MY SUPERJET 701 ENGINE SEIZED...MY QUESTION IS WHY?

[Blue]

135 main and 75 pilot is the recommended jetting for a bpipe. And 1 turn low and 1 &1/2 turn on the high it best starting point for a nonported SJ. This is the same set up we have used hundreds of times and it always works. Fine tuning usually ends up at 3/4 turn on low and 1 &1/4 on high after breakin. I just did a pair of 2013 for a customer and they run perfect.

 

[JMew03]

For some reason I would listen to Blue when it comes to jet settings. Lol he is pretty smart.

 

[JetManiac]

Like Blue said, your jetting was right, but the adjustment screws were too far in especially on the high speed one.

 

[CRJ]

Actually 130 is stock.

your right, im thinking single carb.

 

[dlrainer0217]

Ok. So I'll keep those size high and low Jets. Do you know what my fuel valve pop off pressure should be set at? Is stock seat/spring/needle sufficient?

Thanks guys!

 

[dlrainer0217]

Also one more question...what thickness cylinder base gasket would you guys suggest considering that I have the ADA o-ring head? The gasket that I removed from the engine measures .020". A friend of mine was saying I should go with a .016" for better low end power?

 

[Blue]

You have to be careful if your cylinder top deck has ever been surfaced you can run into squish clearance issues. If it has not been cut you can easily run the thinner gasket but .004 will not make much difference.

 

[dlrainer0217]

Ok. Sounds like it's best to stick with the .020" gasket and I'll be sure to measure my squish band when I put it back together!

Thank you!

 

[dlrainer0217]

How much would you say is not enough squish band?

 

[Blue]

On smaller motors with a piston size from 81mm to 83mm.
Between .025 and .045 is fine. Less than .025 its possible for the piston to hit the dome at high rpms as the cylinder wears and the piston begins to rock.

 

[dlrainer0217]

Hey guys! Got her all back together today! Went with Pro X std pistons and honed the cylinders. The measured to be true and round, so i went the cheaper route. While i had the carbs aparts, i measured the pop off pressure. I was a little alarmed to see it at 85psi! Is this normal? It has a 1.5 seat. When i apply air, the needles start to leak/flow ait at 32psi amd then "pop up" at about 85psi. So which number is actually my pop off pressure?

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[Roseand]

Lube it with wd40 to get an accurate reading.

 

[augustaf]

Yes, you'll need to push a low viscosity liquid past the needle

 

[DAG]

test popoff with the fuel/oil ratio you are going to run in the ski.

if your popoff dribbles before you get a clean pop you need to replace your n/s. otherwise you will have a tuning nightmare

 

[dlrainer0217]

Yes, I lubed it with wd40

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[CRJ]

like dag said, if its leaking, replace it.