Super Jet 701 bench test

[JT_Freeride]

So long story short me and my friend had to do a bench test, here are some pic of our contraption. We thought it would be funny to post them, also it worked perfectly except for the water everywhere.

 

[Matt_E]

You went through a lot of trouble! If it's just a short bench test, you can do it without the water and without the pipe.

 

[JT_Freeride]

The motor had a air leak so we need to find out if it was going to run away again. So far it seems to be the carbs we replaced them with ones that we knew worked. also did a leak down and found nothing cases are sealed

 

[Matt_E]

An air leak has to be below the throttle plates to do anything. Are you sure it was the carbs?

 

[JT_Freeride]

To be honest no, we are going to try it now with the old carbs and see if it runs away. our guess is the base gasket to the carbs or the base surface of the carbs where it meets the manifold.

 

[JT_Freeride]

Okay so we tried the old carbs and it ran away again. within 2 minutes (we timed it lol) we put the good ones on and it ran perfect. Jetting is identical as well as the screws.

 

[ajmps1]

new gaskets?

 

[Dirtyace14]

Same base gasket, but it was new at the begining of our test. The ski ran great when we rebuilt it, then we jetted the carbs for the pipe and head and it ran away. We jetted the second set of carbs the same way and all things being equal it no longer runs away. Swap the original carbs on and boom runs away again. I guess the carbs need a rebuild but I dont seen how they would cause a run away unless maybe air is getting in through the diaphragms somehow?

 

[JT_Freeride]

Can i mod move this thread to general or superjet? Thank you

 

[BruceSki]

Did you pull the high and low speed adjuster screws all the way out and inspect/clean them? Weren't the carbs on the ski all junked up?

 

[JT_Freeride]

No we did not check them i have 3 brand new ones i could put on. and yes the carbs where a little junked up.

 

[Devilock]

sounds like thats your problem u need to clean out thoses circuts ...and the needles ..thats why it running away on those carbs..to lean

 

[JT_Freeride]

Here is the two low speed screws they are different then one another. Could this cause it? These carbs came off of a running ski they are not the junk that was in mine. Everything else looks fine and all of the fuel circuits are clean.

 

[BruceSki]

try the low speed screws from the good carbs in the bad carbs and see. Then you can rule that out and try something else

 

[BruceSki]

I've been bench testing em like that for years. It's pretty funny watching a motor walk around the driveway.

You don't need to worry about running water through em as long as you don't run it too long. There's 0 load on the motor so it takes a while to build up heat.

 

[JT_Freeride]

Here's a vid of the motor with the old carbs freshly rebuilt. It seems like it still wants to run away but it doesn't. any ideas on what it could be.

 

[Bobert540]

Make sure those orings are in good shape on the screws and also make sure the springs move freely. I like to clean them and then put some marine grease on them. If you turn the screw in, then back it out and the spring does not seal the oring you can get an air leak in the carb.

 

[BruceSki]

What jetting and what springs are you running? What size seats are in the two sets of carbs you have? Have you made sure its exactly the same?

Is the little pinhole in the return side of the non fuel pump carb clogged?

 

[Dirtyace14]

It has 115g springs 135 main and 75 pilot. No clogs, I had them completely apart last night and put back together with all new minkuni gaskets. We ed with it some more today and its running away some more, dialing in these ing things is such a PITA I am starting to think the o ring around the highspeed/lowspeed adjusters need to be replaced but I really do not know. I tested pop-off and it was around 55 psi maybe a little less.

 

[Dirtyace14]

Make sure those orings are in good shape on the screws and also make sure the springs move freely. I like to clean them and then put some marine grease on them. If you turn the screw in, then back it out and the spring does not seal the oring you can get an air leak in the carb.

Yeah the springs all moved and the o rings looked good but that does not mean they are, where do I get replacment o rings for that lol?