Fixing A 86 FJ1200 with bad compression on #3 cyl.

[Mark Olson]

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 . 

[andyoutandabout]

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.

[Pat Conlon]

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?

[Mark Olson]

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.

[Tuned forks]

What about the starter clutch while the case is apart?

Joe

[Mark Olson]

Starter clutch was worked over. All good.

[Mark Olson]

Piston is broken at ring lands , also rings broken . gonna need a new piston. 

[aviationfred]

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



Fred

[Old Rider]

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

[Mark Olson]

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



Fred

You are the devil  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.

[Mark Olson]

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.   

[Mark Olson]

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.

[Old Rider]

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.

[Mark Olson]

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. 

[Pat Conlon]

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.