YZ125K Rebuild

[Lozza]

with a dial gauge you are only checking a static amount of advance really needs to be set with a timing light

[alexbrown64]

Hey Loz, bike isnt running yet.. needs a lot of work to get it all up and running.  Engine is going up town to be checked over.  Just wanted to see if timing was still set at 1.2mm btdc and nothing drastic had changed. Tried to do it tonight and digital dial gauge had flat batteries.. its still going up in the morning..
I have emailed PVL in the US with my details, but whats the deal with having that timing curve in a digital cdi that is sold for 125's. I have printed out the curves, and will give to Ray Easson to look at.

Cheers,

[Lozza]

I still don't think relying on setting the timing by "x.xmm BTDC" is any good at all with this ignition. The only way it will be set correctly will be with the engine running at 4000 rpm. Look at how much the timing changes in 1500 rpm and the amount of static advance you're giving the ignition is added to this curve.

[alexbrown64]

I got an email back from pvl saying my stator is a 3000 winches one. He reckons my cdi was designed and tested for a 5000 winches stator and he can't provide a curve. Does this make sense?

[Momus]

I'm going through something similar having been given a PVL analogue ignition supposedly to run a 500cc 4 stroke single, that when correctly i'd, was an 1800 windings 2 stroke unit for a kart.
 
PVL's site says, at least in regard to the analog systems " the approval of an ignition coil/stator unit combination must be registered by PVL. We urgently discourage random combinations with a view to obtaining a different ignition curve, as we do not know if the electronic components are compatible..."

[Lozza]

Marcus if the stator is a 1443,1419 or 1424 I would buy the stator rotor if you don't want it the ignitions I use will work with those stators

I got an email back from pvl saying my stator is a 3000 winches one. He reckons my cdi was designed and tested for a 5000 winches stator and he can't provide a curve. Does this make sense?

Sort of I think the 5000 winds has more retard in the curve 3000 has less retard

[Momus]

I'll have a look tonight Lozza.

Stator: 1442    54/A/18
Coil:    105458
Rotor:  940 - with a 3/4" bore from the B50 crank.

[ralph311]

I am putting a standard ignition on anyway for a while, but I am not sure about these mapping issues.

Yeah I vote for this. Once you get it running reliably you're in a position to evaluate step by step modifications. Its hard to make progress when it keeps failing.

[alexbrown64]

Yep Ralph.  I got another email from PVL saying the curve is a combination of stator windings and the CDI.  They can't give me the curve for my 3000 windings (they call them winches) stator, but they are sending me the curve for the cdi i have with the 5000 windings stator. As loss said, my 3000 stator probably advances the the curve.
I took the motor up to Ray Easson and he is going to take some time and measure everything up again and check compression, squish, bore, clearance etc.. I showed him the curves i had.. and he was interested. I will give him more info from PVL as i get it.
I would like to check the values from the PVL ignition and see what curve i have been running. I am betting up around 10,000 rpm i am way advanced. I think most 125's should be around 13*, but the curve i have is showing about 16* and it may be more if i factor in the stator, as i believe the pvl curve that i have been posting up is for the 5000 windings stator.
Anyway, when it is all said and done, i am pretty much over it all and just want a reliable bike. So, the option is to put my Yamaha standard ignition on to start back at first base.

I think its parked up over Christmas... so this project wont be going very far until the new year...

Cheers,

[sleepy]

I've seen the last of the air cooled 125's[G] do the same thing to the piston when the stock ignition goes off. When checked the stator coil resistance is low and the timing retards by about 10 to 15 deg at the top end. It is really important to check the timing up around 10k to see what it is, forget 4k as the motor is never there whilst being ridden hard. I would have thought if it was to much advance you would see detination damage as well. I'd think 16deg at 10k would be safe. 

[alexbrown64]

Hey Sleepy, the piston did show signs of detonation. It was all melted around the tip and was black underneath.
Yep, my G back in the day had a stater that went bad... bike just run like shit though.

This is what PVL has sent me and says it cdi 537202 with the 5000 windings stator.  I can't make heads or tails of the diagram.  Would i add my 16* to this or is this based on some sort of base setting with the bikes static advance already set?  I think the guys i am talking too are German, because i cant seem to get any straight answers.  I ask them what parts are suitable for my bike, and they waffle on about "change the setup from the ignition".  Hmmmmm



Ive put an add up on facebook asking for a K genuine igniton setup.  Half my parts are junk or missing. Anyone have a full K ignition? I need stator, rotor, cdi and coil/plug lead/cap.  I am fedup with trialing PVL's box of parts....and may just put them up for sale. I have coil 466-100, rotor 9918, stator 1013 110mm, cdi 537-202.
I was also thinking HPI, but at the moment i just want to go standard and make sure the bike doesn't go kamikaze on me again.

Cheers,

[sleepy]

That a very ordinary looking curve for a 125. To much timing change.
Don't know what their reference is. If I was trying to sort it I have a bench rig that I can run up to around 12k and then work back to the PVL timing mark.
If you were running it at those timing figures[black curve] it's no wonder it failed. Looks like 37deg at 10k.
Did you say you have the stock Yamaha curve to compare it to.

[alexbrown64]

I do sleepy and here it is.
Genuine 1983 YZ125K ignition curve and info. The reference point is set at 1.88 btdc using 50mm stroke and 98mm rod length.



Some other updates.  I have my new genuine Mikuni 34 to replace the 36. I have just ordered all the jets to get the original 34mm size carb back to stock.  290 main, 65 pilot, 6f21 jet needle.  Got these from nichecycle who have nice low shipping charges and have some hard to get bits.

Also lined up a genuine stator and coil.  Will use my original Yamaha rotor and cdi. But had to order a cdi rubber holder and rotor woodruff key from partzilla.  Partzilla also has really cheap shipping.  Only $6 from US.

Cheers,

[sleepy]

From that curve your timing marks would align at 9k with 20 deg timing and max advance of 28 deg at 3k and the 11 k timing of 13 deg. That all way different to  the PVL. Did the PVL guys tell you which curve is yours, red or black.
The black curve may even work for a 500 single pommy motor with 1000 rpm timing at 8* giving max advance at 38* 7000rpm. Even that would be wrong as max advance should be around 3.5 to 4 k.
Don't know what to suggest you do with the PVL other than bin it. Could suggest HPI but have had very poor dealings over faulty product although most people seem to like them. 

Be careful with the carb as some of the new bodies have different size air correction jets and idle passage sizes. Which means just fitting the stock size jets, needles and needle jet doesn't get your carb the same as OEM.

[Lozza]

Your only reference points you need are 1000 rpm and 3000 rpm check them with a timing light and disregard the 1.88mm static setting. At 1000 the standard ignition is 13* (which you can check with a drill turning the engine over and plug grounded out)and at 3000 it is 28* move the stator to get as close as possible to those 2 known points. The ignition timing will be fine across the range  checked at those 2 points. Don't be  afraid to remove the woodruff key altogether if you can't those 2 points to match.All the Hitachi ignitions have a similar curve. IIRC when I used one it was set to  13* static that came back to about 7* at 12,500.
Thats how you need to set the PVL at 4000 rpm vs the amount of advance you want which is +6deg as the PVL advances 22* at 4000 so you will have a total of 28*.