It’s like Shakespeare’s dilemma “to be or not to be”…not about life thought – too simple, but about PR7’s Idle Control Valve and Idle Control Screw! Need it, need not. Want it, want not. Change it, change not!

Here is a thing, while riding around on my AJP pr7, it lost its ability to keep the idle revs. Naturally I tried to reset the ECU a couple of times first as the ECU is responsible for controlling the idle stepper motor, but nothing happened… in fact it did not even respond in the usual way! Revs didnt go up, like they normally do and in fact it didn’t even want to start at all. Eventually I started the engine again with the throttle slightly open and kept it open till I got back home… 

While riding home I kept thinking, “if I can keep the throttle open like that and the bike runs fine, why not make some changes for the future – so I didn’t have to? And perhaps get rid of the Idle air control valve completely too?” – what i didn’t know, that that will turn out to be the best and the worst idea ever! Keep reading.

Since on the AJP PR7 idle control bolt / screw is fitted only to stop the butterfly from hitting the inner walls of the throttle body” (or at least that’s what i thought at the time), idle control stepper takes up all the work of controlling the idle, but when it stops working like it did on mine – AJP is starved from air and wont idle or run unless throttle is opened up again by twisting the throttle grip for example.

What i thought before was that for a simple bike like AJP PR7, there was no need for something “high tech” like a stepper motor to control the idle – a simple flexi bolt or normal bolt would have been plenty. Stepper motor is just something extra that can break, and extremely annoying when it is not working as it should too…

Anyway, at home after checking the PR7’s wiring diagram, it seemed like the stepper motor is attached directly to the ECU, no splits, no joints anywhere, so it’s very likely the motor itself stopped working, the question was – why? At the same time I had set my mind on making changes as I have never liked IACV anyway and that just gave me a good push forward, so I also ordered a good old flexi bolt, that completely did not match the thread, but was easy to fix.

It didn’t take long to sort IACV out, and the funny part – nothing was broken there, it was completely my own fault for not checking if the plug was inserted properly! What happened was that i didn’t push the plug all the way in the last time i worked on the bike, and the next time it took it for a spin – it slipped out mid ride! Huh! 

After IACV was fixed and while the air filter box and the rest of the stuff was off, I thought I’d go ahead and fit that flexi screw as a replacement for the original idle screw. Had to rethread it thought, as the thread on the flexi screw that originally came from Mikuni carbs was much finer, but it came out just perfect and after a few test’s I was very pleased how the engine runs, and eventually decided to block off IACV’s air channel completely.

It was like a magic cure at the time. I started the bike and it started straight away, idle was at constant speed and where it should be, adjustable, and always where I wanted it to be and most importantly – it didn’t bounce up and down like with IACV. I thought – “what a great idea” and I left my PR7 with a flexi screw and blocked off IACV, however “victory” was short celebrated.

Next time I decided to go for a spin, I noticed that I had to adjust the idle with an idle screw to keep the engine running smoothly, and then I had to play with it again, and again, and again… and I realised that IACV does a lot more than I originally thought it does. Had to do my homework on it and get to the bottom of it as I clearly didn’t know something about it- something I had to do in the first place.

After some research I realised that I have turned my throttle body basically into an old school carb, but with an injector… So after a while, even if I don’t like the IACV – I decided to remove the plug from the IACV’s air channel (unblock it) as it makes life so much easier!I decided to leave a flexi screw as a fail safe – just in case the IACV breaks, or the plug slips out again. So if something happens with it, I won’t have to keep the throttle open manually, just adjust the flexi screw and continue on with my adventure.

Oh, and to keep the flexi screw secure, I 3D printed a bracket that mounts over the seat lock, and has a “hook” to keep a turn knob safe. I’ll include the gcode file in the downloads page under the 3d printed parts section (printed with ABS 1.75mm 0.4 nozzle, 100c bed temp and 230 print temp) if anyone needs it. 

To wrap it up, this mod was just an experiment and… totally unnecessary. I highly suggest reading a bit more about IACV, what it actually does, how to troubleshoot it and a few more interesting things in my other post here! 

And if you still want to add the flexi screw on your ajp, I used a flexi screw for Mikuni RS Carburettors, total length about 27cm, kit included flexi idle screw + washer + spring. Had to be rethreaded.

Explore more!

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• Important things to know about your AJP PR7 – Torque Vales / Bearing / Seal Sizes / Manuals and Stuff.
• How I stored All my Trail Tools and Spares on my AJP PR7.
• AJP PR7 Tool Sizes.
• Cheap ways to make your motorcycles clutch lighter! (Part 2/3).
• How to make a Hydraulic clutch lighter on your motorcycle! (Part 3/3).
• Is it possible to fit the New Athena ECU on the old AJP PR7?

All AJP PR7 MODS:

OR

AJP PR7 Faults, Fails and Fixes

• AJP PR7 Wheel Spacers.
• AJP PR7 Wiring Problem and how to fix it (random stalling problem).
• Not AJP’s Fault – Radiator cap that nearly gave me a heart attack!