Export thread

kawasaki FR691v smoking

#1

A

ACF

have a kawasaki fr691v-bs29 that smokes light gray/blue smoke looks like a smokestack while running. did compression test each cylinder was 130 psi. did leak down on both cylinders had air coming out muffler. so do i have bad rings and bad valve on discharge side. was thinking value guides maybe but not sure to how to check them. any suggestion would be great help
thanks AC


#2

S

slomo

Were all the valves closed when you did the leak down? All must be closed (TDC).

Continual smoking is piston rings/bore slash sealing.


#3

A

Auto Doc's

Hello ACF,

How many hours are on this engine? Any maintenance history?

Having 130 PSI compression does not support failed rings, but they can stick the oil control rings. Change the oil and add a 1/2 cup of Marvel Mystery oil in with the new oil and that will unstick the oil control rings after a few hours of running.

As for your leak down test, it is best to remove the valve covers and verify both rockers on each head are loose fitted, and the piston is held at top dead center in the cylinder. Better yet, back the rockers off and remove the pushrods to get the best results to verify if there is actually a leak down past the valves. A little air from the dip stick tube is normal, but a lot is not good.

If you happen do the heads, lap in the valves to ensure proper sealing and replace the valve seals.


#4

A

ACF

engine has 135 hours, removed valve covers to verify tdc, got nothing from dip stick just muffler
slomo said:
Were all the valves closed when you did the leak down? All must be closed (TDC).

Continual smoking is piston rings/bore slash sealing.
Click to expand...
135 hours and was tdc had valve covers removed watched springs


#5

S

slomo

Check valve lash per your engine manual.


#6

T

txmowman

Pull the rubber tube for the air filter off from the intake pipe (before the carburetor). If you live in the south, the engine is possibly dirt ingested due to inadequate air filter maintenance. Sorry to say but I see a lot of it. Valve guides are not the issue.


#7

A

ACF

Auto Doc's said:
Hello ACF,

How many hours are on this engine? Any maintenance history?

Having 130 PSI compression does not support failed rings, but they can stick the oil control rings. Change the oil and add a 1/2 cup of Marvel Mystery oil in with the new oil and that will unstick the oil control rings after a few hours of running.

As for your leak down test, it is best to remove the valve covers and verify both rockers on each head are loose fitted, and the piston is held at top dead center in the cylinder. Better yet, back the rockers off and remove the pushrods to get the best results to verify if there is actually a leak down past the valves. A little air from the dip stick tube is normal, but a lot is not good.

If you happen do the heads, lap in the valves to ensure proper sealing and replace the valve seals.
Click to expand...
changed oil and added marvel mystery oil ran for over 2 hours was worried at beginning but after over 2 hours no smoke, do get a little puff when throttle increased, now would you adjust the valves


#8

A

Auto Doc's

Hello ACF,

A little puff of smoke at throttle up is not a bad thing. It will likely clear up with more use. Using Marvel Mystery oil is a very slow way to break down sticky carbon on the piston rings and ring grooves. Your power will likely improve slightly as well.

Yes, adjust the valves would be the next thing to do. Adjust when cold. Pull the plugs so you can rotate the engine by hand using the top flywheel screen. Do one valve at a time while the adjacent one is fully open on the same cylinder.

Here is a video:
https://www.bing.com/videos/rivervi...8CD77450E24618145DD88CD77450E246&&FORM=VRDGAR

Also, check out a site called Teryl fixes all, he knows his stuff. He does dress funny and has some "creative skits" in most of his videos, but he knows his stuff when it comes to small engine equipment.

As for the Marvel oil, it does more good than harm to leave it is there for a while, then do a regular oil change before you park it for winter, or before you start it in the spring.

Air cooled engines are bad about carbon sticky rings, especially if the fuel sits too long.


#9

A

ACF

well Auto Doc went out and checked the oil in the engine and it did not show any on dip stick, so added until got to lower mark on dip stick. started engine smoked like it did before, no need to adjust valves since it looks like will have to replace rings


#10

A

Auto Doc's

Sorry to hear that.

Failed piston rings are not very common on this design from what I have seen over the years. Hopefully the cylinders are not scored badly.

There is a chance the heads have warped in the pushrod area near the cylinders. That was an issue on some due to repeated overheating

As this engine been run in dusty with the air cleaner off for any length of time?

EDIT: Don't overlook the breather valve located under a cover on top of the engine block. These have been known to fail the flutter valve and the gasket before.

Having 130 PSI compression just does not sound like failed rings. Scoring of the cylinder is still a possibility.


#11

A

ACF

Auto Doc's said:
Sorry to hear that.

Failed piston rings are not very common on this design from what I have seen over the years. Hopefully the cylinders are not scored badly.
i know have 2 mowers with this engine one is over 10 years old
There is a chance the heads have warped in the pushrod area near the cylinders. That was an issue on some due to repeated overheating

As this engine been run in dusty with the air cleaner off for any length of time?
not sure but there was a build up of dirt in carb intake
EDIT: Don't overlook the breather valve located under a cover on top of the engine block. These have been known to fail the flutter valve and the gasket before.
there is a lot of dust/dirt build up on the cover of the breather valve
Having 130 PSI compression just does not sound like failed rings. Scoring of the cylinder is still a possibility.
Click to expand...


#12

M

MParr

Is the engine past it's 3 year warranty?


#13

A

ACF

yes. pulled engine lots of carbon on top of piston and head cleaned both,
found the oil rings were compressed into groove completely even with the piston, also there was no movement when trying to push in. the compression rings had movement and stuck out from the piston grooves like i have seen in the past. there were no hash marks on cylinder walls and i know that it is needed, is there a way to put back without buying that ball hone


#14

S

slomo

Unstick the rings. Clean the ring grooves in the piston. CLEAN as in hospital clean. Put it back together. Forget about the hash marks. Run the sucker at max revs all the time. Keep the oil on the full mark at EVERY mow.

New rings will require honing slash bore prep. Current rings are already broken in.

Make sure the rings rotate around the piston loosely before putting the piston back in the bore. Oil the rings before reinstalling. Clock the rings 120 degrees apart or whatever the engine manual says to.


#15

StarTech

StarTech

Actual ball or flex hones are for breaking the glaze and will make taper and out of round worst. You would need a ridge hone to true a cylinder. and you go pass
0.005 of the current spec you need to hone to the next oversize.


#16

7394

7394

I NEVER start my engines before I check the oil level...


#17

T

txmowman

7394 said:
I NEVER start my engines before I check the oil level...
Click to expand...
👍🏻👍🏻 Awesome! Everyone print @7394 post and attach it to your mower as a reminder every time you use it!!


#18

sgkent

sgkent

check your fuel to be sure that it has not aged poorly. Ethanol can cause issues when it sits. So can gasoline dripping into cylinder, be sure the oil is not being diluted with gasoline. It may not be the MMO that improved things but rather clean oil. I did a scientific study many years ago. Took some carbon chunks off the intake valves of a the CJ7 I had at the time. Soaked each piece, about half the size of a marble in different fluids for a week. Water - zero effect, Acetone - zero effect, MMO - zero effect, GM Upper cylinder cleaner (No longer available except old stock on ebay etc) softened it to like toothpaste in a few hours and completely dissolved it in about 3 or 4 days, Berryman's B-12 - some softening, Traditional Berrymans carb dip - dissolved it about the same as the GM product but different chemical. So based on that I would say it is not the MMO cleaning up your engine.

Really should not throw used rings back in a cylinder. It is a bush type fix. Should be new rings and a Sunnen hone to break the glaze and cross hatch the cylinder. It will also straighten out the cylinder a small amount. The way to test a guide is to pull the keepers and retainers off, then push the valve so it is open may 3/8". Rock the head. Should be minimal movement. If you get say .006 to .008" movement then the guide is worn. Replacing them on an engine of this kind is a real rabbit hole. Also, each guide made will be slightly different where the center line is. So when guides are replaced, the valve seats have to be touched up too. Normally the guides have about .003" to .004" clearance for oil, and half of that is what each side of the stem sees. If the valve rocks .008" then the clearance around the valve is .004", which is so much it will let oil burn and keep the valve from properly seating.

here is a video of a small mower head being properly rebuilt. You won't find many shops that have the ability to do this. They were doing this one for a neighbor. Normally you just buy a new head except valve in block engines. Then find a machine shop that builds go cart racing engines.



#19

A

Auto Doc's

Hello ACF,

Check on Ebay for a "small engine cylinder hone". (They are very affordable) They have 3- stones usually. You need a fine grit in the 320-400 range, just enough to see a pattern (Watch some videos online to get a feel for it). Avoid a ball hone design, they were good to use for the older cast iron blocks, but not so good for newer engine cylinder designs.

This is not the space shuttle we are talking about.

Replace the rings as a set and follow the service manual procedures.


#20

Scrubcadet10

Scrubcadet10

FRs didn't have to best air filtration.
Pull your air filter off and check for excess dirt in the air intake.


#21

A

ACF

have new rings but the service manual i have says that the second ring should have a white stripe on it but the rings i got from Kawaski have a blue on one and other is pink so which is the top ring


#22

T

txmowman

ACF said:
have new rings but the service manual i have says that the second ring should have a white stripe on it but the rings i got from Kawaski have a blue on one and other is pink so which is the top ring
Click to expand...
The top ring is barrel faced, the second is tapered. The wider part of the taper goes up. The paint stripe should be to the right of the gap. The paint color is irrelevant.


#23

T

txmowman

Scrubcadet10 said:
FRs didn't have to best air filtration.
Pull your air filter off and check for excess dirt in the air intake.
Click to expand...
The FR air filtration is fine for what is was designed for. Under the hood of a tractor or mowing grass not dirt. The problem is education on proper maintenance. Or buying the wrong mower for what it is being used for.


Footer Links 1

Top