Coming Down

Hello everyone! I haven't been working on the Seca much lately as I no longer have a shop (since April), and as such haven't been lurking here much either. Anyway, my motor is finally back in frame and all together and the bike runs great with the rebuild and the mods completed.

Here's a rundown:

1982 Seca 750
-re-ring and gaskets complete
-new chain and sliders installed
-Supertrapp muffler with 4-1 head pipe
-K&N pod filters (I know, I'm a sucker for punishment)
-Carbs rebuilt with 43 Pilots and 124 Mains (clunk test approved!)
-new clutch plates
-new brakes
-new bars
-CRG Mirrors
-Aztec 8 Dual Headlights
-LED Signals

The bike pulls like an absolute freight train from 2000 RPM till an indicated 5000 and falls flat on it's face. I literally idle around town in 5th gear and it will extend the front fork with a blip on the throttle at 35 mph. Unfortunately this does not continue through to redline anymore.

I obviously have some carb tweaking necessary but have a primary concern first. When I approach a red light and downshift through the gears there is much less braking effect than before, and the RPM's refuse to drop once stopped with the clutch pulled in. Usually after coming to a stop I just ease out the clutch and "drag" the motor back down to idle. Once this is done it sits at 1100 RPM without a problem till the next time revs are increased. If I "snap" the throttle with the clutch pulled it is quite responsive but a little slow to come back down to idle after.

Any ideas would be greatly appreciated.

 

I have a 1982 750 Maxim that had the same issue with the RPM's refusing to drop. All that I needed to do to fix the issue was adjust the throttle tension. Once I loosend up the cable and put just a very slight bit of play in the throttle it has been fine since.

Hope this helps.

 

lack of braking on the engine could meen low compression, perhaps the rings are bedding in, or maybe it needed a rebore, what does the compression read?

 

a hanging idle is usually a pilot screw adjustment, try leaning it out some more.

 

My Suzuki GS450 does the same thing. I've been over everything and I mean everything. The only thing left is the vacuum line that goes to the pet**** . Is it possible that the pet**** could be causing a vacuum leak?

 

Have you done a WOT plug chop?
Sounds like you have great midrange response.
You MENTION bad +5K response, but say nothing of the <2k section.

Plug reads will be your friend.
http://www.usaimports.co.uk/Mopar_Tech_ ... eading.htm
The pods through EVERYTHING off that EYE know.
Good luck, and I think your running sluggish in the higher revs b/c your main is making it rich.

 

Must admit I haven't tried a Plug Chop yet, and I think it is a good time to practice with my Colortune.

I also have a feeling that it is running rich on the main. I removed all the plates from the Supertrapp at lunch today and it seems to run better and is more responsive. I will ride it "wide open" for the trip home and see how it does. Sure does sound good. :wink:

The "idle that hangs" is my primary concern as it makes it less enjoyable to stop or go around a slow curve, but as of this morning it seemed a little better. I think one of the slides may have been sticking as I had to turn up the idle a bit as well to get it back to 1050.