caleb93

Got the bike back together tonight and wow! The top end is so so much quieter and pulls way harder. I guess that makes sense looking back now but I just thought the noise was a Gas Gas thing. Anyways once again thanks for the input from everyone!

280. Yes from Jim. Another 170ish for Piston. They come in a set from Jim as the cylinder is matched exactly to a specific piston to get the clearances just so.

The cylinder had a decent groove in it from the most recent eating of the ring. I was able to do a cylinder exchange and they think they can fix it so more power to them. I am going to to as sectionone advised and update to the new mains and seals since everything is apart anyways. I was actually advised to not replace the big end bearing since it has no play so I guess I'm leaving that. Miner, it is unlikely that the octane killed it, it was never detonating especially because the 1mm spacer was installed for whatever reason. Oni nou explained it all very well. Anyways the bike should be going in a week or two with a forward facing piston so that's nice. Thanks to everyone for the advice and for helping me come to the reason for top end bits coming apart!

I never did get anything to work with the other ignition system, just went to the kokusan. The piston was installed backwards. The little pins that live in the ring lands to keep the piston rings from moving about were facing the front of the bike towards the exhaust port. The cylinder has two wear grooves exactly where these pins are and most importantly where the ends of the rings were who caused the wear. The exhaust port is also chipped where these wear lines are. If the piston were flipped the ends of the rings would live in between the intake ports and have a solid surface to ride on through the whole stroke. So I just want to know if that came from the factory and went these 14 years or if someone else put it in backwards. I guess it doesn't really matter because I get to fix it...

Dale I think you are right. I cleaned the top of the piston and found a triangular arrow (in the right side of the picture) that was definitely facing the intake side of the cylinder. Should be flipped around right? The other thing I noticed is it is a Vertex piston. Is this stock or did a previous owner install that in backwards? Can you get over sized pistons for these bikes or am I looking at both a new cylinder and piston rather than boring to OS? Dadof2 when you mean the big end is failing do you just mean it would need a new roller to freshen it up and call it good or does it wear on the journal of the connecting rod? Thank you all for the advice I really appreciate it and hopefully I get this thing running around again!

That is a very good point. I didn't notice the carbon on the broken edge of the crown. I will pull the cases apart today to get a better look at the crank and likely pull pieces out of it and the crank case. So would this be something I did to it or just a unlucky failure? No one seems offended by the gas and oil I use which is a good sign.

There may be a very very slight amount of play straight up and down and it has some side to side play. The big end bearing sounded and felt a little grainy to me but I don't know if that is just piston pieces in it or if it is actually failing.

Went for a ride today, usual nonsense on my 04 280 Pro when I break off the shift lever. So I think no big deal I'll just play around in 1st for awhile. This worked great until 15 minutes later the top end starts making a terrible noise and the bike starts struggling then dies. This is all at idle and I really was not doing anything different than normal. I pulled it apart and the top of the piston on the exhaust side broke off along with the rings and all the other exciting things that happen. So why would it do that?! Its been running fine for months. Other possible relevant information... I use 91 Octane non ethanol gas, mix 4.25 oz of Schaeffers Premium two cycle oil to 2.5 Gallons of gas aiming for slightly richer than 80/1. The head also has a 1mm spacer to lower compression. I was about halfway through my newly mixed tank of gas, air filter was changed a few rides ago. I am just lost as to why it would do this unless this is a common thing and that just happens when the bike gets 14+ years old. What I don't want to do is get a new piston cylinder and head and have it do the same thing because I am missing something. Any thoughts would be appreciated! Thanks.

So I replaced my original t-stat on my 05ish 280 pro with a pretty standard 1/8" NPT automotive stat, with the idea that it is easier to find and (hopefully) more reliable. It has been working great for a few weeks now but the only question is what temperature should I be aiming for? I have not been able to find any answers trolling through the internet yet. I got one that turns on at 180 and off at 165. Does anyone know about what temperature the stock stat turns on and off at?

When I was fighting with my Ducati system I was in contact with Jim to help find a solution and he sent me all of the following information which was very helpful and interesting. This is word for word what Jim sent me. Hope this helps! As I remember it, in my 25 years, GG had In the older engine Trials and Pampera bikes that ended in 2002 Motoplat Ducati Kokusan Leonelli In the Pro models 2002 Kokusan (one year only system like the used one that I just sold. VERY good system, almost no problems ever.) 2003-04 gen. 2 Kokusan, also very good 2005 Ducati first gen with programmable CDI, (we had to buy programming software and interface hardware for this and it only worked in Windows 95 which was already obsolete by that time.. I have a Windows 95 vintage PC still operable solely for programming these CDI units. grrrrrr. Perfect example of how much the old GG lacked simple common sense. - some stator failures that year, especially on the 300cc bikes for some reason.) 2006 Ducati second gen., and back to Kokusan in 250/280 bikes 2007-08-09 Kokusan but different again 2010-11-12 they were using whatever they could find at the time but mostly Kokusan but sometimes Ducati 2013 Hidria early versions but another version of Kokusan on the Raga Replica 2014 Hidria early version and the new "D/C" version on the Raga Replica 30th anniversary edition 2015 Hidria hodge-podge as they spiraled into the final closing.

Should dissipate heat well. Are you ever worried about hitting the CDI? Thanks for sharing what you have done!

Have you got a picture of what you have done? I fit everything behind the steering head and it is an unsightly rat nest with no issues yet but it is winter though...

I figured I should update this to potentially help anyone else who may have similar issues. Unfortunately the correct fix is what sectionone mentioned in the beginning which is to somehow find a used kokusan ignition from another pro. This is what I have done and its been great for a month and a half so far. I am more convinced now that the CDI does want unregulated high AC voltage from the stator, that is how both the kokusan and hydria (and a lot of other systems) work. However, if someone is more brave than I and wants to mess with this more, I was thinking of finding a small transformer to step the voltage down and effectively isolate the high voltage for the CDI down from the lower voltage that way I would have been able to regulate and rectify power for the fan. I have no idea if this would work but that was what I was going to try next until I was able to score a kokusan. I did have another plan to get the new Hydria stator, flywheel and CDI which is readily available but the wiring harness is not available. That means I would have had to make my own harness which should not be a big deal except for the plug into the CDI. Someone would either have to find something that fits or make something that would work. Then you would have to figure out which wires go to which on the CDI. IF somehow all that worked then the normal ignition coil, fan regulator and AC regulator could work. This option is very desperate and I would have only done it if I was unable to find a used system but I believe it could work (the stator and flywheel will still bolt up to an older bike), with lots of work and head scratching. I hope this helps anyone with a Ducati system because I believe the black plug regulators are gone but Jim Snell does have some blue plug regulators as of now.

I agree! However I really don't know how many of the Ducati systems are still alive today or how well people are getting along with them. I don't know if it advances the spark or not. I am not sure if there is any way to tell other than when it is running. If I get it going again I'll put a timing light on it and see what comes from it. I am considering trying to find a different CDI and coil and seeing if I can make something else work. I do have an old XR 200 AC CDI and coil laying around so maybe I'll hook it up and see what happens! I did consider running a battery but my resistors did work arguably better than a battery but its still not the right fix for the thing.

Well the update has bad news. I have more information but possibly made more questions. I tried the voltage divider with little success. I had basically the same success wiring in a voltage divider vs just a resistor. I made a wiring diagram to more clearly show what I did. What I've done is unplug the "faulty regulator" and jump between the two yellow wires as shown in the diagram. I then pull off the big yellow wire and run a few 25 watt resistors in series to a total of 55 Ohms. I came up with this number because the higher the ohms the less voltage would come out the other side and the fan wouldn't run. This was the comprise I felt was what I could do with the fan still working and the resistors dissipating anywhere between roughly 18 to 125 watts. I felt this was "safe" because its only going to use 125 Watts plus at very high revs which the bike never really goes to, and the stator should safely produce 75 watts of continuous power as that's what my lights option draws. Additionally I used different values of resistors so if the power dissipated exceed 75 watts one of them would burn up saving the stator. After the resistors I run the power through a diode to make some half rectified DC to run the fan. The voltage coming out of the DC side was roughly 5-10 V DC. I ran the bike like this partly because I was itching to ride and partly to see how it works and ran. It seemed to do so fine, it never missed and the fan came on and ran like it should just a bit slower then it ought to because of the low voltage. It is an inefficient use of power as it heats the resistors a bunch but it seemed crude. The problem came when I started to have too much fun and went OTB. I got up bike still running and killed it with the switch. I recollected myself and went to start it and nothing. I couldn't do anything to get it to start. I pushed home and verified all of my wiring being still good. The stator ohmed out the same and the voltage produced was the same, along with the pickup coil which just leaves my CDI and coil as the problem. This leaves me with two possibilities of whats happened. Either the CDI actually wants regulated AC to a degree from the stator and since mine was not strictly regulated it very well could have burned up the CDI and coil. The other option is the CDI and coil was what was going bad in the first place and I just finished it off with my trashy riding skills. I can argue for either because my regulator never did have the burning or any signs that it got too hot, but it is very possible and honestly very likely that I burned up the CDI with all my messing about. I am unsure as to how I am going to proceed, I would like to find at least something helpful to keep these trashy systems alive because the options to replace them are drying up. I am going to talk to Jim again, he is the man with the answers. If I come up with something useful I will post back at least there is a bit information out there now.

So i'll bet my CDI wants similar voltage and everything else definitely doesn't want the 150+ voltage. I think that your voltage divider is the answer! According to your page I should use a 1000 ohm resistor and seperate the voltage out and then a 400ish resistor after that to ground. With the impedance so high they shouldn't waste much power by turning it into heat and I think the two resistors will solve my voltage drop! Thanks for checking the voltage on your own bike it makes me think the CDI wants real high AC voltage which its getting anyways. I think this is the answer but we will see tonight.

mcman that is exactly what I have tried to do with limited success. I had a few different rectifiers and regulators laying around and I played with all of them. The issue is when I hook up any the rectifiers it either shorts the AC side or drops the voltage too low to make a spark i'm really not sure why it is not working. I have wondered if its an issue that both the trigger coil and I guess power coil (I forgot the real name as of now) as well as the dc circuit all share the same ground but once again I really have no idea. Ducati made it work somehow so onward I experiment! So the next thing I am going to try is to put resistors off the yellow wire, i'm thinking about 150 ohms+ to keep the wattage down and essentially keep the AC voltage high and "separate" the DC circuit enough that I can regulate the voltage down on the DC side. I have doubts however because the voltage drop across the resistor is going to be severe in theory according to ohms law but its just on paper so maybe. Just maybe. I'll post back with results probably tomorrow so hopefully I stumble across some sort of success.

No I am in Washington state but still talking to Steve would be a good idea. Once I run out of ideas I'll give him a call. That is a great site! I will keep checking them to see if anything comes up. I'll see if Jim still has his. I'll take your regulators if you just want to get rid of them, I don't know if I can make any good of them but I am not shy to try.

I agree with you copemech but I am having issues hooking up a full bridge rectifier without cutting out the spark. The way to hook up the rectifier would be to put one AC side on the yellow wire on the bike and the other AC side to the ground, I believe as the other leg of the stator is grounded. Then I should have DC outputs to hook to the fan. I have tried hooking up the rectifier the "wrong way" and lots of other ways with the same results, being as soon as the ground is hooked up the spark quits. I have been unable to get around this but I have tried using a diode as a half wave rectifier (input to yellow, output to fan) and this will make the fan work with some trashy DC but the voltage is unregulated and runs real high which will burn out the fan quickly. I tried today to put a DC to DC regulator (30-60v input, 12v output) after the diode and once the ground is hooked up no spark. I played today with resistors off the yellow wire to power my supposed DC circuit and I still couldn't make a spark with a full rectifier wired in but I only had 24 ohms of resistors. I'm getting more and I will try out higher resistances to see if the CDI circuit voltage stays high and if can cut down my DC circuit voltage. I looked further into the trigger coil wires and it appears that the white wire is in common to ground. It reads a direct short between ground inside the CDI and to test if this is more or less normal I cut it, it produced no spark, then grounded the white wire to the frame and it started and ran fine being disconnected from the CDI. sectionone I had read that thread and it is what lead to me taking my regulator apart in the first place to look for the problematic diode but mine didn't have one like the example in the picture. Switching to Kokusan is the right fix and I would like to do that but I have been unable to find any with the little looking I did. Ill play some more with resistors once I get them in and post back with whatever I find. Thanks for the replies

So I did get the 12V AC regulator today and hooked the yellow wire to the yellows on the bike and grounded the black. I started the bike and AC voltage was right about 15V (as my meter reads) and everything seemed fine until I tried to rev up the bike and it just refused to rev at all. Sounded like it was missing left and right. So I unplug it and it starts runs and revs great just like normal. So this tells me that the CDI unit is powered from the yellow wire coming out of the regulator and it wants either unregulated AC or a much higher voltage than 15. This makes sense to me because as the rpms increase compression goes up and it is harder to jump the gap on the plug so the extra voltage would be needed to fire the thing. So my original plan will not work it seems unless someone else has an idea. I do believe that the bike can be run this way the only problem is there is no fan so it could easily overheat. Tomorrow I get a high voltage rectifier and a DC regulator so I will try to wire them in and see if I can get the fan to work and run about 12V DC. I tested the leads coming from the trigger coil to ground and it seems the green is in common with ground, I never got any voltage out of it and the white wire has about the same as reading between the two wires (green and white) around 1.5V. They have 250 Ohms between the green and white which I believe is close to what it should be but i'm not 100%. Yellow to ground reads .7 Ohms. I have no idea if that is even close.

I have checked for voltage between green and white and got around 1.5V AC, I have not checked for power to ground on either wires, I will do that. Both the green and the white go to the very small trigger coil so I don't believe it powers the CDI but I don't really know. I jump big yellow to small yellow to make the bike run with the regulator unpluged. The two terminals are soldered together inside of the regulator (I have already cut it open and looked, looking for a burned out resistor as some people have said can be an issue but not on mine as far as I can see). I already purchased the AC voltage regulator I talked about in the first post and hopefully I get it today, but when I do I am going to wire it up and see if the CDI unit will still work and go from there. I will post back with results. As well as looking for power to ground from the trigger coil on both terminals.

Look at the wiring diagram for the Ducati ignition that I posted above. There are three wires coming out of the stator, the green and white are both the AC pickup coil which supplies a pulse of AC to the CDI unit to tell it to spark. The third wire is the yellow that powers everything else with the other leg of the winding being grounded. The yellow wire goes straight up into the regulator rectifier and internally connects directly (the terminals are soldered together on the inside) to the little yellow wire that provides the AC for the CDI unit. They are separate coils on most bikes like in the wiring diagram that mcman posted above, but not on mine unfortunately as this would be far easier to sort out. Thanks for the idea

The diagram for my model... I believe that you are correct about the oscilloscope, I didn't think about that. It makes more sense because it hit me once and it seemed like it hit much harder than 60v AC. I got the idea from the kokusan ignition close to my year which is very very similar. If the voltage in reality is actually that high for the CDI and because I only have one lead off the stator I don't believe that I can chop that voltage down to "12v" and still make the CDI happy. Who knows if the regulator can even handle that kind of voltage anyways. The other way I could see this working is rectifying the high voltage AC to high voltage DC and then chopping it down to a manageable 12v and hoping that doesn't draw the AC voltage down too low.

I just bought a 04 Gas Gas 280 pro with the Ducati Ignition system, and on the third ride it just sputtered to a stop. I've done extensive testing and I believe that I have narrowed the problem to the very problematic regulator/rectifier. I can make the bike run if I unplug the regulator and jump the AC power from the stator over to the CDI unit/coil. (The regulator does this internally) The bike will run and produce anywhere from 30v AC at idle and upwards of 60v AC revved up. Due to the difficulty of locating a new regulator/ the high price tag/ the general unreliability of the regulator I would like to make something else that could be easier to work on and hopefully be more reliable. The question is does the AC power to the CDI unit/coil need to be regulated to a specific voltage (like 12v AC) or does it just take whatever voltage the stator throws at it? (like 30-60v+) I was thinking of buying a 12v AC regulator like this https://trialssuperstore.com/products/voltage-level-regulator to bring the voltage down to 12v AC and then run a fan regulator like this https://trialssuperstore.com/products/fan-regulator-gasgas to run the dc fan. My understanding of the fan regulator is its a half wave rectifier with a smoothing capacitor. If I am thinking about this correctly I should be able to run lights off the regulated AC, the fan off the fan regulator, and hope the CDI unit works great with 12v AC. If this is the case then I could potentially cut out the expensive Ducati regulator and run modern, cheaper and readily available parts. Has anyone done something similar to this with any success and without changing the CDI or the Flywheel/stator to the kokusan type? Thanks for reading though my thoughts and I appreciate any insight anyone may have!