Challenger 1800 787 Setting carbs... where to start?

[Davet6740]

Just dropped in a after a top end rebuild and can’t get her running. I’m thinking I may have an issue with my carbs, which I did disassemble and clean up. But not sure where to set the high and low screws. The engine turns over... tries to start... but only fires once or twice and shuts down.

Here’s a little video... would my carb settings cause this? Ughh... looks like I can’t post a video

 

[mikidymac]

WHat year is your boat?

Follow this thread exactly to do your carbs...Carb Rebuild Thread.

Typically these carbs need an actual rebuild with new Genuine Mikuni parts, not just an open and spray.

 

[Davet6740]

Rebuilt carbs.... still won’t run? I pulled the plugs, covered the plug holes, and cranked her cuz I thought I may have flooded. One of the pistons is blowing a ton of gas/oil out.... carb setting??

 

[mikidymac]

Did you follow the carb rebuild thread to the letter?
Did you check pop-off and leak down?
Did you use new Genuine Mikuni parts?
Did you change the needle and seats?
Did you change the springs?

I see what looks like a cylinder base gasket on the floor, why was the engine apart?

 

[Davet6740]

I did use the rebuild thread. I set the pop-offs to 35psi. I did not replace needles/ seats. I tried new and old springs until I got both to pop at 35psi. And no... I did not use Mikuni kits.

The top end of this motor was just rebuilt. That’s how this whole thing started. I blew a ring last year, so I rebuilt the top end and carbs. So it now has 155-160psi compression and I have spark.

I adjusted the high and low settings. The high is out 1/4 and low 1-1/4. It’s not dumping all the fuel in anymore but still won’t run. Turns over and really sounds like it wants to run, but doesn’t.

 

[mikidymac]

Buy the mikuni kits and new needles and seats. Until you do this you are never going to get it to run correctly and there is nothing else we can do for you.

Not trying to be mean but the junk carb parts are your issue.

 

[Ckrawiec]

Listen to the man....genuine MIKUNI carb kits...PERIOD, end of story.

Beating your head against a wall doesn't really annoy the wall that much.....so stop that. Many have been down this road...only to come back to Mikuni.....TAKE THE SHORTCUT!

 

[JeremyD615]

And just so that it’s completely clear and out there, you ARE putting that brand new top end at risk by attempting to run it with the aftermarket carb parts installed... Brand new motors wind up getting junked all the time by either putting old poorly running carbs back on, or using the wrong carb kits.

You need to go pull the carbs back apart and completely rebuild them using Mikuni parts, along with new OEM needles and seats and the old original springs. (as long as the old springs were not cut) You also want to be absolutely sure that the transition ports are completely clean. Don’t risk all the work you’ve already done on the motor by taking shortcuts on the carbs.

 

[Davet6740]

Okay okay... I get it... OEM rebuild.

But would an aftermarket rebuild result in a non-running motor? Actually I rebuilt both sets of carbs, using aftermarket kits, and I have the same results with both sets (on the same motor). So I’ve got 2 sets of carb rebuild kits that are faulty to the point that the motor will not run at all? Not just poor performance... it won’t start.

 

[JeremyD615]

That’s not uncommon at all. That’s why we harp on the issue as hard as we do... When everyone says the aftermarket kits are junk, it’s not exaggeration at all...