konrad

Ignition coils for CDIs are neither 6 volt nor 12 volt. CDI coils work on a completely different principle than "induction coils". The capacitor inside the CDI gets charged to on the order of 200 - 300 volts, and then is discharged into the ignition coil. Technically, such ignition coils are "pulse transformers". They typically have somewhere around a 1 : 100 (primary : secondary) turns ratio. Their primary resistance is very low (usually under 1 ohm). I just searched "CDI ignition coil" on eBay and found something for $8.25 USD shipped from China. Better yet: https://www.ebay.com/itm/IGNITION-COIL-YAMAHA-TTR125-TTR125L-TT-R125-TT-R125LE-2000-2009-2011-MOTORCYCLE/281087430819?hash=item41721dd0a3:g:iFIAAOSwDk5T1Lw~:sc:USPSFirstClass!55066!US!-1

Regarding item #7 (I called it a "beauty cover"). Perhaps a better name could be "access cover" or "body cover" or just "cover"? It's called "airbox cover" in the OSSA parts book. But that's not a good translation. They call the actual airbox cover the "air filter manifold". Although it's desirable to keep item #7 installed, I suggested testing without it. I rode my bike for an entire day without that cover (which made getting to the diagnostic port easier on the 2011 model). I can tell you the fan was loud, very loud, objectionably loud! Also, the 2014 cover has louvered openings whereas the 2011 cover does not. So I think the cover must have some affect on cooling.

I think it's both. Item 7 below is what I am calling the "beauty cover". I see what you mean about VR wire! I was told by a knowledgeable person that works with Arctic Cat snowmobiles (also uses similar Kokusan Denki ECU) the fuel pump is powered separately. A lot of what I found lead me to agree with that. But I'm not so sure now. I don't have a running bike right now to investigate further. When you run K-Scan, "pump voltage" and "battery voltage" are reported separately. P.S. I recently found out that the OSSA fuel pump is a standard part used in other motorcycles. This makes me think it odd not to just run it from 12V (battery) power.

Possible, yes. But risky too. Power comes from the stator, but rectification/regulation happens inside the ECU. This additional load could cause that part of the ECU to fail, or create enough extra heat inside the ECU to cause something else to fail. If the additional load of the fan caused a drop in voltage, the fuel pump pressure would be decreased which would have an effect on fuel injection volume. I have a couple other thoughts... Does the boiling occur as you are riding or when stopped and the fan stops? (Install a small clear "catch bottle" on the radiator overflow to see when fluid loss occurs.) Maybe it's better to ride around slowly after a steep assent? What happens if you remove the plastic "beauty cover" that goes over the airbox/fan/ecu area? Does that improve airflow enough to decrease the operating temperature? I would install a temperature gauge so you know what help/hurts.

Some (slight) fluid loss due to thermal expansion of the coolant is normal. I was going to suggest using a 1.6 bar Kawasaki radiator cap, but just tested this and it does not fit my radiator. Still, you can probably find a higher pressure cap than standard (which is 1.2 bar) that will fit. You can use distilled water instead of antifreeze (coolant). Pure water has better heat transfer properties than antifreeze and this will lower the system operating temperature somewhat. But using pure water has drawbacks, namely: lower boiling point; no corrosion protection; no freeze protection. I use Motul's MoCool to provide some corrosion protection. The recommend concentration is 5%. You can unplug the coolant temperature sensor. This will make the fan run 100% of the time. As you mentioned, running the fan at a higher voltage (maybe fabricate a DC-to-DC boost converter?) would make it turn faster, but would probably also decrease its life. P.S. you can also use K-Scan to enrich the A/F mixture up to 5%, but this will likely have a detrimental affect on power (but you may be able to tolerate a few percent).

Great tip, thanks! I'll order one. That photo was taken even before I used flywheel weights. I ended up just heating and bending the stock levers to clear. (Also slid the levers out on the splined shaft a bit, too). Not shown in that photo is a Nylon washer I machined that goes between the engine case and the shift lever. I'm hoping this will prevents the shifting mechanism from being damaged if/when I crash the lever into a rock. The OSSA's entire shift mechanism looks quite fragile. I would have sacrificed some weight there for durability.

Pindie, you don't need to remove the cover completely. Just loosen the screws and pull the cover away from the engine case slightly. But this makes a mess! I made this little extension specifically for trials bikes to keep the mess at bay. Works fine on the 2011, but I can't get anywhere near all the oil out of the 2014 via the drain plug alone. Anyone know why this is? Does the locker shaft have something to do with it? My 2014 has some additional machining that allows clutch cavity oil to drain by removing one case screw.

As above, and additionally... The thing about the OSSA is that motion of the bike does not force air through the radiator -- it's all up to the fan. The ECU is programmed to turn the fan on at a coolant (in the head) temperature of 80 C (176 F) and off at 70 C (158 F), which is consistent with your numbers. It's likely the ECU is programmed to enrich the mixture at elevated coolant temperature in a self-preservation mode. This would account for the drop in idle speed you see. This is common in high-power cars that can't sustain flash dyno readings due to radiators limited by other constraints. Basically, the bike was not designed for extended climbs.

Matteo, I agree, OSSA's Easy-Start retrofitting instructions could be improved. (Part of the problem is a Spanish author writing in English for an Italian reader.) The instructions apply only to bikes that did not have Easy-Start fitted at the factory. But they should help you better understand the system. FWAC only works with bikes that had Easy-Start fitted from the factory. This is because some of the wires (from stator to ECU) are not easily accessible. But FWAC is possible on all bikes, if you add these wires. Yes, you can add a second switch to control the easy start "on demand". Yes, the 2014 models use the flywheel "check" mode by default to know when to arm the system.

Thanks Andy, that optimizer is fabulous! I thought 14.5 MB seemed excessive for mostly text. The small pics were not very good to start.

Correct. The Administrator here will be posting the complete documentation for retrofitting the Easy-Start System to older bikes. The Easy Start uses a momentary-contact kill button to "arm" the system in addition to killing the engine. However, the 2014 bikes will also arm without pressing the kill button (by sensing flywheel rotation during kickstarting). I recommend connecting your lanyard (magnetic cap) kill switch on the output side of the Easy-Start for maximum safety (should the Easy-Start ever fail).

I just attempted to uploaded version 1.1 to the first post. (It contains a few minor additions, plus wire colors and functionality of the Easy Start connector for matteo.lavaggi). Apparently, I'm all out of space for attachments. Okay, got it now. Apparently I also needed to delete the link to the uploaded file (as well as the upload itself) in order to recover the attachment space. I'm not used to this board software.

I'm not sure where to go with this question. There is already a topic here on the Easy Start: https://www.trialscentral.com/forums/topic/60767-ossa-easy-start-unit/ I would like to upload the complete Easy-Start Instruction Manual, entitled "INTRODUCTION OF OSSA START SYSTEM ASSIST" but it's a 14.5 MB .pdf file, and I that exceeds my allotted storage space.

If I'm not mistaken, that engine is based on Yamaha's TT-R125. The pilot jet on the TT-R is notoriously small and easily plugged. Just spraying carb clean at the carb won't fix it. Remove the pilot jet and make sure you can see light through the orifice. You can gently pass a fine wire thought the jet's orifice to clean it.

When you do this, may I suggest adopting a standardize testing methodology. I would suggest testing a fully-warmed bike, and letting it sit 5 - 6 minutes between tests.

I suspect it's just been misassembled. You must wind the kickstart return spring up slightly from its relaxed position prior to putting the clutch cover back on. Make note of the thrust washer at the end of the kickstart shaft (not shown in the photo below). It's easy for this to fall off during reassembly. I grease this washer to help keep it in place, and lean the bike to the right when installing the clutch cover. Take reference photos during disassembly. The "loop" in the kickstart spring fits into a mating area in the engine casting.

That's the filter capacitor. Because you removed the Easy-start, I would not remove the filter capacitor. It's possible the life of the ECU and fan could be shortened without it.

I used IRF18650 cells rated at 1100 mAh. It's certainly possible you could get by with less, I did not do an analysis. One other thing... Mark has had very good luck with 1-kick starting, whereas my bikes require 2 to 2.5 kicks. I'm wondering if there is any correlation between kick-starting and fuel pump voltage/pressure? The ECU assumes a particular fuel pressure when it decides how much fuel to inject. The fuel pressure does not stabilize until the engine has run for, I'm guessing, a second (it's some short non-zero time, anyway). A higher battery voltage would cause more fuel to be injected. I don't know if there is anything to this, but I'm throwing it out as a possibility. Seemingly small changes have had a big impact my OSSAs.

That's a bit like asking, "What's the best religion" isn't it? I'll try to be objective. I can't disagree with anything written above, but will add... I've always loved the challenge of tuning 2T engines, but can't get away from the fact they are very dirty (environmentally). A 4T is going to get better fuel economy and emit far fewer unburned hydrocarbons than a 2T. I'll also state up-front that the vast majority of my motorcycles have been built in the land of the rising sun and I'm relatively new to trials (6 years). The Japanese have an attention to detail second to none. So, my acquaintance with the quality control (or lack thereof) of modern trials bikes came as quite a rude surprise. When I think 4T trials, I only think HRC Montesa. I have ridden two of them, one very old and one very new for about an hour each. Neither instantly made me a better rider. (I also rode a 4T Sherco that was very difficult to start but probably had setup/maintenance issues.) Some 4T pros: Really great service manual -- download one and see for yourself. Auto-decompressor makes them easy to kick. Can buy one from a Honda dealer. Some 4T cons: Higher initial cost. Heavy, but maybe not really objectionable until you have to drag one out of a ravine. I've heard owners complain about expensive parts. In the end, I'll stick with 2Ts until the Japanese produce a usable electric (are you listening Yamaha?). P.S. I really wanted to love the 4RT.

I'm not sure about the Explorer, but on the trials bikes the connector is near the cylinder head. The connector should have a "blanking plug" installed to keep dirt out. You are correct about the wire colors and polarities. If you have not seen it already, there's some relevant information here: https://www.trialscentral.com/forums/topic/69622-efi-ossa-notebook-formerly-tr280i-wiring-diagram-annotated-in-english/ Just BTW, the fuel pump does not run initially when using the Easy-Start system. Noticed Mark used 3 lithium-ion cells. These have a nominal cell voltage of 3.6 to 3.7 (a 3-cell series pack gives 10.8 to 11.1 V). I used a different battery chemistry (lithium-iron-phosphate) which has a nominal cell voltage of 3 to 3.4 (a 4-cell series pack gives 12 to 13.6 V). The advantage of LiFePO4 is that it may be charged directly from the OSSA's electrical system.

Yes, and still does. My understanding is that Curtis Leaverton, a big player in aftermarket parts here in the US http://www.pivotworks.com/CompanyHistory.aspx was the original importer. Curt is still into classic OSSAs https://www.vintco.biz/ossa-world

Version 1.0 is now available in the first post. I've fixed a lot of typos, some flat-out wrong information (mostly about gearbox ratios), and added 6 pages of content. The stuff I added on disc springs, XiU-rdi's clutch components, flywheel weights, and the Clake OLC may be of general interest. As an aside, this document has been downloaded 50 times. For comparison, my document about fabricating a diagnostic interface has been downloaded 155 times. I would have expected those numbers to be reversed. Happy New Year!

Curiosity, mostly. But also to get an idea how many potential donor bikes might exist -- I'd like to keep mine running until they're considered "vintage." ? I have also read the 1250 number, but think it's optimistic. Inside the gearbox on my 2011 280 there's some CNC engraving that says "T.A.S. 212 10/49". I'm wondering if that means it was the 10th engine in a production run of 49 good castings? I assumed the runs would be small, but that quantity does not seem economical. My 2014 250 says "13/25".

If this topic has been discussed elsewhere, I could not find it. I'm curious how many bikes (and of what type) were actually produced. If the numbers are unknown, maybe we can estimate them from VINs? I think my 2011 280 was a very early arrival in the US. Its VIN ends in 165. Same with my 2014 250, its VIN ends in 35.

Call me overly-cautious. Where?