97 Seadoo Spx build

[glsmohio]

Yep looks good. Thanks for taking the time to test it.

The only reason I suggested to do windex was for the color, a couple of drops of food coloring would work in the alcohol too.

It would be nice to see an SBT head measured too to verify they are cutting for increased cc.


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ill do that tonight, it was just getting late last night. I dont even think i need to test the cc of the SBT head lol, Ill post a pic of the stock head , Group K head and the sbt head (all in a row), you can see where they cut the head right at the squish band (its like a damn step)

 

[glsmohio]

Looks like you did a great job and the results are about what I figured. It's nice to know for sure.

Thanks matt, so with that being said would you still get go with a stock head or you think im ok to run the 43cc head but up around that .050" squish ? If i had to guess ill be around 165 psi at that, but if i put the head down to .040" not sure how much it would go up to.

 

[Krispy]

Haha, that would be awesome! But putting numbers to it would be good so we know where SBT is going with the change.

Another thing that could be done if someone was curious is looking at the contour of the squish band, this would allow someone to replicate dome shapes. Beyond the scope of your project, but someone trying to make new domes would be interested in seeing the data.

What head do you think you are going to end up running?


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[racerxxx]

Here's the compression on my 98, bone stock head, bored to the first over. Squish is right in the middle of the range iirc

Compression tester had been compared to a snap on

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[glsmohio]

Haha, that would be awesome! But putting numbers to it would be good so we know where SBT is going with the change.

Another thing that could be done if someone was curious is looking at the contour of the squish band, this would allow someone to replicate dome shapes. Beyond the scope of your project, but someone trying to make new domes would be interested in seeing the data.

What head do you think you are going to end up running?


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thats a good idea, not really sure yet. If i dont use the head on this build or my xp tho ill make sure you end up with it one way

 

[Krispy]

thats a good idea, not really sure yet. If i dont use the head on this build or my xp tho ill make sure you end up with it one way

Yep, I don't know how set I am on having it yet, but it just may be the reason I need to build this core engine that has been sitting in my shop for a year.

Whatever setup you end with I bet it is going to rip!


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[glsmohio]

Here's the compression on my 98, bone stock head, bored to the first over. Squish is right in the middle of the range iirc

Compression tester had been compared to a snap on

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dang, im 1st over on my xp that i did and its right at 150. you must got some good rings in that thing lol

 

[racerxxx]

OEM pistons and rings, piston to wall clearance is 0.0045". I tell the machine shop what clearance I want, I don't let them come up with the specs.

 

[glsmohio]

Well got the head done today. Going to check the cc on the sbt head tomorrow and plan to get the motor all together.

 

[Matt Braley]

That head cover looks great I love that look.

I'm guessing the SBT head will have about the same cc as the stock. My thinking is that their motors blow 150psi like stock ones do. They cut out the squish band aggressively(I would also if I offered a no fault warranty plus most the heads they get are detonated). I think they compensate for that by decking(shaving) the head.

 

[glsmohio]

Well got the engine back together over the weekend. I am going to run the groupk head. I set the head at .055" after talking to matt, I will try to run pump gass but if i need to i will run the race gas. Some picks of the engine together ( note I dont have the carbs on it yet, it has the stock intake still on it that i need to take off and put my nice yellow one on.

I do have some questions, The head temp sensor what is the best way to clean it up?


Another question: on the raves when i took them apart the PO had zip ties on them ? My other 96 xp did not have them? Should they be there?

So for now i started to take the ski down to nothing so i can flip the ski and buff the bottom. this is one part that i would like to buy new, not sure if i can get them still?

I still need to check the cc on the sbt head, I hope to do that tonight as a watch the CBJ game.

 

[glsmohio]

[MENTION=51824]Matt Braley[/MENTION]

Is this the prop that you where thinking i need? what you think on the $$

http://www.ebay.com/itm/401043246781?ssPageName=STRK:MEBIDX:IT&fromMakeTrack=true

 

[racerxxx]

Lightly put the temp sensor in a cordless drill, grab a little bit of 0000 steel wool and let r rip.

The vent mushroom, no longer available. You can buy the correct lower spring for the rave bellow, look at the 951 explosion drawings for the part number.

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[glsmohio]

Lightly put the temp sensor in a cordless drill, grab a little bit of 0000 steel wool and let r rip.

The vent mushroom, no longer available. You can buy the correct lower spring for the rave bellow, look at the 951 explosion drawings for the part number.

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Found this in my bag of parts...is this what I need race? I just looked at my 96 xp and it's got nothing on them

 

[racerxxx]

Yes, that would be the lower spring. It was never advertised on the 787 (carbed engine) but the 98' 787 RFI's and 951's got them. The 951 and 787 use the same bellow for the rave. Now you just need another one, much cleaner than a janky cable tie under there or a piece of safety wire, IMO.

 

[racerxxx]

I see your head cover is an SBT head cover.

 

[Krispy]

I see your head cover is an SBT head cover.

Alright, teach us something else. How can you tell?


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[racerxxx]

Alright, teach us something else. How can you tell?


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Let's see if I'm right first, then I'll spill.

 

[fitty650sx]

The head bolt heads are recessed into the head cover?

 

[fitty650sx]

 

[glsmohio]

Let's see if I'm right first, then I'll spill.

Funny you say that. The only difference I see is the head bolts but the sbt head that I got looks like this

This head was on my engine and it was never opened and was not a sbt engine

My 96 xp has the one like this

So what am I missing lol?

 

[racerxxx]

Well I was wrong then, possibly. The nipple on the top left head looks like it was replaced. SBT cuts off the bad ones and has a machined nipple they glue in. That one just looks a tad larger in diameter and is also nice and smooth where the others have some pitting. I noticed this when I installed 2 787 in a 99 challenger.

I think that recessed head is from a 98/99 787. If you look at the twins in my Speedster you'll see the recessed areas it's a 99 and I'll check the original head from my 98 SPX but I'm almost 100% positive it's the same (recessed).

Speedster

 

[Minnetonka4me]

I gotta say...Im surprised with all this squish/compression debate. I am def surprised what Harry is telling you. I think he needs to read his articles we all have read over and over.

First....put that cut head on and get the motor all together. Do a compression test and see where it lands. 180 is what Harry said was the cutoff for premium gas. I ran that setup for MANY years with zero issues both with a Rossier and a Spec 1 pipe. Squish is critical for maximum HP, but the squish band is the real critical part. Thats what Harry is known for. The funny thing is most people say over 200 and its 100% race gas...well on my black boat before i put the 920 in that motor was running 205psi with a spec 2 and I ran 50/50 and raced it! And Jim raced it before me a whole season! The motor did come apart, but when apart I found a WSM crank that had a bearing race fail. Completely unrelated to what I was running.

While I do agree with Matt's statements, I personally run it a little closer to .045 w/o issues.


And lastly...much of your "line" depends on what you actually do with it. If you plan to hold it wide open for a minute, then yes you want to go to the higher end of the spec to be safe. Racing...well it depends on if you wanna walk the line or be safe. My kind of rec riding...I dont hold it wide open for longer than 10-15sec so I can get away with it being a bit tighter.

 

[glsmohio]

I gotta say...Im surprised with all this squish/compression debate. I am def surprised what Harry is telling you. I think he needs to read his articles we all have read over and over.

First....put that cut head on and get the motor all together. Do a compression test and see where it lands. 180 is what Harry said was the cutoff for premium gas. I ran that setup for MANY years with zero issues both with a Rossier and a Spec 1 pipe. Squish is critical for maximum HP, but the squish band is the real critical part. Thats what Harry is known for. The funny thing is most people say over 200 and its 100% race gas...well on my black boat before i put the 920 in that motor was running 205psi with a spec 2 and I ran 50/50 and raced it! And Jim raced it before me a whole season! The motor did come apart, but when apart I found a WSM crank that had a bearing race fail. Completely unrelated to what I was running.

While I do agree with Matt's statements, I personally run it a little closer to .045 w/o issues.


And lastly...much of your "line" depends on what you actually do with it. If you plan to hold it wide open for a minute, then yes you want to go to the higher end of the spec to be safe. Racing...well it depends on if you wanna walk the line or be safe. My kind of rec riding...I dont hold it wide open for longer than 10-15sec so I can get away with it being a bit tighter.

thanks for all the info nick, I do got to say though harry is a good guy every time i have called him he has took time to talk to me. I didnt end up putting the cut head on, after talking to matt i set it at .055". just trying to get the ski around now to put the motor back it and see what I got.

ill be sending you another parts list sometime today.

 

[glsmohio]

Well I was wrong then, possibly. The nipple on the top left head looks like it was replaced. SBT cuts off the bad ones and has a machined nipple they glue in. That one just looks a tad larger in diameter and is also nice and smooth where the others have some pitting. I noticed this when I installed 2 787 in a 99 challenger.

I think that recessed head is from a 98/99 787. If you look at the twins in my Speedster you'll see the recessed areas it's a 99 and I'll check the original head from my 98 SPX but I'm almost 100% positive it's the same (recessed).

Speedster

good point on that nipple. ill have a better look when i get off work