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Hi have a 1998 Sea-Doo Sportster with twin 717s the starboard engine isn't getting any pulse from the engine to the fuel pump

Larson83

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I have a 1998 Sportster 1800 with twin 717s. The stbd engine isn't getting any pulse from the crankcase to the fuel pump
 

Beachbummer

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Really?? Did you compare to Port engine? Any chance the pump has an issue instead? I think swapping pumps might confirm.

Worst case troubleshoot with an electric pump.

The pulse is pretty much designed into the case. I'm not sure how that breaks beyond the hose coming disconnected, or having some sort of tear.
 

Larson83

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I've tried swapping carbs, fuel pumps replaced hoses. I pull the hose off the port engine and getting a strong pulse and my compression is 150 on both cylinders
 

Larson83

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Does the o-ring on the rotary valve go bad
 

Beachbummer

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Weird, sorry, not sure where that air might be escaping from.

I have troubleshot pump issues with a small electric pump on that boat with great results.
 

Cobra Jet Steering LLC

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the pump is driven by a push and pull effect from inside the crank case , anything can be causing the loss of suction and a pulse however that would also effect the cylinder even a bad crankshaft seal can effect that . The model engine you have has had a lot of issues with the rotary valve section having bad seals and allowing the oil to leak out of the rotary valve section of the crank case and cause some smoke that everyone in town would notice. I would get a reading on that section while it is cranking over and see but it is most likely a bad seal
 

Larson83

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the pump is driven by a push and pull effect from inside the crank case , anything can be causing the loss of suction and a pulse however that would also effect the cylinder even a bad crankshaft seal can effect that . The model engine you have has had a lot of issues with the rotary valve section having bad seals and allowing the oil to leak out of the rotary valve section of the crank case and cause some smoke that everyone in town would notice. I would get a reading on that section while it is cranking over and see but it is most likely a bad seal
 

Larson83

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I'm going to replace the rotary valve cover o-ring and the intake o-ring
 

Cobra Jet Steering LLC

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I always got rid of my pulse fuel pumps and replaced them with small electric fuel pumps that put out 3 to 4 lbs of pressure and put a flow restrictor in the fuel return line, did that to all my 2 stroke outboards also they always ran great
 

Beachbummer

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The fuel return is already smaller than the inlet on that Mikuni carb (my Sportster 1800 had one per engine). I have added just the pump (No flow restrictor in my case) and it worked like a charm while I figured out what the problem was.
 

Larson83

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Thx cobrajet are you saying it's the seal on the rotary valve shaft or a crank seal
 

Larson83

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I just rebuilt the topend and both cylinders have 150 compression
 

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Crank seal most likely and that would not have any effect on the compression but it could burn a piston due to causing a lean running condition from a vacuum leak in the crank.
 

Larson83

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Can I replace the crank seals without pulling the topend
 

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I believe you would need to tear down the engine and split the cases to do it correctly did you check the connecting rod bearings when you did the top end? usually you do it all at the same time, Rotate the engine by the P T O on the end of the crank with the spark plugs removed, watch the pistons come up and then start back down as soon as the piston starts to go down stop turning the p t o and take a big Phillips screwdriver and push down on the top of the piston if it is tight the rod bearings are ok if you feel the piston move a bit as you push down or worse actually feel it clunk when you push on it then you have a bad bearing. in any case you need try to narrow down the problem because if it isn't fixed correctly the first time you end up doing a lot of work and spending money for nothing. Did your engine smoke a lot when you first started it after it sat for a few days or longer , if so your rotary valve crank seals are bad that section is isolated from both of the end sections where the connecting rods are for the pistons, Now remember I have not worked on one of the old 720 engines for a very long time but I recall they had other issues with water leaking in under the carb on the intake manifold due to crappy bolts I always re tapped those holes with larger bolts. and I recall the splines going bad on the P T O where the drive shaft went in.
 

Larson83

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The rods were right when I had it apart
 

Larson83

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I'll let you know when I put the o-rings on this week on the cover thx for the advice
 

Cobra Jet Steering LLC

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ok did it smoke before you tore in to it
 

Larson83

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It sat for several years it's a side job I'm doing
 
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