Running out of ideas (pto cylinder not firing)

9

97srxXT

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Dec 2, 2007
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Michigan
Been through the carbs 5 times or more now, Switching everything I can think of. cleaned, re-cleaned and replaced pilot jet blew out pilot circuit. Compression is 125ish across the board. Swapped another set of carbs on with same results. Float bowls are always full. Doesn't seem like its getting gas though, Plug is slightly wet, but it seems to just be oil?? I changed the stator with a known good one, swapped plugs, swapped coil, electrocuted myself twice so its getting spark. Two things are in question. One side of the reed cage the petals are up and not flat, Tried flipping them with the same results. I don't think one side would cause that cylinder to not fire though?? Other thing I thought of was bad crank seal. I sprayed starting fluid behind the clutch while it was running and nothing changed or no fluctuation in rpm's. My next avenue is doing a leak down to see for sure and swap out the reeds. When its running you can hear that cylinder wanting to fire, but even with higher rpm's it doesn't seem to fire either. At first I thought it was flooded so I pulled the reeds out and put the engine at tdc and blew air in the lower end to get any gas out of there that might have leaked by, But nothing was down there. This engine was out of a wrecked sled. I even thought about pulling the engine back out and inspecting the bottom side of the cases for any cracks I didn't see when I put it in. Maybe that is causing a leak?? Though if that was the case the other two cylinders would have a problem too and I don't think the fuel pump would work correctly. Just looking for any other ideas I haven't already thought of.

Thanks,
Nick :o|
 
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I tried an entire diff set of carbs and a different coil/wire/cap from a running sled...All same results. Im going to swap the cages around and see what happens
 
Exhaust free on the PTO side?Also, If he took the top off the airbox and then fired it up would he be able to feel any suction at the carb intake? without leaning it out too much. Just asking.......
 
Just switched reeds around with no change, Then put my hand on the back of the pto carb and YES you are correct their is NO suction. So I guess it has to be some form of leak, Either the crank seals or there is a crack somewhere. Going to do a leak down test now to find this son of a bitch.
 
I would pull that pto exhaust off. Have someone pull it over and see what Happens. Check intake and exhaust. Maybe boots or gaskets on that cylinder are shot?
 
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how many miles are on the engine? if you have no suction at all you have a major air leak. i worked on one similar to this one time and it had the piston skirt on the exhaust side broke off , the piece went out the exhaust and did no damage to the engine but with the skirt missing the crankcase is open to the exhaust so it had no suction at the carb and no crankcase compression. you could check this with the exhaust manifold off or with the reeds removed you might be able to see the skirt that way.
 
What sled r u working on. I had a mouse nest in pto exhaust pipe on my srx and had almost same issue you r describing. Triple pipes though. Sled with single pipe would have to b bloched at the manifold. Worth a look
 
ottawaair said:
What sled r u working on. I had a mouse nest in pto exhaust pipe on my srx and had almost same issue you r describing. Triple pipes though. Sled with single pipe would have to b bloched at the manifold. Worth a look
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Kinda like stickin a potato in somebodys tailpipe.
 
If you have good compression yet you cannot pull a vacuum at the intake then the exhaust must be blocked. It would take one heck of a leak in the crankcase to case this. If you find the exhaust is not blocked then you could seal off the intake and the exhaust and pressurize engine with compressed air to find the leak.
 
like 9801srx said the the piston skirt could be broke off. A friend of mine had that happen to his and It still had good compression
 
9801srx said:
how many miles are on the engine? if you have no suction at all you have a major air leak. i worked on one similar to this one time and it had the piston skirt on the exhaust side broke off , the piece went out the exhaust and did no damage to the engine but with the skirt missing the crankcase is open to the exhaust so it had no suction at the carb and no crankcase compression. you could check this with the exhaust manifold off or with the reeds removed you might be able to see the skirt that way.
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Thats exactly my first thought when I read this thread!! ;)!
Broken piston skirt
 
crank seals

If you have torches shut off the oxy and shoot acetelyne around the pto side piston if it clears then you know its the seals thats what i think it is anyway.
 
This is not your problem, but flipping the reeds over can cause them to break off - which can be an expensive problem. Best put them back the way they were. Flipping them over can also cause a preload on the reeds - which there should not be. A small gap will cause no problem.
 
Not the piston skirt, checked that. Engine is coming out. I'm leaning towards a crack in the lower end or a really blown out crank seal. The engine only has 3500 miles on it.
 
Should gas come out of the oil line inlet on the fuel pump? I know gas and oil get mixed in the pump, Just not 100% sure if gas should actually come out of there when the line is taken off.
 
sxr1000 said:
Gas comes out of the oil line on my srx when it is disconected.
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Ok thanks just checking. This thing really has be double questioning everything and scratching my head good.

Nick
 
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