Freestyle Diagnosing Powervalves- Rear works, front doesnt! Help! Stumped!!!

[dcptr]

Hey guys, I've been working on fixing this for the last 2 days- trying to identify and resolve this problem & just finally found one inconsistency.


Basically I noticed after maidening my new motor I noticed the front cylinder powervalve wasn't moving at all but rear was.


I've done every possible diagnostic with the engine together. Comp & squish even, swapped ignition leads so its not timing.
Running ATP flame so single pickup, even spark.


I then swapped front pv to rear, same thing, rear moves out, front doesn't- so it's not the pv itself.


Pulled head off and inspected- everything perfect even in every way!


This is the only comparable difference I found from front to rear cylinders- the wash on the domes!
So how does this translate to causing my front powervale not to move?
(Front piston is the dome on the right in pic)

48novi's were rebuilt exactly the same in all aspects so im pretty darn sure it aint them either!


Full engine specs as follows.
Xs1000 90.5mm, 200psi, 1.15mm squish
48 novi's, VF2's
ATP Flame total loss
Power factor pipe




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[Pablo]

If the guillotine is able to freely move on the problem PV then it's either a leaking bellows or a spark/compression/exhaust pressure malady on that cylinder. When u rev the engine can u slide the PV up and down with ur hand?

1. Fresh plugs?
2. Plug wires known to b good?
3. Inspect the bellows and seal on that PV. I will Honda bond or 1211 my bellows to the PV piston.
4. Confirm a fat blue spark on the good side is equal to the problem side.
5. I've never run a Flame TL so don't know the system well, but what's used for coils? I've had a failing MSD coil give similar results. Ohm test both coils.
6. A dying channel on the MSD brains will act this way too (when the engine has no load on the prop the spark was fine, but under load that channel would crap out).

Good luck. Gremlin hunting sucks.

 

[Matt_E]

The clean side: Looks like you're way too rich on that side, or the plug isn't firing on that side, or you're leaking cooling water into that side.

 

[norcal ex]

I have heard of this problem is about 3 x -scream motors. They always deny it is them but I think otherwise. Never had this or heard of it in a DASA. I would contact X-scream

 

[Lucaumpits]

check your 2 head bolts that sits right on top the power valves , the are bit to long put a washer on each bolt and problem will be solved,

 

[BruceSki]

they send two bolts in their cylinder kits with some machinist bluing on them. It is hard to see, but they are cut a thread or two shorter than the rest of the head bolts to clear the powervalves.

 

[Marcgraham27]

I have seen this problem also, Check the guillotines to see if there are Very light scribe marks on them from the head bolt hitting

 

[dcptr]

Thanks for all the great info guys, but I did pretty much all that too-
Brand new bellows on both pv's both 1211'd but remember, both the pv's work, just not on that front cylinder!
Spark/comp/exhaust pressure all matching one another
New plugs of course
Brand new oem coils (swapped leads on plugs too)

Lucaumpits- thanks, that's the ONE thing I didn't check but it's still doesn't check out as a problem- no scratching plus the valves move out freely by hand on the front cylinder.

Now after a good nights sleep (where I do most my subconscience diagnosing) I've come to the conclusion that my vf2 reeds are stuffed! Well just the front piston side anyway!
Can this be the culprit causing lower crankcase pressure of mixture/ignition stopping the pv from moving??

If the guillotine is able to freely move on the problem PV then it's either a leaking bellows or a spark/compression/exhaust pressure malady on that cylinder. When u rev the engine can u slide the PV up and down with ur hand?

1. Fresh plugs?
2. Plug wires known to b good?
3. Inspect the bellows and seal on that PV. I will Honda bond or 1211 my bellows to the PV piston.
4. Confirm a fat blue spark on the good side is equal to the problem side.
5. I've never run a Flame TL so don't know the system well, but what's used for coils? I've had a failing MSD coil give similar results. Ohm test both coils.
6. A dying channel on the MSD brains will act this way too (when the engine has no load on the prop the spark was fine, but under load that channel would crap out).

Good luck. Gremlin hunting sucks.

 

[Jayski]

check your 2 head bolts that sits right on top the power valves , the are bit to long put a washer on each bolt and problem will be solved,

Would be nice if that was the issue..

 

[special fx]

I assume there's no blockage of the little passage from the exhaust port to the bellows? Maybe some 1211 got in there?

 

[dcptr]

Good theory but no, first thing I checked to clear out!

I assume there's no blockage of the little passage from the exhaust port to the bellows? Maybe some 1211 got in there?

 

[dcptr]

I'm assuming crankcase pressure regulates the powervalves rather than sheer compression itself? An answer to this would be great!

 

[Proformance1]

Take bellows off and turn motor by hand and see if air blows out of tiny hole?

Brand new motor or used?

Ever worked fine before?

 

[dcptr]

Take bellows off and turn motor by hand and see if air blows out of tiny hole?

Brand new motor or used?

Ever worked fine before?

Ok here's the update: put brand new vf2s in.. Still hasn't fixed the problem! Pv's don't move.
Took the bellows off and tried turning over by hand with plugs in and out, couldn't seem to figure if air was comming outta the holes or not, even when cranking it..?

Ride report for yesterday- it seems the revs can't stay very low, seems it stalls too early and also the revs don't come down off throttle quick enough..? Almost like if I Brap Brap it up round midrange and take finger off for a second, it stalls wayy too easily straight away..

It's a used motor from thrust, all rebuilt.

 

[js/sj]

Check exhaust Mani to cylinder gasket.

 

[speedysprocket]

You check that the hole in the cylinder lines up with the hole in the valve housing so that that gas pressure can actually getting to the bellow...?

 

[keith t]

Did you pressure (leakdown test) the motor ? The PVs will move out during this test, and pressure should hold. I have previously seen a tiny pressure weep under the centre allen bolt head, although extremely small

 

[Proformance1]

Pressure test then call Brian at Thrust.

 

[DangerBoy]

that front cylinder isnt even running, thats why the valve isn't opening, it dosn't open with crankcase pressure it needs exhaust gas pressure
If you are POSITIVE your ignition is working, (front cylinder even get warm ?)

I would re-check your front carb

Db

 

[dcptr]

that front cylinder isnt even running, thats why the valve isn't opening, it dosn't open with crankcase pressure it needs exhaust gas pressure
If you are POSITIVE your ignition is working, (front cylinder even get warm ?)

I would re-check your front carb

Db

Thanks guys you've been really helpful, although I'm still not there yet. Did a quick leak down test and went as far as blocking off the top f/a sides of the 48 novi's and blocking off the end of the PF manifold. Put around 8-10psi in and both pv's moved out simultaneously at around 5psi (rear piston on TDC)
Earlier today though, I ran the ski on the water quickly, front pv not moving while revving on the trailer- checked plugs after a few mins and front plug came out dry brown on the tip, ceramic section brown too while rear plug came out as it normally would: wet black tip/ washed & oily outer ring, ceramic still white.
Ignition spark is evenly as bright both plugs.

So what does this tell me? :/