2005 Venox 250 Firing issue

[djones]

I have an issue where the rear cylinder is much hotter than the front one.  The rear also doesn't fire 100% of the time (that I can tell).  It sat for about 2 years before it got put back into use.  Had a dirty gas tank but cleaned it best I could and also cleaned carburetor but did not replace any of the jets.

When cold it runs fine and doesn't die.  But when warm/hot the idle won't hold but I never have a problem while riding.  My guess is that it's a fuel issue but don't know for sure.  The idle screws are at factory settings but have been messed with.

My thought is that it might be the pilot jet but I cleaned out all of the jets best I could.

Any ideas on how to figure this out would be much appreciated!

Sound/Video File

[max oradea]

Hi, 1st of all there are few things you can check, number one: pull the plugs to see who is running rich and who is running lean, as you said the mixture screw are factory setting with all the washers and o-ring in the right order then both plugs should be running the same color.
2. two years you might as well get a new air filter, they do expire with time, so do that 1st before you check the plugs.
3.are the carb balanced, you will need a vacuum gauge for that, which if 1 and 2 are fine then it most likely be 3.
lastly is the choke sticking, if you have gone through 1, 2 and 3 then the choke will be the final thing i would check.
and with a 2 year bike check that the fuel tap diaphragm is not broken and leaking fuel into the rear manifold directly.
good luck, we look forward to hear from you.

[max oradea]

from the video and sound i can hear, you might have a modified exhaust, which will require new jetting depending if you did a full baffle removal or just a baffle pull out.
the engine is miss firing in idle, feel the pulse from individual exhaust and trace back to which cylinder is not firing. you probably need to balance the carbs that is all, and a new air filter wont hurt.   
if your baffles are modified be careful of the jetting buddy

[djones]

I don't have the vacuum equipment to do adjust the carb.  I don't believe there are any modifications on the motorcycle. The jets are stock and It doesn't look like the baffles are aftermarket. 

I know it's the rear cylinder that is having the trouble.  The pressure coming from it is not consistent like the front one.

I'll check the spark plugs tomorrow and let you know what I find.

[max oradea]

if it is rich it might be the fuel tap leak i was talking about earlier, you must really check the balance of the carbs, its not a big engine so one cylinder not working 100% is a big deal. most venox are out of balance. and as i have observed even by taking the carbs off for a clean will unbalance them. the screw that adjust the two carbs run as well so when you do get around to balance them make sure you mark it and but some lock tight on the treads. but even with the rear getting more fuel from the fuel tap it will not make the rear cylinder switch off in idle.
since you have identified which cylinder is miss firing you can see if it is really just in idle that this happens, if so you can do a blind adjust on the balance screw and see if it helps. but to dial in all the power you really must have a vacuum gauge.
Good luck

[djones]

Here are the spark plugs.  The left one is the rear cylinder and the right one is the front cylinder.

[djones]

Here is also a spark plug chart.  I don't know where my spark plugs fit the most.

[djones]

I've also put an inline filter because it has a dirty gas tank.  But I'm wondering if it is causing the idle issue or at least part of it.

[djones]

Another View

[max oradea]

ok buddy you are running rich, if the idle mixture are set correctly then its time you changed your air filter. putting a inline filter will not cause you to run rich in any situation, most probable leaner but no way richer.
paper air filter will expire no matter how many km you out on them after around 2 years once used.
one cylinder miss fire can be possible too rich in idle and also as i said before unbalanced
i had a show room bike with 100km on the clock, the filter was spanking new but dead on arrival after 300km the bike was running so rich that it fouled my plugs even with iridium plugs.
my suggestion is to get new plugs and new filters, it will read totally different once the new filter is in, trust me on this. after that the engine is running in normal mixture you can even throw in the old plugs to clean them up. i bet your exhaust are full with carbon too, stick your finger in the exhaust and you will see, they should be near to no carbon at all.
the venox was designed to restrict some air to fuel ratio on hard throttle to let the engine run slightly richer, but at low rpm and idle it run really clean.

[max oradea]

i am looking through my computer to see if i can find my old plug photos for you to compare.

[max oradea]

here it is, the resolution is not the best but you can get a idea of the shades of color

[djones]

Thanks so much!  It will be a while before I can fix the bike but I'll let you know when I've fixed it.

[max oradea]

very good buddy! good luck!