Air Intake Stabilizer

Hey guys, just bought my 1982 XJ750 Maxim. Very happy.

The bike has the standard air filter/intake boot replaced with four K&N filters on the carbs. I've heard this can be bad, as the outer cylinders will receive cooler air, and the inner cylinders will receive warmer air, producing a different amount of power, meaning reliability issues. I've also heard this will make the bike run hotter overall, as the engine has unrestricted access to air. of course this will improve performance, but I'm more interested in long term reliability.

Can anybody comment on this?

 

This one can REALLY open a can of worms :wink: ! Some members think it's :twisted: BLASPHEMY :twisted: to even think about it! Others use them with no problems. They will definitely make your bike run leaner which is REALLY bad. To correct this, you're gonna have to retune your carbs (rejet) and there is no hard and fast rule for how much larger to go. There's a real possibility of having to do it more than once to get it right. Do a "search", this subject has been discussed more than once...

skillet
BTW there are several members that have done this mod with no rejetting or anything...

 

Are you having drivability issues? Does the bike bog at low or high speeds?
What color are your plug ceramics?
Check your valves. Tight exhaust valves on a lean-hot motor can burn / warp / drop , and that ends all your fun !

 

I rethought the whole issue on my bike, I really like the closed crankcase vent system and have seen great performance increases in cars by converting them to closed, ram air systems. So I blocked off the stock inlet and re-positioned the ignitor and a couple of relays and hogged out a 3" hole in the left side of the air box with a non-dedicated 1 1/2" scoop (unattached) bonded to the side cover. With the air filter and mufflers removed it'll jump right off the ground with sudden roll on in 1st & 2nd around 3000 rpm's with stock jetting. All four plugs read about the same, in fact the right was running richer than the left and I discovered a restriction in the right exhaust and vacum leaks around #s 1&2 vacum ports. It's too lean if I run it that way and the economy hasn't been kind to my bike. I plan on going to 126 mains and #42 pilots which admittedly is slightly on the rich side on paper but it stays between 100 -120*f 4 mos a year here. Oil did tend to accumulate in the carb side of the air box if ridden over 90 mph very far though, so I placed a puke can (trap) at the end of the end of the air box drain hose.

A test ride from Vegas-Searchlight with the stock filter element in the box, it used 1/2 quart of oil and ran too lean so I placed 1 3/4-1 1/2 adapters (restrictors) and gassed up with 91 octane (I had been using 89) and it ran great to Laughlin and back to Vegas and didn't use a noticeable amount of oil. I was going kinda fast too, even for Nevada.

 

Hi Joe,
I found that the dynojet kit was the way to go for me. It has adjustable needle clip positions and four different main jet sizes for all four carbs and the instructions are pretty helpfull in tuning it in.

James

 

The main comments I'm getting are in regards to how the jets are adjusted, which is obviously the main concern when installing aftermarket parts which affect fuel flow.

However... I'm not installing them - they were installed by the previous owner. So if the engine revs smooth, no bogging down, etc should I be concerned?

Thanks lowlife - very helpful comment.

 

no

 

If its already been done and the bike runs good than I wouldn't mess with the jets either. If you can roll on the throttle from 3k in 3rd gear to WOT with no hicups or boggs to 9k than rock on.

Lean is fast, but too lean will burn a hole in your pistons. Check the plugs frequently like after every ride for the first 3 or 4 rides. If the plugs are white to light grey your running lean. If you can see any sings that the electrodes are detierating(i cann't spell) or if the insulater around the electrode has any sings of blistering STOP riding it its way too lean. or the plugs maybe too hot.
Let us know what those plugs look like pics would be great taken from the electrode end so you can see down inside the plug around the insulator.

James

 

Great help guys, I'll let you know.

 

If your not trying to go any faster, it works, and it looks cool; don't fix it.