Super Jet '96 Superjet brand new motor runs TERRIBLE

[YooperScott]

If you could even really call it running........

The background. I bought a round nose Superjet that had a 650 engine in it. I only started it with the 650 and it started up immediately and seemed to run fine. Got a blown 62t/62t engine with it as part of the deal. I rebuilt the 62t engine with new pistons and milled stock 64u head good for "175 psi". Electronics were used from the 650 and I did the resistor mod to raise the rev limiter. The exhaust (for now) is stock 61x RN SJ stuff (used helicoils to retain the M8 exhaust bolts). Totally stock intake side dual 38mm carbs, airbox etc that I bought from someone off here and they came from Florida (hot, humid) and had sat at least a year but everything looked just great externally. So that is the ski setup, now the issues.....

When I started it it did not want to idle at all and had to keep giving it gas or it would die and it ran rough. It was smoking pretty good and spitting tons of oily black sludge out the exhaust. Got better than 175 psi compression both sides on a brand new had never been used Craftsman gauge. Plugs were WET. I assume the electronics were fine, engine ok and it's carbs. I took them off the machine and brought them home (ski is 375 miles away at the lake). I ordered rebuild kits, new N/S, new jets last night. I also started dissassembling the carbs. Nothing 'seemed' wrong but the end of both needles were black (I assume they should be bronze?). So the plan is rebuild the carbs with the new N/S and jets. Since I will not be up there until Labor Day (need to wait for and do the carb rebuilds anyways) want to put my mind at ease and agree it's likely the carbs?

Second issue a couple of times when I hit the start button I got nothing. No click, nothing. Then a little while later it would work fine. Guess it's something in the start/stop switches? Is there really much you can do other than just replace it?

Thanks

 

[SXIPro]

Yes, rebuilding the carbs should fix the rough running and the sludge issue. You can tear apart your start/stop and clean everything up with contact cleaner and see if that fixes the other issue, or send the switch off to JSS for a rebuild and it will come back better than new.

 

[OCD Solutions]

You are likely on the right track with the carbs and even if it turns out to be something else, it certainly will not have hurt to have rebuilt them. One less thing to worry about for awhile.

When you clean the start/stop switch, be sure to disconnect the connector at the ebox end and look for green corrosion. That is a very common failure point. Depending on how bad it is you can usually clean them up or you may need to replace them altogether. The terminals themselves are available cheap enough.

If you don't already have it as a habit, go out and buy yourself a tube of silicone dielectric grease and make sure you fill all electrical connectors each time you have them apart. You can never do enough to keep water out and the best way to deal with corrosion is to prevent it from startig in the first place.

 

[callmefinch]

my start stop switch also had issues. did the same thing. i took it apart and the saw that the bronze pieces used to make contact on the terminals. i asumed that there were small springs that were supposed to push them on the terminal for contact and they were nowhere to be seen, i used a wd40 straw to make the bronze pieces stick out more to make contact, it actually fixed my problem.