FJowners.com

General Category => FJ Project Writeups => Topic started by: Mark Olson on January 13, 2019, 10:06:47 PM



Title: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 13, 2019, 10:06:47 PM
It was a sunny day here today and I really wanted to ride but it was time to get into the engine and see what was causing the low compression in #3 and smoke out the breather at idle.
It has been tough riding around with everyone at the stoplight telling me my bike was on fire. So after trying some alternative fixes I should not mention, I removed the engine from the bike with the help of Craig Z. He had never removed an engine from the FJ before so I was more than happy to let him lend a helping hand.
Well the engine is out and will be disassembled shortly .... stay tuned . 


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: andyoutandabout on January 13, 2019, 11:33:46 PM
What’s it going to take? Team work.
Well done the Sacramento posse for digging deep and getting her done.
Good luck Mark on your road to recovery.
We’re rooting for you.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Pat Conlon on January 14, 2019, 12:44:56 PM
Best case: cylinder hone, fresh rings, fresh viton valve seals and lap the valves.
Might as well put a new starter chain and valve timing chain on while you’re in there.
How many miles are on your engine Mark?


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 14, 2019, 06:33:42 PM
Gonna gear it down tonight...soon.
I am hoping for rings.
This engine was rebuilt 20k ago by previous owner.
Bike only has 36k miles.
2nd time opened up.
Trans was rebuilt by RPM and they Took care of any problems down low.
All timing marks are perfect.
Promised Craig to wait for him.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Tuned forks on January 14, 2019, 06:34:18 PM
What about the starter clutch while the case is apart?

Joe


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 14, 2019, 06:36:06 PM
Starter clutch was worked over. All good.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 14, 2019, 10:37:43 PM
Piston is broken at ring lands , also rings broken . gonna need a new piston.  :ireful:


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: aviationfred on January 14, 2019, 11:16:08 PM
How does the #3 cylinder wall look?

If you have a non-repairable cylinder block...... This is a drop in kit that requires no machine work.

 https://www.ebay.com/itm/Yamaha-FJ-Big-Bore-FJ1100-Block-1250cc-Wiseco-Piston-Kit-Cylinder-Block/181220128398?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 (https://www.ebay.com/itm/Yamaha-FJ-Big-Bore-FJ1100-Block-1250cc-Wiseco-Piston-Kit-Cylinder-Block/181220128398?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649)



Fred


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Old Rider on January 15, 2019, 03:00:50 AM
Very interesting .Im in the middle of rebuilding my engine .Do you know what was done with the pistons and if the previus owner honed the cylinders and installed new pistonrings?
I honed the cylinders on mine yesterday but to be honest i dont know what im doing only working from what i have read about honing.
Please post some pics of the cylinders


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 15, 2019, 02:35:01 PM
How does the #3 cylinder wall look?

If you have a non-repairable cylinder block...... This is a drop in kit that requires no machine work.

 https://www.ebay.com/itm/Yamaha-FJ-Big-Bore-FJ1100-Block-1250cc-Wiseco-Piston-Kit-Cylinder-Block/181220128398?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 (https://www.ebay.com/itm/Yamaha-FJ-Big-Bore-FJ1100-Block-1250cc-Wiseco-Piston-Kit-Cylinder-Block/181220128398?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649)



Fred

You are the devil  :diablo: Fred.

Of course I would love to go big bore kit .... however it is not in the cards at this time. The cylinder block is in good shape and the hatch pattern is still visible , I am probably just gonna ring it and go.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 15, 2019, 02:45:07 PM
Very interesting .Im in the middle of rebuilding my engine .Do you know what was done with the pistons and if the previus owner honed the cylinders and installed new pistonrings?
I honed the cylinders on mine yesterday but to be honest i dont know what im doing only working from what i have read about honing.
Please post some pics of the cylinders

On my engine the previous owner had an alleged rebuild done with new pistons. What I found was stock pistons .. It appears that only a set of rings was changed and a valve job on the head.

On your engine , you will need to get accurate measurements of the pistons and cylinders to see it you are within clearance limits. How much wear and taper do you have from top to bottom?
If the wear is not to bad you can run a hone to break the glaze and put a 45 degree cross hatch pattern on your cylinders.
I will post pics when I am at that stage of reassembly.   


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 20, 2019, 09:11:39 PM
upon further inspection , the number 2 piston is cracked at the ring lands between top and second groove.

I will be checking out some standard pistons from a local source later this week.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Old Rider on January 21, 2019, 03:43:46 AM
Very interesting .Im in the middle of rebuilding my engine .Do you know what was done with the pistons and if the previus owner honed the cylinders and installed new pistonrings?
I honed the cylinders on mine yesterday but to be honest i dont know what im doing only working from what i have read about honing.
Please post some pics of the cylinders

On my engine the previous owner had an alleged rebuild done with new pistons. What I found was stock pistons .. It appears that only a set of rings was changed and a valve job on the head.

On your engine , you will need to get accurate measurements of the pistons and cylinders to see it you are within clearance limits. How much wear and taper do you have from top to bottom?
If the wear is not to bad you can run a hone to break the glaze and put a 45 degree cross hatch pattern on your cylinders.
I will post pics when I am at that stage of reassembly.   

That looks bad did the bore get damaged beyond repair or can it be rebored or change cylinder sleeve? What do you think caused this ? can it be that there was a ridge on top of
cylinders and the new pistonrings broke off after hammering that ridge? are there honemarks in cylinders?
About my engine rebuild yes i need to get more accurate measurements i have ordered a dial bore gauge.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 21, 2019, 05:51:31 PM

That looks bad did the bore get damaged beyond repair or can it be rebored or change cylinder sleeve?yes and no , checking if rings were even done before What do you think caused this ?my unique riding style can it be that there was a ridge on top of
cylinders and the new pistonrings broke off after hammering that ridge?maybe are there honemarks in cylinders? yes , they appear factory or very good machine shop
About my engine rebuild yes i need to get more accurate measurements i have ordered a dial bore gauge.

I have been watching your rebuild thread and must say I am not a fan of plastiguage . I use micrometers and snap guages , inside mics.

My engine has only 36k miles on it . I have been quite aggressive with it for a lot of those miles.
some might say i simply burned it up..
The damaged pistons show that the intake side of the cylinder got very hot. I have thrashed the engine on very hot days up to 105 degrees at times. It goes to logic that I will need a larger oil cooler if I continue in my evil ways.

pics and measurements will be posted soon. 


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Pat Conlon on January 21, 2019, 08:04:17 PM
The damaged pistons show that the intake side of the cylinder got very hot...It goes to logic that I will need a larger oil cooler if I continue in my evil ways.

No doubt a RPM Oil cooler is good, high quality ester base oil is good, but they are no substitute for jetting.

Jetting, jetting, jetting...nice fat jetting for hot weather kookaloo rides. Your engine will thank you.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 22, 2019, 08:48:37 PM
It has been determined that my piston lands were cracked from poor rebuild methods.
So 20k ago when the PO had the bent rod fixed and they reringed the Pistons and rebuilt the head, they screwed up and cocked the 2_3 Pistons upon install and cracked the ring lands.

It's kinda amazing the engine ran for 20k before finally craping out.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Tuned forks on January 22, 2019, 10:28:15 PM
Shows how tough that lump of aluminum is.

Joe


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: FJmonkey on January 22, 2019, 11:22:36 PM
It's kinda amazing the engine ran for 20k before finally craping out.

20K of your flogging it like it owed you money.  :mad: That's like "Dog Years"

But I know you love it, you slid under your FJ when it lost traction.  :blush:


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: ribbert on January 23, 2019, 07:24:39 AM
It has been determined that my piston lands were cracked from poor rebuild methods.
So 20k ago when the PO had the bent rod fixed and they reringed the Pistons and rebuilt the head, they screwed up and cocked the 2_3 Pistons upon install and cracked the ring lands.

It's kinda amazing the engine ran for 20k before finally craping out.

Who made that determination? That would be uncommon for pistons fitted from the bottom.

Mark, you allude to the fact you ride it hard, how high do you rev it when flogging it?

Noel


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: FJ_Hooligan on January 23, 2019, 10:38:05 AM
Noel,
It's very easy to screw it up if you don't use ring compressors. 

I've seen people try to install the pistons without using one.  They compress the rings by hand or use a screwdriver. 

Some are successful, some are not.  The unsuccessful ones usually (unknowingly) break a ring or crack the ring land.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Pat Conlon on January 23, 2019, 04:19:10 PM
Yea, along with not clocking the ring gaps correctly or installing the #2 compression ring upside down can cause grief.

I’m surprised with the piston damage, the cylinder walls were not affected.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: ribbert on January 24, 2019, 07:44:12 AM
Noel,
It's very easy to screw it up if you don't use ring compressors. 

I've seen people try to install the pistons without using one.  They compress the rings by hand or use a screwdriver. 

Some are successful, some are not.  The unsuccessful ones usually (unknowingly) break a ring or crack the ring land.

I had read it as a cracked piston. Having a ring compressor is no guarantee of not screwing it up either, I've seen plenty, however a large tension wrench in the hands of someone with a workshop manual and no "feel" does the most damage.

Noel


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: FJ_Hooligan on January 24, 2019, 08:09:33 PM
….a large tension wrench in the hands of someone with a workshop manual and no "feel" does the most damage.


So so true.  I know many of those types.  Like handing a baby a loaded gun.

They are usually the ones that ask for the torque on every single fastener.  I'll use a torque wrench on engine components (head bolts/nuts, cam/crank/rod caps, etc), brake calipers and axles.  Just about everything else gets torqued by hand.  Always been a bit hesitant about using a torque wrench on small(ish) fasteners in aluminum.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: andyoutandabout on January 24, 2019, 10:25:00 PM
Yep especially when one is armed with a cheap torque wrench. Would you believe I once tried to torque the little bolts on the clutch. Well I only needed the sheered bolt head off the first one to stop me trying the others that is. Live and learn.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 25, 2019, 11:14:47 PM
It has been determined that my piston lands were cracked from poor rebuild methods.
So 20k ago when the PO had the bent rod fixed and they reringed the Pistons and rebuilt the head, they screwed up and cocked the 2_3 Pistons upon install and cracked the ring lands.

It's kinda amazing the engine ran for 20k before finally craping out.

Who made that determination? That would be uncommon for pistons fitted from the bottom.   i did after my research.

Mark, you allude to the fact you ride it hard, how high do you rev it when flogging it?   all the way to the rev limiter

Noel

 Hey Noel , long time since I heard from you . How Ya been?



Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 25, 2019, 11:24:09 PM
Yea, along with not clocking the ring gaps correctly or installing the #2 compression ring upside down can cause grief.

I’m surprised with the piston damage, the cylinder walls were not affected.

well pat , that is because of the oil I used.   AMSOIL   :blum1:


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 25, 2019, 11:32:06 PM
It's kinda amazing the engine ran for 20k before finally craping out.

20K of your flogging it like it owed you money.  :mad: That's like "Dog Years"

But I know you love it, you slid under your FJ when it lost traction.  :blush:

Monkey , I did not realize those were dog years ... and of course I love my FJ enough to protect it from hitting the ground.  :crazy:
maybe it is time for case guards.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 25, 2019, 11:36:00 PM
….a large tension wrench in the hands of someone with a workshop manual and no "feel" does the most damage.


So so true.  I know many of those types.  Like handing a baby a loaded gun.

They are usually the ones that ask for the torque on every single fastener.  I'll use a torque wrench on engine components (head bolts/nuts, cam/crank/rod caps, etc), brake calipers and axles.  Just about everything else gets torqued by hand.  Always been a bit hesitant about using a torque wrench on small(ish) fasteners in aluminum.

So true .. I am with you on that.


Title: Re: Fixing A 86 FJ1200 with bad compression on #3 cyl.
Post by: Mark Olson on January 26, 2019, 08:53:41 PM
I picked up some donor pistons today. Now I just have to check them out.  :yahoo: