Lower Max RPM and idle

[TubecatGS]

So, finally finished rebuilding carbs and replaced all grey fuel lines on the 99 GTX limited (951). Ran awesome for a day and a half and a few tanks of gas. Then all of the sudden if wouldn't rev past 5900-6000 RPM at WOT and idling just a little less at about 750-900 RPM. It's like it lost 15 % power overall..

Where should I start to investigate? Thanks

 

[POPPS]

I would check compression,,,see if they are within 10%.

 

[TubecatGS]

Will check compression. Here are the spark plugs. Front one looks a lot darker to me...

 

[Mraw]

Looks like water on the plugs, check for a leak where the exhaist pipe and manifold meet

 

[TubecatGS]

Looks like water on the plugs, check for a leak where the exhaist pipe and manifold meet

Thanks. How do I go about doing that? These are new to me? I saw another post that showed wet plugs and the front plug darker than the rear and with water on them and someone said possibly crank seal? I guess I need to run a compression test still..

 

[POPPS]

I have to agree with M...the white specs are presence of water,,,more than likely from the exhaust/manifold gasket,,,usually occurs bcause that "heavy"pipe was not installled with proper "balance",using the front bracket,,, if you do remove the pipe,,,do it in 1 piece,,,or you are in for trouble,,, that plug looks fouled,,,

 

[TubecatGS]

Thanks. When you say Exhaust Pipe and Manifold meet... hmmm do you mean where the black exhaust pipe connects to the head (above the carbs)? does water flow all the way up there? sorry, my first jet skis. yes the front plug looks fouled to me as well. Both plugs look tan and I don't think that's normal either, is it?

 

[TubecatGS]

So, you guys were right about the leaking exhaust/manifold leak I think......I didn't notice this before.... but... a bolt fell out of the exhaust manifold and another was loose. Could this cause the water to leak in the cylinders (hence wet plugs)? Or foul a spark plug and/or lose some power (the drop in wide open throttle rpms and lower idle RPMs? Compression is about 135 in the cylinder with the black plug and 140 in the cylinders with the tan plug. I found the bolt and was hoping I could just put it back in and tighten all the bolts back up... what are the chances the gasket is still good? Thanks

 

[Mraw]

You should replace the gasket, make sure to follow the torque pattern and torque spec. You should be able to find it by Googleing it.

 

[TubecatGS]

Thanks. Can you replace the gasket without removing the exhaust? If you take out the bolts is there generally enough room to slide a new gasket in?

 

[POPPS]

Is that bolt sheared?,,,do you have the large 17 mm I believe that supports the front pipe bracket,,,often they are not there or often sheared,,,hopefully its there,,,the missing bolt in the exhaust may also have a stripped thred?,,which could explain why its missing.

 

[TubecatGS]

Is that bolt sheared?,,,do you have the large 17 mm I believe that supports the front pipe bracket,,,often they are not there or often sheared,,,hopefully its there,,,the missing bolt in the exhaust may also have a stripped thred?,,which could explain why its missing.

Thanks. I found the missing bolt, it doesn't look sheared. Seams to thread in as it should. The big 17mm bolt is there and tight. I think someone was in this motor not too long ago as it looks very clean and maybe didn't tighten the exhaust bolts properly as one other was loose. Do you think if I loosen the 17mm bolt I will have enough wiggle room to insert a new gasket? And do you need to take the carbs out and/or the air box to get to the bottom exhaust bolts out?

If I need to take the exhaust off or move it out of the way to clean the surfaces, it looks like it's just the big 17mm bolt besides the exhaust intake bolts? (Leave connected at other end?) Thanks