anyone heard of or tried this?

i am a memba on another forum for owners of honda shadow's.there is a popular modification that numerous members have tried and on various models and engine sizes called 'the 4 degree mod'.basically it involves elongating the fixing holes on the pick up coils in order to advance the timing by 4 degrees.i dont know if it has been done in conjunction with pods,but one of the main reasons it is done on there is due to straight thro exhausts being fitted,as its stops the popping and misfiring that comes with fitting them.they are supposedly retarded as standard to squeeze thro emmision laws.i dont know if this only works on a v-twin,or whether it would work on a 4 cyl.rightly or wrongly,i am going to be fitting pods on my project,and this is something i am seriously conssidering trying.the good thing is,it is reversible,so if it goes tits up,i can just rotate the pick ups back to where they were......i hope (and before anyone starts,i know this mod alone wont be enough.i will be re jetting etc too).just thought i would ask if anybody else had heard of this before,or if anyone had tried it,what the results were.as i say,on the twins it seems to stop the popping and misfiring,but some say it improves throttle response too,tho they admit it may be more because theyre looking for it,than actually feeling it.anyways,all input,poss pro's and cons greatfully appreciated.

 

I'll tag along and ask if anyone knows the initial (idle) and total advance on a typical XJ. (Thanks).

 

It varies from model to model; I believe the "curve" is spelled out in the factory books.

 

just googled xj600 timing advance and found this http://www.factorypro.com/products/rotors.html
i know its not my model of xj,but it answers my question of can it be done.i know my method will be a very crued version of timing advance,but it can obviously be made to work.i know they dont always do what they say on the tin,but it begs the question if you have pods fitted and jet your carbs to the point where they are nearly right but not quite,could advancing the timing be the final piece of the jigsaw?

 

Sure. But remember this: IN GENERAL, advancing the timing makes the motor run hotter, and be more susceptible to running lean.

Since XJs run lean to begin with, and a pod-equipped XJ that has not been rejetted is probably going to be running leaner yet, I'd be REAL CAREFUL with this one-- it might also be a quick-ticket to Holed-Pistonville.

Your method isn't such a crude form of timing advance, because you're moving the pickup you're shifting the entire curve slightly more advanced. I'd be really concerned that while performance might improve at lower RPMs, once fully advanced from your new "starting point" the motor could be dangerously over-advanced.

I'm NOT saying this won't work; but blindly advancing the timing by 4 degrees across the entire curve COULD spell danger for the motor at full advance.

 

point taken.i had thought about advancing about a degree at a time to see if there is any differance.and if so whether there is an improvement or not,and if it would be over a certain rev range.the fact that it seems to cure popping on over run and backfire in twins with open pipes suggest it may be a good thing,however it has crossed my mind that a lot of racers alter the timing to alter the power characteristics of their race bikes.i dont want to make it top endy,in fact i would rather the opposite.
it is something i would like to try and at some point i probably will,but only because i know it can be undone.
as i said at the start,i dont really know enough about it to dive right in as yet,but the bike isnt together again yet so i have plenty of time to research and take your advice into consideration.im guessing no-one on here has tried this before?
but has anybody thought about it and decided not to because of bad feedback?

 

a lot of bikes you can buy an advance kit but never seen 1 for an xj. all it is a different rotor. I bought 1 for my zx11 a long time ago it was like 15 bucks back then

 

they used to change weights and springs back in the day in car distributors, older KZ's advance the timing but those are both points ignition
i've read of changing the timing of bmw k bikes but it's a pain to do, so i never tried
just watch out for pinging and knock from detonation with this stuff they call gas now

 

This would be an interesting thing to check on a dyno tuner. The bike
complete could be run standard and then run at the various timing
adjustments that you want to make.

 

The TCI on the 900 (for example) ... Adjusts from 5-Degrees Before to a Max of 40-Degrees Before (@ 6K rpm's).

The TCI and "Programmed Curve" doesn't need to be any further advanced.

What needs to be accomplished is altering the PROGRAMMING of the Box altering the Programmed Advance to some-other "Performance Profile"

Or, ... having the ability to select from a variety of Timing Curves for various riding styles.
(Standard, Sport, Tour, Drag, Quarter, Half & Full Race, etc.)

I once saw an aftermarket BOX offered with "Dip-Switches" which claimed to allow the Timing to be set for conditions.
After a CycleWorld Test, the Unit was debunked as a Fraud and shown to be nothing but a "Knock-off" of the OEM Unit.

 

TCI Transistor Controlled Ignition uses transistors, resistors and
diodes to controll the timing of the spark to the engine.

 

A little more info: In the 650 book, its from 10 degrees at 1050 rpm to a peak of 37.5 degress PLUS OR MINUS TWO degrees at 5000rpm.

I didn't go out in the garage and look in the 550 book because it's just too cold.

You are correct; if you advance the pickups by 4 degress then it would run from 9-44 (in Rick's example.)

Another tip: My 1974 Norton (made with 50s technology) doesn't like "that stuff we call gas these days" one bit, so I run the timing about 2 degrees RETARDED and the motor runs much better, no "pinking."

Keep in mind too, that popping on deceleration generally indicates a lean condition, not something you want to combine with a beyond-spec advance. 40 degrees is pretty "hot" to begin with.

 

hmmm...hadnt even thought about retarding it.that is a good point,and as you say,it may run better as standard retarded slightly because of modern fuel specs.tho tbh,mine didnt run that bad before,well apart from the rusty fuel tank deciding the carbs needed something to chew on.

going back to the 'factory retard timing to squeeze bikes thro emmission laws' thing.i have no idea if this statement is true or not tbh,but if it is the case,and as you all say advancing the timing makes the bike run 'hotter'.if the factorys didnt have emmissions to worry about,do you think they would have run a better cooling system to compensate for the extra heat? or maybe......they dont retard them for emmissions,perhaps its because they cant cool the bike enough without doing so.maybe watercooled bikes would be a differant story,the vt's that i heard used this idea,were obviously all watercooled,and maybe can handle the heat better.

this is why places like this are soooo wonderful.you come up with an idea,and theres plenty of peoples who come along and say 'great idea,but think about this,or think about that' or those that come along and say dont do it because this or because that.and then all the other little factors that you hadnt already thought of,and probably never would have,come to light.thankyou everyone for your input and advice,and thankyou xjbikes for being such a cool place with thousands of differant opinions,ideas and good advice.

 

"Another tip: My 1974 Norton (made with 50s technology) doesn't like "that stuff we call gas these days" one bit, so I run the timing about 2 degrees RETARDED and the motor runs much better, no "pinking."

I have the same problem on my H2's. Understand that a 2 stroke will hole a piston in less then five miles at "gettin it" rpms. The factory setting is 23 degrees BTDC however that was based on the availability of 93 RON. Even with the best Tier 1 fuels, they will detonate when set at factory settings. I had squish bands cut into my heads of my ported 74 but have retarded the timing in my 75 to compensate without modifying the engine in any way.

I went to Mexico back in the early 80's and remember when filling the rented Jeep, the gas smelled like tar......the same way OUR gas smells today!

jeff

 

There was somebody from New Zealand selling replacement TCI's on ebay for about £100. He claimed the timing was optimised. If I can find the link, I'll post it. http://cgi.ebay.co.uk/YAMAHA-FJ-XJ-400- ... 2eb2cd42d5

 

Interesting. The Norton is spec'ed at 28 degrees, I run it at around 26.

But then again, it has valves, so the 5-degree difference does make sense.

FORTY is a really "hot" advance to my old-school way of thinking, lots of valve overlap I guess; but I sure don't think it's an indication of being "retarded to beat emissions," not at ~40 degrees peak advance.

 

Fitz, consider your experience with the norty as compared to how I learned to set timing on my first bike when minimal tools are available. Timing light, multi-meter, continuity tester... just a screwdriver, what's in your pockets and a wrench or three.

Top it up with the shittiest gas you can find in town (Usually arco) and confirm all the timing marks line up (static check). Set it a bit retarded and warm it up good and hot (let an aircooled motor idle say 1.5 x cigarette breaks)
Now with the points cover off and the motor running carefully and slowly advance timing until it starts to ping. Back off one RCH and run midgrade gas in it thereafter.