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Discussion Starter #1
I ran the 183 for a while, until the Man told me I couldn't modify the capacity on my bike without updating the papers, and I couldn't update the papers without homologation (type approval, something like DOT-approval) papers- which obviously don't exist. So now I am back to 125cc.

While I had it, I was using the finbro ECU together with Moriwaki megaphone exhaust and stock airbox just with the usual internal airbox pipe modification.

Anyway... the problem I had was getting the damned thing to start. Here's a video of how that went:


I found that once the bike was started and warm, I could adjust the idle screw and have it idle really smooth about 1,500rpm. Some said this is too low, but for me it was absolutely fine and any higher meant it would 'lean hang' at 3,000rpm on the way back down to idle.


Once warm it would start much better, but still not really great.


From a few Facebook page threads I have the feeling I am not the only one who had that same issue. So here's what I suggest as a solution - however please note this is untested and you try it at your own risk.

Here's a wiring diagram for the Grom. You can see down in the bottom right there's the 'fast idle solenoid valve'. We know the Thailand models don't have this, and we know the Finbro ECU doesn't have an output for it. It's my belief that this is why the bike wouldn't start. It'd be nice to have a decomp on the camshaft too, but I don't think it was the main problem.



The cold start valve is just a simple solenoid as opposed to the stepper motor type on some more advanced EFi systems. It takes a live feed from the EFi fuse (Black/White) and has a switched earth (Yellow/Orange). My guess is the stock ECU switches to earth depending on what the EOT (Engine Oil Temperature) sensor is reading. But we know the Finbro ECU doesn't have this feature.

So why not manually give the solenoid an earth when you want it to operate? Before I had to revert to 125cc I was going to get a simple handlebar switch, and wire it in between the Y/O wire and earth. Switch it on to activate the solenoid, or off to deactivate. If I am right, this should give you a manual cold start option.



You can also buy thermo switches in the right kind of range. I wondered if it might be possible to put a low range (say 45 celsius) switch between the solenoid and earth, to have a kind of auto choke?
KSD 9700 Temperature Switch Thermostat Normally Closed (NC) Thermal Protector | eBay

I'm not sure if there is a way to use the existing EOT for this, or if that might interrupt something else the ECU might be using that signal for.

Be interested to see what you guys do with this information/idea. It's something that's really essential unless you live in the desert, and it's just plain missing on the Finbro ECU. This could be a super simple fix for like $5 and a little of your time. I can see this being something for Cisco and his ongoing R&D projects - but this could be a lifesaver for anyone for whom that first video has become normal life.
 

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Wow I'm guessing the Man must be relatively knowledgeable in your area. I had my cbr250 Grom inspected by the man as part of my titling process, he thought it was a 125 and I wasn't saying any different. It passed.
 

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Discussion Starter #4
Wow I'm guessing the Man must be relatively knowledgeable in your area. I had my cbr250 Grom inspected by the man as part of my titling process, he thought it was a 125 and I wasn't saying any different. It passed.
There was a fuck up at the customs desk when I was importing the parts - I went to collect them on my MSX. The customs man spoke to the police colleague and my number was noted. I live in a REALLY small place.

The no cold start feature SUCKS. Might as well have a 40yr old carbed bike.
So here it is - give it back to yourself with this mod.
 

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You can also buy thermo switches in the right kind of range. I wondered if it might be possible to put a low range (say 45 celsius) switch between the solenoid and earth, to have a kind of auto choke?
KSD 9700 Temperature Switch Thermostat Normally Closed (NC) Thermal Protector | eBay

I'm not sure if there is a way to use the existing EOT for this, or if that might interrupt something else the ECU might be using that signal for.
If you were to go the the thermo-switch route, youd need a way to get it into/get the heat from the engine decently, rather than just taping it to the cylinder or head.

If you wanted, you could tap off the EOT sensor, using a wheatstone bridge (or this: https://en.wikipedia.org/wiki/Resistance_thermometer#Two-wire_configuration), coupled with some sort of switch dependent on the voltage out of the wheatstone bridge. This switch would most likely have some zener diodes in it and some other stuff... hmmm... Ill look around, draw some diagrams, yaknow.
 

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I could never get the A/F mixture to settle down to 13.2-13.9 range when cruzing or just nomal riding with the Finbro ECM and cold start was worst like you said and I was using the USA wire harness with the a couple of wire moved around and one disconnected and I was getting indication of very lean A/F reading about 16-18 while riding and when going to WOT the grom would sort of hesitated then speed up then lose power so I removed the Finbro ECM and went back to the PCV-WB02 unit. I guess I would have continued testing with the Finbro ECM but I had other projects in the way such as restoring my 1982 RX7 and getting the car smog and I just wanted to enjoy riding both my Finbro 183 and the BrianS 170 groms.

Looking at the idle circuit unit that goes on the throttle body, it looks like the spring and plunger unit that is mounted on the side of the throttle body blocks a hole that lets in a little more air than normal and looks like when you turn on your key to start your grom the circuit will pull the plunger away from the hole to unblock it and let more air into the throttle body for start up.
 

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Discussion Starter #7
I don't have an AF gauge but seat of the pants dyno says the bike ran great on the finbro ECU - when it was warm. It did take a good 5 mile ride to settle itself down though.
I was using the 6 hole injector from Finbro and the big fuel line.
 

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Hmm haven't installed mine yet, and my bike will be mostly a summer bike here in Tx

Hopefully won't be a prob

sent from the batcloset in the batcave on the batphone
 

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its my plan to pop a lil switch on the bike to activate the solenoid when i get my finbro ecu. Shouldnt be hard as like the OP stated the ecu simply grounds out the line opening up the lil port.

Its pretty common on fuel injected dirbikes to essentially have the same thing but manual. My WR450F has a lil plunger on the throttle body that you pull out when its cold.
 

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I don't find it that hard really. On my bike once I made sure the high idle valve was disconnected and the iat sensor disconnected. I have mine idle right around 1500 rpm (warm) with the throttle plate full close and air screw used to adjust idle. When it's cold I crank it till it fires and let it idle with the throttle cracked open just barely. It sputters and pops till she is warmed up then the bikey runs fine. Only takes a couple mins at most. Once warm she fires right up.


If you guys do run the solenoid with a switch might want to make sure it's 12v going to it. A lot of sensors only run on 5v not sure if the solenoid does or not.
 

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I don't find it that hard really. On my bike once I made sure the high idle valve was disconnected and the iat sensor disconnected. I have mine idle right around 1500 rpm (warm) with the throttle plate full close and air screw used to adjust idle. When it's cold I crank it till it fires and let it idle with the throttle cracked open just barely. It sputters and pops till she is warmed up then the bikey runs fine. Only takes a couple mins at most. Once warm she fires right up.


If you guys do run the solenoid with a switch might want to make sure it's 12v going to it. A lot of sensors only run on 5v not sure if the solenoid does or not.
take a look at the wiring diagram.... 12v is fed right to the solenoid from the battery (same with the injector, fuel pump, coil.... anything off the "FI Fuse") I will pop a volt meter on the solenoid though just to confirm that the ecu does in fact actually ground it out completely. I have seen things where an ecu might leave it an open circuit (so something of the sort is not activated) but say it needs 5 volts, the ecu will supply 7 to the "negative" side and the forward bias across the solenoid would be 5. But if i had to put money on it, its a simple 12v solenoid that gets grounded out by the ecu.
 

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It was just a suggestion. I know for a fact that the tps and iat run off 5 volts. Now as for the o2 and such I have no idea I didn't get that far.
 

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Discussion Starter #13
I'm glad someone / someones who know a little about electronics have taken an interest.
 

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It was just a suggestion. I know for a fact that the tps and iat run off 5 volts. Now as for the o2 and such I have no idea I didn't get that far.
The reason the TPS, engine oil temp and air intake temp sensors run off 5 volts is by nature of the sensor. They need to be fed a VERY smooth regulated voltage so the ecu can see the voltage change out of the sensor and compare it to the voltage its feeding the sensor. The reason why its 5v that they see is well, the voltage has to be regulated, and its easier to regulate down voltage from a voltage source thats above what you want, vs smoothing out a higher voltage.

Things like the Injector, coil, fuel pump, cold start solenoid are much less fine. Injector just gets grounded out 50% of the time if the ecu wants a duty cycle of 50%, coil gets grounded when motor needs a spark, same goes for fuel pump n cold start.

o2 Sensor generates voltage hence why its only 1 wire coming from that.

I have a finbro ecu on the way. My thought was to pop in a switch to turn on the cold start solenoid and because the check engine light wire gets cut for the finbro ecu i was going to wire that in as well, so when the cold start valve is on so is the engine light so i dont forget about it. Realistically its not hard to tell that its on just by the sound but i thought it would be cool to use the unused engine light of the finbro ecu.

I have also had the idea of making it a simple manual high idle like i have on my 2014 WR450F's throttle body.


But its Definitely worthwhile to check that its a 12v solenoid... i shall check tonight for everyone. I love this lil grom. its the perfect lil toy to wrench and try things on as its simple, easy and worst case.... i blow it up and now have to rebuild it which gives me another project to wrench on.
 

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Alrighty, some updates.

I did some poking around and my hunches are correct. The solenoid is 12v and i was able to activate it very easily by grounding out the wire that goes to the ecu, i was also able to get the CEL to turn on whenever i wanted by grounding out its wire that goes to the ecu..... AKA the CEL and cold start solenoid are both ground switched via the ecu.

this is awesome news for my idea above. I will be able to make a very simple switch that turns on the CEL and cold start solenoid at the same time to make easy starting a thing with the finbro ecu as well as put to use the CEL that doesnt get used with the finbro ecu. The CEL will turn on when high idle is activated to show the rider that its on and should be turned off when necessary.

I cant wait to get my finbro ecu now!
 

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Alrighty, some updates.

I did some poking around and my hunches are correct. The solenoid is 12v and i was able to activate it very easily by grounding out the wire that goes to the ecu, i was also able to get the CEL to turn on whenever i wanted by grounding out its wire that goes to the ecu..... AKA the CEL and cold start solenoid are both ground switched via the ecu.

this is awesome news for my idea above. I will be able to make a very simple switch that turns on the CEL and cold start solenoid at the same time to make easy starting a thing with the finbro ecu as well as put to use the CEL that doesnt get used with the finbro ecu. The CEL will turn on when high idle is activated to show the rider that its on and should be turned off when necessary.

I cant wait to get my finbro ecu now!
Wow this is great. I would love to be able to do this once its confirmed that u succeeded
 

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SEE POST 54 for an ACTUAL working way... the way below does not add extra fuel!

POST 54 ->>>>> http://www.hondagrom.net/forums/7-grom-talk/10270-finbro-ecu-cold-starting-6.html#post140551







Pin 20 and 22 on the ecu

blue white - CEL, and yellow red - high idle solenoid, they are right next to each other, and its the blue white WITHOUT the lil silver bands, its the blue white that is on the very edge of the plug in the middle row (pin 22), then there is a blank pin, then the yellow red in pin 20.


I peeled back the loom, chopped the two wires right about 3 in off the ecu so if needed i could always re-attach. I crimped on two female bullet connectors to the non plug side (the side that actually goes to the CEL / high idle)

Next i made a Y piece, with two inline Diodes to isolate the circuits, then that went into a SPST switch that goes to ground. I just so happened to have a handle bar mountable kill switch that fit perfectly up in the center of the bars. when in the "running" position the connection was broken, perfect thats exactly what i want.

See attached for the wiring. I made it all out of spare parts, the diodes are there to separate the circuits so i could use the single pole switch. You could get away without using the diodes if you used a DPST / DPDT switch... essentially you do not want the circuits to be able to flow current between them when they are not grounded out.

 

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