ACCT Installed Wrong?

[WMarshy]

OK, I just read the entire post... whoa.

From Post #56:

Hey Guys. I'll get to checking the valve clearances after class today. But, to clear up the confusion, I'll briefly give a re-cap of what happened over the weekend.

After getting the cams re-aligned, I rotated the crank a bunch of times to make sure they stay aligned. The next morning I synced the carbs (did not re-check the valves), then took it for a ride. My best guess was a mildly bent valve on the number one cylinder as it felt a tad off on power and sound, however all four cylinder pipes were equally hot. I took it for a ten minute ride. No abnormal noise, etc. I got it home and back into the garage for a simple compression test. I disconnected the coil leads so I did not have to mess with grounding the disconnected spark plug, and hooked ny compression tester to cylinder number one. Hit start and got 90 psi, 120 psi a half second later, then 0 with a tapping noise. Hooked it up to cylinder's 2, 3, 4, and got 0 as well. I thought to myself it was a bad gauge, so dug out my back-up gauge. 0 psi across all four cylinders. I hooked up the coils again and tried starting the bike and got nothing.

That's the re-cap.

Maybe I missed something but how can you jump to the conclusion of bent valves when the bike was running fine in your description?
One thing I never read was how you verified all your valves were actually bent. Were you just making that assumption based on the whanky compression numbers you got?
Whom or how were the bent valves verified?

Where are you in the process of things, did you remove the head yet or taken anything apart?
Have you tried to start and run the bike after the compression test in the above post?


You said you checked compression and had cylinder 1 up to 120 for second but then 0,0,0,0 across the board. If you had a bent valve then I dont believe you would have gotten the 120 psi. All compression testers I've ever used have a check valve in them to record max pressure, so why did yours go back to zero? Something doesnt add up here...

The bigger question is why do you suspect bent valves after it was running and you made no physical changes internally between your ride and compression check?

Lesson #1, never make more than one change at a time. I'd tend to believe that your carb sync is responsible for the power decline and possibly the noise you heard prior to testing compression.

Here's my advice (if you havent torn into the head yet) spin the engine over by hand and if there is no interference, try to start the bike. Possibly ask Scott to check compression again brfore trying to start it but as long as you can rotate it without and interference I would try starting it.

[IanDMacDonald]

Hey, I was just going off common sense that I bent the valves. Not sure how going on a ride, parking it and running a test bent them, but I assumed worst-case when I found 0 psi across all cylinders with two different gauges. The bike was not able to be started, and I heard a metallic clanking sound in the #1 cylinder when cranking it. Head is off the bike now, laying in my basement. If I have time tomorrow, I'll pull the valves and take a look at them. My concern was a hole in the piston, which there is not. So, all I can hope for is that this head work won't cost me too much. Not sure what the cost is to get the valves cut.

[WMarshy]

Hey, I was just going off common sense that I bent the valves. Not sure how going on a ride, parking it and running a test bent them, but I assumed worst-case when I found 0 psi across all cylinders with two different gauges. The bike was not able to be started, and I heard a metallic clanking sound in the #1 cylinder when cranking it. Head is off the bike now, laying in my basement. If I have time tomorrow, I'll pull the valves and take a look at them. My concern was a hole in the piston, which there is not. So, all I can hope for is that this head work won't cost me too much. Not sure what the cost is to get the valves cut.

Easy way to test bent valve is to turn the lights out and stick a small flash light in the port and look for light leakage around the valve seat... otherwise you could flip it over so the valves face up, fill the combustion chamber up with some water and see if it leaks into the ports.

I have not read of anyone damaging pistons from bent valves due to the cam chain jumping teeth. You indicated the head was decked and the valve to piston clearance is reduced (over stock) so your engine will be less forgiving to out of phase valves.

[crazy steve]

Best way with the head off is pull the cams and pour some gas in each port...

[DGXSER]

Pour some gas in will tell you if the valve is seating properly or not. If you pull the valves, and put them in a drill press on slow speed, you will definitely see if it is bent.

[IanDMacDonald]

Good to see the site back up. I'll check tonight when I pull the buckets to see if the valves are indeed bent. But, I found a machine shop willing to do all the head work (cut seats, grind valves, re-assemble) for $55.

[skids]

Good price! I hope you can find a shim size for reassembly.

[IanDMacDonald]

I'm confused by that comment Skids. Why wouldn't I? I have tons of extra valve shims.

[WMarshy]

You start cutting the seat in the head and you ultimately need a thinner shim. Take some more off the valve and that shim just got thinner. Mamaha only made shims so small, once you dip into the smallest sizes you have to shorten the valve stem.

[IanDMacDonald]

Gotcha. From my understanding, the seats may not need to be cut if the guides are good.

[skids]

Guides really have nothing do do with seats. Guides are the side-to-side, and removal of material from seats/valves have averything to do with shim thickness...

[IanDMacDonald]

Hmm. Well, hopefully everything works out.

[BA80]

Guides really have nothing do do with seats. Guides are the side-to-side, and removal of material from seats/valves have averything to do with shim thickness...

I MUST disagree skids. The guides will have an effect on the seating/sealing of the valves and grinding the faces and seats will remove material that WILL have to be compensated for by valve lash adjustment. That's exactly why the valves need to be adjusted over time. The seats and faces wear and a thinner shim is needed to correct the clearances.

Ian, when you talk to the people who grind the seats and faces as them to dress the top of the valve stem also. Have them grind .002 or .003 off so you don't have to find some real thin shims. The thinner ones are getting harder and harder to come by.

[crazy steve]

...once you dip into the smallest sizes you have to shorten the valve stem.

That won't even work. You have to move the valve lock groove on the stem which means custom valves. The shim actually rides on the end of the valve stem, the bucket is only there to keep it place and keep side loads off the valve guides. Shorten the stock valve, and now the shim is on the bucket and you run the risk of the valve locks getting loose...

[IanDMacDonald]

This is good info. Thanks Greg.