Compression Test 130 , 125 ,,130 ,115 , OK or Not

[wainot-Phil]

Hi all , I picked up a 1990 3CV Motor only  that I might fit into one of my FJ Bikes if required later on ,
The Plan was to fit a new clutch ,new Carby Rubbers , Set the Shims and Paint the Motor up to make it look pretty,   ready to fit one day ,
RESULTS OF COMPRESSION TEST
The Motor has not been run for about a Year , I done a Cold Compression Test on the motor  130 , 125 , 130 , 115 ,,
I then put 3 squirts of Oil in each Cylinder and retested ,,Every Cylinder came up and then read 160 psi in all 4 Pots, 
JUST ASKING ,,
What do you all think ,
Would You Leave the Motor as it is   Or   pull it apart  give it a Hone and fit a new set of Standard FJ1200 Rings ,,
Please advise what you would do with this Motor ,,
thanks for your advise regards Phil

[fj1289]

Depends on what you want to do ...

If you want an engine on the shelf at the ready, then pickle it and store it!

If you're looking for an excuse to rebuild it, big bore, valve job, mill the head and a little clean up, then go for it!  Do a little at a time as money and time allows, then when it's ready swap it out with a runner and pickle that one ....

[aviationfred]

Depends on what you want to do ...

If you want an engine on the shelf at the ready, then pickle it and store it!

If you're looking for an excuse to rebuild it, big bore, valve job, mill the head and a little clean up, then go for it!  Do a little at a time as money and time allows, then when it's ready swap it out with a runner and pickle that one ....

I like Chris's answer. 

The numbers are a bit low..... they are close to what my 89 3CV motor was showing before I did the Big Bore rebuild. The engine should run and run well, with the exception of burning a quart of oil in 500 miles.

Not knowing what the mileage and running condition of your currently ridden FJ.... these are my thoughts to your question...

The inexpensive route. Assuming you do the work yourself.
Purchase a base gasket, head gasket, cam chain tensioner gasket, a set of green rubber oil passage grommets and a pair of copper cylinder head washers. Pull the head and cylinder block. Use a ball hone on the cylinder walls. Install the new rings and all of the associated gaskets.... and you have a fresh top end.

A bit more expensive, but way more bang for your buck.
Install an Andrew's Motorsports drop in 1250cc or 1297cc cylinder kit. These kits utilize a special cylinder sleeve that allows the use of an unmodified FJ1100/FJ1200 lower case.

More expensive, but a basically new engine when finished.
Tear everything down and split the cases. Replace Main, Rod and all roller bearings. New springs and rollers in the starter clutch, new cam and starter clutch chains, new chain sliders and the short RPM starter clutch oil nozzle. Reassemble with either of the above mentioned piston refresh ideas.



Fred

[wainot-Phil]

  Thanks for your reply
Will a Motor with these Compressions still run fine and still have plenty of Power ,
if I remove the Head and Barrel ,  I would only ever be replacing the Rings , that's if every one on here says it has to be done ??,,
I would Not  be Boring the Motor or Playing around with the Head for extra performance
Would only be Just a Hone and fitting Standard Rings only ,
cheers  

[wainot-Phil]

Depends on what you want to do ...

If you want an engine on the shelf at the ready, then pickle it and store it!

If you're looking for an excuse to rebuild it, big bore, valve job, mill the head and a little clean up, then go for it!  Do a little at a time as money and time allows, then when it's ready swap it out with a runner and pickle that one ....

I like Chris's answer. 

The numbers are a bit low..... they are close to what my 89 3CV motor was showing before I did the Big Bore rebuild. The engine should run and run well, with the exception of burning a quart of oil in 500 miles.

Not knowing what the mileage and running condition of your currently ridden FJ.... these are my thoughts to your question...

The inexpensive route. Assuming you do the work yourself.
Purchase a base gasket, head gasket, cam chain tensioner gasket, a set of green rubber oil passage grommets and a pair of copper cylinder head washers. Pull the head and cylinder block. Use a ball hone on the cylinder walls. Install the new rings and all of the associated gaskets.... and you have a fresh top end.

A bit more expensive, but way more bang for your buck.
Install an Andrew's Motorsports drop in 1250cc or 1297cc cylinder kit. These kits utilize a special cylinder sleeve that allows the use of an unmodified FJ1100/FJ1200 lower case.

More expensive, but a basically new engine when finished.
Tear everything down and split the cases. Replace Main, Rod and all roller bearings. New springs and rollers in the starter clutch, new cam and starter clutch chains, new chain sliders and the short RPM starter clutch oil nozzle. Reassemble with either of the above mentioned piston refresh ideas.



Fred
  Thanks Fred ,, I think that your 1st option would be the one for me to do , I will be doing the work myself , First time for every thing , I do have a New set of FJ1200 Rings ,which I bought years ago as the seller told be  they fitted my  FJ1100, but going by the Yamaha Part # thery are 100% Standard FJ1200 Rings ,,So that would be a start ,if I decide to re ring the Motor ,,thanks again cheers  ,

[aviationfred]

Pm sent



Fred

[wainot-Phil]

Pm sent



Fred
  I am in Australia ,, Fred

[Bones]

Phil, from memory going by the Haynes manual I think the minimum comp ratio is about 120psi, so going by that you only have one that is a bit lower than that spec. I have read before where people say they have a good running engine with good power and are surprised after a compression test that their numbers are a lot lower than optimal. I'd say at least try it and see for yourself how it runs and go from there.

[wainot-Phil]

Phil, from memory going by the Haynes manual I think the minimum comp ratio is about 120psi, so going by that you only have one that is a bit lower than that spec. I have read before where people say they have a good running engine with good power and are surprised after a compression test that their numbers are a lot lower than optimal. I'd say at least try it and see for yourself how it runs and go from there.

OK thanks Mate for the info ,
I am thinking along those lines of just giving it a go as is ,
As I said the Motor has not been started for a year .
You never know that low Cyl  might come back up a bit once its run for a while , Tonight I have checked the Valve Clearances and they are all spot on , I also noticed tonight that the Rubber Rocker cover gasket and the Rubber Bolt Grommet's are  really nice and soft  so I would say that the Valves setting has not long been done before she was taken of the road and rested about a  year ago .
thanks for your input , cheers Phil

[Pat Conlon]

Remember folks, these are cold numbers....put some heat in the engine and those piston rings will expand.

[red]

RESULTS OF COMPRESSION TEST
The Motor has not been run for about a Year , I done a Cold Compression Test on the motor  130 , 125 , 130 , 115 ,,
I then put 3 squirts of Oil in each Cylinder and retested ,,Every Cylinder came up and then read 160 psi in all 4 Pots, 
JUST ASKING ,, What do you all think ?
regards Phil

Phil,

Yamaha makes an additive called Ring-Free (intended for use in their outboard motors), but it works just as well in a bike.
I would want to know that the valve clearances are all within specs, to be sure. 
A too-tight valve clearance can cost compression; then later, it may break things.
The Ring-Free treatment may be all you need there, unless you want an excuse to tear into things.

[gdfj12]

I've used Ring Free in my FJ, about every other oil change. I treat it in the 2 tanks of gas before the oil change & it helps keep the combustion chamber clean. My FJ has had the cylinders milled down to boost compression and if I don't use Ring Free it starts to get a slight ringing noise, especially as the RPMs increase. Two of the mechanics I know recommended it to keep on top of carbon deposits in the combustion chamber. Which reminds me I need some more before my next oil change.

George D

[Old Rider]

Sometimes if the engine has not been running for a long time the compression can be down.Then after you run it for a while everything settles and compression can be good.I would just ride it for some days and see what comp is then

[Sparky84]

 Thanks for your reply
Will a Motor with these Compressions still run fine and still have plenty of Power ,
if I remove the Head and Barrel ,  I would only ever be replacing the Rings , that's if every one on here says it has to be done ??,,
I would Not  be Boring the Motor or Playing around with the Head for extra performance
Would only be Just a Hone and fitting Standard Rings only ,
cheers  

wainot the head, Phil ?, thought this might have been a cheapish option?
would a "port n polish" give you a little more performance or would it open a can of worms?

[wainot-Phil]

OK , I am going to leave the Motor as it is and fit it and see how she goes ,,
Last night I thought I would see how dirty the Oil real was so I took the Oil Filler Cap off and used a large screw Driver as a Dip Stick ,
Surprise  Surprise , when I pulled the Screw driver out it was covered in Fuel ,with a small amount of Oil mixed with it ,About 80% Fuel 20% Oil ,
So I ended up draining  out 4.5 litres  of the Fuel / Oil mix out of the Motor  ,,
I then removed the Clutch Cover and had a look ,,every thing looked fine inside but while I was in the Clutch ,I removed the 3 steal rings and wire  and added the extra Large friction Plate etc
I Fitted a new Gasket
I then put some New top class Motorbike Oil in the Motor
I then Removed the Plugs and gave it another  compression test again ,
So with the nice new Oil in the Motor , instead of Fuel  ,Up came the Compression's
I am now getting 135 ,140 ,135  and the Cylinder that was low at 110 ,Is now reading 140 ,
So it looks to me like the past owner had the  Float Needle stuck open and this flooded the Motor with Fuel ,
Which in turned washed most of the Oil out of the Rings and Bore ,
I noticed today that
the more I cranked the Motor over while doing the 2nd and 3rd Compression  Test the more each Cylinder's Compression would climb because of all the New Oil was now where it is meant to be in the Rings and Bore area  ,
 So I am now very happy with the  Compression Readings and think this motor will prove to be a strong runner
I am hoping to fit the Motor sometime in the next 4 weeks  and see how she goes ,,"Finger Crossed"
A  Big
THANK YOU to every one for your in-put ,,regards Phil from Aussie