, "They are done right, and if you have a problem with them after the install let me know, The clearance I measured at the thrust face not at the skirt".....That shop was Vance and Hines in Ca...Best cylinder work I ever had done...Absolutely no blow by....Anyway I just wanted to share this experience with you....I say .002" max.....And the ring end gap should be around .012" to .016" top and second ring....Wiseco says .004" per inch of bore.....Standard.....Billy

[cyclefvr2]

you should get a new spec sheet with the kit, stick with that ,n there shouldnt be any problems, i havent had any probs with wiseco i love there stuff

[wheatdog]

I didn't realize the rings were already sized for the piston kit ordered + .002. I'm used to file to fit and setting my ring gaps after getting the bore where I wanted it. Looks like I better stick with the .002 spec to avoid excessive ring gap and associated blow by.

Thanks again for the input gents.

Mike

[Nessism]

Following the mfgers directions is safe. The questions start when you deviate from them, not when you follow them.

[GregT]

When you tear the motor down after some mileage - Typically in a roadrace application at seasons end - you'll find that the forged pistons have shrunk maybe .0005in. Seems to be a charcteristic of the forgings after enough heat cycles.

[gearhead13]

http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf

http://www.wiseco.com/InstallationManuals.aspx

[cyclefvr2]

http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf
http://www.wiseco.com/InstallationManuals.aspx

nice reply gearhead

[cyclefvr2]

piston/cyl

well i got my motor apart, guy i got it from rebuilt it ...
transmission was popping out of 2nd, and the compression was at the least amount to run but still ran. 99-125 on a good day
the rings look shiny and new, cyl has cross hatch still, bike says 30k?
ring gap is tight,rigs werent stuck,main bearings are in great shape
-- havent checked head yet (leaky valves)?, but from the looks it looks good
a lot of screws,and bolts were loose!, so thank GOD i tore into it before it flew apart on the highway, i got enough problems in life
wondering why the comp was at minimal?....
also wondering if crank is a actual 750 and not a 700!
i forgot to check top dead center on the pistons, since i figured it was a original 750,possibly low comp,because of 700 crank,n rods?, ill check the book i think the rods,and crank are shorter,stroke
i guess thats whayt happens when you get someone elses old junker
more to come

[wheatdog]

Well, I got everything back together without getting too uptight except when installing the cylinder block. Was pretty much a PIA until I decided to install the pistons in the cylinders on the bench and then stab the wrist pins in the rods (engine is still in the frame). Went with Cam Motion G3 cams. Don't know why I didn't go with Webcam. Very noticable lobe ramp asymmetry. Fast open, slow close.

Fired up instantly and was a bit tight for the first 50 miles or so. Honked on it a little to get the rings set then put a couple of hundred 50-60 mph miles on it. Changed the oil after the first 75 miles and it kinda looked like metal flake paint. I'd say the rings seated OK.

Noticeable increase in power off idle to 6K rpms. Wanted to get a couple of hundred more miles on it before trying any max rpm stuff. I'll probably take a look under the rocker cover pretty soon to make sure the rocker pads are OK with the new cam install. Coated the lobes with Isky Rev Lube to head off any initial high wear issues at start up. That stuff works well on the high lift, high spring pressure V-8 builds I've done so I figured it couldn't hurt on the Zuke.

I should check with Cam Motion and some of the Star Racing folks on cam timing. Better yet, seek possible insight from Rapid Ray. I set it up like stock but it may work better with a few degrees advance/retard on the cams. I've done mucho high perf car stuff but I have no experience with bikes; but I always listen to those who have done it. Now if I could borrow a degree wheel that will fit the bike.

Meanwhile I'm gonna ride this monster.

Wheatdog

[posplayr]

Well, I got everything back together without getting too uptight except when installing the cylinder block. Was pretty much a PIA until I decided to install the pistons in the cylinders on the bench and then stab the wrist pins in the rods (engine is still in the frame). Went with Cam Motion G3 cams. Don't know why I didn't go with Webcam. Very noticable lobe ramp asymmetry. Fast open, slow close.

Fired up instantly and was a bit tight for the first 50 miles or so. Honked on it a little to get the rings set then put a couple of hundred 50-60 mph miles on it. Changed the oil after the first 75 miles and it kinda looked like metal flake paint. I'd say the rings seated OK.

Noticeable increase in power off idle to 6K rpms. Wanted to get a couple of hundred more miles on it before trying any max rpm stuff. I'll probably take a look under the rocker cover pretty soon to make sure the rocker pads are OK with the new cam install. Coated the lobes with Isky Rev Lube to head off any initial high wear issues at start up. That stuff works well on the high lift, high spring pressure V-8 builds I've done so I figured it couldn't hurt on the Zuke.

I should check with Cam Motion and some of the Star Racing folks on cam timing. Better yet, seek possible insight from Rapid Ray. I set it up like stock but it may work better with a few degrees advance/retard on the cams. I've done mucho high perf car stuff but I have no experience with bikes; but I always listen to those who have done it. Now if I could borrow a degree wheel that will fit the bike.

Meanwhile I'm gonna ride this monster.

Wheatdog

give Ray a call, he will answer all your questions.