Blowback through both carbs

[Jeffspx]

The reason for flipping the valve over (going by my memory) is to get the timing dead nuts. The valve is symmetrical but flipping it over changes the position by 1/2 spline?

Yes this is what i meant. When i timed my 580, i know that the valve was different timing when flipping it and I went with what was the closest.

 

[BoJaXz]

And I'd have to agree when you "give it the throttle" if a plume of fuel spits out of the carbs this makes me wonder if the RV timing isn't right. If fire spits out, this makes me wonder about ignition timing, can't recall ever seeing backfire coming out of the carbs on a 2-stroke but then again if the ignition occurred really late then maybe but then it probably wouldn't idle well or at least the idle screws would need to be turned in way far.

How did you locate TDC for setting the RV, did you use a piston stop or a dial gauge?

It has a flame arrestor in case it does fire improperly, or ignites a buildup of fumes/fuel. Maybe if the woodruff key sheared and there was one badly timed spark that ignited out the carbs. A backfire in a rotary would be extremely out of time I would imagine.

I don't have any sort of backfiring, only the blowback.
I used a screwdriver to get TDC, one tooth makes a big difference, so even if TDC was a degree or two off, the tooth difference would be way off.
I'm wondering if I do need to flip the rv and line it up with the 149 degree mark. I even looked at other sources besides the manual to set the timing, and as far as I can tell, it's timed correctly, but it doesn't run like it's timed correctly. I won't be able to mess with it until tomorrow.

Thank you all for your input, it's appreciated. I've been frustrated trying to figure this out, going through multiple causes and scenarios. Hopefully I can get this thing working before I decide to take it to the lake and sink it...

I will take pictures of my marks and the rv lined up tomorrow. Luckily I already took everything off earlier today before work.

 

[Sportster-2001-951C-Stock]

Yes this is what i meant. When i timed my 580, i know that the valve was different timing when flipping it and I went with what was the closest.

That's what I thought you were saying. Was just clarifying b/c OP said his went on same side out and that seems like a 50/50 chance.

Grasping at straws, not much else I can think of LOL.

 

[Sportster-2001-951C-Stock]

If you can make a piston stop from an old spark plug you can mark the crank damper on either side of TDC then half way between is TDC, handy for ignition timing and checking advance curve too.

If the connecting rod pin is offset (I don't believe this is the case here) a dial gauge is preferable IMO.

WARNING WARNING WARNING!!! Be careful not to hit the starter while a piston stop is installed, it'll pop a hole in the piston.

 

[Sportster-2001-951C-Stock]

A backfire in a rotary would be extremely out of time I would imagine.

Agreed, it's doubtful ignition timing issues are the issue but I never say never... Remember, I thought there was fuel in the tank but I was wrong....

Even more difficult to have fire come backward through an intact reed valve nun the less every marine engine will have a flame arrestor.

 

[BoJaXz]

If you can make a piston stop from an old spark plug you can mark the crank damper on either side of TDC then half way between is TDC, handy for ignition timing and checking advance curve too.

If the connecting rod pin is offset (I don't believe this is the case here) a dial gauge is preferable IMO.

WARNING WARNING WARNING!!! Be careful not to hit the starter while a piston stop is installed, it'll pop a hole in the piston.

I always pull the lanyard while working on it, especially before exposing the rv. That's a quick way to lose a finger... Lol. I do have a dial indicator, I just didn't see the need when you can literally get it within a couple degrees just by eyeballing it.

 

[Sportster-2001-951C-Stock]

Cos(0)=1.000, and Cos(5)=0.996; If Stroke is 3.5 then piston height at +/-5 degrees is .007 from TDC

Cos(0)-Cos(5)*Stroke/2=0.007"

You're thinking of the Model T factory procedure!

 

[etemplet]

I have a question... did you verify "Why" the engine took in water? You could have a bad cylinder or perhaps a head issue. What made it limp back to the dock. Could be you still have the initial problem and have not identified and eliminated it. Pressure is obviously getting from the top of the piston chamber to the bottom. You had water in the cylinder, bad crank.... I'd sure go over all that with a fine tooth comb. Good Luck.

 

[BoJaXz]

I have a question... did you verify "Why" the engine took in water? You could have a bad cylinder or perhaps a head issue. What made it limp back to the dock. Could be you still have the initial problem and have not identified and eliminated it. Pressure is obviously getting from the top of the piston chamber to the bottom. You had water in the cylinder, bad crank.... I'd sure go over all that with a fine tooth comb. Good Luck.

The water got in when a couple cylinder bolt heads broke off. The water in the head runs down the cylinder to the base gasket and up into the exhaust. Broken bolt=loose cylinder =water into crankcase. Wasn't much water, 2 of the 4 bolts broke.

 

[mwat65]

The valve plate is asymmetrical. Flipping it over will change the setting.

 

[BoJaXz]

This is with the valve flipped, which looks closer than before, I didn't think I should flip it, cause that's not how it was before, but maybe the new crank has a new position that requires it? I'll put it together and try it.

 

[Jeffspx]

Certainly does look close. I would try it. As you said, perhaps the gear on the crank is Indexed differently causing the splines to be in a different location then the motor that valve was previously installed in. I know it gets discouraging constantly disassembling and reassembling. Hopefully it works out

 

[mikidymac]

Just by looking at it your timing doesn’t look correct. It’s 65 degrees clockwise from the top of the intake port and 130 degrees from the bottom of the intake port counterclockwise. If I am remembering the degrees correctly. Yours looks too far counterclockwise.

 

[BoJaXz]

Just by looking at it your timing doesn’t look correct. It’s 65 degrees clockwise from the top of the intake port and 130 degrees from the bottom of the intake port counterclockwise. If I am remembering the degrees correctly. Yours looks too far counterclockwise.

Mine is the xp. It's 149 +-5 degrees.
Put it together, still has some hesitation, but doesn't seem to have the blowback it had before. Hopefully this works out...

 

[BoJaXz]

Sorry, I guess I didn't flip it, when I flipped it, it was at least 5 degrees off in either direction. Guess I could still try it. I'll flip it so the intake closes faster, maybe that will stop the issue, still had blowback while cranking, so I'm sure it's still there while running.

 

[R-u-n2it]

I agree it would seem to be the RV or carb issue, one thing not mentioned that may cause a lean condition and backfire (maybe) is when you ingest water it can be forced through the pulse line and into the fuel pump(s) and distort the plastic discs and not seal on reverse pulse, had this happen once. On the subject of check valves might as well check the small one on the fuel block also, they can wrinkle and curl, since you're running out of things to verify.

 

[Jeffspx]

So flipping it didnt change it much? Thinking about the rotary gear being indexed got me thinking.
I doubt this is the case, but where did you get the reman crank? Think its possible the crank split isnt indexed perfectly?
Just a thought

 

[Mekanix]

So what is the clearance between the RV cover.
A lean mixture can do this. Usually timing either electrical or rv will also do this.
Have a video ?

 

[etemplet]

This is good stuff !!! You guys need to help me with my GTX.....

 

[BoJaXz]

Update: still had some blowback, not much, flipping the valve wouldn't allow the ski to start. I started spraying brake cleaner around the cylinder bases, and spraying it under the exhaust manifold caused the ski to die. So I have a leak back there somewhere.
I even used copper spray with a copper gasket to help prevent any leaks. I had the cylinders checked for warpage, and they were within .001 before assembly. I'm pulling the head right now.

I had a couple issues in the past where the base gasket would blow out, which is why I switched to a copper gasket in the first place.

Clearance is about .013" within spec. I got the crank from sbt.

 

[BoJaXz]

Finished tearing down, cleaning, and replacing the base gaskets with an extra paper gasket I had. Got it all put back together, now I have to wait for the loctite to cure. I guess I'll be back with an update after tomorrow.

 

[etemplet]

Good luck but I am very suspicious as to the cause if your blow back. That shouldn't happen and it is significant since you are loosing base gaskets. Seems to me head pressure is finding its way to the bottom end and you need to locate and address the root cause. Could it be getting through the cylinder sleeve?

 

[BoJaXz]

Good luck but I am very suspicious as to the cause if your blow back. That shouldn't happen and it is significant since you are loosing base gaskets. Seems to me head pressure is finding its way to the bottom end and you need to locate and address the root cause. Could it be getting through the cylinder sleeve?

It shouldn't, with 150psi, the pressure shouldn't be getting to the crankcase. Turning the crank by hand, the cylinder coming down creates the blowback even with the head off. The piston starts to come down right before the valve closes. I'm not sure if the amount is normal to create a "pulse" in the fuel circuit or not. But holding the choke 3/4 closed removed the hesitation, which is why I looked for a leak with brake cleaner.

 

[Sportster-2001-951C-Stock]

Base gaskets shouldn't be blowing out unless maybe there's water in the crankcase, otherwise the pressure is relatively low. I'm wondering if the cooling system pressure is exceptionally high (plumbing mistake or obstruction)?

 

[etemplet]

I haven't had the need to check it that way so I don't have any data. As I go along I will get numbers on such things. I am very distrustful of that little fuel pump in the carbs. LOL It's like a mystery pump with no way to check its performance.