701 bog after holding 80% throttle or WOT for 5 seconds

[Lumberjack]

Twin carb factory piped 701 in my FS2 has developed a bog when holding a constant speed at high rpm then clears out and rides fine. Before it started doing this it died once like chopping the throttle during a 3 second pull at wot then started up fine but recently developed the high rpm bog. Otherwise it rides 100% fine everywhere else in the rpm range and you would never noticed unless you held 80% throttle or WOT continuously for around 5 seconds.

701 is 100% stock besides a complete factory pipe. It's had the same tune and pipe setup the last 6 years and i haven't changed anything and it's always run perfectly

New battery, new plugs, new fuel, excellent compression, fuel vent works, original plug caps but the carbs haven't been opened up since I've owned it because it's always ran fine. 100% fresh water ski.

Any advice what to check next? Should the carbs be gone through or does this sound electrical? Need to order parts to Canada So i dont want to miss anything

Thanks everyone

 

[john zigler]

If nothing has changed to change your fuel requirements, it sounds like it is time for a tune up, fuel filter, rebuild carbs, etc.

 

[Lumberjack]

If nothing has changed to change your fuel requirements, it sounds like it is time for a tune up, fuel filter, rebuild carbs, etc.

Thanks John,

Yes zero changes when this sustained high rpm power loss starting happening. Ski has been the exact same 6+ years. Just wanted to be sure if I should check anything else before having to order parts to Canada.

The ski still seams to ride 100% fine everywhere else in the throttle range until you hold a high rpm pull for multiple seconds or wot for multiple seconds otherwise you would never notice the power loss scenario.

 

[sjetrider]

I would go through the carbs and filters first. Internal carb filters and external.
And be very careful testing as that sounds like potential detonation.
I assume you have twisted the top screw out a 1/4 turn? Lower Water temp can cause it to need a little more fuel at top end.
and as things get older they sometimes need a different fuel mix as well. If compression is same as always this may not be the case, but wear on reeds and other components can change what a motor needs.
I ran half this season without an issue and then the water got warm and I ended up dropping from a 135 to a 130 pilot jet after going completely through the carbs making sure there was no other issues going on.
Will be back to 135 jet next spring most likely.

 

[sjetrider]

also check diaphrams in your fuel pump / pumps. Sounds like they may not be keeping up at sustained demand.

 

[Lumberjack]

Thanks every pulled my strainers and they were perfectly clean, removed and drained my inline filter and blew through it and it was 99% blocked. I can't beleive it was even running that restricted. Swapped filters with my SJ and It ran perfectly again

 

[motoxracer1551]

A small exhaust leak can cause this as well, as it runs out of fresh air to burn.