sudden change

[Dan M]

Ever since my PCIII has been installed with an off the shelf map for my approximate mods (FBF X-over & M4 mufflers), my bike has run seamlessly. Smooth strong power, and not even a hiccup. Yesterday I noticed when riding at 3000 to 4000 rpm with a small throttle opening, there was an occasional miss & surge. Today I rode about 150 miles and it was happening often, as well as missing when leaving a stop until the throttle was opened 30% or more. Idle is smooth, full throttle is OK as is anything above 4500 rpm. It is hotter the last two days than it has been, mid 90's with substantial humidity. I'm wondering if it is just too rich at that throttle opening for the hot temps, and I'm getting the plugs sooty. I haven't looked at the plugs yet or checked CO output.

 

Any thoughts out there?

[Ballacraine]

Humidity is the main culprit, I would suspect.

 

Don't rush into changing any PC settings until the atmospherics are more 'normal' for your area.

 

As a bit of a correlation, my T500 Suzuki twin always ran a lot better when it was slightly damp...

 

Wet and it would cut out!

 

I found this to be the case with most two strokes.

 

OK I know we are talking different strokes, but I do think humidity still has an effect on 4 strokes.

 

If symptoms stay the same when it is cooler and drier, then look at the mapping and maybe do a plug chop at the offending revs.

 

Nige.

[jrt]

This is pretty common behavior- it occasionally does it on my bike (no PCIII). I would just run at higher rpm. I would suspect that it is a heat and lean condition, rather than rich. Todd is the PCIII guru- you might just ask him what he thinks about remapping.

[dlaing]

You may just have to give it a basic tuneup.

Valves, TPS, etc.

[KiloSjon]

You may just have to give it a basic tuneup.

Valves, TPS, etc.

 

I Had the same, and after service (syncing) it runs very smooth, no more misfires and hick ups...

[Dan M]

You may just have to give it a basic tuneup.

Valves, TPS, etc.

 

 

Yea, I'll go through everything this week. It hasn't been too many miles since valve adj & t-body sync, but I'll check it all anyway. It just seemed so sudden. Not a slow degradation, it went from perfect to crap within 100 miles.

[docc]

I just tuned the Sport after about 5000 miles ( I usually do the 6000 mile interval at 4000).

 

The valves looked good having loosened from 0.005/0.007 to 0.006/0.008 and the plugs had good color but the typical dark stripe down one side, maybe a lttle crusty on the grounding electrode. No difference in the ride at that point.

 

I then reset the TPS to 160mV ( from 150) and resynched the throttle bodies at 4000 rpm.

 

What a difference in the ride!! The revving is so eager, no hiccups, flat spots or hesitation even just off idle or at low revs. It wasn't like it was running 'badly' before, but what an enjoyable improvement!

 

PS: of course there is always a price to pay. At 4000 rpm on the side stand the bike waked backwards about a foot and a haly while the vibration pitched my VOM to the floor. The TPS idle measure went from 525mV to 575 mV. I fear my Triplett meter is a casualty of home wrenching.