'86 Connie Owner - Is this normal engine behavior?

[CobraKai]

Hi guys,

I have a quick question about my 1986 Connie with 30k miles on her. I've gone through the bike doing all the basic maintenance - cleaning carbs, replacing the plugs, valve adjustment, etc.

The bike runs awesome in the city and at all sorts of throttle openings. It's perfectly smooth from idle approaching 7,000RPM. However, once I hit 7,000RPM and above, the engine sounds really loud. Like it's going to explode. It still pulls well, it just gets really rough and loud. I get pretty severe vibrations and it is just screaming at me to shift or slow down.

I manage mid-40's mpg on the highway, 30's average, and it pulls decently up to a 125mph top speed. Is this a normal behavior for this engine, or should I check something? I was thinking of checking the plugs wires, but I'm not sure if this could cause this issue. I tried looking up videos on Youtube, but there aren't any videos of Connies being flogged that I can find to see if its normal.

Thanks

[MAN OF BLUES]

Sounds about right, not sure what you are expecting for a 1986 bike.... I owned an 86, and sold it with 138k miles on it in 2009, and it was probably the best running Silverdammit bike in COG at the time...

Flogging an '86 isn't wise, it is what it is,  its meant to be ridden a long time, for many miles, and when in a perfect state of tune will perform great, just don't hover above 7k rpm.... run it up there and shift... you have 6 gears, use them... but I'll also say don't ride around at 40mph in sixth gear either... the bike loves the 4500-6000 rpm range, and that's its happy zone,  I regularly hit the zones you speak of, in twisties and such, but its on and off throttle cycling on a bike I did the tuning on...

As for top speed, in its OEM configuration, it will see about 135-138 mph max.. just letting you know...and that's pushing it, and should not be done for long distances, or on a regular basis.

[CobraKai]

I expect it to rev to the moon without any hint of hesitation!  Just kidding - but really, most I4's I've ridden have excelled at high RPMs, to make up for their lack of oompfh down low.

But really - okay that's good to know! This bike is surprisingly good when flogged. I am constantly blown away by how well composed the chassis is. Compared to a 2004 ST1300, the Connie was much more stable, and even kept up in a straight line. The ST is far more refined though.

[DC Concours]

You like to ride at 7k or over?

Note to self. If every on sale, don't buy cobrakai's c10. Even if it's an awesome deal.

[CobraKai]

Haha... I rarely go there. Even when canyon carving, I short shift to stay in the meat of the power band. I just find it odd how much it hates going over 7k. If the power dropped off, that's one thing, but it keeps making power - it just hates doing so! Maybe I will grab a video to show you guys just how angry she gets.

That said, I definitely put my Silverdammit through the wringer. Yet it has never skipped a beat. A truly great bike.

[ronbuell]

If the graph I just looked up is correct, the power levels off starting at 110 and peaks at around 120.  So you're in the ballpark.  My 98 signs off about like yours, but I'm happy tooling around at 75 or less.  And I agree with the other comments of stability.  Most street bikes have a speed they run well at.  My 80 Suzuki 850 liked 45 in 3rd gear and 65 in top gear.  It got buzzy above those levels.  Just run it where is runs best, live with it, or get a Busa for more spirited riding. 

You might check the motor mounts to see if they are loose, or consider replacing the exhaust system.

[RFH87_Connie]

Perhaps you are getting valve float?  Check the valve clearance, it may be a little tight.  Running any type of fuel filter?  That might be restricting it.  Not that I go there often, but mine will go up to near 10k without any stumbling issues or changes, other than sound pitch.  The sound kind of implies you shouldn't be there though.  I usually just use it up to 6.5k mostly (or a little less), as that's about were it feels like it starts the drop off.