Misfire- The lady that interrupts... ????

[Ross]

I have an Omega ignition system fitted to my bitsa 1983/1994 R80/R100. Staintune exhaust system with 135 jets.

Running the bike 2 up at $150 yesterday she had a hesitation with a small loss of power. I backed off the throttle and engine feels fine. Could this have been a misfire? Caused my the Omega system?

Note I have not run the bike at this speed 2 up for some time.

[Ross]

I should add that since fitting the Omega I have found that low end and mid range are way better than before fitting. I notice that it can be adjusted in someway so maybe the adjustment/fiddle would get rid of the hesitation at high speed.

Funny thing is in say 3rd gear I can rev the engine out to nearly redline with no hesitation from the engine at all.

[StephenB]

I should add that since fitting the Omega I have found that low end and mid range are way better than before fitting. I notice that it can be adjusted in someway so maybe the adjustment/fiddle would get rid of the hesitation at high speed.

Funny thing is in say 3rd gear I can rev the engine out to nearly redline with no hesitation from the engine at all.

Sounds more like fuel starvation to me ... electronics are stupid, they calculate from input rpm whether in 3rd 4th or 5th gear. Check fuel flow, float bowel level, both petcocks on under load etc.

[Jean]

For an R80/R100 135 main jets seem sort of small. My R80 likes 140, but it's a '78 engine and I'm running a pair of 64/32/9-10.
So...I agree with Stephen, fuel inadequate.
Maybe your petcock screens are clogged with "stuff" or your fuel lines need replacing. The magic chemicals being added to gasoline now is cabable of really making a mess of various older "rubber" parts.
BING recommends changing diaphragms every 2 years, By the way...How long for yours? (They really last longer but I guess that's how they make money!)

[mattcfish]

I doubt it's the ignition too. An ignition issue wouldn't care what gear you're in or how much load your bike is under. Float levels, carb balance, water in gas, diaphrams, valve adjustment?.....Does it do this all the time under the load of higher gears? Where is your F mark at 3000rpm and beyond (full advance at 3000rpm for an Omega). Use setting 4 for single plugged heads.

[melville]

I've had a coil go bad, and had the symptoms (misfire) first manifest themselves under heavy load, but return to normal when the load was reduced. However, later it took less and less load to cause the miss, progressing to stopped by the side of the road in 50 miles.

[Ross]

It has a new coil.

Carbs have never been overhauled in the time I have had the bike. 3 years. So will check these over and see what might need replacing.

135 main jet is standard according to owners manual for 32mm Bings. I have had 145s fitted and had put the 135s back in for fuel economy reasons. 145s suck fuel so quickly at speed.

I will also have to check the fuel cocks to see if they are getting clogged up.

The bike starts first go no probs. Comes of the choke no porbs and runs well. Will rev through the rev range in each gear with gusto. Just in top and slowly winding her out that she hits this hesitation.

Thanks guys.

[ME 109]

Fuel for me too. Float level first, then screens/filters.
Diaphragms won't give symptoms your describing, imo.

[SteveD]

I'm thinking fuel also, but as 150kph two up is a rare thing, and will eventually have the problem solved for you, I'd be inclined to just do some routine maintenance stuff and not spend any money on it. Clean carbs, check floats, maybe diaphragms...

[Bob Bennett]

I would go with fuel probs as well Ross, do the carbs etc, also check the fuel taps, but cloged screens above the
taps in the tank have caused me probs simmilar to yours.