HELP... SJ 701 Problems

kkwedell

kkwedell

x-h20.com
Location
Walnut Creek
So I have been chasing this problem all summer. It started when I hydro locked my ski (time for a rebuild anyway). I bought new: prox pistons, had it bored over 83mm, ATP water box, new stator, and i had my flywheel lightened by #zero. I put it all together and went to start it. It just cranked and cranked without starting. I checked the spark and it is good and strong. Then I checked fuel. It was pumping fuel well. So then I checked compression. 210 both cylinders. I have an ada head, but Im not sure what domes. So fuel-compression-spark=start. So I cranked it over again..... BAM...... biggest backfire I have ever heard. So I looked at the carbs to make sure I did by mess them up. They were al good as was the exhaust. I checked the timing and it is 1 deg advance. The key was also good for the flywheel. So I looked around and that was one of the symptoms of a bad msd enhancer. So I went ahead and bought a new one. Put it all together and same thing. Only thing I can think of is a bad stator or that the crank was put together wrong by SBT. It seemed exactly like my old one. Im at a loss and am seriously just at the point where I am going to walk away.

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kkwedell

kkwedell

x-h20.com
Location
Walnut Creek
I also checked the boots. Are the 61x/62t stators different? Is that compression too much to not run race gas. I didnt change the domes and it was 185 compression before the build. Did boring change it? Also when I hold the started sometimes it just stops.

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Harbor

Harbor

Location
Stockton
kkwedell said:
I also checked the boots. Are the 61x/62t stators different? Is that compression too much to not run race gas. I didnt change the domes and it was 185 compression before the build. Did boring change it? Also when I hold the started sometimes it just stops.

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Yes the 61x and 62t stators are different and so are the flywheels, your stator needs to match the flywheel you have on the engine.

On the compression, that's too high for 91 pump gas. We have a 5 mil running 210 with 50/50 91 & 110 ERC race gas. No more than 3 seconds wide open and mostly low end, low speed brap

This 5 mil was 200 psi after build and after 2 tanks went up by 10 psi per hole so yours might too. You may also have a lot of build oil on your Pistons if you didn't install them with only a light film of oil. That may also contribute to false overly high reading. The increased bore diameter is also raising it. Once you get it started youll find out what it really is, then after the 2 tanks check it again and decide if you like it and what octan you want to pay for.

Let me see if I can give a pic of the 62 and 61x

All I had was 62t
image.jpg
 
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kkwedell

kkwedell

x-h20.com
Location
Walnut Creek
Online I bought a stator for the 62t because im pretty sure i have a 62t flywheel because there are no gaps in the magnets. . https://www.amazon.com/gp/aw/d/B00MATCQHY/ref=ya_aw_oh_pii I have 62t cases and and 61x cylinders. The stator I bought did not have a mark for the timing, so I just measured the same as my old one. Also should I get new ada domes to bring the compression down. If so which ones

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Harbor

Harbor

Location
Stockton
I'd prolly not worry about the compression until you get the no start issue sorted. The compression isn't the cause. After you get it running on the work stand and water hose for a bit you can take another reading and get a better idea where your at. You'll also have to read your dome to know where your at now and adjust from their. ERC is in San Lorenzo or Morgan machine by you has race gas if you want to toss 1 gallon in your tank while you get this sorted of if you want to mix some once running to get thru the 2 tank break in and see what your compression is then and adjust you domes. Minimum at Morgan's might be 5 gallons, ERC sells at the pump by the gallon, $9:75 ish

Does your flywheel and stator match my pic ?
 
Harbor

Harbor

Location
Stockton
Very strange...... I use a cut front cover and msd timing tape and a timing light to read timing. Cranking timing with my enhancer was 12 degrees both cylinders.. Can you check this way ?

Where did you get that stator and why did you replace it? Can you try your old one
 
Harbor

Harbor

Location
Stockton
Anyways I bave to go to sleep. Your in NorCal walnut creek?

If so I can stop by next Monday/Tuesday night with the above mentioned stuff, plus already taped 62t wheel, dial indicator, degree wheel, extra timing tape, complet ignition system, timing light, cut front cover... Then we can both scratch our heads lol
 
mike b

mike b

Michael "Mayhem" Bevacqua aka MikeyChan
Location
California
I would get compression to no more than 185 to run pump 91 or get some race fuel if your going to run 210. I had a huge backfire last year first start on my JM781. It was just that I cranked it over to prime it, must have had a low idle to it wasn't wanting to start, filled up the exhaust with extra fuel and BAM. Scary poop. What I do is all my first starts on built motors in the water (i'm always afraid of run aways) it will also help you hear things better because it will be quiet compared to a dry start, atleast this is something I like to do. IF you have even compression, Spark, and Fuel the motor will start up.

Maybe off brand stator is no good but chances are it will work for a short amount of time, same thing with the crank. They just will fail sooner. If you just want to finish the season start it up and rebuild during the winter with better parts, OR rebuild with the proper stuff now and then ride whatever time left you have if you don't run all year.

And I would assume the crank is fine but if you want to check take the head off and make sure your pistons get to TDC. Other than that im sure the crank is fine...just cheaper quality

Im thinking you just had a build up leading to backfire since it is a first start. If it was doing that every time than something is definitely wrong but I wouldn't think so here. Good luck!
 
JetManiac

JetManiac

Stoked
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Location
orlando
kkwedell said:
Is it possible that the cranks isn't right?

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Possible but not likely. They use a special machine they developed to phase cranks after assembly. Then they are welded into position. We have never seen an SBT crank out of alignment out of many hundreds sold.

Electrical problem is much more likely. If you had a backfire then check the flywheel position, you might have sheared the woodruff key.
 
Harbor

Harbor

Location
Stockton
kkwedell said:
The woodruff key looked good when I inspected before the rebuild

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He means it may have sheared or may have sheared as a result of the back fire.

If you pull the flywheel for a visual inspection and find nothing wrong would it be possible to toss in your old stator to elimianste your new one ?
 
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