cranking compression test 2006 F250??

[TownsendsFJR1300]

At any position of the crank shaft some cam lobes are loaded (spring pressure) and some are not. If the cam shaft caps that are loaded are removed first then bad juju can happen. One might hear a simple "dink" type of sound. I have heard it. It is the cam shaft snapping in two.

If it's like my bike (pic's posted above), ONLY at TDC, compression stroke, cylinder # 1 is there NO PRESSURE ON ANY VALVES (all are closed)..

[rodbolt17]

did ya look at the wee lil footynote?
did not think so.
it is what gives Yamaha an out.
I tried it once.
needless to say I did not get a new powerhead.
they referred me back to an industry standard of 20% highest to lowest.
most Yamaha four strokes already have the flywheel indexed.
the 4.2 and the V8 do not yet it is easy to find TDC and count the teeth and do a tad o math to mark the correct TDC for the other cylinders.
still faster than pulling the plugs and climbing in and out to get to the keyswitch.
line it up at TDC and simply run the firing order and never get off the ladder.
I had an F115 that the ring gaps lined up,compression was about 135 but the leakdown was 85%.
plug was oil fouling.
I did get a powerhead on that one.

[boscoe99]

Yes, I read the note. It might give Yamaha an "out" with respect to a motor that is under warranty or under a YES contract. But the fool mechanics should have paid attention to the service manual "reference" value after having performed the compression check. And then moved on to the leak down check.

We are talking about a 15 year old motor that was not running correctly yes?

Now if this was a newer under warranty motor that failed both a compression test, and a leak down test, and which had a running problem (idled poorly and was down on power), then I suspect that Yamaha would have covered the repair.

[panasonic]

At any position of the crank shaft some cam lobes are loaded (spring pressure) and some are not. If the cam shaft caps that are loaded are removed first then bad juju can happen. One might hear a simple "dink" type of sound. I have heard it. It is the cam shaft snapping in two.

That's very interesting...never heard of breaking a cam shaft off like that, but see how It can happen. Is this common on other outboards or just a Yamaha thing?

I have had to fix several bike cylinder heads with the cam cap hole threads torn out from trying to "draw" down the cams against the spring pressure of the valves using the cap bolts. Many Heli-coils installed.

[boscoe99]

I suspect that it is common on all over head cam shafts given the brittleness of the steel.

https://www.dropbox.com/s/rmza67msrk...akage.pdf?dl=0

https://www.allhead.com.au/wp-conten...t-breakage.pdf

[zenoahphobic]

I suspect that it is common on all over head cam shafts given the brittleness of the steel.

https://www.dropbox.com/s/rmza67msrk...akage.pdf?dl=0

https://www.allhead.com.au/wp-conten...t-breakage.pdf

That second link referred to Nissan Xtrail heads. Interesting that the document definitively states the camshaft WILL break if the exact order is not undertaken. It also states that all breakages were caused by customers incorrectly undoing the caps. Hard to believe that none of the breakages weren't done by ignorant dealer mechanics.

[boscoe99]

That second link referred to Nissan Xtrail heads. Interesting that the document definitively states the camshaft WILL break if the exact order is not undertaken. It also states that all breakages were caused by customers incorrectly undoing the caps. Hard to believe that none of the breakages weren't done by ignorant dealer mechanics.

There is a reason why the other article was written and it was not directed to ignorant customers breaking cam shafts.

[TownsendsFJR1300]

My service manual (for the bike), shows the same thing, tightening in stages, from the inside outward.

As stated earlier, at least for my engine, at TDC (COMPRESSION STROKE) for cylinder #1, there is NO PRESSURE ON ANY OF THE VALVES.

I'd be curious if other engines DO, ALWAYS have pressure (no matter what spot your at) when you install the cam. I have to doubt it...


Camshaft cam "caps" are torqued to only 7.2 lbs / ft

[rodbolt17]

most Yamaha motors have at least one,some several lobes loaded.
take it apart wrong and TINK. that's partly why the V6 and V8 motors are now assembled longblocks with the timing belt installed. to many dealer screw-ups.
back before about 2017 you got three boxes and the first thing you had to do was remove the cams from the new heads.

[zenoahphobic]

My service manual (for the bike), shows the same thing, tightening in stages, from the inside outward.

As stated earlier, at least for my engine, at TDC (COMPRESSION STROKE) for cylinder #1, there is NO PRESSURE ON ANY OF THE VALVES.

I'd be curious if other engines DO, ALWAYS have pressure (no matter what spot your at) when you install the cam. I have to doubt it...


Camshaft cam "caps" are torqued to only 7.2 lbs / ft

There may very well be. Modern trends are to alter (or dabble wth) firing orders from symmetric or regular every X degrees to non symmetric.
However, I suspect trends in increasing valve overlaps would reduce the possibility, although cams are becoming squarer through better metallurgy and treatments enabling them to exert considerable pressure longer for less wear, may allow them to be "off" or seated longer.

I guess one can only really find out by actually rotating each engine to find out if there is an all " off" moment.

I am going to research your Yammy motorcycle engine.

[zenoahphobic]

The FZ6 motorcycle crankshaft appears to be conventional, that is, the centre two pistons are together at TDC when the outer two pistons are together at BDC.
There are four cylinder straight 4 stroke engines out there where pistons aren't paired, where the pistons are all in different positions.
This is in cars as well as motorcycles. This extends to all number of cylinders and configurations.

[TownsendsFJR1300]

There may very well be. Modern trends are to alter (or dabble wth) firing orders from symmetric or regular every X degrees to non symmetric.
However, I suspect trends in increasing valve overlaps would reduce the possibility, although cams are becoming squarer through better metallurgy and treatments enabling them to exert considerable pressure longer for less wear, may allow them to be "off" or seated longer.

I guess one can only really find out by actually rotating each engine to find out if there is an all " off" moment.

I am going to research your Yammy motorcycle engine.

Tks Rodbolt,


Zeno,
My firing order is 1,2,4, 3. It IS an interference engine (2007, FZ6). I can send you a PDF of the Yamaha shop manual if you PM me an e-mail address to send it to..

[zenoahphobic]

Tks Rodbolt,


Zeno,
My firing order is 1,2,4, 3. It IS an interference engine (2007, FZ6). I can send you a PDF of the Yamaha shop manual if you PM me an e-mail address to send it to..

Thanks we must have posted at the same time. Your FZ6 is a flatplane crankshaft whereas the R1 through its evolution changed to a crossplane crankshaft.
My understanding why that configuration is used is to reduce vibration at high revs.
Interesting stuff. Motorcycles are relatively affordable, small and easy to work on.
I first noticed this type of change many decades ago with the three cylinder Laverda Jota; the note or sound had changed on a newer release. They completely altered the crank with the uneven firing order but it was smoother.
My Yamaha XSR 700 is only a vertical twin, with 270 degree crank pins, sounds exactly like a 90 degree V twin (indistinguishable).

[pstephens46]

Anybody have a SM for a Honda V-5?

[TownsendsFJR1300]

Thanks we must have posted at the same time. Your FZ6 is a flatplane crankshaft whereas the R1 through its evolution changed to a crossplane crankshaft.
My understanding why that configuration is used is to reduce vibration at high revs.
Interesting stuff. Motorcycles are relatively affordable, small and easy to work on.
I first noticed this type of change many decades ago with the three cylinder Laverda Jota; the note or sound had changed on a newer release. They completely altered the crank with the uneven firing order but it was smoother.
My Yamaha XSR 700 is only a vertical twin, with 270 degree crank pins, sounds exactly like a 90 degree V twin (indistinguishable).

I had a 1980 Yamaha XS650, vertical twin (air cooled) way back. Looked like a Triumph, Great simple bike.. Sounds like your XSR.