More VF500 problems

I have recently experienced problems with a lot of backfire and pinging after changng exhausts. After changing to the coldest plugs NGK makes the ping is still there and now after my bike gets warm the left 2 clinders quit firing. When it is cold it runs beautifully.

Anyone have any ideas?

 

plugs

What do the plugs look like ?Do you have temp gun to measure exhaust heat?Did it run well before exhaust change and why did you replace?

 

Before I put in the colder plugs the plugs looked orange and burned and one plug on the left side wasn't orange but black (carbon deposits?) so i figure it wasn't firing or at least not running as hot as the rest of them. I can tell a big difference in the smoothness of the engine since switching exhaust so I'm fairly sure that cylinder wasn't firing at all.

I dont have a temp gun but my exhaust is 2-2 (full vance and hines system) so i can just put my hand at the end of the muffler on the left side and feel that the air is not nearly as hot as the right side exhaust.

It ran good before I changed exhausts. I had F1 mufflers before and the stock collector. It still crackled a little bit but just a touch of choke stopped that.

 

hmmmmmmm......

Not to sound like a butthead...but...are you sure there is not a blockage in the pipe?If it ran fine before it stands to reason the problem may be in the exhaust.

 

It runs great until it warms up and that is when the cylinders start cutting out on the left so I'm pretty sure there is not a blockage in the pipes but of course I am not certain about that.

The PO told me he installed a stage 1 jet kit (which is what I need with the vance and hines) but I also have not checked that out and since switching exhausts is feels a little weak in the midrange.

I was running cold weather plugs and with those only one cylinder would drop on the left side and now with the colder plugs both of them are dropping.

Is there any electrical component that has to do only with the left 2 cylinders? I had the wiring harness off my bike while i was doing quite a few mods to the rest of it and there is a possibility I hooked something up wrong or backwards. After it drops both cylinders on the left side one of them will intermittently cut in and out

I'm stumped! I've had this bike for 3 years now and this just started happening. I put an '86 motor in it (it is an '85) about 3 months before putting on the vance and hines and it was all working great. Before so I do believe it is something electrical or it is the exhaust.

Could the bike just be running lean? My next move is to buy a jet kit and install it just to make sure it has the right jets in it

 

sounds like to me that the jetting isnt correct if it "ping" or "nocking" that's a sign of detonation...if it keeps up with out being fixed than kiss those piston's good bye. oh what grade of fuel are you running?

 

Have you check this out

Hey Guys

I mostly agree matt1986vf500f but if is not that then here is some more.Check your choke (because you say it runs good when it is cold then the choke is on).Carbon fouled spark plugs are too cold plugs,weak ignition,dirty air filter,too rich mixture and excessive idling.And the last synchorising the carbs.Motor that backfires has improper ignition time (explains the spark plugs),Carbs need adjusting or lean fuel mixture.

Best regards

Gunnar

 

I am running 93 octane and i sometimes put octane booster in it but not all the time.

Since i have put on the vance and hines the choke has not helped the backfire problem.

The carbon fouled plug was a plug made for cold temps so it is most likely not the plug being cold. I have since changed to standard heat range plugs and the problem still persists. The air filter is brand new and the new exhaust would lean it out so it is not running rich for sure.

I am concerned that i have messed up the piston rings and those two cylinders are loosing compression after they get warm.

How can I check my ignition to make sure it is not weak? Is the ignition timing adjustable? I know the cam timing isn't

Thanks for the suggestions guys! Keep them coming!!

 

i dont think you can adjust the ignition timing, i know i've seen something like that on jamie.D website, and your still spark nocking with 93.hmm next step rejet it unless you can adjust the air/fuel screw on the side of the carbs...but you would be better off to rejet it.....detonation can and will burn a hole through the piston " not good" so if your still riding it like this then you better be looking for a new motor.....unless both coil packs are going bad.... thats just a guess....

 

Mesure the pulse genaretor

Hey

When the pulse genaretor is 20 degrees celcius warm you should mesure it 480 ohms the coils.That is the only one that could explain why your engine is okay when it is cold and bad when it is hot.I will explain here is EXAMPLE: we have here one of the coil(one of two) that are 470 ohms at 10 degrees when your bike warms the coils should be maybe 520 at 90 degrees.Then you have the other coil it is 490 ohms at 10 degrees and 540 ohm at 90 degrees.There you get wrong ignition.More the ohms are longer it is for the signal to reach and less the ohms are quicker it is.But remember this was EXEMPLE.Not right numbers.The only right number in this text is at 20 degrees you should mesure the pulse generator 480 ohm +- 1 ohm not more.

Best regards

Gunnar

 

If it is to complex here is another version

Hey

Take the right cover off and take a hair blower then heat up the coils untill they are slighty warm (20 celcius) get a ohm meter (know this only on vf700 bikes but I think this is the same) you should find a 6 plug with 5 wires in 1 blue/red,1 white/yellow, 1 yellow, 1 white/blue and 1 blue.Mesure between white/yellow and yellow (No.1 and No.3 cylinder) then there is white/blue and blue (No.2 and No.4 cylinder).But like I say not 100% sure that the pulse genarators are the same just 95% sure.Hope this helps

Best regards

Gunnar