What Tuning Countermeasures Are Needed For K&N Box Filters?

I debugged a Maxim that was sold as a running Bike.

We got her firing on all four after figuring-out the PO tried to maker her go with a set of Accel Coils he rigged-up to have the Bike fire (1-2) - (3-4).

This Bike acts like it has a HUGE Air Leak.
I sprayed it down with Starting Fluid and nothing up-front seems to be leaking.

The Cleaned Carbs we have on her got the Full Monte including Bores.
The ColorTune Plug won't give me any Blue.

The ONLY Non-Stock element is this K&N Air Filter.
Are the New K&N Filters so unrestrictive it messes-up Tuning with Stock Jetting?

80 750 Seca Unk/miles K&N Airbx Filter
___________________________________________

 

I have a K&N in my XS1100 and the only change was to up the main jet by two sizes, pilot jet stayed the same. It should run with stock jets, it might be a little lean.

 

It depends a lot on the airbox and the condition of the K & N.

My answer, based on non-XJ experience was going to be a resounding yes.

The best tuning countermeasure for a K & N is to replace it with a stock fibre filter (they're only sorta paper.)

IMHO. And you know what opinions are like...

 

the pilot circuit should remain unchanged by a KN filter. there should be constant atmospheric pressure at the mouths of the carbs even with a dirty stock filter if the engine is only using pilot circuit.

thats not to say that it doesnt need to be rejetted to accommodate the newish 10% ethanol fuel that leaned everything out.

 

What Fitz said.
"based on other experience... yes"
I heard a rule of thumb once (really rough rule of thumb at that) that said one jet size for a K&N, two for pods and another one size for debaffled exhaust.

I'd tuck in a ten or twenty thou needle shim and back the Idle screws out to 2 or 2.5 turns and use that as a base line. but that's a pretty bad SWAG from this distance.

How's it run on the enrichening circuit?

Also, I thought the Seca 750's were only '81-'83?
(with a few oddball exceptions due to factory overstock, see also titles printed in '84 and New Zealand police bikes circa '85)

 

Re: What Tuning Countermeasures Are Needed For K&N Box Filte

What are the stock jet sizes for an 82 XJ 1100? I want to make sure someone didn't mess with mine already.

 

I think the stock jets are 110 mains and 42.5 pilot

 

Re: What Tuning Countermeasures Are Needed For K&N Box Filte

Rick,
Take this for what it's worth... :lol:

When I put the K&N filter in my Seca's air box I was able to re tune the pilot circuit perfectly but I am still running lean at anything over 1500rpm. I wrapped the K&N with filter paper and got the air flow down enough to have non critical but still lean burn. I am going to up my mains one size and shim the needles when I tear the carbs down this winter. It looks like I'm going to have to replace the rings and hone the cylinders also but that is certainly not related to the filter issues.