Cylinder specs

[FRITZ]

Hi guys, I am going to pull the motor apart to see if Rings alone will fic my problem. Can anyone tell me what the spec measurement should be within for rings only will work before I have to bore out??

thanks Fritz

[TopCatGr58]

Hey Fritz,

If you'll do a search for online manuals, you'll find some threads and replies, a fellow....I think it's CatatonicBug has one hosted on his ISP for download!

Bore is 71.5mm / 2.8150" Limit is :71.6mm / 2.8189"
Cylinder taper limit is 0.05mm / 0.0020 "
Out of round limit: 0.01mm / 0.0004"
Piston clearance: 0.050 - 0.055mm/ 0.0020 - 0.0022 "

Ring End gaps, top and second: 0.2 to 0.4mm Limit 1.0mm
Oil: 0.2 to 0.9mm limit 1.5mm

Side clearance: top: 0.04 - 0.08 mm Limit: 0.15mm
2nd and oil: 0.03 - 0.07mm Limit: 0.15mm

Now, for the other questions, what symptoms are you describing?? What's the history of the bike, how long have you had it, how many miles, etc.??

Don't know if you know, but standard oversize pistons are NOT available from Yamaha anymore! SO...unless your engine is severely worn, about the only option you'll have is to do the big bore sizes, 1179 or 1196, unless you have some custom pistons made. See posts by Dan Hodges about this option!

Doing a honing and using 1st oversize piston rings is a possibility if the engine is in otherwise good specs, again recent threads about this option have also been made, concern about the Oversize rings going slightly out of round being compressed into the smaller standard bore, but it's thought that they will just take a little longer to break in, but will work nonetheless, and cheaper than a full rebore.
T.C.

T.C.

[FRITZ]

cylinder specs

Thanks TC. Working a lot of hours so it is hard to get the time to respond quicker.
Mileage on the Bike is 61000 kilometers.
Symptoms - Bike would not start cold. If gave it a shot of quickstart it would run pretty well once warm and restart when warm.
When cold there was very little compression on the number one cylinder. the other three were within spec.
Carbs werre cleaned several times and synchronized. new coil so spark was good. Proper plugs used and proper grade fuel. Last fall bike made it to top of mount washington with wife on the back not problem.
Once running and warm all cylinders fire well and bike does not miss or sputter. As the bike is fairly new to me I can not tell how much power it has lost with this problem.
Did a Chemical clean on bad cylinder to see if just dirt around the rings withno luck on that.
Have not taken the engine apart yet.

Any suggestions to try before I take the engine apart?

Thanks again very much for the help.

Fritz

[TopCatGr58]

No Rush on replies, we'll be here!

Hey Fritz,

YEAH, don't take it apart, at least not the bottom end. Let's see, 61 K Kilos is only around 37 K miles, barely broken in!

You will want to take the valve cover off and check the valve clearances, they tend to get tighter as the engine wears, not due to wear on the shims, but due to the valve seat hammering in deeper into the head, moves the valve end closer to the cam. The reduced compression may be just too tight valves! You'll need to reshim them if they are not in spec.

BTW, did you do the compression test with wide open throttle, gas turned off, ALL plugs out, engine warmed up??

What do you mean about a chemical clean of the cylinder....like Mystery Marvel oil down the cylinder, or in the oil?? Running some of that or SEAFOAM in the oil for 5-10 minutes WITHOUT ANY LOAD on the engine can help free up stuck rings, but you need to change the oil right afterwards, don't DRIVE/RIDE it with it in the oil, can damage bearings!

Hard cold starting is more likely CARBS.....they are notorious for getting gummed up from sitting with fuel in them! IF time is hard to find, then take that same can of SEAFOAM and put about 1/2 can in gastank, fill it up, run it a few miles to get it into the carbs, park it and let it sit over night or so, then run the tank out. You may find it starting easier after that!? But if not, then you can just take the carb float bowls off, there's a pressed in jet down in the bowl, get it clear, carb spray, possibly small wire to poke to get grunge out until sprays thru...wear eye protection. I know you said the carbs were cleaned several times, but did you know about the bowl jet?? If not, then not as clean as you thought!

Otherwise, take the carbs off and do a proper tear down and cleaning, PLEASE READ The tech tips beforehand, DO NOT SOAK ENTIRE CARB BODY in cleaner, will damage butterfly shaft seals!!

New Coils, hopefully new wires and plug caps also??
T.C.

[petejw]

Hey Fritz,
Just what TC said.

Are you blowing smoke? on acceleration or deceleration?
When the bike is warmed up is there any blow-by coming from the vent hose?
What do your plugs look like?

Theres many things to look at before pulling the motor to replace rings,
61000 isnt a lot of k's for one of these bikes, mine has over 140,000 and
theres plenty on here with many more km's.

What have you set your mixture screws at?

[FRITZ]

cylinder spec

Hey TC & Pete

Ok guys I will hold off on taking the bottom end apart.

TC I will check the valves first. I did not do the Chemical clean myself ( they called it a chemi-tune) it was done by a bike shop. It did nothing. Good news they did not charge me.They never statred the engine in measuring the compression, it was always done cold. Actually they never started the engine at all. I am not sure what they put in as a chemical to try and free up the rings but they did do it by pouring in the plug hole.

They told me they did put a little oil in the plug hole and cranked it over to test compression and it came right up to acceptable range but when they let it set there and tried again without oil in the top it dropped right back again. ( If it was valves would it do that ???) Because they did the oil trick they told me it was not the valves so they did not check them. What do you think ???

I will do the seafoam trick at top and bottom in the oil first. I will check the valves as mentioned.

When my son and I cleaned the carbs we did clean all the jets including the one in the bowl you referred to but certainly can do that again. When I had it done in the bike shops I do not know if they did all the jets.?

Now Pete as per you question. The bike only seemed to smoke when it was cold and just out of one side of the ehaust. Can not see smoke once warmed up and running. By the way compression always seems fine when bike warmed up even in the so called bad cylinder. The guys at the bike shop said the plugs looked real good when they pulled them ( burning right they said)
Never saw any blow by in the vent hose but never really looked for it.

any other questions for me fire away as I appreciate all the help.

thanks Fritz

[tarzan]

It doesnt sound like valves from the way they checked the comression.It is rings I'm pretty sure.I would take out the plugs and pour seafoam in the cylinder or cylinders and let it soak a couple days.Then start it up and run it.
It will probably smoke until it burns that stuff out of the cylinders.But if the rings are stuck the seafoam could dissolve the carbon.
I wouldnt put seafoam in my crankcase unless I could see sludge or the oil gets real dirty easy.A lot of guys do clean theirs that way though and say it works.
Rick