Honda V4 plugs

Hey ya'll. Since I got my bike it never run like it supposed to.

Problem: it always back fired when descending and RPM is 4k or lower.
I thought maybe because the bike had been sitting up for awhile and just had some build up in the fuel systems. I broke it down and clean the carburetors real good and it still run the same.

Solution: I took the plugs out, re-gap, clean, and reinstall. It ran great and without back firing during descending. It was awesome ride for about 30-40 miles, then started to back fire again.

I clean the plugs again, and again ran fine for anther 30-40 miles. What can cause this kind of behavior? Do I need to replace the plugs, wirings, or coils? Budgets is limited so I can't afford to replace something that I don't have to.

Thanks in advance.

Sounds like carb issues. You may have some trash in the fuel or rust in the tank that is getting in the carbs causing rich/lean conditions. I would start with inspecting the fuel tank for rust then cleaning your carbs.

When you remove the carbs you will probably have to re-synch them which is a pain on any 4 cylinder bike. But don't let it stop you, they may not be in sync now anyway.

Plugs are cheap, so if you don't know how old they are then I would replace them also.

+1. I would change the plugs. When you pull them out.....how do they look. Are the tips black? Knowing how they look will help to diagnose the problem. Also....check for an exhaust leak. It will cause a lean condition and backfire. Do you have aftermarket exhaust on it? Sometimes the pipes will get changed and the carbs will need to be re-jeted.

Can you describe what the plugs looked like? A picture would be even better. That can tell you a lot about whats going on with the rest of the motor.

hayweed wrote:....Sometimes the pipes will get changed and the carbs will need to be re-jeted.

I didn't think of this, but it is absolutely true. If they are not factory pipes the jetting could be wrong.

Brother the Honda V4 engines have a fuel screw on each carburetor that is located between the bowl and the intake manifolds, for a lean deceleration backfire which is worse when cold unscrew the fuel screws a 1/2 turn at a time and for a rich deceleration backfire which is worse when hot screw in the fuel screw a 1/2 turn at a time.

The final fuel screw settings should be between one and a half and three and a half turns out, if it is more than three and a half turns out increase your pilot jet one size.

If your plugs are fouling and you have to clean them as you mentioned it is probably a rich deceleration backfire.

I would replace the spark plugs as well however they are normally $8 to $10 each.

Thank you everyone with your expert and opinions. I've been cleaning it since home from work. It started with spark plugs, than, BAM! The seats, then the battery came off. The next thing I knew I was down on my knees...... well, scrubing of corse.

Anyway..... The bike is bone stock. The previous owner did remove the baffles so it's a little louder, which really amplified the backfire.
If I'm not mistaken, the plugs are original since 2000.
1st picture below is about 55 miles after they are cleaned. All 4 has same ware on them.
2nd picture is after finished cleaning. Used 100 grit then 220 grit.
I'll be picking new ones tomorrow a.m. Hopefully some one will have in stock.

I'll throw the plugs in first and see how it run before I move on to the jets/carbs. I'll give y'all feedback tomorrow.

Looks pretty good in both pics. If the baffle has been removed. It's probly a little lean. But most pipes will pop with no baffle in them. You may need to adjust the carbs.

Dental work had ruined my weekend and just able to eat let alone ride. Hope everyone had a great weekend though.

That's enough of that stuff.
I was able to pull the bike out of the garage this afternoon and fired her up with the plugs that I cleaned Friday night. I think this girl need a professional help!
From all of your opinions. It let me to believe it's carb problem.
Need to make sure that they're all synced and jets adjust properly.

I've been reading over the repair/service manual trying to get the understand of it before I spend that $.
Any Honda tech here or know of a good shop I can take it to?

Thanks in advance guys

Edit: Service exchange - I offer home and business networking. Include PC, Server, wireless security, and printer setup. Work can be perform on weekend at you home or business.
If you own a dealership (new or used / auto or powersports), I can hook you up with Dealer Management System as well.
Hope this is allow in the forum!

Yes. That is allowed. Wish I had the time to help you with it. If you want to rise it into mobile you van bring it by my shop and I will give you my .02 worth.

hayweed; I believe I will take you up on that offer Sir. Check your PM