3D Choking off in action

[johna56]

Bought a 2004 3D 787 rfi several seasons ago after previous owner had reputable sea doo mechanic rebuild the top end. It has run fine, but the last two times we went out the plugs fouled and cut off after about 15 minutes of riding. It wont start and run for more than 20 seconds after it cuts off, but fires right up after i swap plugs. It then repeats. The first time i chalked it up to bad gas and possibly forgetting to swap plugs after burning off the fogging oil. This time, my son mentioned it seemed like it was being starved of fuel and then we noticed some smoke (r exhaust) coming from the engine bay. Im not a mechanic but if a 2 stroke does not get enough fuel, but still gets the oil injected i can see why it would foul plugs and smoke. Right now i plan on checking the battery voltage at idle and at 3500 rpm's to make sure voltage is where its supposed to be, checking the compression and looking over the exhaust to make sure there are no holes. Is there anything else I should be checking? Has anyone on here come across this type of issue? Does this sound like something i should just let a sea doo mechanic have a crack at?

Thanks in advance.

 

[Robbo96]

I had a very similar situation with low power output engine kept on cutting out. And a lot of smoke coming from the engine bay, while looking for the problem I took a look inside the rear foot board and I found that the t section on the standard exhaust hose had over heated and caused a hole in the pipe.

I then did an exhaust mod which removed all exhaust resonators no real performance gains but solved the issue I had

 

[johna56]

Update.... similar to Robbo and then some........ "T" connector in exhaust melted, pistons were physically damaged (hole in one), one motor mount broken and a couple holes in the exhaust pipe (the fat one over the engine) - not clear if any of these are related or parts wearing out around the same time. Fairly certain damaged pistons was caused by improper break in procedure by previous owner and I (he provided incorrect instructions - i did not verify). Anyway, had the engine rebuilt by a fellow in northern Delaware - great work. Replaced all the motor mounts, throttle cable, and a carbon seal at the same time. Also had the the "T" replaced with PVC, the fat pipe welded, one of the straight pipes switched to pvc (from plastic) and throttle cable replaced. Im only about 1/4 of the way through breaking it in but ill be running through the first two tanks of gas exactly as spec'd.