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NGK shows BR7ES having a 19mm reach: https://www.ngk.com/ngk-5122-br7es-nickel-spark-plug You must then navigate to Product Specifications.

I owned 3 Montesa bikes at the same time, a 250, a 260 and a 300. I swapped out parts assemblies between all of them to trouble-shoot issues at one point and I found that absolutely everything was interchangeable without causing issues.

Stainless steel and the same size as my size 8 wedding ring. Too bad you don't reside in Canada I have all that stuff sitting in my spare parts drawer, if you lived local I'd give it all to you to mess with. I think altering the fuel mapping on the 4RT would be a complete waste of effort considering the stock fuel mapping does not need to be changed when you remove all the mechanical intake and exhaust restrictors, it sorts itself out just fine. The fuel injection works great corked or uncorked, they just have less power response when they are corked so why would you want to mess with the fuel to air ratios. I had one 4RT with the 2 position map switch and left it in high or dry power setting all the time, same as with my TRS machines more power is better, I think all the map switch changes is to slightly alter the ignition timing, like an ignition advance.

Well the manual shows a BR7ES which is not a long reach, so its confusing to be told I need a BP7ES which is a long reach plug. The manual doesnt state a BP, so my question is the manual printed wrong or was the BP found to be a better plug to use. Thanks

I'm in the US. Are those top hat pieces aluminium or steel? I assume the ones from the original bike were made for the smaller head pipe so would not fit but I could make new ones. If it reduced the 26 mm pipe to 18, maybe 22 mmm would be appriate for the 30 mm 300 exhaust? That would equal the same 50% reduction in area which seems quite large. I don't see the pipe avilable but it sounds like a pricy experiment. I did spend some time looking for the software and dongle to tune the engine. It was unclear if what I found would work work for this bike. If you are interested in selling the used unit, PM me. I also found this link but it looks like they just sell maps and just for max power. It does not mention hardware. https://oldskulltuning.com/montesa-cota-4rt-keihin-tuning-maps/

Do you not mean a BPR7ES same long reach plug but the resistor type.

You have not hijacked anything what you are talking about relates to what mick mcmanus is wanting resolved.

None. Unfortunately, have not yet even tried. The unit was purchased secondhand, and it came with a variety of example maps (I guess "map modifiers" would be more accurate) including the 300. The concept is the same as that used on Honda's EFI MX bikes. Sorry for the hijack, mcman56.

See the tailpiece part # 23 and see the tailpiece that it replacers with rivets, I have one of those as spare and I bet lots of other do too. The rest of the restrictors are simple to make on a lathe if you don't want to source them as original Honda parts.

That is interesting Konrad. What ECU have you managed to connect to? On the silver sticker with the part number there is also a 2ED, 3ED and HRC. The early Repsol 4rt’s were all fitted with the HRC version which was programmable. Due to customers fiddling without proper knowledge of what they were doing some ECU’s were causing headaches for the dealers which in turn resulted in future ECUs becoming locked and then the 2 map switch as a compromise. There are also a few “works” ECU’s about from factory bikes. They connect to the software via a 9 pin plug rather than the usual 4.

Did you read the SCALVINI system discussion that jrsunt put on , It sounds like it will give you what you are wanting or are you on a low budget.

This is very interesting to me! I talked a friend into buying an HRC "Setting Tool" for his 4RT. I'd never see one for sale in the USA, but he was able to get it out of the UK. It's been in my lab for over a year now, as he seems to have lost interest in riding trials. So I have yet to connect it to a bike. It appears to be able to work with any of the non-homologated ECUs (which should be all the 4RTs in the USA). It does not permit unlimited mapping. What it does allow is a "safe" deviation from the map for any given throttle position and RPM range. It works for both fueling and ignition timing. I'm attaching a screenshot below.

I presume you’re uk based, the street legal or ED and 2ED bikes weren’t really ordered by dealers in the uk as there isn’t a market for them, the 4ride filled that market. The 3ED and 4ED are the competition versions that came more or less ready for trials without having to swap parts. The 4 ride (2ED) does come with the road legal front pipe as well as a 3ED/4ED front pipe in a kit. It was generally swapped for the 3ED parts as it made the bike a lot better. This is only a 26mm pipe as with all the 260’s. The parts list shown by lemur is from a 2005/2006 bike. Which only had to fulfill Euro4 requirements. The restrictor was a very basic top hat design, something that could easily be fabricated to fit the 300 pipe. It may be worth looking in to. If you could find one off the original 4rt it would fit, the cylinder head is exactly the same from the 1st 250’s right through to the current 301rr

This is a 2018 300RR. I don't see anything like that on the parts diagram. (The power bomb pipe with O2 sensor is for the street version) I would like a softer off idle response.

Hi all hope some one can help here, my bike has a ngk bp7es fitted but the manual sais to use a br7es plug. I emailed beta uk and they said to use a bp5es or the 7. Said the R ristore is for if your running lights which I can assume the ignition is abit noisy with emf I beleave. The bp7es is a long reach plug where as the br7es is not. I would think the long reach is not correct.

In the Montesa 4RT parts manual. There are different versions of the muffler and tailpiece depending on what year and model you are working with, any dealer or customer that has done a competition prep on a homologated 4RT will have the restrictor parts. There is also an intake restrictor plate but you don't want those installed unless you want to completely disable about half the bikes normal power. ... the exhaust restrictors are all 18mm inside diameter.

Where can you find these restrictors? I have found nothing.

hanson racing on Facebook sold one on their ebay shop UK for around £450.00.

I’m not sure you will get a Mont to feel like a Beta. The injection vs carb response is very noticeable. Mapping would be the way to do it, getting hold of a HRC (fully programmable) throttle body may be impossible though. But, it has been done before with various header pipe set ups, there were some posts on here a few years ago. It would be worth a read. I think the standard 250 and 260 header is 26mm and the 301 is about 30mm. There should be plenty of standard 250/260’s available second hand fairly cheap. The 250 pipes did change around 2009 they are slightly longer to accommodate the newer style silencers. Aftermarket headers are about 28mm. Getting the right gasket to fit the combinations might be tricky.

There are an assortment of restrictors available to detune the 4RT all the way down to ~125cc performance ( learner license ). one plate goes into the intake and 3 are available for the exhaust including a different tailpiece that can be riveted on the tail end of the muffler. ... if you really want to detune one it's not hard, the fuel injection will even sort itself for everything except idle screw setting.

Worth checking your throttle tube again to see if it really is the slow version as the black anodized aluminium (aluminum) versions have no cam/ramp and dia should be only slightly larger than your handlebars. An extra carb slide return spring will help avoiding whisky throttle, but at the expense of sensitive throttle adjustments. If you have a coloured S3 cyl head fitted then low compression insert available. Believe the 2012 was the first year of the external stator sensor so adjusting stator plate wont help retard the timing. Ultimately no substitution for time on the pegs. Rick Agans has a wealth of Sherco experience so try to reach out to him.

If you want less performance to soften response you need a wider bore pipe not a smaller one , this decreases back pressure and therefore lessen low end torque that makes for instant action off the bottom. Its complicated on a four stroke motor. I would recommend you read up on it before trying any amateur tuning tweeks. Honda 4rt with a BETA 4t motor grafted in? Send a message to BANYERES perhaps he may have something to help you get what you want.

Has anyone tried a 260 head pipe on a 300. It looks a good bit smaller and I wonder if it would soften the response. I would like my 300 4RT to run more like a Beta 300.

Didn't want to hunt the correct spark plug so I ordered one on Amazon, should receive it tomorrow. In the meantime I sent the PWK carb back and plan to buy one made by Polini (don't know if you guys know the brand). It's an italian brand that makes big bore kits for 2 strokes, exhausts, variators, automatic clutches for scooters etc. - I already fitted one of their PWK carbs on a Beta Rev and they're obviously much better than the generic chinese clones.