little flat spots that go away

I've experienced this a few times in the last weeks: I ride the bike at mid-range on country roads, then I open the throtlle wide to pass, and I feel like two or three flat spots while accelerating, between 5000 and 7000 rpms. It goes away beyond 7000. If I try to repeat the experience with the same kind of acceleration just a little bit later, it won't do it, it is a very smooth and constant acceleration.

I felt the same flat spots when entering the highway and opening the throttle almost fully.

Any idea what would cause this ? Fuel mix looked fine when I showed you my spark plugs a few weeks ago.

 

Clutch slip maybe?
Drain the float bowls into seperate containers. What does the fuel look like?

 

It doesn't feel like clutch slippage, because the flat spots don't last more than 1/4 second each.

I'll drain the bowls tomorrow and report what I'll find. I have an inline fuel filter, but it could be faulty.

I can't tell for sure if the flat spots actually go away or if I very slightly change the way I accelerate when I notice this behaviour.

I may add that I can't hear any change in engine note when it happens, so if it is fuel supply cuts, they should be very very short.

 

How old is your throttle cable?

 

I'm more curious about the fuel quality. Sometimes bad things get into the holding tanks, and then into your tank.

 

How clean are your pilot jets ?

 

They might be clean, I did them last fall.

 

I haven't had time to drain the bowls, but I had the thought this morning that it may be caused by low levels of fuel in one or two bowls (fuel starvation at WOT). I'll have to re-check my floats heights later this fall.

 

when I got the little flat spots that you as you discribed I cleaned my air filter and replaced the spark plugs and they went away

 

"Simple things first" is a good rule. This said, I changed the plugs in 2013 when I bought the bike and I've almost not ridden it since. Air filter shoudl be clean to but I'll check to make sure.

 

could it be the diaphragms in the carbs have some wrinkles that need worked out.
demerits to you for not riding it enough

 

Yeah I spent too much time rebuilding the forks and the fornt brakes, then I had some trouble with the fuel supply and thought it was the carbs, pulled the carbs out and cleaned them, then realized my fuel line hold a bubble !

I thought it could be the slides diaprhragms too , if so it should be a new issue because they looked good when I cleaned the carbs. I'll have to check that too later this fall when it gets too cold to ride.

 

Update: I had a look at the air filter this afternoon, it is super clean.

Then I drained the carb bowls, and found a significant amount of tiny debris in fuel from carbs #1 and #2. It seems that the small bronze element inline filter doesn't perform well. Any suggestions for a small filter performing better filtration?

 

What about this model? It is supposedly reusable, just have to clean the paper element.

 

paper elements are not recomended for motorcycles.
sometimes the bronze element works its way from being seated in the filter push it back down with a drill bit dull end

this filter comes highly recomended

http://www.ebay.com/itm/ALLLOY-FUEL...LX-KX-Black-/222144647726?hash=item33b8da522e

http://www.ebay.com/itm/ALLLOY-FUEL...LX-KX-Black-/221713408942?hash=item339f2623ae

 

I use this filter buy at napa but number works at most autoparts stores

a Primeline part number 7-02357.



http://www.xjbikes.com/forums/threads/inline-fuel-filter-longevity-alert.34020/#post-294113

http://www.xjbikes.com/forums/threads/how-to-install-a-fuel-filter.6352/#post-208637

 

What's the problem with paper element filters?

 

I realize I prefer to be able to see through the filter. What about these paper elements filters with a small magnet in them to gather the metal particles? Gadget?

 

they can affect fuel flow and colapse. I think thats what being said about them. made for lawn mowers

this one is 4 cyl motorcycle rated Primeline part number 7-02357

if paper works for you then go with paper

 

Actually, I don't have any experience with paper filters, that's why i ask.