Engine hesitation

Hello, my 82 Seca 550 hesitates around 6000/6500 RPM. The previous owner had the carbs jetted and synchronized. The bike has a 4 into 1 exhaust and stock airbox with k&n filter. I've done this; rebuild fuel cap, fuel petcock, new fuel line and filter, spark plugs, flushed the tank, checked the cam chain tension. Any thoughts?

 

That's the transition point from needles to main jet.
Do a plug chop at that rpm to see if it's lean or rich

 

Thanks for responding, by chop do you mean pull plugs and check color?

 

Yes chop is hitting kill switch when accelerating through that trouble rpm range and then pull over and remove plugs,then take a pic and then post it

 

change the k&n air filter back to the emgo paper filter
Condition: New Brand:
Emgo
Manufacturer Part Number:12-94410


put new plugs in for the chop

also if filter does not solve the problem

I would check the asperator tubes under the main jets to make sure they are clean if the little holes in them are clogged it will cause you problems

main jets are well into play at 5k rpm

do you know what jets were replaced and the sizes of them?

do you know the brand of 4 to 1 exhaust?

 

TALKIN' TECH: Various thoughts on various issues

from section on plug chops
"The pilot fuel circuit is active from idle up to about 2500-3500 rpms, and at about 3000 rpms the main fuel circuit starts becoming involved, and by 4000+ rpms the main fuel circuit is responsible for about 80%+ of the engine's fuel supply conditions. So where you do the "chops" tell you not only what the fuel mixture and combustion conditions are like, but also, which circuits are responsible for those conditions."

 

back to basics
are your valves clearances in spec?

 

Thanks again for all of the info. It is a kerker 4 to 1. I got the bike with 9340 miles last summer. It came with the factory's exhaust in a box in mint condition. Engine is very quiet, runs nice and smooth just cruising till about 70mph. I have storms in the area today so not riding till tomorrow. Thoughts on putting factory exhaust back on?

 

Yes

 

my kirker was rusted out in the headers. factory exhaust is very heavy compared to a mac4 to 1 do not know compared to kirker.

stock is nice I would stay with the kirker unless you are going for the complete original look.

 

Mine is rusted as well. The muffler has a hole rusted through on the bottom. I do like the factory look. You have been a huge help. Thanks again. Tomorrow I shall do the chop.

 

I forgot, I have not checked valve clearances. I need to find a gasket first. This bike was rode very little, less than 500 miles a year in Wisconsin. Once I get all the bugs out, on to paint work.