Author Topic: Timing Question? (Read 8830 times)

gowen · « **on:** November 23, 2004, 05:01:48 PM »

I've installed a PVL ignition, which is a little inner rotating flywheel and is a whole new ignition and I have a question about setting the timing, maybe Cam or Doordie or anybody!! can help.

PVL recommends the ignition setting to be set at 2.2mm-2.4mm before top dead center. Well, I used a dial indicator and set the mark at 2.3mm (.090in). It is a little harder to start, but has good revs and get this! The vibes are waaaaaay down!!!!!!! Anyway, for my question, they say in the manual that modified engines need to be retarded from the above figures. Now, is retarding the ignition going from a 2.3mm to 2.4mm or the other way? Also, does anybody have any clue as to how much I should retard? I'm very lost in this process and just plan to just play with it, but should I start by retarding the timing or advancing it? I favor the topend.

Thanks

Paul · « **Reply #1 on:** November 23, 2004, 06:32:56 PM »

getting closer to TDC retards the timing. So 2.3 -> 2.2

doordie · « **Reply #2 on:** November 23, 2004, 09:20:35 PM »

gowen,

Paul is right!
I will check up what timing you should use.
Don?t overadvance it ,you can ruin the engine!
The teory is so low advance as possibly.

//doordie

gowen · « **Reply #3 on:** November 24, 2004, 02:16:38 AM »

Doordie, that would be awesome if you could do that! Thanks! Penton Imports told me the exact opposite. They also said, that all the modifications I will need to further advance it. Is this true? Or retard it? I remember on the stock ignition that I retarted the timing to bring up the top-end. Thanks doordie

Gabe

doordie · « **Reply #4 on:** November 24, 2004, 06:47:35 AM »

gowen,

Alt 1:
A=Cos(P2+R2-L2)/2*P*R

A=ignition advance in degrees
R=Stroke divided by 2 in (mm)
L=conrod length (mm)
P=R+L-T

Alt 2:
T=ignition timing in (mm)

T=L+R*(I-Cos A)- "ROT"(don?t know word) L2-(R*Sin A)2

This is the formulas!

At 5000 rpm stock timing is about 17 degrees ,then fall back to XX degrees to it reach max rpm.(Don?t know what KX500-CDI have for set-up programed).

I will not say what you should use for timing,will not be responsbility!

Start at low advance and step up in 0,1mm and run it and check
if it runs better.Then when you have reach the best performance,fall back a little and see if you loss Hp.
My advice is to use the least of amount of advance conducive to peak performance.

Good luck!

//doordie

gowen · « **Reply #5 on:** November 24, 2004, 07:49:59 AM »

Thanks Doordie, I will be taking tomarrow to work with the timing. Went from jetting to timing now.

I need to find me a degree wheel.

Now, the formula I will be using is the Alt 2. Cause I do not have a degree wheel.

Just a dial indicator.

T=L+R*(I-Cos A)- "ROT"(don?t know word) L2-(R*Sin A)2

I'm unsure of the "ROT", but if I can find that missing forumla.

Would you happen to know the connection rod length? I don't have anything that has measurements besides tearing down the motor? It is a Hot Rod, but is stock length. Thanks

KXcam22 · « **Reply #6 on:** November 25, 2004, 02:42:54 AM »

Gabe,
If you have access (of know someone) who has a CAD program, for an easy degree wheel you can draw one, print it on a large self adhesive label (8.5x11 avery) and stick it a piece of tin (or even cardboard or an old CD if the hole is not too bid). Over the years, i've made a few of these and they work quite well. Heck you can just glue the paper on if you have no label. If you're stuck, drop me a pm and I can email you mine (6") in a pdf or autocad. You could print it off at home. As far as timing, Doordie and Paul are correct. Think that as your piston approaches TDC the sooner the ign fires before the piston gets to TDC, the more advanced it is (the timing), therefore as you reduce to 2.2mm the piston is closer to TDC when the ign fires, hence retarded. Modified 4-strokes like more advance, 2-stokes not necessarily - take a few tests to find the best setting. Although I always thought that retarding was better for bottom end power but likely depends on the engine. Have fun. I have too much snow to test anything now. Rebuild season. Cam.

KXcam22 · « **Reply #7 on:** November 25, 2004, 02:46:44 AM »

Gabe,
One more thing. You might want to stay fairly close to the PVL specs. Too much advance can torch a hole through the piston really fast. You don't get much warning either. Bike kicks over quite easily afterwards though (Ha Ha). Cam.

doordie · « **Reply #8 on:** November 25, 2004, 05:23:35 AM »

gowen,

Conrod lenght is 145 mm.

I think the word I mean is "squere rot" ,sorry if wrong spelling!

T=2.3mm (example)
P=R+L-T=43+145-2.3=185.7mm
R=86/2=43mm
L=145mm

Now YOU calculate it!

//doordie

gowen · « **Reply #9 on:** November 25, 2004, 02:22:40 PM »

Hi Doordie, thanks, that helps alot and I understand now. I have a question though, I now run into a problem I never did with the stock ignition, the kick starter now kicks back on me while trying to start it. Is this normal? What does this mean? Thanks

doordie · « **Reply #10 on:** November 25, 2004, 10:04:39 PM »

gowen,

Ask any preowner of old (before1984)Husky 488cr with motoplat rotor-ignitionsystem.Many broken wrists

Yes, that?s a problem you have to live with.

Many vintagebikers here start the bike with pulling first, so it?s more easy
to start it when warm close to race.

Little "inertiaweight" reduce the helping rotating force with a rotor.
(I have reduce the stock flywheel weight only,good for revving on iceroadracing but spinns the backwheel more easy though).

//doordie

gowen · « **Reply #11 on:** November 26, 2004, 03:00:08 PM »

Well, just a small update on the timing. I did reduce the kick backs by retarding the timing. It's been fun, but now I'm running into another problem, it is a pain to start! I just replaced my kickstarter last year and now it is bent a little outward and it is now slipping slightly from the kick backs. When I get it started and it is HOT it is still hard to start, just as hard as cold. There is no way anybody could live with this bad starting on the KX. I will reinstall the stock ignition if that is the case. But, I will try to advance it tomarrow and see if that helps. Was wearing my riding boots (AXO RC5) and now have a huge bruise on the bottom of my foot from kicking. A little discusting.

Cam, a degree wheel would be awesome! my e-mail is gabeowen@earthlink.net

I'm also thinking I should go with a EIX plug instead of a ES plug. I will try tomarrow if my lower foot doesn't hurt as bad as it does now.

Any thoughts?

doordie · « **Reply #12 on:** November 26, 2004, 09:28:11 PM »

gowen,

Here is some calculating:

2.4mm=16.9*
2.3mm=16.5*
2.2mm=16.2*

Stock is not 17* at 5000rpm it?s at 6000 rpm!

Some info about more or less advance:

If you want fast big "hit" in low and midrange adjust for more advance,but it will be more heat and easier to sieze at long straights.
The opposite with less advance with more topend and more "space" to siezing.

So, more advance with many sharp corners,and the opposite with long straights!

Just my idea.

(We have a good tuner from Finland as member,he will correct me if
I have wrong ideas).

// doordie who?s waitng for ice.

mun · « **Reply #13 on:** November 27, 2004, 07:21:40 AM »

I guess Doordie mean me

. Eric Gorr is good tuner, not me, but i agree what Doordie said about advance.

Maybe this can help you too:
If diameter of flywheel is 80mm, so circle is 80mm x pi(3,14..) = 251,3mm.
251,3mm / 360degrees = 0,698deg/1mm = 1mm in the circle is 0,688deg.
So 2,4mm in the circle is: 2,4mm * 0,698deg/1mm = 1,6755mm.

I like write and ask more here, but my english, d**n

doordie · « **Reply #14 on:** November 27, 2004, 10:33:09 PM »

mun,
Don?t worry,they understand my bad spelling so it?s no problem for you,I promise!

Everyone look at his website,and you understand mun can "a lot" of tuning.

//doordie