S-Maxx 3.3 wide open

[SiN360]

Hello everyone,

I have an S-Maxx with a 3.3 that I recently rebuilt and it was running great untill I broke a rod. I took the engine apart and the sleeve and piston looked good. So I ordered new rod and pin and rebuilt it. Now it starts up, but it's wide open even though the carb is fully closed to idle. I disconnected the linkage and have the same issue.

It seems like I have an air leak I checked it with brake clean and I can get it to shut off by spraying around the block. I took the motor apart again and made sure all the seals were good. Then I sprayed with soapy water and blew into it trying see if I see bubbles, but nothing. When I was blowing into it with everything else plugged it felt like it was sealed. Start it back up and I have the same issue.

Does anyone have any ideas or suggestions?


Thanks

 

[fstnd]

Do you know where the leak is? If it's in the bearings, you can buy new bearings obviously or reinstall them the proper way with high temperature differences etc. Or you can seal the bearing with high temperature sealant. If it's the carb, you can use high temp sealant where it is fitted into the block. 2 most common places for an engine to suck unwanted air from

 

[Weezel]

Make sure to reset carb needles back to factory.
Did you reinstall the copper head gasket? Double check the backplate o-ring isn't damaged?

 

[SiN360]

I put new bearings in when I rebuilt it after buying it from someone. I have the copper head gasket on there and I doubled checked the o-ring on the back plate when I took it apart again after replacing the rod. I though it might have been the bottom carb o-ring since it was messed up when I pulled the carb out to check. I replaced that one when I took it apart to make sure everything was good, but still had the same issue. Thanks for the suggestions, I'll take it apart tomorrow again to go over it it. I didn't have time today to take look at it.

 

[Weezel]

When you test for air leak by blowing into engine check that the crankshaft opening is pointed toward the carb. It can help. When it is closed air isn't supposed to flow through to block area.

An air leak can be a pain to find.