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FJ 1100 piston ring grooves

Started by NAVRIG, October 22, 2015, 06:06:28 AM

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NAVRIG

Hi All

Not sure if anyone has tried this but I do believe it is not an uncommon practice. As I understand it standard rings are not available for 74 mm bore. I can source ring sets for a 74 mm bore but the top ring groove is to narrow. Has anyone tried to machine the ring groove slightly wider to accommodate a thicker ring. I am only talking a very small amount. I will post measurements but need new battery for my digital vernier. I am considering this as my pistons are within spec and bores will be honed Also can't really afford a 1200 mod at this time. Thought it might be worth a try as the pistons are really useless if I can't source rings for them.

Any comments most welcome even if you think it is a dumb idea or been there done that didn't work.

Kevin

FJ1100mjk

Sounds feasible, that is, if you are indeed taking a very small amount of material from the top land. As long as the material properties (wear and thermal expansion concerns) are the same, and the gap and its tolerance between the ring and its groove is kept the same as the OEM ones, it may work out fine. Curious to see the proposal on how you will accurately remove the material from the groove to maintain the proper fit between the ring and its groove.

Perhaps a call to some kind soul in the Engineering area at one of the piston manufacturers (MAHLE, JE Pistons, Wiseco, etc.) can provide some expert advice to see if it is indeed feasible to do what you propose.

Good luck.
Platinum Zircon-encrusted Gold Member

Iron Balls #00002175
www.ironballs.com


CutterBill

Re-cutting ring grooves is very common in the world of custom engine building.  But, as mentioned, you must have enough material left between the first and second rings to support the first ring.  The other problem is holding the piston accurately.  Pistons are not round; they are slightly elliptical so you can't simply clamp them in a 3-jaw chuck on a lathe and start cutting.  Shops that do this kind of work make a custom split sleeve that holds the piston by the oil ring groove.  That way the top ring groove will be exactly parallel to the other grooves.

Hopefully, you're not going to try this with a file and a drill press.  Good luck.
Bill
Never Slow Down, Never Grow Old.

Current Stable:                                                     
FJ1100                                              
FJ1200 (4)
1999 Yamaha WR400 (street-legal)
2015 Super Tenere
2002 Honda Goldwing

Harvy

THIS http://datsun1200.com/modules/mediawiki/index.php?title=Pistons site discusses Nissan/Datsun 1200 pistons and rings.

Standard bore size is 73mm, however, 1mm oversize rings are available....... I see down the bottom of the page 2 different ring thickness's are listed.

Might be worth investigating?

Cheers
Harvy
FJZ1 1200 - It'll do me just fine.
Timing has much to do with the success of a rain dance.

racerrad8

A little birdie has told me I will have 36Y-11610-01 on the shelf sometime around February or March.

Randy - RPM
Randy - RPM

Pat Conlon

Quote from: CutterBill on October 22, 2015, 02:53:31 PM
... The other problem is holding the piston accurately.  Pistons are not round; they are slightly elliptical so you can't simply clamp them in a 3-jaw chuck on a lathe and start cutting.  Shops that do this kind of work make a custom split sleeve that holds the piston by the oil ring groove.  That way the top ring groove will be exactly parallel to the other grooves....

Thank you Bill for this insight. I am in the same situation as Kevin except it will the the ring land for my oil rings that will be cut deeper, so I wonder how that would work if the oil ring land was the point being worked on....a split sleeve on the compression ring land?.
Let me explain, I have the early 82mm Weisco (Hank Scott) pistons in my 1350 engine. Since the early design, Weisco has since redesigned the oil ring to be thicker (not wider) so Randy @ RPM will be cutting the forged big pistons so the thicker oil ring can be installed. This is a good thing, expensive, but a good thing. The current weaker oil ring has less tension so under vacuum (high rpm throttle closed) produced those big pistons, oil is pulled up into my combustion chamber. I use about 1 quart every 800 miles. Kind of a hassle when I ride across country.  

Here is a side by side picture of my original FJ1100 (74mm) piston and my current 82mm forged piston. Looking the compression ring land on the 74mm piston it appears that a slightly wider compression ring can be made to fit.... Of course this is a moot point if Randy comes up with oem 74mm ring packs.

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NAVRIG

Thanks All

Such a wealth of info and gives me a lot to think about

Regards

Kevin

simi_ed

-- RKBA Regards,

Ed
===
Ed Thiele 
Simi Valley, CA -- I no longer have SoCal manners.
'89 FJ12C (Theft deterrent Silver/White)


- All that is necessary for the forces of evil to win in the world is for
enough good men to do nothing.

- Edmund Burke

fj1289

Quote from: simi_ed on October 22, 2015, 04:29:19 PM
Just a thought ...
http://andrewsmotorsports.mybigcommerce.com/legends-race-car-yamaha-fj-fj1100-36y-11610-01-standard-oem-yamaha-piston-rings/


"Sorry but this item is currently unavailable. Please check back at a later stage. "

I'll bet another little birdy knows who will get them in stock first...

CutterBill

Pat, you're right... looks like the FJ1100 pistons have plenty of room for a slightly wider (thicker?) top ring.

As for holding your pistons for cutting the oil groove... easy peasy.  All it would take is machine up a sleeve that would grab the top ring groove.  Shouldn't take a competent machinist more than an hour, two tops, to make something like that.  Mount a block of aluminum to a face plate, turn to dead-nuts size, slip the piston in and Bob's your uncle.  How many ya want?   :biggrin:
Bill
Never Slow Down, Never Grow Old.

Current Stable:                                                     
FJ1100                                              
FJ1200 (4)
1999 Yamaha WR400 (street-legal)
2015 Super Tenere
2002 Honda Goldwing

JMR

 Total Seal does a good job of cutting grooves. I have also had grooves cut to accommodate a spacer ring and a thinner top ring (for out of date, non existent rings).

JMR

Quote from: Pat Conlon on October 22, 2015, 04:03:08 PM
Quote from: CutterBill on October 22, 2015, 02:53:31 PM
... The other problem is holding the piston accurately.  Pistons are not round; they are slightly elliptical so you can't simply clamp them in a 3-jaw chuck on a lathe and start cutting.  Shops that do this kind of work make a custom split sleeve that holds the piston by the oil ring groove.  That way the top ring groove will be exactly parallel to the other grooves....

Thank you Bill for this insight. I am in the same situation as Kevin except it will the the ring land for my oil rings that will be cut deeper, so I wonder how that would work if the oil ring land was the point being worked on....a split sleeve on the compression ring land?.
Let me explain, I have the early 82mm Weisco (Hank Scott) pistons in my 1350 engine. Since the early design, Weisco has since redesigned the oil ring to be thicker (not wider) so Randy @ RPM will be cutting the forged big pistons so the thicker oil ring can be installed. This is a good thing, expensive, but a good thing. The current weaker oil ring has less tension so under vacuum (high rpm throttle closed) produced those big pistons, oil is pulled up into my combustion chamber. I use about 1 quart every 800 miles. Kind of a hassle when I ride across country.  

Here is a side by side picture of my original FJ1100 (74mm) piston and my current 82mm forged piston. Looking the compression ring land on the 74mm piston it appears that a slightly wider compression ring can be made to fit.... Of course this is a moot point if Randy comes up with oem 74mm ring packs.


Sounds like they changed to an XC ring pack from an XG Pat. My 1314 Wiseco pistons used an XG pack but I haven't noticed oil use. Maybe that's because it only gets about 1,000 miles a year on it. :sorry:
We are using XA rings on 71/72mm CB750 pistons (8/9mm overbore). I haven't put enough miles on mine to judge oil use but large bores, short skirts and a long stroke will definitely increase piston rock and affect ring seal.

CutterBill

Quote from: racerrad8 on October 22, 2015, 03:53:46 PM
A little birdie has told me I will have 36Y-11610-01 on the shelf sometime around February or March.
That is very good news.   :good2:
Never Slow Down, Never Grow Old.

Current Stable:                                                     
FJ1100                                              
FJ1200 (4)
1999 Yamaha WR400 (street-legal)
2015 Super Tenere
2002 Honda Goldwing

racerrad8

Randy - RPM

4everFJ

Quote from: racerrad8 on January 27, 2016, 09:16:13 AM
The FJ1100 Piston rings are now in stock: Yamaha FJ1100 STD Piston Ring Set


Randy - RPM

"Sorry, this product is not currently available."   :unknown:
1985 - Yamaha FJ1100 36Y
1978 - Yamaha SR500
1983 - Kawasaki GPZ550 (sold)
1977 - Kawasaki Z400 (sold)