sportsawyer

Have you done the changes in the Full Power Version manual -- headpipe, muffler endcap, removing intake restriction, and so on?

Thanks, but I'm hardly a guru. I'm just another rider who likes 4RTs and is always trying to learn more about them. I still have a lot to learn.

The P.N. is 16400-NN4-M11, so that's the standard TB/ECU for ED/2ED street versions. It has a Mode 2 map (green/white wire connected to green ground wire) that's used when the O2 sensor, catalytic converter, and intake / exhaust restrictions are on the bike. Its Mode 1 map (green/white wire NOT connected to green ground wire) is used when the catalytic converter and O2 sensor headpipe is replaced with "race" headpipe and the intake / exhaust restrictions are removed. Map switches are not normally used with this TB/ECU. The wiring is changed (green/white removed from 4-pin connector) to put the TB/ECU in the "full power" map when all the street version (ED/2ED) restriction is removed. Here's a link to Full Power Version 2017 instructions. Look at pages 4 & 5, they show pulling the green/white (map selection) wire from the 4-pin connector to use the "full power" map on the 16400-NN4-M11 TB/ECU. If you can get your friend with the 2018 bike to pull the fender, you can see if it has the 16400-NN4-L31 TB/ECU. That's a two-map "race" TB/ECU that comes on 3ED/4ED racing version bikes, and it has dry and wet terrain maps (see your Owners Manual, page 1-9). I suspect the 2018 bike is a racing version 3ED/4ED, and the difference in feel is the 16400-NN4-L31 TB/ECU. The 16400-NN4-L31 TB/ECU should be available from Honda OEM parts suppliers like KFM.

I'm thinking one possible cause might be the throttle cable is tight when cold, and opens the butterfly valve slightly. When the cable heats up (it's running fairly close to a lot of hot stuff) it could relax that tightness some, closing the butterfly valve and lowering the idle. Check the "Throttle Grip Free Play" per page 1-6 in the 2015 Owners Manual. If it is tight, adjust it to have enough free play. After that, you'll probably need to open up the idle air adjust screw a little on the throttle body to bring the idle back up to the right amount.

The cost of intellectual property. Too bad I have none to sell.

Link to 2017 4RT260 Parts List, English Link to 2018 4RT260 Parts List, English

The 2017 and 2018 parts manuals aren't showing any difference in parts numbers for top end components. And both years' TB/ECUs are shown with P.N.16400-NN4-M11 for the ED/2ED street versions and P.N. 16400-NN4-L31 for the 3ED/4ED racing versions. Maybe comparing a -M11 to a -L31 TB/ECU? Have you pulled the fenders to see the TB/ECU part numbers?

He's also a regular fixture on the Repsol Honda team. So he knows something about the bikes too.

I saw in another post that your bike is a 2016 4RT260. Something I'm curious about is the 2-Map Programmable TB/ECU. Is it for 2016+ bikes or is the standard one programmable? What I'm trying to understand -- because I haven't seen details for newer optional PTB/ECUs and am still not clear on whether or not the standard 2016+ TB/ECUs are programmable -- is if an optional PTB/ECU for 2015 and earlier bikes will work correctly. The reason is the fuel pump system changed in 2016. Earlier fuel pump systems used an external (attached to injector assembly) fuel pressure regulator driven by intake port vacuum. The purpose is to keep injector fuel pressure at a constant value above intake port vacuum. So the injector always has a (nearly) constant pressure difference from its input to output. The 2016+ fuel pump system doesn't have the external, intake vacuum controlled pressure regulator. It has a pop-off valve in the internal fuel pump assembly to keep pressure (nearly) constant going to the injector input. If this is uncorrected, it means there's a higher pressure across the injector when there's higher intake vacuum. That would change the amount of fuel delivered in a given squirt duration. But I suspect there's some correction with the 2016+ ECUs, based on MAP sensor input, to offset the fuel discharge duration and compensate for fuel differential pressure variability at the injector. It's just electronic correction rather than vacuum driven diaphragm correction. With a programmable TB/ECU, the user can add / remove fuel from the basic amount based on two variables, rpm and throttle opening percent. The user doesn't have the ability to correct fuel amount based on intake vacuum, that's done behind the scenes. And I suspect the 2016+ TB/ECUs have some additional correction to mimic the external pressure regulator on 2015 and earlier 4RTs. I haven't seen a detailed explanation from Montesa / Honda. So all of the above is just guesswork. Anyone have real information from the Honda engineers?

Could be. But the coil listed above at Banyeres looks identical to a 2017 CRF450R coil, P.N. 30500-MKE-A01, fitted with a spark plug wire for the 4RT. That one might be compatible because the standard 4RT coil, P.N. 30500-ML7-013, was also used on EFI CRF450R bikes from 2009 to 2013. I haven't done it, but checking a 2017 CRF450R shop manual for primary & secondary coil resistance and comparing to those in the 4RT shop manual might give some more insight.

Check the vacuum line that goes from a tap into the intake port on the head to the pressure regulator for cracks / leaks. Don't know if that'll fix your problem, but it's something that's easy to check.

On the 4RT, the coolant temperature sensor sends data to the ECU. The ECU uses temperature data for fuel adjustments and to start the fan by signalling the fan relay. So the next thing to check is the fan relay. See the schematic in your owners manual, and Page 6-9 shows how to check the fan relay.

2017 4RIDE Shop Manual, see Chapter 5 for Electrical Servicing and Schematic: http://motos.honda.es/montesa/manuales/2017 4-RIDE SM (EN).pdf

Other than the bore, the only air-way is the idle air passage. There's a small hole on the engine side of the butterfly valve, but that goes to the MAP sensor and is not a through-hole or passage. The air temperature sensor (in bore channel on air filter side of the butterfly valve) and MAP sensor mount directly to the ECU PC-board, and have seals to protect the electronics from the TB bore. So I'd avoid compressed air in the bore to blow things out, as it may damage the sensor seals. If you take out the idle-adjust screw, you may be able to carefully use compressed air to blow out the idle air circuit / passages from the idle-adjust screw hole (TB/ECU off bike). For cleaning the TB/ECU, I recall Honda recommending warm, soapy water and to NOT use carb cleaner.

Standard is CR6EH-9, optional hotter plug for cold weather is CR5EH-9. May want to try the cold weather plug. And the idle may still be too low, you may want to try the process Barfy mentioned. Or, I've found setting the idle screw 3-turns out from full-in will usually get to starting. You may have to turn it in a little from there once it's going, since it may be a little high. If you don't have an Owners Manual, you can download one HERE.

I think the 2010 RTL260R "setting program" software is the same, or at least equivalent, to the 2007 & 2008 software. The difference in the installation may be the newer CP210x driver software to work with VISTA and the USB wiring. Earlier versions only supported up to XP. FWIW, if you use the USB wiring you can download and install the newest Silicon Labs CP210x driver and run on newer Windows versions. I have it running on both Windows 7 and Windows 10 laptops with driver version 6.7.5. The 2010 manual says this: "The setting program of ‘08-’10 model is the same as ‘07 model." So that's why I'm thinking it's the same, and has nothing new that makes it work with the 2017 300RR (if it's really a programmable ECU). In the 2010 installation, the program still has the same name: 07RTL.exe and in my installation the file version is: 1.3.0.4 And according to the manual, this and earlier dual-map software should work with a single-map programmable TB/ECU by selecting 05 RTL rather than 07 RTL under the "Model" option. I still haven't seen anything about newer software for the 300RR yet. With the CRFs, there was a change in 2013 and the "setting program" started using a different map-file format that has file extension *.fsd rather than the older (and same as 4RT) *.e2p extension.

I have the 2010 RTL software. I've only used it for dual-map ECUs, but I think it can be set to work for single-map ECUs by selecting "05 RTL" under the "Model" menu-bar option. If you have everything else, might want to try that first.

I've already looked into this a little. The 2016 and later bikes use a P.N. 16700-NX7-003 fuel pump assembly. This is originally from the 2012 HRC NSF250R road racer. In the Montesa parts lists, it's just shown as a complete assembly. But in the 2012 NSF250R parts list, the assembly is broken down into component parts. The NSF250R break-out doesn't show a separate number for the pump itself, but it does show the number of the teabag filter kit (includes filter and o-rings for reassembly) which is 06160-MEN-A31. That filter assembly comes from the 2009-2010 CRF450R, so it is widely available. This may be of interest if anyone is looking to replace the filter assembly on their 2016+ 4RT260 or 300RR.

Thanks for the update. I've continued searching for information on an Optional Tuning Kit for the 2016/2017 300RR (or RTL300R) and 4RT260 bikes. But haven't found anything yet that's specific to the 300RR. Have seen some suggestions that the 2016 / 2017 4RT260 3ED/4ED TB/ECU (16400-NN4-L31) is also programmable, but no "I've done it and used this" reports. Have found that Honda has unified the cable set (38880-N1C-770 UNIT ASSY, SERIAL-USB I/F), and it's used for every other programmable FI bike since MY 2012 that I've found information on -- CBR250R, NSF250R, MSX125, CBR1000RR, CRF450R, CRF250R, and probably more. I suspect this supersedes the 38880-NN4-H00 cable set (first came out for the 2010 Japanese RTL260F), which superseded the 38880-NN4-306 cable set. I have the 38880-NN4-H00 set (use it with the 2010 RTL260F software 38771-NN4-H00) and it appears to be the same as the newer 38880-N1C-770 down to all the connectors and lettering on the switch box. I'll update with any new information I find. And hopefully Honda will get around to publishing something about the kit.

Adding to jimmyl's last post, the Honda News press release for the 2016 300RR includes this: ... and it has a programmable ECU that allows fine-tuning for varying weather and terrain conditions. What still makes it vague for me is that no optional HRC FI tuning kit or parts of that kit are referenced in the 300RR Parts List or Owner's Manual. The HRC sites (World and Japan) list tuning kits for CRFs and the NSF250R, but they don't list one for the 300RR or RTL300R. And the Honda UK, US Honda, and Honda-Montesa Spain websites don't list the tuning kit under options and/or accessories. The 2016 300RR Kit Parts List does show the standard 4ED model throttle body (THROTTLE BODY ASSY 16400-NN4-L72) that would be added to a street legal 2ED model which comes with a 16400-NN4-L62 that has mode 2 for restricted engine with O2 sensor & cat. But doesn't list the Serial-USB Wiring Unit or ECM Setting Tool (software) that's needed to program the system. The 2017 300RR Kit Parts List shows the same, standard 4ED model throttle body (THROTTLE BODY ASSY 16400-NN4-M71), but no Serial-USB Wiring Unit or ECM Setting Tool. That said, Honda did put a 16400-NN4-H01 two-stage programmable TB/ECU on the Japanese 2010 RTL260F, and the parts list shows the optional Serial-USB Wiring Unit and ECM Setting Tool. So it's been done. And based on the information, it looks like the 300RR comes with a programmable unit rather than it being part of the optional kit. But it's still hazy to me because I haven't seen anything about the 300RR (or RTL300R) optional programming kit. So I'm still interested in hearing from someone who's done it, and part numbers of the Serial-USB Wiring Unit and ECM Setting Tool that were used.

If you try it, and it's programmable (or not), please post a followup if you would. Thanks.

Thanks for the report. Now I'm wanting a 300RR a little more. Is the stock 300RR TB/ECU programmable?

According to the 2003 parts list, it's a: 96001-06032-00 BOLT, flange, 6 x 32 So 6mm x 32mm. If you want OEM, the Honda bolt is available using the P.N. .

The 300RR went to the new, slightly shorter and tucked-in brake pedal in 2017. It doesn't look like it's made its way to the 2018 4RT260 models.

I think it's still the 2014 3ED / 4ED / Full Power Kit P.N. 18330-NN4-G10 header. Looks shiny in the photos, though. The new skid plate looks like the one on the RG Team bikes. The 2018 also comes with a case protector for the chain. Part numbers show some changes in the brake calipers and handlebar master cylinders, but I don't know the details.