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XP 800 won't run

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Adzy110

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Hey guys. So I have recently bought a 1997 XP 800 that was in pieces. I put a new crank in it and have put it all back together. Now when I go to start it it has a really harsh "bang" from the engine, so harsh it has already snapped one starter motor. It even does it with the spark plug caps off but with no spark plugs it's like normal. I have tried messing around with the rotary valve and still does it. Can anyone shed some light on what this might be? Cheers
 
Are the pistons in correct?

Can you turn it over and over by hand with the plugs out?
 
That's what I was thinking. I have set it like it says in the book and also set it like a JetSki mechanic has told me and both ways won't work. The starter was an SBT
 
Well the SBT and aftermarket starters are junk as you found. They are known to shear off.

As for the timing there is only one correct way and that’s per the manual. You need exact TDC on the MAG cylinder and a degree wheel.
 
I have checked the timing so many times and it always seems to be right. I've even pulled the pump now. Still doing it
 
Im bored and at a stopping point on my ski so I'm just throwing this out there but have you looked at the top of the pistons to see if it's contacting the plugs? Bangs with plugs in but not with them out. Does the electrode look smashed at all? Glad to see someone posting in the forum beside just me. Winter is slow
 
checked all that and is fine. This is really confusing me. Well for me in Australia it's summer so that's why I'm trying to get this thing going
 
Did you change rods and piston when you replaced the crank? Sounds like compression is the contributing factor to the sound.
 
I am by no means the expert on here and probably ask more question anyone, but I will try to help you until the experts get back on here. It is 1:57am here in the central u.s.
 
To me it seems almost like there's too much compression. New crank which came with rods but it has the original pistons and rings
 
Did you use the same is cylinder base gasket? Don't know if lowering you quash gap would change your compression. I am out of my element as I have never done lower end work. Just trying to throw ideas out there for you. However, do not take anything I am saying as truth. I know you said it only makes noise with compression but have you checked to make sure nothing got caught up in the rotary gear during the rebuild? And you verified you had the correct bearing for you crank right? Racking my brain trying to think of what would be "banging" because of compression. The compression must be causing something to be slapping. Does it sound like a piston slap?
 
i made the base gaskets but I belive they were right thickness. It's really hard to explain what's going on. It's so confusing
 
If you can turn it over by hand it isn’t hitting anything and the pistons can’t hit the spark plugs.

You need to check the squish gap for sure. You can’t just make a gasket on these as they sell different thicknesses for a reason.

If it cranks with the plugs out but not in it would be starter related. I have seen them when you try to start with plugs in it keeps going clunk, clunk, clunk but doesn’t fully turn the engine over.

It is either crap starter, corroded cables or bad connections, bad battery or starter solenoid.
 
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