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Thank you! They really are nice looking, I enjoy seeing other people's all cleaned up as it gives me inspiration. I've read a lot of bultaco threads on here already

Excellent. Model 49s are a wonderful looking bike.

The motorcycle frame and engine casings are the earth/ground for the motorcycle. Most people ground their kill switch at the HT ignition coil mount.

Did anyone find any good options for these flex force replacement straps? I need one. Is there any way to have them made? It seems like there is a bit of demand for these still

I’m have a similar situation. It appears my black wire is not grounded unless it is grounded in the head light. Is there a spot on the frame that it is supposed to be grounded?

Hi everyone, I'm new here from southwestern Ontario, Canada! I found the site as I've been restoring a Bultaco M49 Sherpa T that was left to me by my late Uncle I've done many restorations on other things (tractors, lawn equipment, radios and arcade equipment to name a few) but this is my first bike project. I have been given a lot of good information from Facebook groups but I always enjoy making a forum thread so I plan to document my project here, hopefully in the future my info may help someone else 😊. Mikey.

Can only buy the correct plug as a Honda replacement part in Canada and Honda dealers don't sell that bike here now 😐 NGK does not import it here. Parts are very expensive when your closest supplier is 2000km away and almost nobody owns one 😎 but if price is no object they sure do work good.

I feel your pain. They can be pricy from trials shops. I believe the same CR6EH-9 plug is used in small Honda and Yamaha outboard motors so a boat shop is another option. We can buy that plug for around AU$11 at the local car parts stores. Even cheaper online (except for the postage).

👍 Even more wily Now if they can just sell the spark plugs for under 20$ 👍

Yup - for the first 0.5 of a second. Then "normal" non-wasted after that.

So Wasted it is 😎

Hi Everyone, can anyone point me in the right direction to get a new plastics set for the old (2011ish) Oset 16? I’m really struggling to find anything at all. Uk or European based ideally.

Hi jrsunt Here is an explanation of this picoscope recording, which is just a simple compression test - where I measure pressure/vacuum over a period of 720 degrees, and at the same time I also measure the ignition voltage on the spark plug. The compression test is done with the kick starter on - so the engine is not running. The fact that the engine is not running causes the RPM to fluctuate a lot during the valve timing measurement, and therefore the measurement is not as accurate as if it were a multi-cylinder engine - where the RPM is much more stable - this is actually the same as aussiechris has explained in previous answers. But as aussiechris writes - it can be used as a guideline regarding valve timing.

I was told they were made for Pete but don't know who by. Last I heard was Pete was not well. I have 2 of these clutches work very well.

Honda_freak can answer you better but I believe the red line on both his captures is cylinder pressure. In the most recent pic, the blue line is the fuel injector voltage. In his earlier image, the blue line was the ignition coil secondary voltage. He is showing the relationship between those voltages and the crank position based on cylinder compression pressure. It's not easy to directly correlate time on the x-axis with degrees of crank rotation because during kick starting, the RPM is varying. But it gives a good idea of what stroke it's on and roughly where in the stroke these events occur.

Wish I understood the data, I have no idea what the red or blue lines indicate 🤣( X axis crank degrees and time? Y axis voltage?) That was from my 250 manual. Looks like Honda freak was also been testing the 250.

It doesn't have much bearing on what we've been discussing but it does show that these engines have a very short overlap (just 7° in your case). But thanks for posting it. I'm guessing the cam profiles changed slightly over the years/models. These are the figures from my 2022 301RR... 14° of overlap in this case.

Does this have any relevance to anyone’s data: Intake valve opens 6 degrees before TDC Intake valve closes 27 degrees after BDC Exhaust valve opens 30 degrees before BDC Exhaust valve closes 1 degree after TDC

Hi Chris These are really good oscilloscope captures you have recorded here and will certainly benefit people when they have an ignition-related problem. I myself am also a little surprised at how it goes from wasted spark to non-wasted spark in such a short time horizon - I would not have believed this if it were not for your fine evidence here. I also find your note regarding an injection timing in the combustion stroke just after TDC a bit strange. But I can also confirm that this matches my captures of injection timing in the compression stroke TDC and which occurs 25 degrees after TDC. This is very important evidence of when and how the ignition system works on a Honda Montesa 4RT and other motorcycles / scooters with similar battery-less systems. It seems that there are quite a few secrets that need to be discovered. Just keep up the good work. Regards Honda Freak

It appears to be that the 4rt was the first bike with batteryless fuel injection and the test bed for everything else. With regards to your tests and findings, why is the high tick over so critical for the starting procedure?

These diagrams are drawings I did to explain a fault on my 2008. They are not going to be relevant to other years and configurations so be careful. All the Beta owners manuals including wiring diagrams from 2006 and up are available on-line from the US, UK importers. Anything earlier is tough to find as it will have to be scanned from written owners manuals.

The standard modification is to change to a Techno kick start shaft. Then you can bolt up an Evo lever.

Thank you for all of your efforts with proving this, a very interesting read. It reminds me of a non starting 6cyl BMW diesel in a Range Rover I was asked to repair. It ran Bosch common rail injection. The car would crank, fire a few times, then die. Never any more than a few firing events. What I found was that the engine ecu could not make use of the camshaft position sensor to synchronise the crank and cam to decide when to inject fuel. In my training I was told that the system would not start to inject until the fuel rail pressure sensor was above a certain threshold. I proved this not to be the case with my 4 channel Pico. What actually happened is that the engine ecu would allow each injector to inject 3 times - Basically to give the engine a quicker go at starting. This allowed a few firing events, but it would never start because the analogue to digital converter had failed in the ecu for the cam sensor so it would not synchronise and allow it to start. The ecu was sent off for repair and the car was fine after. Sorry for the long, slightly off topic post, but like you guys I'm fascinated by what actually goes on, and how it all works. And another vote for the Picoscope and WPS500 - expensive, but VERY good.

Ok, some interesting findings for those watching… For info, in the following oscilloscope traces, the bottom (yellow) trace shows the pulse trigger coil. A burst of 9 short pulses occurs once every revolution of the crankshaft. Note, all traces are referenced to +12v power. That’s because the ignition coil and fuel injector are switched by the ECU applying a ground. I have confirmed that full +12v power is available within one revolution of the crank. Each trace covers a one second period but some are offset by differing amounts to get a better view. 1. My first test was to remove the spark plug and kick the engine over. This trace closely matches the one above posted by Honda Freak. The ignition pulses (in blue) are virtually identical to his with the first two sparks about 83mS apart (720rpm) and the next about 120mS (500rpm) later, in my example. This confirms Honda Freak’s finding that the engine sparks once per revolution of the crank - wasted spark ignition. And yes, you only get three sparks total and only one or two of them will be on the correct stroke (and that’s with the plug removed). Also note, the fuel injector initially fires two shots (once per crank revolution) and then once every 2nd rotation after that. 2. Kick start and run. This is where it gets interesting. On the left, you can see the initial fuel injector pulse followed by the first spark. The engine starts on that first spark as evidenced by the increase in magnitude and frequency of the trigger pulses. The spark plug continues to fire every crank revolution. The injector is firing every 2nd revolution. However, it appears from the first spark (when I believe the engine fired) that fuel is injected just 10mS after the spark which would be just after TDC on the power stroke when the intake valve is closed. But then a strange thing happens… About 8 revolutions after starting (about halfway across the above trace), the fuel injector timing skips a complete revolution and then, after next spark, the ignition timing changes to non-wasted spark or “normal” four stroke running. Fuel injection is now occurring on the intake stroke (halfway between spark events). I ran this test numerous times with the same result. Somehow, it always started on that first spark event, never the second. The injection timing had to correct itself every time and ECU dropped the unwanted spark events on the next cycle. I’m guessing that if the engine started on the 2nd spark (due to crank position), the fuel injection would not need to correct itself and the ECU would just drop the unwanted sparks. 3. I tested a start, shutdown, followed by a rapid re-start. The above sequence was repeated each time. The ECU does not appear to remember where it’s timing was previously. 4. Wide Open Throttle cranking. On my bike at least, holding the throttle open kills both the spark and fuel injection. This trace has the same conditions as the first one except the throttle is held wide open. Even half throttle will kill it. I can’t explain why doing this helps with a bad start but maybe it just clears out excess fuel. It doesn’t appear to reset anything - the ECU has already lost power. 5. ECU "Power Relay" (engine running signal). This signal is used to turn on the power relay to supply 12v power to the headlight. I can confirm that signal is pulled low (turning on the relay) at the same time as the fuel injector pulse is corrected. This occurs about 500mS after starting. Green trace below… Anyway, I hope you’ve enjoyed my ramblings. Honda Freak and I were both right - the 4RT starts out with wasted spark ignition and then reverts to normal 4 stroke ignition about half a second (10 to 12 crank revolutions) later. And I tend to agree with sportsawyer that it is all timed off the MAP sensor pulses.

The only setting I have for the pre TXT PRO motors is 2.7mm before BTDC.