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Pop off test not working...

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Pointhunter75

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Fuel pump cover removed, the plate on other side also removed exposing needle and seat. Fresh rebuild wiyh new mikuni needle and seat. Hose on inlet, finger over inlet hole in the carb body and its going to 70 psi and still not popping. Am i doing something wrong?

This is why i have the fuel pump cover off

From sbt:
NOTE: You cannot accurately test with the pump body and fuel filter still attatched to the carb - you MUST disassemble it and test directly into the fuel inlet orifice, where the fuel filter sets. Otherwise you are testing through the pump checkvalves, throwing your readings off, too high. If you have an external fuel pump, this does not apply.
 
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if the check valves are doing their job, there won't be any real resistance on the air pressure going to the needle/seat.
 
I did that one and it worked out. This is the one that didnt work. I hope i didnt put the little clear plasic disks in backwards.... I put the ink lines side out away from the metal on both as it said to do. They were a pain to get the rubber through the hole.


Fuel Pump Verification

Check fuel pump valves operation as follows:

Connect a clean plastic tubing to the fuel inlet nipple (see Picture A) and alternately apply pressure and vacuum with the mouth. The fuel inlet valve should release with pressure and hold under vacuum.
CAUTION: Some fuel may be present in fuel pump. Be careful not to swallow fuel when testing.
Repeat the same procedure at the fuel outlet nipple.
This time the outlet valve should hold with pressure and release under vacuum.
 
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if you can suck and blow through both sides, then you need to inspect the check valves in the pump and replace as necessary.
 
Took the pump cover with pulse nipple back off. I can blow through the main(the one the main fuel line from fuel valve hooks to) fuel inlet on the piece that has the valves in it but cant suck so that one appears right. I was blowing on the other inlet as shown in that pic on the test page. That part is confusing..... The other two nipples on the carb body blow in and out freely. Why isnt this pic using the main fuel inlet from the tank(fuel valve)?
image.jpg
 
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you have three fuel lines hooked to your carb? on a single carb you should have just the pulse, fuel IN, and the fuel RETURN nipples. the dual carbs have two outlets, one goes to the second carb and the other goes to a Y that connects to the return on the second carb.

maybe if you post a pic of your carb and how its set up it would help.
 
Yep its a 95 xp twin carbs. The main line from tank, a pulse and the in and out. Second carb has an in and out. Everything in both are new mikuni except the springs, they're the originals.

image.jpg
 
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In pointhunter pic, on the right carb center nipple I can blow not suck. And suck not blow on the outlet. On the second carb I guess it doesn't matter cause there are no check valves?
 
I guess what we are asking, there is no need to perform the CPR test on the second carb, one on the left? Cause there are no check valves?
 
I think that's right on the second carb. My biggest confusion is why that site I was going by doesn't mention the main inlet that comes from the tank....looks like that inlet should be tested.that's the only one that does work right on mine..... The other two don't. Wish somebody would give me more detail on this test. I need to be flipping check valves I guess but first I wanna make sure I'm even doing this test right. I'm 95% positive I faced the check valve concave properly. Wish lou would weigh in on it.
 
Another question, loctite or anti seize on external carb bolts? With the two stripped carb mount bolts and the broken exhaust bolt hell I've been through due to corrosion I'm TERRIFIED of loctite! almost Every bolt I've removed is covered in corrosion powder. Only been in salt water once years ago and was flushed according to my brother.
 
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Well, lok-tite can keep water from penetrating and it's a good idea to use lok-tite in some critical places but I use anti-seize much more often than I use lok-tite. Stuff I take apart often, gets anti-seize. my rave bases, my pump nozzle and pump bearing cone, carb exterior screws and mount bolts all have anti-seize on them. I would use lok-tite on exhaust manifold bolts as specified, then deal with it (probably helicoil inserts) if the threads were to let go.

I don't know what you were saying about the fuel pump valves being concave, they're flat round mylar disks aren't they? They shouldn't be wrinkled or bent, otherwise they won't seal, and the rubber grommets that hold them in place shouldn't be punched through.

Maybe I don't recognize which fuel pump you're working on..........
 
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goat,

by cpr test, I think you're referring to the fuel pump test. your 2nd carb doesn't have the fuel pump like the first one does, so no cpr test on that one, just pop-off in that case.
 
I used anti seize on the carb bolt shoulders, and then put blue loctite on the threads after they were poking out the bottom. Best of both worlds, the 4 stuck carb bolts I've taken off are enough for me. The corrosion on the gtx carbs also cost a carb bolt, since it was so stuck it had to be hammered out with a steel punch.

This was after all the bolts in the air box and carbs weren't as tight as I left them after only a few hours of riding.
 
Check valves are curved a little according to the instructions and must be installed with the side with the blue ink line facing away from the body to function properly. I wore the ink lines off while installing them. Im still pretty sure they were right.
 
Thats the one i used and the one that has me confused. Why dont you blow through the main fuel inlet from the tank for the test? Thats the only one that actually seems to seal off right on mine. Lol the other two dont seal whether pressured or vacuumed.
 
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