Air Filter Question:

[Russ]

When I purchased my '86 VR it had a K&N filter in it. I have no clue if the carbs were adjusted after it was installed. I've complained about it before, but for those that aren't up to speed on my problems, I can't get over 95 MPH regardless of gear and THAT has to be going downhill with a good tailwind. generally my top end is around 85 mph. My gas mileage is crappy, generally around 31 miles per gallon. All other possible problems with the bike aside, do ya'll think that there's a remote possibility that replacing this K&N with a stock air filter would fix my performance problems? If so, I can pick up a filter on my way home today and see what happens.. I just want the opinion of ya'll first 'cause I'm grasping at straws at this point.

[gibvel]

Hmmmm running at 85mph, no wonder your gas mileage is 31.

 

That aside I don't think a new filter would do much good as the K&Ns would make it run leaner if anything. They let more air in than a normal filter does. I'm assuming that the K&N is clean. What about plugs and wires, how are they and have you changed them lately? Fuel filter? Have you checked the diaphrams for pin holes?

[Leeway]

My '91 VR has the K&N, I think Givel, steering you the right direction, I experienced simialar problem, with the help of my Harley riding friend we found it to itermittently running 3 cyl. & possibly only two cyl. at times. The only thing I would add to Givel's reply is a compression test on your cylinders.

wayne

[gibvel]

The only thing I would add to Givel's reply is a compression test on your cylinders.

wayne

 

And Darned if I wasn't going to suggest that too, just got lost in typing all the others.

[bongobobny]

I tend not to blame the air filter unless it needs cleaning. About the only thing the K&N may affect would be the idle speed due to the increased air flow but that's stretching it a bit. The idle and the syncronizatrion are all internal to the carbs regardless of air cleaners. The carbs require a sertain volume of air for wherever the throttle puts them at. The free flow of the K&N allows less restriction to the change in air flow, which results in better acceleration, but does not affect the mixture ratio once the air is in the carbs. That ratio is determined by the mixture jets.

 

Another way to look at it is a normal vacuum cleaner that develops less suction as the bag or filter gets clogged. Nothing has changed with the motor or the suction turbine, but due to the fact that the path of incoming air is reduced, the less the suction. So, keeping the air input unclogged is the secret to better performance. K&N has larger pores for air to pass through so more volume of air is available for the carbs. Keep in mind that the carbs are only going to take as much air as they need which is really determined by the piston in the intake (down) stroke. The carb's main function is to mix a precise amount of gasoline into the airflow as it passes through. This is done by the oriface size of the metering jets and works on a principle that Mr Ventura developed from Mr. Bernouli's studys.

Now, the downside of a K&N is that it does allow larger particulate matter to pass through it which means more contaminants entering the carb and engine. Not big enough to cause damage, but it will dirty a carb faster than an air filter that won't allow as large of particles. Such is the price you pay for performance. As far as fuel economy, the K&N filter will, in some cases actually slightly improve fuel economy. What really affects fuel economy is driving habits...

[Cutty]

Check your filter for excessive oil. To much will tend to make some run rich, if you think this is the case start with cleaning it out. Than test ride, if you see improvement than add a little oil.

[91nwl]

Once, mine was running rough and I checked the plug wires to find one of them was loose. I think I was running on 3 cylinders. Now I'm real careful to make sure they click all the way down.

 

Otherwise, why not check a stock filter? Its a relatively cheap fix.

 

I assume you have checked to make sure the plugs are tight in the holes also. Sometimes, if you don't get a good crush on the washer, the plugs will loosen up and suck air/blow gas, causing it to run crappy.

[Gearhead]

I haven't had my 87 VR for too long, and I have a stock filter. In the past I've only had good luck with K&N filters. I like the cleanability, the increased airflow capacity esp. when dirty, and there's debate on whether they filter the air better or worse than paper. I will say this, however, about the VR - it seems very sensitive to intake changes. I was doing tune-up work on it and ran it in the garage without the filter. It will idle, but simply won't take any throttle - if I try to rev it, it just gasps and dies! If I hold the paper filter in place with my hand (airbox lid still off), it improves just slightly. If I put the lid on with the filter out, the problem pretty much goes away. Of course, with the filter and lid properly assembled, there is no problem. Thus, it seems that the LID imposes a significant enough restriction (the intake hole does look puny) to significantly affect mixture, which is not something I've seen before, at least not this much. I would think, however, that mine would be OK with a K&N filter.

 

Jeremy

[Burninator]

I had the same problem. I checked the diaphragms on the four carbs and they had many many holes in them. The result was that when I openned the throttle, the vacuum was not capable of moving the needles on the sliders so the engine was starving for fuel. I replaced the sliders and diaphragms and restored the performance. The difference was startling.

 

Check your diaphragms for holes.

[Guest driscollms]

When I purchased my '86 VR it had a K&N filter in it. I have no clue if the carbs were adjusted after it was installed. I've complained about it before, but for those that aren't up to speed on my problems, I can't get over 95 MPH regardless of gear and THAT has to be going downhill with a good tailwind. generally my top end is around 85 mph. My gas mileage is crappy, generally around 31 miles per gallon. All other possible problems with the bike aside, do ya'll think that there's a remote possibility that replacing this K&N with a stock air filter would fix my performance problems? If so, I can pick up a filter on my way home today and see what happens.. I just want the opinion of ya'll first 'cause I'm grasping at straws at this point.

 

Russ, I have about 6k on my RSV with K&N filters, no problems. I will clean and relub them at about 10k. Sorry to hear of your problems.

 

Mark

[Guest Popeye]

For what it's worth...my 86 VR had holes in each of the diaphragms & purred like a kitten & would do 90 mph easy. It also idled well & performed at all speeds.

 

Replaced diaphragms, sliders, carbs redone, sync, plugs, etc., when rust in tank let loose & messed e/thing up.

 

After all this work, it's running again, but no better than before.

But 'before' was excellent.

 

Doesn't make any sense to me. [i use OEM air filter].