Engine Surge

[catchee]

Re: Engine Surge

The thing is it starts fine and idles OK..little on the high side 1000 rpms on a set of muffs without backpressure.

 

[HighTrim]

Re: Engine Surge

Still sounds like a bottom carb issue, or related fuel supply to that carb. Have you replaced all lines running to the lower carb, checked all fittings? Sprayed pre mix into bottom carb and observed results?

 

[catchee]

Re: Engine Surge

Yes I've checked, double and tripled checked...I know the bottom carb is getting fuel because when I remove it the bowl is full. Just not sure if it's getting into the intake.

 

[JB]

Re: Engine Surge

As JB and ondarvr advised, spray some fuel into the bottom carb and observe result. Eyeball inspection is worthless in locating carb restrictions.

#4 is still very slightly out of spec on compression. I think an inspection of the head gasket might be advisable.

It is possible that there is a leak between #3 and #4 or common to #3 and #4 crankcases, interfering with efficient scavenging, but I am still not satisfied that that bottom carb has been taken off the suspect list.

 

[catchee]

Re: Engine Surge

JB, I just didn't eyeball the carbs...I ran a soft 22 gauge solid copper wire through each orifice without meeting any restriction and without seeing any debris come out. I think you may be right about the head gasket...I will replace both head and water jacket gaskets and do a total cleanup in the near future. I just want to get this running properly for now though. What I did this am is to swap carbs around and will see if the trouble follows. Going to have some breakfast first. Don't think clearly on an empty stomach....thanks for the support.

 

[catchee]

Re: Engine Surge

Just got through running the motor with the carbs swapped around and it does seem to be running much better....still have a high idle so will adjust that when I'm on the water tomorrow as I believe you need to have back pressure for a correct adjustment (???). I'm still going to pull the heads and install new head and water jacket gaskets soon. When checking the heads to see if they are warped I've always used a 3/8" X 18" square piece of glass and polished the head surface with a sheet of extremely fine emory paper in a figure eight motion. Is this still acceptable? I love this forum...a wealth of info can be found.