cord Posted November 5, 2023 Report Share Posted November 5, 2023 Got a 2021 Combat works 250, and its really hard to start from cold. Once its hot, not problem, 1 or 2 kicks every time. I've read that i should be doing 3/4 slow kicks, then quarter throttle and kick it properley. I'm usually into about 20 kicks before it comes alive? It's got a brand new BPMR4A plug in (previously a 6 but same symptoms). Fuel is super unleaded with 30ml (170:1) of rock oil. Any ideas? Quote Link to comment Share on other sites More sharing options...
lemur Posted November 5, 2023 Report Share Posted November 5, 2023 🤔 thats' a fuel injected bike, poor start could be low fuel pressure, pretty sure it has a battery? low voltage at the battery could cause low fuel pressure, fuel injected bikes in general you should not need to mess with the throttle much for cold starting, on some like the Montesa that even messes them up and it won't start unless the idle is spot on. check your battery voltage when it's cold might be worth a try, when the bikes warm the battery is theoretically charging. Quote Link to comment Share on other sites More sharing options...
lowbrow Posted November 6, 2023 Report Share Posted November 6, 2023 Clean and check all connections and the earth under the seat and to the coil. If that doesn't improve things check the fuel filter inside the tank and whilst it's out check the fuel pump pressure. Some might say replace the pump anyway, especially if you haven't the equipment to test it; they're cheap enough online. I keep my fuel tank full when the bike is in the garage because I've heard that the fuel pump can dry out and get stuck. These comments may have changed my luck, but up to now my bike starts third kick from cold after two slow kicks to wake the pump up. Quote Link to comment Share on other sites More sharing options...
cord Posted November 6, 2023 Author Report Share Posted November 6, 2023 1 hour ago, lowbrow said: Clean and check all connections and the earth under the seat and to the coil. If that doesn't improve things check the fuel filter inside the tank and whilst it's out check the fuel pump pressure. Some might say replace the pump anyway, especially if you haven't the equipment to test it; they're cheap enough online. I keep my fuel tank full when the bike is in the garage because I've heard that the fuel pump can dry out and get stuck. These comments may have changed my luck, but up to now my bike starts third kick from cold after two slow kicks to wake the pump up. Cheers, I’ll have a look at that lot. Is there a procedure for checking fuel pressure? Or just simply T a pressure gauge in wherever I can? And any idea what it should be? Incidentally the bike runs perfect once it’s going. Quote Link to comment Share on other sites More sharing options...
lemur Posted November 6, 2023 Report Share Posted November 6, 2023 Fuel injection pump submerged inside the fuel tank is located there for cooling, the motivation to keep lots of fuel in the tank is cooling. IF the fuel pressure became low the first thing I would check is the filter or filters plural if it has a pre-filter. I have seen pre-filters deteriorate in some fuel where the plastic bits get sucked into the fuel pump and second filter on other brands of motorcycles. Generally the canister fuel filter is under high pressure and the hint for that is it will be fabricated from steel and not thin plastic. Fuel pressure is generally tested by a gauge or by operating the pump off a battery and then measuring the fuel volume output over time. Pressure is fairly high on an injector pump, you are talking about 60psi range. Service manual is sure to tell all about it. From my experience with Honda/Montesa Fi the fuel filter is part of the pump assembly and not available as a separate part, the cost of the pump and filter complete is about 1000$ to replace. ymmv "bike runs perfect once it’s going" Once it's running the electric fuel pump is being powered by the alternator and not exclusively by the battery, that's why I recommended check your battery voltage when it is cold and compare that to when it's running. Montesa/Honda runs 100% off the alternator so it has a relatively huge alternator plus a big capacitor to spin the fuel pump. Quote Link to comment Share on other sites More sharing options...
cord Posted November 6, 2023 Author Report Share Posted November 6, 2023 1 hour ago, lemur said: Fuel injection pump submerged inside the fuel tank is located there for cooling, the motivation to keep lots of fuel in the tank is cooling. IF the fuel pressure became low the first thing I would check is the filter or filters plural if it has a pre-filter. I have seen pre-filters deteriorate in some fuel where the plastic bits get sucked into the fuel pump and second filter on other brands of motorcycles. Generally the canister fuel filter is under high pressure and the hint for that is it will be fabricated from steel and not thin plastic. Fuel pressure is generally tested by a gauge or by operating the pump off a battery and then measuring the fuel volume output over time. Pressure is fairly high on an injector pump, you are talking about 60psi range. Service manual is sure to tell all about it. From my experience with Honda/Montesa Fi the fuel filter is part of the pump assembly and not available as a separate part, the cost of the pump and filter complete is about 1000$ to replace. ymmv "bike runs perfect once it’s going" Once it's running the electric fuel pump is being powered by the alternator and not exclusively by the battery, that's why I recommended check your battery voltage when it is cold and compare that to when it's running. Montesa/Honda runs 100% off the alternator so it has a relatively huge alternator plus a big capacitor to spin the fuel pump. Unfortunately i dont have a manual, hence asking if anyone knew the correct pressure. And as far as i know it doesn't have a battery, ao i assume there is some sort of capacitor somehwere? I'm fine with mechanics, but electrickery is not my thing. Quote Link to comment Share on other sites More sharing options...
cord Posted November 6, 2023 Author Report Share Posted November 6, 2023 Found this fuel pressure info on another thread. Pressure when starting 0.7 bar (without spark plug) with engine running 2.7 all the time, no matter which rpm But before i go any deeper, my fuel filter seems to have seen better days, and the pre-filter gauze had fallen off and was in bottom of the tank. I've got a new filter on it's way, i shall report back! 1 Quote Link to comment Share on other sites More sharing options...
lemur Posted November 6, 2023 Report Share Posted November 6, 2023 Did some of the pre-filter get into the pump or is it 100% accounted for? Sure sounds like you found a big enough problem to account for performance issues. Water destroys the treated paper in fuel filters, makes it so fuel does not pass through as easy, replacement is the only reliable option if your bike ingests water 😐 like when you drop it into a lake. Fella riding a Vertigo Nitro here today (close to freezing temps here) after kicking his bike for about 20 kicks, I said sure sounds like you're charging the battery or you need a jump start. About 30 or 40 kicks it finally started and ran fine for the rest of the day. ... he's going to investigate the battery voltage situation as a possible cause. If yours has a capacitor instead they were reportedly less problem cold starting, which makes sense because a power capacitor charges different and is less problem in cold temps compared to a lithium battery lol one or two kicks should be loads enough if the alternator is any good. Quote Link to comment Share on other sites More sharing options...
cord Posted November 7, 2023 Author Report Share Posted November 7, 2023 19 hours ago, lemur said: Did some of the pre-filter get into the pump or is it 100% accounted for? Yep, the gauze is housed in a plastic cylinder that clips (or not!) on to the base of the pump. It has simple fallen off. I’m going to mechanically fix it in place, or maybe epoxy bond. I’ll tackle that when my new filter arrives. I’ll also cut the old filter open to see just how much dirt it has caught. Quote Link to comment Share on other sites More sharing options...
lemur Posted November 7, 2023 Report Share Posted November 7, 2023 (edited) Found this a moment ago: "installed a tiny 12V Lithium rechargeable battery into the airbox 🔋 and a switch to turn off/on. Now when I hit the switch, I can hear the fuel pump energize and kicks first kick no problem every time." Edited November 7, 2023 by lemur Quote Link to comment Share on other sites More sharing options...
cord Posted November 16, 2023 Author Report Share Posted November 16, 2023 New filter fitted. Bike is an absolute dream to start now. 1 Quote Link to comment Share on other sites More sharing options...
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